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  • Development Of A Soil Quality Index For Characterizing Effects Of Land Use Changes On Degradation And Ecological Restoration Of Rangeland Soils In A Semi‐Arid Ecosystem
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-14
    Fayez Raiesi; Soroosh Salek‐Gilani

    The aim of this research was to study the influence of land use‐changes on degradation and ecological restoration of rangeland soils by quantifying fifteen soil attributes and the subsequent development of a soil quality index (SQI). Soil properties were determined to establish a minimum data set (MDS) for the development of an overall weighted additive SQI. The soil attributes were measured on samples (0–15 and 15–30 cm depths) collected in undisturbed rangelands, cultivated rangelands and restored rangelands following cultivation abandonment for 12 or 45 years in a semi‐arid ecosystem, Central Iran. The selected MDS indicators consisted of the mean‐weight diameter (MWD), total nitrogen (TN), microbial respiration (MR), and alkaline phosphomonoesterase activity (ALP). Overall, soil aggregation, N content, microbial activity, and ALP activity were found to be the key indicators contributing considerably to the SQI of rangeland ecosystems. Soil MWD had the highest contribution (31%) to the estimated SQI values, followed by TN (27%), MR (22%) and ALP (21%). Results indicated a clear difference in soil quality among the common land uses with a significant decline of SQI after conversion of native rangelands (0.80) to croplands (0.53). Restored rangeland soils were characterized by a higher value of SQI (0.63–0.73) as compared with cultivated rangelands (0.53). This suggests a good recovery of soil capacity and functions after the abandonment of cropping activity in previously cultivated rangelands. Vegetation restoration and plant productivity appeared to be the major driver of improved soil quality of the abandoned croplands in these rangelands. A soil quality assessment tool would be useful to determine the success of agricultural abandonment and ecological restoration of rangeland soils in the studied semi‐arid environment.

    更新日期:2020-01-14
  • Spatio‐temporal changes in the understory heterogeneity, diversity, and composition after fires of different severities in a semiarid oak (Quercus brantii Lindl.) forest
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-13
    Mehdi Heydari; Hadieh Moradizadeh; Reza Omidipour; Arash Mezbani; David Pothier

    In arid and semiarid forests and rangelands, native ranchers and farmers frequently use fire as a tool to improve soil fertility and vegetation composition, and to facilitate soil tilling. Investigating changes in ecosystem characteristics after these measures is of great importance for establishing management and recovery strategies. This study aimed to investigate spatial–temporal changes in the understory heterogeneity, diversity and composition after fires of different severities in a Brant's oak (Quercus brantii Lindl.) forest. Vegetation sampling was monitored in 14 patches including unburned sites (UBN), burned sites with low fire severity after 1, 5, and 10 years (LFSO, LFSF, and LFST, respectively), and burned sites with high fire severity after 1, 5, and 10 years (HFSO, HFSF, and HFST, respectively). Fire severity and time since fire significantly affected diversity indices with the lowest values of richness, evenness and diversity in high‐severity fires, while the highest values were observed in low‐severity fires. Time since fire did not significantly affect the understory evenness in both fire severities. However, species diversity and richness in low‐severity fires decreased with time since fire while the reverse was observed in high‐severity fires. The results of a detrended correspondence analysis indicated that the severity and time since fire significantly changed vegetation composition. The largest changes in vegetation composition compared to control sites were observed in HFSO, and then in HFSF and HFST. Both fire severity and time since fire caused changes in the heterogeneity of plant communities. We concluded that the use of low‐severity fires can be suitable for maintaining and increasing the heterogeneity of understory vegetation in semiarid forest ecosystems. However, low‐severity fires have also slightly, while not significantly, increased evenness and can therefore potentially reduce the ecosystem functions of dominant species in such semiarid regions. This could mitigate the positive effect of fire on vegetation heterogeneity and necessitate further investigations.

    更新日期:2020-01-13
  • Monitoring soil organic carbon in alpine soils using in situ vis‐NIR spectroscopy and a multilayer perceptron
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-13
    Songchao Chen; Dongyun Xu; Shuo Li; Wenjun Ji; Meihua Yang; Yin Zhou; Bifeng Hu; Hanyi Xu; Zhou Shi

    Soil quality in alpine ecosystems requires regular monitoring to assess its dynamics under changes in climate and land use. Visible near‐infrared (vis‐NIR) spectroscopy could offer an option, as sampling and transporting large numbers of soil samples in the Qinghai‐Tibet Plateau is extremely difficult. However, the potential for in situ vis‐NIR spectra and the optimal algorithms need to be defined in this region. We have therefore evaluated the performance of a deep learning method, multilayer perceptron (MLP), for in situ spectral measurement of soil organic carbon (SOC) with in situ vis‐NIR spectroscopy in southeastern Tibet, China. A total of 39 soil cores (maximum depth 1 m), including 547 soil samples taken from each 5‐cm depth interval, were collected. The spectra were also measured at each 5‐cm depth interval accordingly. After spectral preprocessing, 4,096 MLP models were generated by taking all the combinations from six parameters defined in the MLP. The 10‐fold‐core cross‐validation showed that MLP had a good performance for in situ SOC prediction, and the best MLP model had an R2 of .92, which were much better than those of the partial least squares regression model (R2 = .80). The results also suggested that the number of epochs, number of neurons, and dropout rate were the most important parameters in the MLP model. We concluded that in situ vis‐NIR spectroscopy coupled with an MLP model has high potential for large‐scale SOC monitoring in the Qinghai‐Tibet Plateau. Our results also provide a reference for rapid hyperparameter optimization using MLP for future soil spectroscopic modeling.

    更新日期:2020-01-13
  • Soil organic carbon sequestration and its stability after vegetation restoration in the Loess Hilly Region, China
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-12
    Hongwei Xu; Qing Qu; Minggang Wang; Peng Li; Yuanze Li; Sha Xue; Guobin Liu

    Vegetation restoration is widely recognized as a way to improve soil organic carbon (SOC) stock. However, whether these recovered carbons are stable is yet largely uncertain. Thus, we determined the sequestration and stability of SOC in soils with three different types (Caragana korshinskii (CA) aged for 10, 20, 36, and 47 years, Hippophae rhamnoides (HR) aged for 5, 10, 20, and 30 years, and Robinia pseudoacacia (RP) aged for 5, 10, 20, 37, and 56 years) to compare their SOC sequestration and stability in different depths in this study. The SOC content, SOC stock, very labile fraction of oxidizable carbon (C1), labile fraction of oxidizable carbon (C2), and carbon management index (CMI) in 0–30 cm depths of the three types increased over the chronosequence. The SOC stocks increased by 1.40–3.19 Mg ha−1 in CA during the 47‐year restoration, by 5.76–10.01 Mg ha−1 in HR during the 30‐year restoration and by 1.88–8.93 Mg ha−1 in RP during the 56‐year restoration, respectively, in 0–30 cm depths. The carbon stability index (SI) in 0–10 cm depth of CA, 0–30 cm depths of HR, and 0–50 cm depths of RP decreased with recovery time. Over the recovery time, SOC content, SOC stock, CMI, and SI were lower than those of nature forest (NF aged more than 100 years) in all restored sites at the later stage of recovery. SOC sequestration decreased, but its stability increased, with the soil depths. Overall, HR had a higher SOC sequestration rate and lower SI (0–30 cm) than CA and RP. Our results revealed that although the SOC sequestration appears enhanced over the restoration, but the SOC stability becomes lower, so that the recovery of these site to the level of NF may meet difficulties in this semiarid Loess Hilly Region.

    更新日期:2020-01-13
  • Cropland abandonment altered grassland ecosystem carbon storage and allocation and soil carbon stability in the Loess Hilly Region, China
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-10
    Hongwei Xu; Xiukang Wang; Qing Qu; Jiaying Zhai; Yahui Song; LeiLei Qiao; Guobin Liu; Sha Xue

    Determining changes in grassland ecosystem carbon (C) storage and soil C stability after cropland abandonment is important for estimating the regional C budget and global C cycle. However, the understanding of ecosystem C storage and allocation and soil C stability along the grassland restoration chronosequence is insufficient. Thus, grasslands with different recovery years (0, 2, 5, 8, 11, 15, 18, 26, and 30 years) were chosen to monitor the dynamics of grassland ecosystem C storage, vegetation biomass C storage, soil C storage, and soil C stability in different soil depths, as well as a natural grassland (NG) reference. The results showed that aboveground biomass (AGB), belowground biomass (BGB), soil C storage, ecosystem C storage, the very labile fraction of oxidizable C (C1) (0–0.3 m layers), the labile fraction of oxidizable C (C2) (0–0.3 m layers), and the C management index increased with the recovery years. The vegetation species richness (R), vegetation species evenness (E), and vegetation species diversity (H′) initially increased, peaking at 18a and then decreasing with recovery years, but the soil C stability index (SI) at 0–0.3 m decreased over time. Additionally, the AGB, BGB, litter biomass (LB), R, H′, ecosystem C storage, and SI (0–0.3 m and 0.5–1.0 m layers) of 30‐year grassland (GL30) showed no significant differences relative to those found in the NG. Furthermore, the soil C sequestration rate decreased with decreasing soil depth, while the soil C stability increased. These results suggest an optimistic outlook for the recovery of ecosystem C, but the soil C under these conditions is unstable, posing a risk to soil C sequestration in abandoned cropland on the Loess Plateau without appropriate management.

    更新日期:2020-01-13
  • Soil microbiotic homogenization occurred after long‐term agricultural development in desert areas across northern China
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-10
    Jie Liu; Aiai Xu; Changkun Wang; Zhiying Guo; Shiwen Wu; Kai Pan; Fangfang Zhang; Xianzhang Pan

    Soil microbial communities respond significantly to long‐term agricultural development in desert areas. Because soil microbial communities are distinct in various deserts at different eco‐climate regions, their response patterns to agricultural development are diverse at a local scale. However, whether the different response patterns had some commonalities across various types of deserts at a larger spatial scale remained unclear. To address this question, historical soil samples, collected in different years from pairwise long‐term experimental plots (desert and farmland) at five field stations of the Chinese Ecosystem Research Network across northern China, were analyzed through high‐throughput sequencing approach. Here, we found that soil bacterial communities were sharply different between deserts and agricultural lands. Contrasting to desert soils with higher relative abundances of Actinobacteria and Firmicutes, agricultural soils harbored higher relative abundances of Proteobacteria, Acidobacteria, and Planctomycetes and exhibited higher bacterial α‐diversity with less variation. More importantly, higher community similarities were found in agricultural lands for each station and all stations, suggesting that soil microbiotic homogenization occurred at both local and regional scales after long‐term agricultural development in desert areas. Further analyses revealed that the homogenization was due to the loss of desert‐endemic species and the range expansion of generalist species, which might result from the introduction of crops combined with agricultural practices. The soil microbiotic homogenization associated with the loss of endemic species should be paid special attention to because this might imply the decrease in ecological resilience to perturbations and might lead to rapid desertification in desert margin areas.

    更新日期:2020-01-13
  • Impacts of future climate and land use change on water yield in a semi‐arid basin in Iran
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-13
    Bagher Shirmohammadi; Arash Malekian; Ali Salajegheh; Bahram Taheri; Hosein Azarnivand; Ziga Malek; Peter H Verburg

    Studying the interaction between hydrology, land use and climate change is necessary to support sustainable water resources management. It is unknown how land management interventions in dry climate conditions can benefit water yield in the context of climate and land use change interactions. In this study, we assessed the effects of both land use and climate change on the Mordagh Chay basin water yield using the Integrated Valuation Ecosystem Service and Tradeoffs model (InVEST). First, we modelled the current water yield, followed by developing six combined climate‐land use scenarios until 2030 based on the CCSM4 climate model for the RCP4.5 and RCP8.5 scenarios. We used three future land use scenarios simulated by the Dyna‐CLUE model. The trend scenario of land use change, which does not include any improvements in irrigation efficiency, significantly affected basin water yield under both climate scenarios. Water yield decreases by 19.8% and 31.8% for the RCP4.5 and RCP8.5, respectively. Under all land use scenarios that included improvements in irrigation efficiency the water yield responded positively. For the RCP4.5 scenario, the water yield was projected to increase between 16.6 and 18% depending on the land use scenario. The increase in water yield under the RCP8.5 climate scenario was much lower than for the RCP4.5 scenario (about one third). Overall, the results showed that by adopting appropriate irrigation efficiency, it is possible to achieve a better balance between environmental needs, regional economic and agricultural development. The results provide insight into possible sustainable development options and also provide guidance for managing the other Urmia Lake sub‐basins while the approach of integrated assessment of climate, land use change and land management options is also applicable in other conditions to help inform sustainable management.

    更新日期:2020-01-13
  • Solidago canadensis invasion in abandoned arable fields induces minor changes in soil properties and does not affect the performance of subsequent crops
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-09
    Szymon Zubek; Marta L. Majewska; Paweł Kapusta; Anna M. Stefanowicz; Janusz Błaszkowski; Katarzyna Rożek; Małgorzata Stanek; Filip Karpowicz; Joanna Zalewska‐Gałosz

    The global fast‐growing presence of invasive species requires urgent action to assess their ecological and economic impact. Although a number of recent works have shown that alien plant invasions can affect native plant communities, soil microbial communities, and soil physicochemical properties, rarely the effects of invaders on all these parameters have been examined at once. Moreover, no studies have focused on the effects of invasive plants on the ecosystem services after the removal of invaders. For this study, Solidago canadensis, one of the most successful global invasive species, was chosen. In the first stage, invasion‐induced changes in plant community and soil properties in abandoned arable fields were assessed. In the second stage, the effects of these changes on crops, Helianthus annuus and Zea mays, were assessed in a laboratory soil‐feedback experiment. The invader reduced substantially the richness and cover of native plant species. It had little impact on soil physicochemical and microbiological properties: Soil moisture was lower, whereas mycorrhizal parameters and urease activity were higher in invaded plots. The experiment revealed minor and inconsistent effects of the invader: It affected the mycorrhizal colonization and shoot mass of crop plants, but the direction of changes depended on the origin of the soil used. In conclusion, although S. canadensis invasion clearly displaces native vegetation, it has few and rather weak effects on soil properties that did not affect the performance of subsequent crops. The results are promising from the viewpoint of restoring the agricultural function to abandoned fields invaded by S. canadensis.

    更新日期:2020-01-11
  • Effect of cushion plants on the soil seed bank in overgrazed semiarid regions
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-09
    Reza Erfanzadeh; Shadi Hazhir; Mohammad Jafari

    Evaluation of soil seed bank (SSB) in relation to biotic environmental factors could be important in degraded areas, since SSB is one of the major sources that facilitates the recovery of degraded plant communities after disturbances such as grazing, flooding and drought. The aim of this study was to investigate the role of Astragalus myriacanthus and Acantholimon spinosum on SSB characteristics. Soil sampling was carried out in four different positions (upslope edge, downslope edge, center and outside) of each cushion in semiarid mountainous regions in Iran. Then, SSB composition and density, species diversity and richness of SSB in each position were estimated using the germination method. The results of the nonmetric multidimensional scaling showed that the separation of species composition of SSB in four different positions was not possible in any of the cushion species. Nevertheless, the results indicated that the lowest of SSB density, species diversity and richness were observed in the outside of the two cushions. In both cushions, A. myriacanthus and A. spinosum, the mean SSB density (1,606.4 and 646.5 seeds/m2, respectively) was significantly higher in the upslope edge. Totally, the mean density of SSBs in A. myriacanthus (903.6 seeds/m2) was significantly higher than that of A. spinosum (360.6 seeds/m2). We concluded that the cushion plants can act as seed traps and therefore could facilitate recovery of degraded sites in the steep‐hilly areas, while, the possibility of seed penetration into the soil of different directions of cushion might be significant.

    更新日期:2020-01-11
  • The impact of coastal flooding on agriculture: a case study of Lincolnshire, United Kingdom
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-10
    Iain J Gould; Isobel Wright; Martin Collison; Eric Ruto; Gary Bosworth; Simon Pearson

    Under future climate predictions the incidence of coastal flooding is set to rise. Many coastal regions at risk, such as those surrounding the North Sea, comprise large areas of low‐lying and productive agricultural land. Flood risk assessments typically emphasise the economic consequences of coastal flooding on urban areas and national infrastructure. Impacts on agricultural land have seen less attention, and considerations tend to omit the long term effects of soil salinity. The aim of this study is to develop a universal framework to evaluate the economic impact of coastal flooding to agriculture. We incorporated existing flood models, satellite acquired crop data, soil salinity and crop sensitivity to give a novel and detailed assessment of salt damage to agricultural productivity over time. We focussed our case study on low‐lying, highly productive agricultural land with a history of flooding in Lincolnshire, UK. The potential impact of agricultural flood damage varied across our study region. Assuming typical cropping does not change post‐flood, financial losses range from £1,366/ha to £5,526/ha per inundation; these losses would be reduced by between 35% up to 85% in the likely event that an alternative, more salt‐tolerant, cropping, regime is implemented post‐flood. These losses are substantially higher than loses calculated on the same areas using established flood risk assessment framework conventionally used for freshwater flood assessments, with differences attributed to our longer term salt damage projections impacting over several years. This suggests flood protection policy needs to consider local and long terms impacts of flooding on agricultural land.

    更新日期:2020-01-11
  • Flood frequency analysis of the forward restoration of the impact of land‐use change based on the HEC‐HMS model
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-10
    Xin Yan; Musheng Lin; Xingwei Chen; Huaxia Yao; Chuanming Liu; Bingqing Lin

    To reveal the impacts of land‐use change on flood frequency distribution, a method to forward restore the largest‐gauged annual flood series to current land‐use conditions was proposed, based on the Hydrologic Engineering Center‐Hydrologic Modelling System (HEC‐HMS), with a newly developed iterative asymptotic method to calibrate the model parameters. Using the Xixi basin on the southeastern coast of China as a case study, the HEC‐HMS model was applied to forward restore the largest annual floods between 1956 and 2011 by using the land‐use conditions of 2010. The flood peak flow series derived from forward restoration were used for flood frequency analysis. The results showed that (1) the iterative asymptotic method could calibrate the initial loss ratio and wave velocity relatively well. The physical meaning of the parameter values obtained was clear. The overall model simulation result was satisfactory, with Nash–Sutcliffe efficiency coefficients of 0.827 and 0.843 in the calibration and verification periods, respectively. (2) The calibration method effectively addressed the difficulty in determining the model parameters needed for resolving the restoration of the impacts of land‐use changes on the largest‐gauged annual flood peak flows and provided a newer HEC‐HMS‐based restoration approach for non‐stationary flood frequency analysis. (3) Urbanization in the Xixi basin caused a degradation in forested and arable lands, as well as in grasslands. Its main impact on the flood frequency distribution was that the average flood peak flow increased from 2633.32m3/s to 2889.48m3/s, and the changes in the coefficient of variation and coefficient of skewness were very small.

    更新日期:2020-01-11
  • The mobility of arsenic from highly polluted farmlands to wheat: soil‐plant transfer model and health risk assessment
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-10
    Kamaladdin Karimyan; Mahmood Alimohammadi; Afshin Maleki; Masud Yunesian; Ramin Nabizadeh Nodehi; Abbas Rahimi Foroushani

    Arsenic (As) can be transferred from soil and accumulated in food plants. So far, we have a knowledge gap about transference of As from agricultural soils to wheat plant in the natural polluted environment. The aim of present study was to investigate As transfer from soil to different tissues of wheat at a highly As polluted area. In this regard, the mobility indices were used to explain As transfer and accumulation from soil to wheat plant. Moreover, the relationships between soil properties including soil As content, pH, cation‐exchange capacity (CEC), electrical conductivity (EC), organic matter (OM), Fe and Al percentage with As concentrations in wheat root, straw and grain were investigated. Finally, the potential health risks of As exposure to humans through consumption of the local wheat crops were assessed. According to the results, harmful degree of As were accumulated in different parts of wheat plant. The impact of different soil properties on As accumulation in wheat were found to be as follows: soil As content > Al % > Fe % > OM > pH > CEC > EC. High carcinogenic and non‐carcinogenic risks in all age groups of consumers were found. The minimum and maximum values for target hazard quotient (THQ) and excess lifetime cancer risk (ELCR) were found to be 1.22, 102.97 and 0.000061, 0.33, respectively. These findings strongly support the notion that As can be entered to food chain through agricultural products cultivated in polluted soils.

    更新日期:2020-01-11
  • New problems of food security in Northwest China: A sustainability perspective
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-08
    Xian Liu; Lijie Shi; Haiyang Qian; Shikun Sun; Pute Wu; Xining Zhao; Bernie A. Engel; Yubao Wang

    China's food security has met standards set by the United Nations Food and Agriculture Organization. However, this development is based on excessive resource input and sacrificing the environment. There are few studies on how to evaluate food production systems with a sustainability framework. In order to guarantee the food security in Northwest China, and realize the sustainable development of agricultural production, this study was carried out. On the basis of comprehensive analysis of new problems faced, including water resources, cultivated land resources and ecological security, several indicators such as water resources development and utilization rate, cultivated land pressure index, cultivated land quality index, N and P emissions and emission intensity are proposed to comprehensively evaluate the sustainability of grain production in Northwest China and put forward countermeasures to realize regional sustainable development. The results show that the water resources are already at a high‐stress level as the development and utilization rate of water resources is 42.7% in 2015. Industrial and domestic water continues to squeeze agricultural water use (annual average reduction of 0.1%). The amount of per capita cultivated land in 2015 has decreased by 9.7% compared to 2000. The quality index of cultivated land is as low as 0.22. A series of ecological problems caused by agricultural production have intensified the ecological crisis in the Northwest, which in turn will further affect food security. Suggestions to address these issues include improving agricultural water use efficiency, strengthening the measures of arable land conservation, improving fertilizer utilization efficiency and reducing plastic‐film mulch residues.

    更新日期:2020-01-09
  • A new grading system for evaluating China's cultivated land quality
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-09
    Liming Liu; De Zhou; Xiao Chang; Zhulu Lin

    Cultivated land is crucial to food security, social and economic stability, environmental quality, and sustainable urban–rural development in China and around the world. However, most of the current grading systems for evaluating cultivated land quality in China tend to generate homogeneous results and inadequate spatial descriptions mainly due to the use of a composite index method that often fails to recognize the matching relationship between land use needs and the quality of cultivated land. The purpose of this study is to propose a new grading system for evaluating China's cultivated land quality that involves two index systems and a scoring and grading scheme. In the proposed system, cultivated land quality is redefined in terms of production capacity quality and environmental quality, and the minimum limiting factor method and the weighted linear model are coupled for factor scoring and grading. The new system is demonstrated by a case study in Yimen Town, a loess plateau region in Western China's Shaanxi Province. The results of this study clearly indicate that the new grading system is superior to the current system when compared using two methods: the spatial pattern comparison method and the crop performance validation method. The results are also favorable in terms of matching relationships between the subclasses of cultivated land quality versus soil types and landforms. The new grading system not only helps to better understand the cultivated land quality but also provides a clear direction for science‐based remediation and amelioration of cultivated land.

    更新日期:2020-01-09
  • Quantifying regional effects of plastic mulch on soil nitrogen pools, cycles, and fluxes in rain‐fed agro‐ecosystems of the Loess Plateau
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-09
    Fei Mo; Juan Han; Xiao‐Xia Wen; Xiu‐Kang Wang; Pu‐Fang Li; Nangia Vinay; Zhi‐Kuan Jia; You‐Cai Xiong; Yun‐Cheng Liao

    Plastic mulch is extensively used to enhance agricultural productivity in the Loess Plateau (LP). However, the effect of mulching on the key processes that dominate soil nitrogen dynamics is rarely assessed quantitatively. We quantified the responses of agro–ecosystem nitrogen–cycling to plastic mulching using a comprehensive database drawn from mulching experiments in the LP. Our results indicated that through increasing the soil mineral and dissolved organic nitrogen concentrations, plastic mulching significantly enhanced the soil nitrogen availability by 36.6% at the regional scale, compared to traditional non‐mulching. Mulching pattern, nitrogen application and soil type were found to be the most significant drivers in determining nitrogen availability. Furthermore, nitrogen gaseous releases and hydrological leaching were significantly reduced by 7.0% and 9.4% respectively, under plastic mulching, which led to an insignificant change in the soil total nitrogen pool. Nitrogen input level and soil organic carbon appeared to be the most important factors influencing soil nitrogen losses. Critically, along with increased root residue inputs to soil and improved water‐thermal under mulching, soil microbial activity was increased significantly. This was indicated by enhanced microbial biomass nitrogen and soil nitrogen–related extracellular–enzyme activity, and was driven by nitrogen input, mulching duration and soil carbon status. We generalize that in the rain‐fed agro–ecosystems of the LP, plastic mulch will have little impact on nitrogen pool size, largely due to reduced gaseous and hydrological nitrogen losses, and increased crop‐sourced nitrogen inputs, but will strongly stimulate microbial growth, metabolism and activities, which consequently will speed up biogeochemical cycles of soil nutrients.

    更新日期:2020-01-09
  • Tourism impact assessment modeling in vegetation density of protected areas using data mining techniques
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-09
    Ali Jahani; Hamid Goshtasb; Maryam Saffariha

    In protected areas (PAs), the lack of tourism impact prediction models on vegetation has not been accurately predicted that is a shortcoming in PA management. Now the main question is how recovery can be accelerated; or which ecological factors are associated with the rehabilitation of vegetation density? We aimed to compare the Multi‐Layer Perceptron (MLP), Radial Basis Function Neural Network (RBFNN) and Support Vector Machine (SVM) models to predict tourism impact on land vegetation density changes. Three old national parks of Iran with diversity in tourist pressure and ecological condition of the site were selected for analyzing. We recorded 12 ecological and tourist variables in 400 sample plots which are classified in topography, plot soil, and tourist pressure factors. We developed the tourism impact assessment model (TIAM) by MLP, RBFNN, and SVM techniques. Comparing to RBFNN and SVM, the MLP model (TIAMMLP) is introduced as the most accurate model in vegetation density changes for tourism impact assessment in PAs. The MLP model represents the highest value of R2 in training (0.969), test (0.806) and all datasets (0.876). Sensitivity analysis proved that the values of the tourist pressure, soil organic matters, soil moisture, soil porosity, and soil EC are respectively as the most significant inputs which influence TIAMMLP in PAs. We concluded that habitats with higher organic matter and moisture in the soil would likely tolerate more tourists’ pressure. The MLP model, as a tool for, PAs managers, is able to predict vegetation density changes under tourism pressure precisely.

    更新日期:2020-01-09
  • Suppression of amino acid and oligopeptide mineralization by organic manure addition in a semiarid environment
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-08
    Shahid Iqbal; Davey L. Jones; Muhammad Saleem Arif; Tahira Yasmeen; Jianchu Xu; Sehroon Khan; Sadia Nadir

    The rapid mineralization of organic nitrogen (ON) in semiarid soils frequently results in large N losses, reduced crop yields, and environmental pollution. The addition of manures to soil has the potential to promote microbial growth, increase N immobilization, reverse the decline in soil organic matter (SOM), and enhance soil quality. In this study, three contrasting organic manures were used to determine their influences on amino acid and oligopeptide dynamics in soil (as key component of the soil ON‐cycle) as well their effects on the size of the microbial biomass and N immobilization. Laboratory incubation experiments were set up with soil obtained from experimental field trial sites for growing maize. Treatments included soil amended with either: poultry‐manure (PM), farmyard‐manure (FYM), pressmud (PrM), or unamended (control). Radio‐ and stable‐isotope (14C‐15N) techniques were used to assess ON mineralization, immobilization, and leaching using the amino acids alanine (Ala) and valine (Val) as well as the oligopeptides trialanine (Ala‐Ala‐Ala) and valine‐proline‐proline (Val‐Pro‐Pro) as model substrates. qPCR was used to determine soil bacterial biomass. The results showed that all manures increased microbial growth and total soil amino acids as well as protein content. Greater immobilization and subsequently lower mineralization and leaching were also observed in the manure‐amended soils, with this being most pronounced in the PM treatment. The application of PM also enhanced the half‐lives of the ON compounds in soil and increased the size of the bacterial biomass. Overall, our findings indicate that manure amendments, particularly PM, can help promote more efficient ON cycling in semi‐arid ecosystem by controlling N mineralization, reducing amino acid leaching, and elevating oligopeptide immobilization.

    更新日期:2020-01-08
  • Soil Bacterial Community Succession During Desertification in a Desert Steppe Ecosystem
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-08
    Miaochun Fan; Jiajia Li; Zhuangsheng Tang; Zhouping Shangguan

    Desertification often occurs in fragile steppe ecosystems, which may lead to severe soil degradation. Understanding how soil microbial communities respond to desertification is critical for ecological restoration of degraded desert steppes. We used an Ion S5™ XL sequencing platform to explore the soil bacterial community succession across four desertification stages in a desert steppe in Ningxia, China. The results showed that soils from potential to light desertification stage had similar physicochemical properties, whereas significantly lower macronutrients, silt, and clay contents and higher pH, moisture, and sand contents were observed in the severe and very severe stages (p < 0.05). Due to change in soil conditions, bacterial communities shifted drastically across the four stages (p < 0.05). Variation in bacterial community composition was driven mainly by the deterministic processes (i.e., habitat filtering based on resource availability and space limitations), but their effects decreased toward the very severe desertification stage. More potential indicator species including members of the genera Nitrosomonas, Pirellula, and Methylobacterium were selected to predict very severe desertification relative to the other three stages. These potential indicators could survive in a wide range of habitats with low availability of carbon and nitrogen sources. Co‐occurrence network analysis revealed that most of soil microorganisms might form symbiotic relationships in response to the habitat heterogeneity caused by desertification. In conclusion, as desertification intensified, distinct shifts in soil bacterial communities were driven primarily by the deterministic processes, which provide new insights for the restoration of degraded habitats and sustainable development of land resources.

    更新日期:2020-01-08
  • Spatial patterns of large‐scale land transactions and their potential socio‐environmental outcomes in Cambodia, Ethiopia, Liberia and Peru
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-08
    Chuan Liao; Suhyun Jung; Daniel G. Brown; Arun Agrawal

    Recent large‐scale land transactions, often framed as “land grabbing,” are historically unprecedented. Millions of hectares of land have changed hands for agriculture‐driven development over the past decade, and their implementation generates substantial risk of land degradation. This paper aims to investigate land transaction patterns and evaluate their potential socio‐environmental impacts in Cambodia, Ethiopia, Liberia, and Peru. We undertake a novel spatially explicit approach to quantify land transactions, and conduct scenario‐based analyses to explore their implementation consequences on people, land, and carbon emission. Our results demonstrate that existing global datasets on land transactions substantially underestimate their incidence, but can either exaggerate or underreport transacted areas. While confirming that land transactions are more likely to occur in sparsely populated, poorer, and more forested areas, our scenario‐based analyses reveal that if fully implemented for agricultural development, land transactions in the four countries will affect more than one million people, yield over 2 Gt of carbon emissions, and disrupt vast swathes of forests. Our findings refute the “empty land” discourse in government policy, and highlight the consequences of land degradation that can occur at an unexpected scale in the “global land rush.” Future policy‐making needs to anticipate the risk of land degradation in terms of deforestation and carbon emission while pursuing agriculture‐driven development through land transactions.

    更新日期:2020-01-08
  • Assessment of land levelling effects on lowland soil quality indicators and water retention evaluated by multivariate and geostatistical analyses
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-07
    Luís Carlos Timm; Luiz Fernando Pires; Luana Nunes Centeno; Dioni Glei Bonini Bitencourt; José Maria Barbat Parfitt; Alexssandra Dayanne Soares de Campos

    Studies focusing on the impact of levelling on the management of available water for rice growth and on soil hydro‐physical quality indicators cultivated in lowland soils under aerobic conditions are still scarce. The objective of this study was to evaluate the levelling impact on soil water retention and soil quality indicators by multivariate and geostatistical analyses. A 10 × 10 m grid was used to sample the 0‐ to 20‐cm layer in a 1.0‐ha experimental field, before and after levelling. Sand and clay contents, macroporosity, bulk density (Bd), organic matter (OM), weighted average diameter of aggregates, and the water retention curve were measured. Available water capacity, structural stability, and S indexes and relative field capacity were calculated. Descriptive statistics, Kolmogorov–Smirnov test, and geostatistical analysis were used. Maps of all data sets significantly correlated with Bd and OM after levelling were constructed using ordinary and indicator kriging. Kaiser–Meyer–Olkin and Bartlett tests were performed for factorial and principal component analyses which were used to reduce the dimensionality of data and of main principal component maps. Levelling negatively affected the majority of soil quality indicators, caused an increase of their spatial range, and an improved the goodness of fit of the semivariogram models used. The majority of variables were best fitted by the Gaussian model after levelling. Bd and OM probability maps were found to be useful tools for farmers wanting to utilize different strategies for topsoil management, with the goal of improving soil quality of levelled areas for future land recuperation operations.

    更新日期:2020-01-07
  • Determining the effect of land consolidation on agricultural production using a novel assessment framework
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-06
    Changqiao Hong; Xiaobin Jin; Yeting Fan; Xiaomin Xiang; Shuai Cao; Changchun Chen; Guang Zheng; Yinkang Zhou

    Land consolidation (LC) is regarded as a useful tool to improve agricultural production. Measuring the effect of LC on agricultural production (ELCAP) is helpful for the planning of LC activities. In the past, it is difficult to measure ELCAP at regional level due to the lack of field observation, the change of crop planting structure, and high cost of sample collection. Satellite data have large coverage and high spatiotemporal resolution for vegetation observation, which can provide a new idea for estimating ELCAP at regional level. This study aims to build a novel assessment framework to quantitatively investigate ELCAP by developing several satellite‐based metrics. In addition, this study also explored the characteristics of ELCAP using the method of spatial autocorrelation and the geographical detector method in 1,281 LC areas in China. Our results show that agricultural productivity in more than 90% of total LC areas shows an increasing trend during 2001–2016. LC could play the positive but limited effects on agricultural production, and its productivity‐boosting effect (64.87% of total LC areas) is greater than its stability‐improving effect (46.53% of total LC areas). The spatial agglomeration of ELCAP is weak (Moran's I < 0.06), which may be resulted from the differences in field conditions and natural‐social–economic situations across LC areas. The interaction between several factors has a greater effect on the ELCAP than each of these factors. Methodology in this study provides a new and useful framework for evaluating ELCAP, and results can be used to guide the planning of LC activities.

    更新日期:2020-01-07
  • Mapping spatiotemporal decisions for sustainable productivity of bamboo forest land
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-06
    Xuejian Li; Huaqiang Du; Fangjie Mao; Guomo Zhou; Luqi Xing; Tengyan Liu; Ning Han; Enbing Liu; Hongli Ge; Yuli Liu; Yangguang Li; Di'en Zhu; Junlong Zheng; Luofan Dong; Meng Zhang

    Properly mapping the sustainability of bamboo forest production plays an important role in providing basic strategies for decision makers to ensure sustainable use of bamboo resources. Understanding the response pattern of drought, poor management, elevation, and barren soil to bamboo forest ecosystem productivity is critical to formulating appropriate improvement strategies of sustainable management of bamboo forest productivity for addressing growing challenges of bamboo forest land degradation. The objectives of this study were to quantify differences in productivity, meteorological, topographical, soil, and bamboo distribution and structure factors under different sustainable management levels of bamboo forest ecosystem productivity in order to support management decision making in a spatiotemporally explicit context. We constructed an innovative three‐layer index system for the sustainable management of bamboo forest productivity by integrating productivity, meteorological, soil, topographic, bamboo distribution, and structure factors to promote sustainable management and spatiotemporal decision making, particularly in bamboo forest areas with low productivity. The partial least squares (PLS) path model was used to analyze the spatiotemporal effects of different factors on bamboo forest productivity and to create sustainable management maps that could be used for spatially informed decision making regarding bamboo forest production. The results showed the spatial and temporal variations in gross primary productivity (GPP), net primary productivity (NPP), and net ecosystem exchange (NEE) in bamboo forests. The sustainable management index was also mapped each year throughout the study area. We divided the index value range into five management‐friendly classes, which were shown to be directly related to GPP, NPP, NEE, Slope, Aspect, soil texture, hydrolytic nitrogen, and Abundance. We found that the areas with relatively high sustainable management levels (I and II) occupied only 18.94% of the bamboo forest area and exhibited a highly clustered distribution. Most of the other areas (78.67%) had relatively low levels of sustainable management (III and IV), and their distribution was rather scattered. The remaining 2.39% of the bamboo forest area that had the lowest sustainable management level (V) was small in area, fragmented, and not conducive to intensive management. The results of the present study can serve as a useful reference for bamboo forest management, which is of great importance for bamboo‐based ecosystems and economies.

    更新日期:2020-01-07
  • Vertical changes in bacterial community composition down to a depth of 20 m on the degraded Loess Plateau in China
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-07
    Guiyao Liu; Lili Chen; Qiang Deng; Xinrong Shi; T. Ryan Lock; Robert L. Kallenbach; Zhiyou Yuan

    Soil microbes are involved in the fundamental processes that underpin an ecosystem's function. However, little is known about the microbial communities that inhabit deep soil horizons, especially in degraded forest ecosystems. Here, we used high‐throughput sequencing to investigate the vertical distribution of soil bacterial communities to a depth of 20 m in Pinus tabulaeformis and Robinia pseudoacacia forests on the Loess Plateau, China. We found that bacterial richness declined from the topsoil to a depth of 2 m in P. tabulaeformis forests and declined from the topsoil to a depth of 1 m in R. pseudoacacia forests, and thereafter increased. The relative abundance of α‐Proteobacteria was higher in subsoils than in topsoils of P. tabulaeformis forests. It was highest at the depth of 20 or 14 m in both forest types, suggesting that α‐Proteobacteria can survive dry, alkaline, low‐nutrient environments. We also found a higher relative abundance of Acidobacteria in topsoils than in subsoils, indicating that Acidobacteria can grow well in nutrient‐rich environments. Our results suggest that soil bacterial communities respond to nutrient changes associated with soil depth and plant species. These findings revealed that soil microorganisms persisted in deep and carbon‐starved soils, especially for α‐Proteobacteria which may be adapted to resource‐poor environments in deep soils.

    更新日期:2020-01-07
  • Temperature sensitivity of decomposition of soil organic matter fractions increases with their turnover time
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-06
    Yufu Jia; Yakov Kuzyakov; Guoan Wang; Wenbing Tan; Biao Zhu; Xiaojuan Feng

    Soil organic carbon (SOC) is an indicator of soil fertility. Global warming accelerates SOC decomposition, consequently, resulting in land degradation. Characterization of the response of SOC decomposition to temperature is important for predicting land development. A simulation model based on temperature sensitivity (Q10) of SOC decomposition has been used to predict SOC response to climate warming. However, uncertain Q10 leads to substantial uncertainties in the predictions. A major uncertainty comes from the interference of rainfall. To minimize this interference, we sampled surface (0–5 cm) soils along an isohyet across a temperature gradient in the Qinghai–Tibetan Plateau. The Q10 of bulk soil and the four soil fractions, such as light fraction (LightF), particulate organic matter (POM), hydrolyzable fraction (HydrolysF), and recalcitrant fraction (RecalcitF), were studied by 14C dating. Turnover time follows the order: LightF < POM < bulk soil < HydrolysF < RecalcitF. The Q10 follows the order: LightF (1.0) = POM (1.0) < HydrolysF (3.63) < bulk soil (5.93) < RecalcitF (7.46). This indicates that stable fractions are much more sensitive to temperature than labile fractions. We also suggest that protection mechanisms rather than molecular composition regulate SOC turnover. A new concept 'protection sensitivity' of SOC decomposition was proposed. Protection sensitivity relates to protection type and primarily controls Q10 variation. A simulation model based on the Q10 of individual fractions predicted SOC change and land development in the Qinghai–Tibetan Plateau in the next 100 years much effectively as compared to simulations based on one‐pool model (Q10 = 2) or bulk soil (Q10 = 5.93).

    更新日期:2020-01-06
  • Spatial–Temporal variations in urbanization in Kunming and their impact on urban lake water quality
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-06
    Kun Yang; Yi Luo; Kexin Chen; Yang Yang; Chunxue Shang; Zhenyu Yu; Jiaxin Xu; Yisong Zhao

    As a radiation center or hub in Southeast Asia and South Asia and the only Chinese metropolis bordering other ASEAN countries, Kunming has experienced extensive urbanization since the 1980s. This type of human activity has been accompanied by environmental deterioration, especially water quality pollution, in Dianchi Lake, China's sixth largest freshwater lake. This study reveals that the urbanization process has led to land degradation over the past thirty years. First law of geography was introduced to analyze the effects of impervious surface area (ISA) expansion on the lake water environment. The results indicate that the ISA encompassed the Lake and radiated outwards. Since the 1990s, approximately 35% of natural surfaces transformed to ISA, and the urban district density exploded from one in 2001 to four in 2017. The urban district area density exploded from 0.06% to 12.05% over the past 17 years. During the past 30 years, the growth rate of ISA exceeded 21 km2/a and even reached 38 km2/a between 2004 and 2017. The spatial pattern of lake water quality was determined by the spatial influences of ISA (G). Then, the relationship between water quality indicators and G was analyzed, and the threshold between G and water quality was investigated using an exponential regression analysis method. The results of the correlation analysis indicated that a significant correlation exists between G and lake water quality; although the lake water quality showed a cyclical change, the G impact on the lake water quality was notable. This research proposed an effective method to calculate the spatial influence of the impervious surface on the water quality to reveal the effect of urbanization on the water environment quantitatively and helps us to enhance the understanding of ISA expansion impact on lake environment. Moreover, this research provides decision supports for the environmental protection and management of the lake and empirical evidence regarding urban development impacts on watershed planning.

    更新日期:2020-01-06
  • Evaluation of restoration approaches on the Inner Mongolian Steppe based on criteria of the Society for Ecological Restoration
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-05
    Feng Zhang; Christer Nilsson; Zhenzhu Xu; Guangsheng Zhou

    Ecological restoration is becoming an increasingly common management tool worldwide. However, a challenge still exists on how to effectively monitor restoration outcomes and evaluate restoration success for ecological restoration managers. In this review, the goal is to evaluate whether the research in a degraded area has been sufficient for fostering efficient restoration measures and follow‐up of restoration success based on the Society for Ecological Restoration (SER) criteria. We selected the Inner Mongolian Steppe (IMS) in China as a model system. This area has been the subject of substantial research over the most recent years to understand degradation processes and restoration outcomes. We put together the variables used to assess degradation and restoration needs in the IMS and analyzed restoration results based on SER's nine criteria for evaluating restoration success. We found that the accomplished research in the IMS only partially supplied the data needed for evaluation of restoration success. The available results were sufficient for a proper evaluation of species composition and tentatively supported assessments of another seven criteria but not self‐sustainability. Grazing exclusion led to the fastest and most successful recovery of degraded steppe, but landscape‐scale processes during restoration in the IMS are still incompletely known. Our review supports large‐scale restoration of the IMS and emphasizes the need for long‐time monitoring for a more complete evaluation of the outcome of the IMS restoration following all SER's criteria.

    更新日期:2020-01-06
  • A global analysis of the impact of zero‐tillage on soil physical condition, organic carbon content, and plant root response
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-05
    Surajit Mondal; Debashis Chakraborty; Kalikinkar Bandyopadhyay; Pramila Aggarwal; Dharamvir Singh Rana

    Food security involves the sustainable utilization of soil and land resources. Zero‐tillage (ZT) practice is a proponent of better resource utilization, to improve soil physical condition, and a potential sink to atmospheric carbon. However, the impact varies across climates, over the ZT history, cropping systems, and soil depths. A meta‐analysis was performed, based on 4,131 paired data from 522 studies spread globally, to evaluate the effect of ZT in comparison to conventional tillage, on soil physical condition (bulk density; mean weight diameter of aggregates; field capacity water content; and steady‐state infiltration rate), soil organic carbon (SOC) content, and the root response (root length density). Zero‐tillage significantly improved mean weight diameter of aggregates and field capacity water content at surface and subsurface layers by 19–58% and 6–16%, respectively, and resulted in no change in bulk density in either of the layers, but infiltration rate increased by 66%. Surface 0‐ to 5‐ and 5‐ to 10‐cm layers had significantly higher SOC content under ZT, whereas in other layers, the SOC content either reduced or did not change, resulting in a small and insignificant variation in the SOC stock (~1.1%) in favor of ZT. The root length density improved by ~35% in ZT only at 0‐ to 5‐cm soil depth. Effect of climate, soil type, or cropping system could not be broadly recognized, but the impact of ZT certainly increased over time. Improvements in soil aggregation and hydraulic properties are highly convincing with the adoption of ZT, and therefore, this practice leads to the better and sustainable use of soil resources.

    更新日期:2020-01-06
  • Does damming streams alter the water use strategies of riparian trees? A case study in a subtropic climate
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-02
    Pei Zhao; Wim Cornelis; Xiangyu Tang; Peng Zhao; Jialiang Tang

    Understand the mechanism governing degradation of riparian forests in response to damming streams is needed for a comprehensive impact assessment of dams in relation to protection of river ecosystems. However, the ascription of riparian forest degradation to the hydrological changes induced by dams lacks of direct proof and the hypothesis that dam construction alters the water use strategy of riparian trees is yet to be tested. In this study, the water sources of riparian trees grown upstream and downstream of dams at SW China, were investigated by dual isotopes and a Bayesian model. We observed that xylem water in downstream Populus adenopoda had significantly lower line‐conditioned excess values than upstream trees. The water source of upstream trees was barely subjected to evaporation. Upstream mature and young P. adenopoda trees both acquired more streamwater (47.2 ± 9.8% and 44.8 ± 7.9%) than groundwater (28.2 ± 4.4% and 29.2 ± 3.5%) or soil water (24.5 ± 5.6% and 26.0 ± 4.9%). Downstream mature and young P. adenopoda trees both largely used soil water (49.0 ± 11.6% and 53.0 ± 6.2%) as main water source. In contrast, Pterocarya stenoptera highly depended on streamwater, regardless of size and location, implying that damming had little effect on this species. Damming streams may increase water competition among downstream riparian trees, which could explain declines in growth rate, canopy dieback, tree death, and eventually downstream land degradation. We believe that this study is of significant value for research into riparian forest degradation resulting from hydrological changes, and in particular to apprehend the impact of small dams, which has barely been studied.

    更新日期:2020-01-04
  • Biochar's Cost Constraints are Overcome in Small‐Scale Farming in Tropical Soils in Lower‐Income Countries
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-02
    S. Robb; S. Joseph; A. Abdul Aziz; P. Dargusch; C. Tisdell

    Biochar has been lauded for its potential to mitigate climate change, increase crop yields and reverse land degradation in tropical agricultural systems. Despite its benefits, confusion persists about whether the use of biochar is financially feasible as a soil ameliorant. A comprehensive review of previous studies of biochar's financial feasibility was performed (33 relevant publications). Financial performance appraisal (US$ Mg‐1 biochar) and greenhouse gas abatement cost estimates (US$ Mg‐1 CO2e) were used to gauge the financial feasibility of the biochar scenarios within each publication. Ordinary Least Squares Multiple Linear Regression was used to evaluate the predictive capacity of scenario financial feasibility as dependent on variables including national income levels, climatic conditions, pyrolysis technology scales and pyrolysis capabilities. Analysis revealed that scenarios where biochar was applied targeting yield increases in high‐value crops in tropical locations with low incomes and biochar‐focused small‐scale production, were overall significant predictors of biochar scenario financial feasibility. We find that the average abatement cost of biochar applied in ‘lower‐income countries' is ‐US$58 Mg‐1 CO2e (financially feasible) compared with +US$93 Mg‐1 CO2e in ‘higher‐income countries' (not financially feasible). Climate policies of lower‐income countries in tropical climates should consider biochar as an input for small‐scale climate smart agriculture to address land degradation in tropical agricultural systems. Based on recent evidence it is suggested that biochar fertilizers, a value‐added biochar product, could present a commercially feasible pathway for biochar value‐chain development in higher‐income countries.

    更新日期:2020-01-02
  • Conversion of coastal marshes to croplands decreases organic but increases inorganic carbon in saline soils
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-01
    Yuanshan Zhu; Yidong Wang; Changcheng Guo; Dongmei Xue; Jun Li; Qing Chen; Zhaoliang Song; Yilai Lou; Yakov Kuzyakov; Zhong‐Liang Wang; Davey L. Jones

    Over the past century, conversion to agriculture has greatly reduced the global extent of coastal wetlands leading to degradation and loss of these ecosystems. However, it remains unclear how this land conversion affects the confluent soil organic and inorganic carbon (SOC and SIC) storage as well as their localizations in soil matrix. Here, we investigated these issues using wet sieving at two coastal saline‐alkali sites in northern China. Conversion of marshes to cropland (> 60 years) decreased the portion of large macroaggregates (> 2 mm) and correspondingly increased the portion of microaggregates (0.053−0.25 mm) at both sites. Land conversion decreased SOC contents by 31−67% in all fractions (> 2, 0.25−2, 0.053−0.25 and < 0.053 mm) in the top‐ (0−15 cm) and sub‐soil (15−30 cm). In contrast, irrigation‐ and NH4HCO3 fertilization‐derived carbonates increased SIC storages in almost all fractions due to the saline‐alkali soil conditions, especially for the subsoil. This increases in SIC almost offset and compensate for the SOC losses at both sites. Consequently, the irrigation‐ and NH4HCO3‐induced SIC accumulation should be included in the full C balance of saline‐alkali soils. It should be noted, however, that the progressive loss of SOC due to cultivation will lead to soil degradation in fertility and ecological function, thereby hampering long‐term sustainability of coastal ecosystems. Therefore, the compensation of SIC for the loss of SOC is not sustainable in the longer term.

    更新日期:2020-01-02
  • The effects of forest thinning on understory diversity in China: A meta‐analysis
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-01
    Xiankun Li; Yanan Li; Jing Zhang; Shouzhang Peng; Yunming Chen; Yang Cao

    Forest management has been widely used to maintain and improve multiple ecosystem services. However, large‐scale synthesis of the effects of forest management on understory diversity, especially regarding the effects of thinning, has not been well represented in China. Therefore, we synthesized 146 peer‐reviewed publications and conducted a meta‐analysis to evaluate the response of understory diversity (species richness) and 7 related variables to forest thinning in China. Overall, forest thinning significantly increased shrub diversity by 28% and herb diversity by 24%, respectively. Unthinned diversity and recovery time were the two most important drivers of understory diversity. When the unthinned diversity was low, a decline of understory species richness in managed stands could occur, which may be related to the size of the regional species pool. Rather than the recovery time of 1‐2 years after forest thinning, the period of 3‐5 years after thinning found the greatest diversity improvement. The northern arid and semi‐arid ecological domain observed the greatest diversity improvement, which may be due to the specific characteristics in this ecological domain. The coniferous forest was more favourable for understory improvement than in the broadleaved forest. Specific mechanisms on how disturbance (thinning intensity) affect understory diversity need to be further explored. No significant influences of stand stage or sampling quadrat area could be identified. Our study provides a synthetic review of the effects of forest thinning on understory diversity in China and may benefit forest management strategies. Future studies should address changes in compositional or functional diversity after thinning.

    更新日期:2020-01-02
  • Exploring the effect of hydrological connectivity and soil burn severity on sediment yield after wildfire and mulching
    Land Degrad. Dev. (IF 4.275) Pub Date : 2020-01-01
    Cristina Fernández; José M Fernández‐Alonso; José A. Vega

    Soil erosion can potentially threaten different resources inside and outside of burned areas, and the risk of water becoming contaminated with sediment may be particularly severe. Various post‐fire actions, such as applying straw mulch, have been carried out in NW Spain in recent years with the aim of mitigating the risk of soil erosion. Nonetheless, because of the short interval between summer wildfire and autumn rains, careful selection and prioritization of the areas to be treated is crucial. Changes in hydrological connectivity could be measured and used as a criterion for selecting such areas. However, studies addressing changes in hydrological connectivity as a consequence of forest fires are scarce. In the present study, we assessed the effects of fire and post‐fire helimulching on the hydrological connectivity and sediment loads in a forest catchment burned by a wildfire in August 2016. Sediment yields were recorded in 20 plots (180 m2). Hydrological connectivity was computed with a version of the Borselli index and two alternative weighting factors: the C factor from the Revised Universal Soil Loss Equation (RUSLE) and a factor based on field surveys of soil burn severity. The effect of mulching was also considered. The results indicate that the version of the Borselli index based on field measurements of soil burn severity best reflect the susceptibility to post‐fire sediment delivery. Moreover, this method was also suitable for evaluating the effect of mulching on soil erosion. The study findings may help forest managers to plan post‐fire actions.

    更新日期:2020-01-02
  • Effects on the plant stem arrangement onsediment transport capacity of croplands
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-30
    Suhua Fu; Hongli Mu; Baoyuan Liu; Xianju Yu; Guanghui Zhang; Yingna Liu

    Vegetation effectively prevents soil erosion; however, little information is available on the effects of plant stems on sediment transport capacity. The purposes of this study were to investigate the effects of plant stem arrangement patterns on sediment transport capacity and to quantify this relationship. Artificial plant stems (stem diameter, 0.01 m) were arranged in five patterns: tessellated, random, bead, zigzag, and banding. Two discharges, two slope gradients, and two plant basal cover conditions were used to conduct flume experiments. Results revealed that plant stem arrangement affected flow regime, hydraulic parameters, hydrological connectivity, and sediment transport capacity. The structural index of connectivity (i.e., the index of sediment connectivity) and the functional index of connectivity (i.e., flow velocity) were used to quantify the effects of plant stem arrangement on sediment transport capacity. The latter exhibited a significant linear function with hydraulic parameters, including flow velocity (p < .05). Unit stream power had the greatest adjusted R2 value and provided the best estimation of sediment transport capacity. Plant stem arrangement did not affect the relationship between sediment transport capacity and hydraulic parameters. These results are helpful and will enhance our predictions of different plant stem arrangement effects on sediment transport capacity.

    更新日期:2019-12-31
  • Biocrust regulates the effects of water and temperature on soil microbial and nematode communities in a semiarid ecosystem
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-30
    Pingting Guan; Xiaoke Zhang; Yunyun Cheng; Hairui Zheng; Wenju Liang

    Global climate changes in temperature and precipitation are influencing the function of semiarid ecosystems, especially that of biocrust. Biocrust is the key biotic component in semiarid land and delivers multiple functions to belowground ecosystems. However, how biocrust affects belowground biota when temperature and water change remains unclear. We set a microcosm experiment to evaluate how soil micro‐food web responds to biocrust by changing air temperature and water content. Soil microbes and nematodes were sampled at different air temperatures (10 and 25°C) and soil water levels (4, 8, and 16% soil water content) under biocrust and bare soil. The results showed that biocrust highly increased soil microbe and nematode abundances compared with bare soil. Temperature change had no obvious effect on soil micro‐food web. Both microbial and nematode communities were strongly affected by soil water at 10°C under biocrust. Structural equation modeling analysis proved that soil pH and organic carbon were the two main factors that affected soil micro‐food channels under biocrust. Soil organic carbon affected bacterial channel and fungal channel. Soil pH affected soil bacterial channel and omnivores‐predators. Soil with 8% water content could provide the most stable habitat and soil environment to build a relatively complex and more reticulated soil micro‐food web. It can be concluded that colonization of biocrust could buffer temperature effect on soil micro‐food web. Additionally, appropriate increase in water could benefit the top‐down effect between nematodes and microbes under biocrust and could contribute to the resilience of semiarid ecosystems.

    更新日期:2019-12-31
  • Filling a void: Analysis of early tropical soil and vegetative recovery under leguminous, post‐coal mine reforestation plantations in East Kalimantan, Indonesia
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-29
    David J. Woodbury; Ishak Yassir; Arbainsyah; Danica A. Doroski; Simon A. Queenborough; Mark S. Ashton

    Land degradation in Borneo, one of the world's richest biodiversity hotspots, is extensive. In East Kalimantan, 5,000,000 ha of land are zoned for surface‐mined coal. Deforestation from this mining threatens biodiversity and results in soil degradation, erosion, and polluted runoff, all directly impacting human populations. Revegetation methods developed for temperate forests are commonly used globally for mine rehabilitation. However, few empirical studies of native forest restoration as part of mine rehabilitation exist from wet tropical regions. Here, a chronosequence was established to observe forest succession under leguminous plantations at the PT Singlurus Pratama coal mine in East Kalimantan, Indonesia. Soil and natural regeneration data were recorded from samples of ten 20 × 60‐m plots randomly located in plantings aged 2, 7, and, 9 years postmining. Linear models (LMEMs) did not reveal greater soil pH, woody plant diversity, or soil phosphorus and nitrogen in older plantings. Rather, they showed higher soil carbon in older plantings, whereas nitrogen and pH were positively correlated with woody species diversity and abundance. Graminoids were less abundant, but ferns were more abundant in older sites in an ordination analysis. The implications are exotic tree plantations shade‐out competitive understory herbaceous species (such as graminoids), opening growing space for other vegetation. However, the establishment of woody species is spatially limited possibly by differences in soil degradation among sites. Our results suggest that planting leguminous trees alone may not be sufficient to restore native forests, and future management should conserve and facilitate the establishment of tropical forest topsoil.

    更新日期:2019-12-30
  • Method for solidifying desert sands with enzyme‐catalysed mineralization
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-29
    Linchang Miao; Linyu Wu; Xiaohao Sun; Xia Li; Jizhou Zhang

    Sandstorms have been recognized as severe natural disasters worldwide and are currently occurring with increasing frequently due to global warming and land desertification. This study aims to mitigate their development and combat erosion caused by sandstorms and wind by improving sand‐surface stability via enzyme‐catalysed mineralization. It is an environment‐friendly method. The novelty of the reported enzymatically induced carbonate precipitation (EICP) lies in the usage of an enzyme catalyst extracted from soybeans. In contrast to the commonly used method of microbial‐induced carbonate precipitation, which is active at room temperatures between 20 and 30°C, EICP achieves high production efficiency at broader temperatures (ranging from 10 to 70°C). Four methods in appendix to EICP were chosen to solidify desert sands at the test site. Polyacrylamide (PAM) is a harmless and nonionic macromolecular flocculating agent, which forms a hydrogel network in desert sands and has a synergistic effect with EICP. An innovative method combined EICP and PAM and was used to solidify desert sand at a field trial site, realizing high‐performance. Solidifying desert sand field tests demonstrated that the solidification strength of EICP+PAM is 6.0–7.0% higher compared with the EICP method alone under identical conditions. This method could obtain higher resistance for strong wind erosion.

    更新日期:2019-12-30
  • Five‐year soil moisture response of typical cultivated grasslands in a semi‐arid area: Implications for vegetation restoration
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-30
    Zhi‐Qiang Dang; Ze Huang; Fu‐Ping Tian; Yu Liu; Manuel López‐Vicente; Gao‐Lin Wu

    Soil water deficit is one of the important abiotic stresses affecting vegetation restoration. The magnitude and spatio‐temporal dynamics of soil water content (SWC) provide basic guidance for optimal vegetation restoration. In a semi‐arid Chinese area, the changes in the soil water storage (SWS) of five cultivated grasslands and one wasteland were observed, to evaluate the water consumption at different soil depths (0‐100 cm), from 2008 to 2012. The plants of the three leguminous species consumed more water in deep soil layers (80‐100 cm) and produced more above‐ground biomass than the plants of the two gramineous species. The gramineous plants mainly consumed shallow soil water (0 ≤ 30 cm). The soil water deficit in the whole soil profile of Medicago sativa grassland (43%‐48%) was significantly higher than the deficit of the gramineous grasslands (p < 0.05). After five years of planting, the SWC of Agropyron cristatum grassland (21%) was the highest in the 20‐80 cm soil layer. The variation of SWS in M. sativa grassland did not significantly differ during this period, although its mean value was 28% lower than the value in Agropyron cristatum grassland (181 mm). At the end of the experiment, leguminous grasslands caused a serious soil water shortage deficit in the 80‐100 cm soil layers. These results underscore that vegetation type determines the vertical distribution of soil water deficit, in particular in deep layers. To promote long‐term sustainability of water resources, planting A. cristatum may be a good choice for early grassland restoration in arid areas.

    更新日期:2019-12-30
  • Estimation of soil available potassium in Chinese agricultural fields using a modified sodium tetraphenyl boron method
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-30
    Xiaoqin Chen; Ting Li; Dianjun Lu; Liang Cheng; Jianmin Zhou; Huoyan Wang

    China's long history and substantial contribution to global crop production, but lacking in potassium (K) mineral resource, have led to numerous studies of K availability in Chinese agricultural soils. In this study, we collected 2,428 surface soil samples from nine important agricultural regions to investigate available K reserves in Chinese agricultural soils. Soil highly available K (HAK) and maximally available K (MAK) were estimated using a modified sodium tetraphenyl boron (NaTPB) method. With HAK and MAK distribution maps constructed, the characteristics of available K contents distribution was visibly observed as higher in western and northern China, and lower in the east and south. We then used the Kriging method to estimate the HAK reserve and its potential utilization. The soil HAK reserve was predicted to maintain only crops producing > 70% of the relative biomass yield for approximately 10 years in the absence of external K application. With straw returning, this utilization period was predicted to increase to about 40 years. Soil MAK content was generally less than 1,000 mg kg–1, and reached as low as < 500 mg kg–1 throughout most of central and eastern China. The results of this study graphically demonstrate the shortage of K storage in Chinese agricultural soil and its looming sustainability crisis. These findings provide a scientific basis support the improved use and protection of agricultural resources in China.

    更新日期:2019-12-30
  • Scale effects of sediment retention, water yield and NPP: a case study of the Chinese Loess Plateau
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-30
    Changhong Su; Min Dong; Bojie Fu; Guohua Liu

    Ecosystem services are generated by ecological processes over a range of scales. Studying the scale effects on ecosystem services is important for exploring the driving mechanisms and conducive to prudent ecological managements. Unfortunately, quantitative testing the scale effects of ecosystem services’ associations, as well as identifying the driving mechanisms across scales, has rarely been documented. This study used the Loess Plateau as study area to test the scale effects and the correlations between sediment retention, water yield, and net primary production (NPP) and their driving mechanisms. A model of InVEST 3.0 and the Carnegie‐Ames‐Stanford Approach (CASA) were used to assess the services of sediment retention, water yield, and NPP in 2000 and 2008. Canonical correlation analysis (CCA) was used to quantify the driving mechanisms of ecosystem services. The results indicated that the ecosystem services are more varied in spatial patterns at small scale than at large scale. The average values of sediment retention, water yield, and NPP at small scale increased during the period. However, at large scale, the average values of sediment retention and water yield decreased and the NPP value increased simultaneously. Generally, the correlations between ecosystem services weakened when the spatial scale increased. The results from CCA indicated that, at small scale, the natural factors of precipitation, hours of sunshine, and temperature were the principal driving factors underlying ecosystem services. When the scale increased, the socioeconomic factors of population, grain production, and nonfarming production were gradually integrated into the factors driving the patterns of ecosystem services.

    更新日期:2019-12-30
  • Grazing pressure interacts with aridity to determine the development and diversity of biological soil crusts in Patagonian rangelands
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-27
    Sergio Velasco Ayuso; Gastón R. Oñatibia; Fernando T. Maestre; Laura Yahdjian

    Grazing is directly related to land degradation and desertification in global drylands. Grazing impacts on vascular plants, reasonably well‐known, depend on its intensity and are modulated by local aridity conditions. However, we do not know how the interplay of grazing intensity and aridity affect biocrusts, topsoil assemblages dominated by cyanobacteria, lichens, and mosses that provide key ecosystem services in drylands. Here, we determined how grazing affects biomass, total cover, and richness of biocrust structural types across a regional aridity gradient in the Patagonian steppe. On average, grazing by sheep reduced biocrust biomass, total cover and richness of structural types by 55, 90, and 59%, respectively. In general, high grazing pressures had a larger impact on biocrusts than moderate or light grazing pressures. For example, biocrust cover was reduced by 85, 89, and 98% by light, moderate, and high grazing pressures, respectively. Although a slightly different response to grazing was observed under low aridity conditions, these more benign climatic conditions did not compensate for the negative effects of trampling by domestic animals on biocrusts. Nonetheless, estimated biocrust recovery rates under medium aridity conditions were faster than previously thought: it took 24, 18, and 58 years to double biocrust biomass, total cover, and richness of structural types. Sheep cannot be just removed in Patagonian rangelands because the production of meat and wool represents the main local economic activity. But landowners must consider our results to protect the ecosystem functions and services provided by biocrusts for future generations to come.

    更新日期:2019-12-29
  • Target areas for harmonizing the Grain for Green Programme in Chinas Loess Plateau
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-27
    Qingling Geng; Qingfu Ren; Huimin Yan; Longhui Li; Xining Zhao; Xingmin Mu; Pute Wu; Qiang Yu

    Widespread land degradation has stimulated the implementation of a large‐scale ecological restoration programme in China's Loess Plateau—the Grain‐for‐Green Programme (GFGP). This programme has substantially increased vegetation cover and served to control soil erosion, but threatened regional food supply due to widespread cropland conversion. Consequently, a strategy balancing green and grain land uses is required. Here, we establish a dominance index of ecosystem services by quantifying the economic value of four key ecosystem services (net primary productivity, soil conservation, water yield, and food production), by combining spatially explicit datasets and census data. Using the dominance index, we identify the optimal areas to target for GFGP in the Loess Plateau. The identified areas (target areas) were the transition zone from low to high value of ecosystem services (ESV). These areas exhibited low grain productivity in addition to having the highest potential for soil conservation. Compared with other regions of the Loess Plateau, the loss of grain production due to cropland conversion in these target areas could decrease by 42%, whereas ESV could increase by 33%. Therefore, despite the fact that over the past 15 years (2000–2014) in these target areas more cropland was converted into ecological use (i.e. forest/grassland), there is still a need to strengthen ecological restoration in this region in the future. This study proposed a strategy for balancing green and grain from a spatial perspective, which could potentially solve land degradation issues and the tradeoff between ecosystem services in a more beneficial and targeted way.

    更新日期:2019-12-29
  • Land‐use change with pasture and short rotation eucalypts impacts the soil C emissions and organic C stocks in the Cerrado biome
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-26
    Rafael da Silva Teixeira; Ricardo Cardoso Fialho; Daniela Cristina Costa; Rodrigo Nogueira de Sousa; Rafael Silva Santos; Ana Paula Mendes Teixeira; Thalles Guimarães Reis; Ivo Ribeiro da Silva

    The expansion of short rotation eucalypt plantations in low soil organic matter (SOM) sandy soils may offer an alternative to improve soil C sequestration. The goal of this study was to estimate the changes in C stocks and emissions in different SOM fractions following conversion of the native Cerrado to pasture and then to eucalypt plantation. Therefore, we studied soils under native Cerrado, planted pasture (cultivated for 34years following the clearing of the Cerrado) and eucalypt plantation (4years). The C and N stocks in particulate organic matter and mineral‐associated organic matter (MAOM) were determined 4years after eucalypt planting. Soil CO2‐C, CH4‐C fluxes and CO2‐C concentrations in soil profile were measured in different seasons over 4years. Variation in the natural abundance of 13C was used to partition the SOM‐C. The soil CO2‐C and CH4‐C fluxes were influenced by soil surface moisture (r= 0.185o and r= 0.430**, respectively), whereas only the soil CH4‐C fluxes correlated with soil surface temperature (r= 0.355**). The highest soil CO2‐C flux in soil under eucalypt occurred after 4years of eucalypt planting (2.5 kg ha−1h−1, approximately 70%). The pasture soil acted as a CH4‐C source to the atmosphere. The pasture MAOM‐C losses in the 0.0–1.0‐m soil layers were not compensated by the new eucalypt C inputs (MAOM‐C lost ~9.6 Mg ha−1). In summary, the recent worldwide expansion of short rotation eucalypt plantations should be carefully considered, particularly under pasture degraded soil sandy soils, because land uses able to increase SOM are priorities.

    更新日期:2019-12-27
  • Biochar and manure addition influenced soil microbial community structure and enzymatic activities at eroded and depositional landscape positions
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-25
    Udayakumar Sekaran; Saroop S. Sandhu; Yeyan Qiu; Sandeep Kumar; Jose L. Gonzalez Hernandez

    Biochar and manure application can modify soil microbial community structure and enhance biochemical activities. However, the studies about the influence of biochar and manure on the microbial communities on different geomorphological landforms (depositional and eroded landscapes) are scarce. In this study, we investigated the responses of soil biochemical activities and microbial communities to the addition of pinewood biochar, dairy manure (DM), and the dairy manure and pinewood biochar mixture (DMP) at a rate of 10 Mg ha−1, respectively, in comparison with control (CNT) at eroded and depositional landscape positions over 5 years. Data showed that the DMP treatment significantly increased cold‐water‐soluble organic carbon and hot‐water‐soluble organic carbon at the depositional landscape than CNT soils. Application of DMP increased total phospholipid fatty acid (PLFA) and bacterial PLFA by 31% and 20% compared with the CNT at the depositional landscape, respectively. At eroded landscape, total PLFAs and total bacterial PLFAs biomass concentrations were found 39% and 90% higher with DM than CNT soils. The addition of DM and DMP increased the activities of enzymes that are involved in the major nutrient cycling at depositional and eroded landscapes. At the phylum level, the proportion of Bacteroidetes was found lower in DMP, but the proportion of phylum Proteobacteria and Acidobacteria were increased. In conclusion, our study revealed that DMP influenced the labile nutrient pool, altered the microbial community structure, and increased bacterial composition and enzymatic activities at both the landscape positions.

    更新日期:2019-12-27
  • Drivers of tropical forest cover increase: A systematic review
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-25
    Mónica Borda‐Niño; Paula Meli; Pedro H. S. Brancalion

    Promoting natural regeneration can be a viable strategy to achieve ambitious restoration commitments, but predicting where native forest cover is likely to expand is challenging. Different biophysical and socioeconomic factors may determine the chances of native forest re‐growth at different spatial and temporal scales, producing complex spatial patterns in the landscape and adding more and deeper information about potential for different forms of forest restoration. Based on a systematic literature review including 64 peer‐reviewed articles from the global tropics and subtropics published from 1990 to 2017, we assessed the methodologies employed to remotely detect forest cover increase and to identify its biophysical and socioeconomic drivers. Automatic classification of multi‐temporal images and transition matrices were the most popular methods to detect areas of forest re‐growth, whereas regression analysis was the most used analytical approaches to assess drivers. Forest cover increased more often on steeper slopes, close to forest remnants, inside protected areas and far from population centers. However, the effects of most drivers varied among scales of evaluation and may be further affected by the scale of forest re‐growth. The most influential biophysical and socioeconomic drivers of forest cover increase identified here can be used to develop predictive models on the likelihood of native forest re‐growth to guide the implementation of cost‐effective tropical forest restoration, thus contributing to the mitigation of climate change and species extinction. Current remote sensing literature evaluating forest cover changes seems to be largely focused on deforestation dynamics, with little attention given to forest cover increase.

    更新日期:2019-12-27
  • Conjugation of artificial humic acids with inorganic soil matter to restore land for improved conservation of water and nutrients
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-23
    Fan Yang; Shuaishuai Zhang; Qiang Fu; Markus Antonietti

    Artificial soil (AS) with a dark–brown appearance and high soil organic matter (SOM) was manufactured under hydrothermal conditions from poor sandy landfill using the 'hydrothermal humification process.' This approach may retrosynthesize the natural clay–humin complex, which is the main contributor for water and ion binding in fertile, natural soils. The structure and morphology of as‐created organic–inorganic composites was examined, and it was shown that the as‐created artificial SOM (A‐SOM) indeed tightly binds to the mineral surfaces, thus creating remediated soil or more general AS. A‐SOM does not change the bulk structure of the involved inorganic minerals but activates their surface. Depending on the biomass used as the starting product, the high effectivity of synthetic humification improves the organic carbon and nitrogen content when compared with the employed sandy soil (SS). The composition was adjusted to be comparable with a reference sample of cultivated soil (2.92% in C content and 7.8% in SOM) to enable a fair referencing. We then analyzed the most frequently used soil quality indicators for agricultural land use and found strong water retention and nutrient conservation, which reflects the successful restoration of mineral–humus conjugation. Pure ASs provide superior performance in the analyzed series, whereas simulated soils (mixture of SS and AS) still exhibit satisfactory capacities of water and ion bonding. The values were found to be very similar to cultivated soils sampled from Germany and Harbin, China.

    更新日期:2019-12-25
  • Direct and indirect effects of long‐term ditch‐buried straw return on soil bacterial community in a rice–wheat rotation system
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-23
    Haishui Yang; Yi Meng; Jinxia Feng; Yifan Li; Silong Zhai; Jian Liu

    Ditch‐buried straw return (DB‐SR) is a novel soil tillage and fertility building practice that is effective in regulating soil carbon and nitrogen dynamics and hydrothermal processes in rice–wheat rotation systems. However, the effects of DB‐SR on soil bacterial community are still largely unclear. We deciphered soil bacterial community with high‐throughput sequencing under various returning approaches, burial depths, and straw amounts after 6.5 years of DB‐SR application. Our results showed that DB‐SR structured distinctive soil bacterial community with rotary tillage straw return (RT‐SR; one‐way analysis of similarities [ANOSIM]: P < .01). RT‐SR significantly reduced soil bacterial diversity by 3.87%, but DB‐SR could maintain it (P > .05). These variations were mainly caused by water content‐driven changes in soil organic carbon. Also, bacterial community composition was distinctive among burial depth treatment (one‐way ANOSIM: P < .05), and deeper burial reduced species richness and diversity (P < .05). Variation in C/N ratio could mostly explain the alterations in soil bacterial community structure under different burial depths. Moreover, the amount of straw buried had no significant effect on soil bacterial species richness or diversity (P > .05), but bacterial community composition was more dissimilar with increasing straw amount (one‐way ANOSIM: P < .01). Our results suggest that long‐term DB‐SR can maintain the bacterial community structure in the surface soil layers when compared with conventional RT‐SR, but taking the current production level into consideration, the burial depth should not be greater than 20 cm for incorporating the full amounts of straws.

    更新日期:2019-12-25
  • Successive straw biochar amendments reduce nitrous oxide emissions but do not improve the net ecosystem economic benefit in an alkaline sandy loam under a wheat–maize cropping system
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-23
    Yujuan Liu; Yucui Bi; Yingxin Xie; Xu Zhao; Dexian He; Shenqiang Wang; Chenyang Wang; Tiancai Guo; Guangxi Xing

    Crop straw is converted to biochar with subsequent applications to soils as a multi‐benefit strategy for greenhouse gas (GHG) emission mitigation, carbon sequestration, and straw disposal and utilization in intensive agriculture. However, tradeoffs between agronomic, economic, and environmental performance of long‐term agricultural biochar use remain unclear. Using a case study of biochar‐amended alkaline sandy loamy soil, we investigated the effects of field application of straw biochar at 0, 2.25, 6.75, and 11.25 Mg ha−1 to 10 successive wheat and maize crop seasons over five rotation years on crop yield, nitrous oxide (N2O) emissions, soil total organic carbon (TOC), and soil carbon pool (SCP). The net global warming potential (net GWP) and net ecosystem economic benefit (NEEB) were assessed to examine the tension between balancing economic returns and environmental benefits. Results indicated that biochar treatments slightly increased total crop grain yields and greatly reduced the total N2O emissions over five rotation years. The soil total organic carbon content was enhanced while the CO2 emissions during biochar production almost offset the increase in the soil carbon pool. Economic assessment showed that the net ecosystem economic benefit was lowered with enhanced costs of the increasing biochar use under the current low C trade market. These results highlight the promotion of the use of straw biochar in successive applications as a strategy to effectively offset greenhouse gas emissions from agriculture requires optimization of the straw pyrolysis system to reduce the energy consumption and overall biochar costs, and price enhancement of C trade.

    更新日期:2019-12-25
  • A New Analysis Approach for Long‐Term Variations of Forest Loss, Fragmentation and Degradation Resulting from Road‐Network Expansion Using Landsat Time‐Series and OBIA
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-24
    Zeinab Shirvani; Omid Abdi; Manfred F. Buchroithner

    Despite facilitating transport by low‐volume roads for multiple purposes, they also open corridors to the remote pristine forests and accelerate forest dynamics with deleterious consequences to the forest functionalities and indigenous inhabitants. We assessed the spatial variations of Hyrcanian forest loss, fragmentation and degradation resulting from the expansion of rural, logging and mine roads between 1966 and 2016 in northeast Iran. Various data were employed to generate a precise road‐network; the density of road segments was weighted based on their carrying capacity during 1966–1986, 1986–2000 and 2000–2016. Three dimensions of forest changes were retrieved using the Landsat time‐series and object‐based image analysis (OBIA). The spatial patterns of high rates of forest changes were clustered using spatial autocorrelation indicators. The spatial regression models were carried out to explore relationships between forest change and road expansion. The results showed that rural roads were upgraded but forest and mine roads remarkably expanded in recent decades. The spatial variations of forest‐dynamic patterns have been changing from forest loss (1966–2000) to forest fragmentation and degradation (1986–2016). The high density of rural roads was significant on the high rates of forest loss and fragmentation during 1966–2000, while the expansion of forest and mine roads significantly intensified the rates of fragmentation and degradation during 1986–2016. Our findings suggest for mitigating destructive schemes over Hyrcanian forests, developing either protected areas or joining unprotected forests to the reserved areas should be prioritized.

    更新日期:2019-12-25
  • Dynamic monitoring of desertification in Naiman Banner based on feature space models with typical surface parameters derived from Landsat images
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-24
    Bing Guo; WQ Zang; Baomin Han; Fei Yang; Wei Luo; Tianli He; Yewen Fan; Xiao Yang; Shuting Chen

    Naiman Banner is one of the most typical semi‐arid vulnerable ecological zones that characterized by vegetation degradation and severe desertification. Previous studies mostly utilized a single feature space or only the linear correlation model to monitor desertification. In this study, the optimal monitoring model that fully considering the multiple feature spaces and the non‐linear relationship between surface parameters in Naiman Banner was determined and then the spatial–temporal evolution patterns of the desertification from 1989 to 2017 were analyzed. The results showed that: (1) The Albedo‐NDVI point‐to‐point model was applicable to areas with high vegetation coverage, whereas the Albedo‐MSAVI linear model had better applicability in areas with relatively low vegetation coverage. Considering the surface cover, the desertification monitoring index based on Albedo‐MSAVI linear model had the best applicability. (2) During 1989–2017, the total desertification area percentage of Naiman County decreased from 90.85% in 1989 to 63.35% in 2017, showing a significant downward trend. (3) During the past thirty years, the desertification process was significantly influenced by human activities, such as “Three‐North” Shelterbelt, Returning Farmland to Forestry, and Returning Farmland to Grassland (4) The desertification levels of unused land and grassland with low coverage was relatively high, whereas the desertification degree of cultivated and forest lands was low. These results can be used as an effective reference for the remote sensing monitoring and evaluation of desertification and can provide data and decision support for the ecological restoration of the region.

    更新日期:2019-12-25
  • Legacy nitrate in the deep loess deposits after conversion of arable farmland to non‐fertilizer land uses for degraded land restoration
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-24
    Wangjia Ji; Yanan Huang; Bingbing Li; David W Hopkins; Zhi Li

    The legacy nitrate‐nitrogen (NO3−−N) in the soils is a long‐term threat to groundwater in regions with thick unsaturated zones, and it is thus important to investigate the amounts and sources of NO3−−N for effective environmental management. Given the substantial conversions of arable farmlands to non‐fertilizer land uses for the restoration of degraded land, the legacy effects of NO3−−N in thick loessial unsaturated zones in China remain uncertain. We collected soil samples from loess profiles >13 m deep under arable farmland and grassland, apricot, pine, peashrub, willow, and poplar converted from arable farmland over 15–35 years. We determined their nitrate content and isotope compositions to quantify the accumulation and sources of the former and its potential threat to groundwater. The seven NO3−−N profiles exhibited a parabolic shape with peak depths at 2.6–9.2 m. Greater peak depths corresponded to greater NO3−−N values, and the peak nitrate level varied from 0–10 m. The total NO3−−N accumulation ranged 3,181–9,018 kg N ha−1, and the non‐fertilizer profiles accounted for 35%–73% of the arable farmland. The nitrate sources varied with depths. According to the isotope mass balance, the nitrate above, near, and below the peak depths mainly originated from atmospheric NO3− (25%–34%), synthetic N fertilizer (49%–68%), and soil organic N and manure (50%–73%). The estimated residence time of nitrate in the soil ranged from 270–620 yr. As such, the nitrate legacy effects should be given considerable attention for the protection of the soil and groundwater environment.

    更新日期:2019-12-25
  • Soil organic carbon increment sources and crop yields under long‐term conservation tillage practices in wheat‐maize systems
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-24
    Zhen Liu; Tian‐Ping Gao; Shen‐Zhong Tian; Heng‐Yu Hu; Geng Li; Tangyuan Ning

    Long‐term tillage and straw incorporation significantly affect soil organic carbon (SOC) sequestration and crop yield. However, the studies on the SOC sources under multi‐cropping system are relatively few. The objective of this study was to evaluate the effects of conservation tillage on SOC and crop yields, and distinguish the SOC sources from wheat (C3) and maize (C4). Therefore, the dynamics of SOC, SOC sequestration and crop yield were evaluated during 15 years of conservation agriculture under conventional tillage (CT), subsoiling (ST), rotary tillage (RT), and no‐tillage (NT) without or with straw incorporation (CTS, STS, RTS, and NTS, respectively). The results indicated that the highest mean SOC concentration in the 0–30 cm soil was found under STS (11.80 g/kg), which increased by 2.29 g/kg than that under CT, while RT had the lowest mean SOC concentration (8.10 g/kg). The increases in annual yield ranged from 0.58 (NT) to 4.93 (ST) Mg/ha during 2005–2017. In comparison to the annual yield of CT, that of STS increased by 2 Mg/ha and was significantly higher than other treatments (p < 0.05) except NTS and CTS. In comparison to CT, the SOC stock (SOCs) and carbon sequestration rate (CSR) of STS were the highest and increased by 15.64 Mg/ha and 1.05 Mg/ha/yr, respectively, in the 0–30 cm soil. Moreover, the relative contribution of wheat residues to SOC was higher than maize residues under all treatments. Thus, subsoiling combined with C3 straw incorporation was more suitable for restoring degraded land and increasing yields.

    更新日期:2019-12-25
  • Increases in aridity lead to drastic shifts in the assembly of dryland complex microbial networks
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-23
    Manuel Delgado‐Baquerizo; Guilhem Doulcier; David J. Eldridge; Daniel B. Stouffer; Fernando T. Maestre; Juntao Wang; Jeff R. Powell; Thomas C. Jeffries; Brajesh K. Singh

    We have little information on how and why soil microbial community assembly will respond to predicted increases in aridity by the end of this century. Here, we used correlation networks and structural equation modeling to assess the changes in the abundance of the ecological clusters including potential winner and loser microbial taxa associated with predicted increases in aridity. To do this, we conducted a field survey in an environmental gradient from eastern Australia and obtained information on bacterial and fungal community composition for 120 soil samples and multiple abiotic and biotic factors. Overall, our structural equation model explained 83% of the variance in the two mesic modules. Increases in aridity led to marked shifts in the abundance of the two major microbial modules found in our network, which accounted for >99% of all phylotypes. In particular, the relative abundance of one of these modules, the Mesic Module #1, which was positively related to multiple soil properties and plant productivity, declined strongly with aridity. Conversely, the relative abundance of a second dominant module (Xeric Module #2) was positively correlated with increases in aridity. Our study provides evidence that network analysis is a useful tool to identify microbial taxa that are either winners or losers under increasing aridity and therefore potentially under changing climates. Our work further suggests that climate change, and associated land degradation, could potentially lead to extensive microbial phylotypes exchange and local extinctions, as demonstrated by the reductions of up to 97% in the relative abundance of microbial taxa within Mesic Module #1.

    更新日期:2019-12-23
  • Comparative assessment of temporal changes in soil degradation under four contrasting land‐use options along a tropical toposequence
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-22
    Cornelius I. Alarima; Ebenezer Annan‐Afful; Sunday E. Obalum; Joseph M. Awotunde; Tsugimasu Masunaga; Charles A. Igwe; Toshiyuki Wakatsuki

    Assessment of land‐use types has conventionally been on spatial rather than temporal scales, thus limiting the inference on relative potential of land‐use types against soil degradation, needed to validate their allotment to ecosystems on agricultural watersheds. The study assessed the changes in key indices of soil degradation among four land‐use systems of West African 'watershed' agroforestry development over about a decade (1999–2011) along a toposequence in Central Ghana. The land‐use systems were grass‐dominated natural fallow (Fallow), cocoa plantation (CPT), traditional rice farm (TRF), and Sawah ecotechnology for wet inland valley rice farm (Sawah), with sampled land areas covering 2,000, 1,500, 4,500, and 6400 m2, respectively. In 1999 and 2011, soil samples were taken from 0–20, 20–40, and 40–60‐cm depths. Samples were collected from about the same spots in both years. The samples were analyzed for selected physicochemical parameters and, for each land‐use option and depth, comparison made between 1999 and 2011. A mean‐weighted decadal change in degradation status was used to rank the land‐use options. Most of the decadal changes in soil properties (including available micronutrients) were negative, with about two‐third of the significant changes in the top (0–20 cm) soils. For instance, soil pH tended to decrease in 2011 compared with 1999; the decreases (14.51%) were significant in the topsoils under Sawah where no other index showed significant decline. Topsoil total carbon decreased under TRF (49.08%) and CPT (32.80%). Available phosphorus marginally increased only under Sawah. The overall aggregate scores for the mean‐weighted decadal change in degradation status showed that the land‐use options differed in their potential to resist degradation: Sawah (slight), Fallow (mild), and TRF/CPT (moderate). Our findings highlight the extent of temporal changes in soil degradation under different topo‐positions in tropical African ecosystems while pointing to the superiority of Sawah ecotechnology. Increased use of this soil‐and‐water management system in lowland rice farming could, therefore, have some soil conservation benefits.

    更新日期:2019-12-23
  • Responses of secondary wind dispersal to environmental characteristics and diaspore morphology of seven Calligonum species
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-22
    Quanlai Zhou; Zhimin Liu; Zhiming Xin; Stefani Daryanto; Lixin Wang; Xuehua Li; Yongcui Wang; Wei Liang; Xuanping Qin; Yingming Zhao; Xinle Li; Xue Cui; Minghu Liu

    Secondary diaspore dispersal by wind, that is, wind‐driven movement along the ground surface (GS), is important for the structure and dynamics of plant populations and communities. However, how wind velocity (WV), GS, and diaspore morphology influence diaspore secondary dispersal by wind are unclear. We used a wind tunnel and video camera to measure the threshold of WV (TWV) and diaspore velocities (DV) of secondary diaspore dispersal. Diaspores of seven Calligonum species with different appendages (wings, bristles, membranous balloon, and wings + thorns) were used to determine the TWV and DV under variable wind speed (4, 6, 8, and 10 m s‐1) and four GSs (cement, sand, loam, and gravel). GS and diaspore morphological traits explained 37.1 and 18% of diaspore TWV, respectively. Meanwhile, WV, GS, and diaspore morphological traits explained 62.4, 13.6, and 3.2% of DV, respectively. An increasing trend was shown for TWV, and a decreasing trend was shown for DV in the order of cement, sand, loam, and gravel surfaces. Spherical and light diaspores had low TWV and high DV, whereas winged and heavy diaspores had high TWV and low DV. Our results indicated that adaptive features of diaspore appendages might be the result of selection for primary dispersal or secondary dispersal. The mechanism of diaspore secondary dispersal is important for understanding the recovery of degraded sand dunes and providing theoretical support for restoration practices.

    更新日期:2019-12-23
  • Application of electrical resistivity to assess subsurface geological and hydrological conditions at post–tin mining sites in Indonesia
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-20
    Masayuki Itoh; Takashi Matsubara; Satomi Shiodera; Kotaro Iizuka; Ken Sakurai; Yoko Nakajima; Hiroki Ohashi; Ivan Manalu

    In many parts of Southeast Asia, opencast hydraulic tin mining has been carried out since the colonial era. Regardless of its scale, this mining method has significantly affected microtopography and left extremely degraded soil surfaces, where vegetation can hardly grow. Therefore, the identification of a feasible method for the rehabilitation and reforesting of these areas is a long‐term issue. In this study, we aimed to clarify the subsurface geological (soil properties and distribution) and hydrological conditions at a post–tin mining site on an Indonesian island using an electrical resistivity survey combined with microtopographic information. The electrical resistivity survey of the study site provided information about the distribution of bedrock and sandy and clayey soils, reflecting mining activities. Furthermore, direct and continuous groundwater level monitoring showed the ranges of groundwater fluctuation depending on the soil and climate conditions. Our study demonstrates that subsurface assessment by electrical resistivity survey can provide essential information, contributing to the development of feasible plans for reforestation or transformation to agricultural land at post–tin mining sites through the improvement of physical conditions and soil fertility.

    更新日期:2019-12-21
  • Contribution of plant litter and soil variables to organic carbon pools following tropical forest development after slash‐and‐burn agriculture
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-20
    Shaojun Wang; Minkun Chen; Run Cao; Qianbin Cao; Qianqian Zuo; Ping Wang; Bo Yang; Shuang Zhao

    Tropical forest development after slash‐and‐burn agriculture crucially affects soil carbon accumulation. However, it remains unclear how the dynamics of soil organic carbon pools are regulated following tropical forest restoration. Our study aims to quantify the contribution of litter and soil variables to alterations in carbon pools during tropical forest restoration on slash‐and‐burn agricultural land in Xishuangbanna, Yunnan, China. This study observed a significant increase in soil carbon pools along forest restoration. The extent of the increase in labile fractions (1.9–2.5 times) was higher than that of soil organic carbon (1.5 times) during the restoration from early to later stages. The proportion of microbial carbon to total carbon increased from 3.0% to 7.7% during forest restoration, while those of dissolved (5.3% to 3.1%) and readily oxidizable (42.9% to 29.6%) fractions decreased. Clay content determined the accumulation dynamics of soil organic carbon (10.5%) and labile fractions (6.0–13.5%) in the later stage, while free Fe oxides (10.4–15.4%) contributed to these pools mainly in the early stage. Microbial carbon explained 22.4–26.7% and 20.6–28.3% of the variation in soil organic carbon stocks and labile fractions, respectively, whereas litter carbon accounted for 9.5–15.3% of the change in microbial carbon stock. The contribution (8.2–17.1%) of litter‐soil nutrient interactions to carbon pools increased during forest restoration. Our data suggest that carbon dynamics are mainly determined by variations in the clay content, free Fe oxides, and litter and microbial carbon, possibly through nutrient‐level interactions between the litter and soil during tropical forest restoration.

    更新日期:2019-12-21
  • Amendments with humified compost effectively sequester organic carbon in agricultural soils
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-18
    Riccardo Spaccini; Alessandro Piccolo

    Preventing degradation of soil quality and productivity entails development of sustainable practices to enhance soil organic matter. We followed soil organic carbon (OC) accumulation during three years‐long field experiments in two different Italian soils under conventional tillage (TRA), reduced tillage (MIN), green manure (GM) and two rates of mature compost amendments (CMPL and CMPH). Despite soil textures differences, CMP additions enhanced in both field sites OC accumulation in either bulk soils and water‐stable aggregates (WSA), especially for CMPH, that was more pronounced than for MIN and GM. While the sum of OC in WSA showed an average retention of 80‐90 % of cumulative carbon added with compost, incorporated OC in WSA of MIN and GM reached only 26 and 55 % of total carbon amended with fresh biomass for the light and heavy textured soils, respectively. Hence, MIN and GM accumulated SOC only up to the physical saturation limit dictated by soil texture, whereas CMP retained a larger additional SOC than TRA due to hydrophobic affinity among apolar domains progressively added to soil with humified compost. Nuclear Magnetic Resonance (NMR) spectra of humus extracted after the first and third treatment year confirmed this behaviour. While no changes were observed in spectra for MIN and GM, humic extracts from CMP showed significantly larger content of apolar alkyl and aromatic moieties after the third experimental year. Our results suggest that soil amendment with well humified compost is an effective practice to sequester carbon into agricultural soils, besides improving their organic fertility.

    更新日期:2019-12-19
  • Passive and active ecological restoration strategies for abandoned farmland leads to shifts in potential soil nitrogen loss by denitrification and soil denitrifying microbes
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-18
    Honglei Wang; Duntao Shu; Dong Liu; Shuang Liu; Na Deng; Shaoshan An

    Ecological restorations of abandoned farmland have been performed in degraded ecosystems with the goal of increasing ecosystem sustainability. The environmental benefits of ecological restoration can at least be partially neutralized by enhanced nitrogen (N) loss and potential nitrous oxide (N2O) emissions via denitrification. However, few studies have focussed on comparative analysis of the contributions of ecological restoration strategies to soil denitrifying microbes, particularly in arid and semiarid degraded ecosystems, where N is often the limiting nutrient. In this study, artificial afforestation (artificial forest sites) and natural revegetation (grassland sites) of abandoned farmland have an enhanced effect on reducing potential denitrification rates (PDR) compared with farmland sites and orchard sites, leading to lower N losses and potential N2O emissions. Combined analyses indicated that the greatest differences in microbial abundance, species richness, and diversity were observed among different ecological restoration strategies. The abundance, richness and diversities of denitrifying microbes (nirS, nirK, and nosZ genes) were decreased by natural revegetation and artificial afforestation, leading to attenuated denitrifying activity responsible for the reduced PDR. Notably, the abundance and diversity of denitrifying microbes were dominant variables that explained the changes in PDR (up to 0.96). Overall, our results contribute to a better understanding of the feedback of denitrifying microorganisms to ecological restoration strategies and how these microorganisms collaboratively contribute to N loss and potential N2O emissions in arid and semiarid degraded ecosystems.

    更新日期:2019-12-19
  • Landscape‐scale spatial modelling of deforestation, land degradation and regeneration using machine learning tools
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-18
    C. Grinand; G. Vieilledent; T. Razafimbelo; J.R. Rakotoarijaona; M. Nourtier; M. Bernoux

    Land degradation and regeneration are complex processes that greatly impact climate regulation, ecosystem service provision and population wellbeing and require an urgent and appropriate response through land use planning and interventions. Spatially explicit land change models can greatly help decision makers, but traditional regression approaches fail to capture the nonlinearity and complex interactions of the underlying drivers. Our objective was to use a machine learning algorithm combined with high‐resolution datasets to provide simultaneous and spatial forecasts of deforestation, land degradation and regeneration for the next two decades. A 17000 km2 region in the south of Madagascar was taken as the study area. First, an empirical analysis of drivers of change was conducted, and then, an ensemble model was calibrated to predict and map potential changes based on twelve potential explanatory variables. These potential change maps were used to draw three scenarios of land change while considering past trends in intensity of change and expert knowledge. Historical observations displayed clear patterns of land degradation and relatively low regeneration. Amongst the twelve potential explanatory variables, distance to forest edge and elevation were the most important for the three land transitions studied. Random Forest showed slightly better prediction ability compared to MaxEnt and GLM. Business‐as‐usual scenarios highlighted the large areas under deforestation and degradation threat, and an alternative scenario enabled the location of suitable areas for regeneration. The approach developed herein and the spatial outputs provided can help stakeholders target their interventions or develop large‐scale sustainable land management strategies.

    更新日期:2019-12-19
  • Relationship between macro‐pores and soil organic carbon fractions under long‐term organic manure application
    Land Degrad. Dev. (IF 4.275) Pub Date : 2019-12-18
    Lingying Xu; Meiyan Wang; Yutian Tian; Xuezheng Shi; Yijie Shi; Quanbo Yu; Shengxiang Xu; Jinhua Pan; Xiangwei Li; Xinqiao Xie

    Greenhouse vegetable production systems converted from cereal fields often experience a decrease in soil aeration due to intensive land use. Organic fertilization is a method commonly used to solve this problem. While previous studies have considered soil organic carbon (SOC) or soil pores under organic cultivation, the relationship between SOC fractions and soil macro‐pores is unknown. This study analysed the long‐term progressive variations in soil macro‐pore (>50 μm) and SOC fraction characteristics in organic greenhouse vegetable plantations (one‐year‐old, nine‐year‐old, and fourteen‐year‐old fields) converted from rice‐wheat rotation fields and established the relationship with X‐ray computed tomography scanning and 13C solid‐state nuclear magnetic resonance spectroscopy. The results suggested that the total macro‐porosity increased from 7.95% to 16.36% throughout the whole organic plantation, and a similar trend occurred in small (50‐500 μm) and medium (500‐1000 μm) macro‐porosity. Besides, the total SOC content and the contents of its fractions increased with organic planting time. With the total macro‐porosity exhibiting significant associations with SOC (r = 0.81**), the relative proportion of O‐alkyl C (r = ‐0.94**) and the relative proportion of aromatic C (r = 0.89**), a lower O‐alkyl C proportion of SOC might help to increase macro‐porosity. A similar relationship was found between the relative proportion of SOC fractions and the macro‐porosity. The O‐alkyl C proportion had significantly negative relations with aromatic C (r = ‐0.94**) and SOC (r = 0.84**). Overall, both SOC and its fractions can help to improve soil macro‐porosity, but the effects of different fractions on these pores vary.

    更新日期:2019-12-19
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