Original articleResponses of soil organic carbon mineralization and its temperature sensitivity to re-vegetation in the agro-pastoral ecotone of northern China
Introduction
Converting cropland to perennial vegetation has been proposed as an effective measure to mitigate atmospheric CO2 concentration by sequestrating carbon (C) in plants and soils [1]. Soil organic C (OC) sequestration is determined by the balance of organic matter inputs and C outputs [2]. Soil OC mineralization by microorganisms is one of the most important pathways of C outputs [3]. Therefore, understanding OC mineralization and its response to temperature variation is important to estimate the dynamics of soil OC stock after re-vegetation in agricultural soils especially in a global warming context.
Soil OC mineralization has been widely reported to increase after converting cropland to perennial grassland or woodland due to the greater inputs of above- and belowground biomass, ameliorated microclimate and higher microbial activity [[4], [5], [6]]. The specific OC mineralization (OC mineralization per initial OC) can be deemed as an estimate of OC stability with lower values indicating higher OC stability [2,4]. The exclusion of tillage activities could protect OC within aggregates and thus make it to be less accessible to microbes [7], which can lead to lower specific OC mineralization since OC is more stable. For example, Xiao et al. [4] reported that soil microbial respiration was greater while the specific OC mineralization was lower in re-vegetated grassland than in abandoned cropland in Qiaozi watershed of China. Furthermore, according to the carbon-quality temperature (CQT) hypothesis, the temperature sensitivity of microbial respiration was larger for more biogeochemically recalcitrant organic matter [8]. The exclusion of easily decomposable crop residues and incorporation of more recalcitrant plant litter after re-vegetation may increase the temperature sensitivity of soil OC to warming [1]. Therefore, soil OC mineralization and its temperature sensitivity may increase, but specific OC mineralization may decrease after planting perennial plants on former cropland.
Vegetation type and growing age affect litter production and decomposition, and thus control soil OC pools and turnover [8,9]. For example, soils under legumes have higher total and labile C pools and enzyme activities than non-legumes due to the high-quality litter inputs with high nitrogen (N) concentration and low N/lignin ratio [10]. Soil CO2 fluxes were reported to increase with re-vegetation years primarily due to the accumulation of organic material which provide substrates for microbes [11]. Previous studies have pointed out that soil OC storage after plantation in agricultural soils was controlled by plantation year and vegetation type [12,13]. For example, based on the meta-analysis from the Loess Plateau of China, soil OC stock increased first and then changed to net loss when converting cropland to shrubland and grassland, but was in the opposite trend when converting to forest [13]. However, the combined effects of land-use change (conversion cropland to re-vegetated land), re-vegetation type and conversion year on soil OC mineralization and its temperature sensitivity have been less studied. A recent study by Rahman et al. [2] reported that soil heterotrophic respiration increased with plantation age after afforestation on former cropland and increased more so with oak than Norway spruce plantation, and recommended future research on this interaction.
In most terrestrial ecosystems, C cycling is restricted by N availability which controls plant growth and ecosystem primary productivity [14]. Soil N availability also influences the decomposability of soil organic matter (SOM). For instance, Bowden et al. [15] showed that SOM decomposition decreased after long-term N addition in Eastern North American forests. Furthermore, the relative availability of mineral N, namely, the ammonium to nitrate ratio (ANR), has been proposed as a crucial variable in affecting soil OC dynamics [16,17]. Srivastava et al. [17] and Deng et al. [18] both reported that the ANR was lower in cropland than in shrubland or woodland, while CO2 fluxes showed the opposite trend, indicating the negative relationship between ANR and C efflux. Therefore, exploring the relationships between soil N availability and OC mineralization after re-vegetation will help to understand soil C cycling in re-vegetated soils.
The agro-pastoral ecotone in northern China is an ecologically fragile transition zone suffering from soil erosion, grazing and over-cultivation [19]. The warm-drought climatic trend in this ecotone has exceeded the global average, making this area very sensitive to climate change [20]. A high proportion of cropland has been converted to grassland, shrubland and woodland especially in the “Grain for Green” project [21]. In this ecotone, a re-vegetation chronosequence (6–40 yr) for different re-vegetation patterns (natural grassland, artificial grassland and pea shrub woodland) and neighboring croplands have been selected to investigate the combined effect of land-use change (from cropland to re-vegetated land), re-vegetation type and conversion year on soil OC and nutrient concentrations. Results from this re-vegetation chronosequence showed that re-vegetation on former cropland improved soil aggregate stability and accumulated soil OC and N, and the increases of OC and N were greater for leguminous vegetation and about 20 years after conversion [22]. In order to test the cycling and stability of the accumulated OC after re-vegetation, soil OC mineralization and temperature stability were measured with an 84-d incubation experiment from the same chronosequence in this study. We hypothesized that (H1) re-vegetation would increase OC mineralization, temperature sensitivity but decrease specific OC mineralization due to the increased soil OC concentration and aggregation; (H2) the effect of re-vegetation would be greater for legumes and higher at approximately 20 years after conversion according to their influences on soil OC level; (H3) re-vegetation altered the relationships between OC mineralization and N availability.
Section snippets
Study site and soil sampling
The study site is located in the Liudaogou watershed (38°46′ - 38°51′N, 110°21′ - 110°23′E, 1081–1274 m a.s.l.) of the northern agro-pastoral ecotone in China. The watershed has a semiarid continental climate, with mean annual precipitation of 420.8 mm and mean annual temperature of 9.0 °C (from 1961 to 2014). During the growing season (from April to October), the monthly mean precipitation is 56.2 mm and the monthly mean air temperature is 17.6 °C. The soil is a Calcaric Regosol according to
Soil OC mineralization and temperature sensitivity
The Cmin was significantly higher in the 0–10 cm soils than in the 10–20 cm soils both across and within conversion patterns (Table 1, Fig. 1a). Converting cropland to re-vegetated land increased the cumulative OC mineralization (Cmin) from 38.21 ± 1.46 to 57.79 ± 2.62 mg kg−1 soil at the 0–10 cm depth (P < 0.05), but not at the 10–20 cm depth (P > 0.05). The effects of re-vegetation on Cmin at the 0–10 cm depth varied among conversion patterns. The increase in Cmin was greater after conversion
Effects of re-vegetation on OC mineralization and temperature sensitivity
We originally hypothesized that OC mineralization and temperature sensitivity would increase while specific OC mineralization would decrease after re-vegetation on former cropland. Partially supporting H1, converting cropland to re-vegetated land increased Cmin at the top 10 cm depth while Cmin/C0 and Q10 were not significantly influenced by re-vegetation for either the 0–10 cm or 10–20 cm depth (Fig. 1). The increase of Cmin in the 0–10 cm soil layer could be mainly explained by higher organic
Conclusions
In our study, cumulative OC mineralization in soils at the 0–10 cm depth increased after re-vegetation in cropland especially in artificial grassland, but the effect was similar among conversion times. The specific OC mineralization and Q10 were similar in cropland and re-vegetated land for each species and age, indicating that the OC decomposability would be relatively stable under land-use change and future warming in this ecotone. Variations in cumulative OC mineralization was mostly
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This study was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA23070202 and XDB40020000), National Natural Science Foundation of China (41977068, 41571130082, 41571296 and 41622105), Chinese Academy of Sciences (QYZDB-SSW-DQC039) program and Northwest A & F University (2452017028), the Special-Funds of Scientific Research Program of State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau (A314021403-Q5), and the China
References (43)
- et al.
Tree species and time since afforestation drive soil C and N mineralization on former cropland
Geoderma
(2017) Sources of CO2 efflux from soil and review of partitioning methods
Soil Biol. Biochem.
(2006)- et al.
Changes in microbial communities and respiration following the revegetation of eroded soil
Agric. Ecosyst. Environ.
(2017) - et al.
The influence of land-use change on the organic carbon distribution and microbial respiration in a volcanic soil of the Chilean Patagonia
Forest Ecol. Manag.
(2009) - et al.
Mechanisms of carbon sequestration and stabilization by restoration of arable soils after abandonment: a chronosequence study on Phaeozems and Chernozems
Geoderma
(2019) - et al.
Do legumes and non-legumes tree species affect soil properties in unmanaged forests and plantations in Costa Rican dry forests?
Soil Biol. Biochem.
(2013) - et al.
Assessment of carbon sequestration potential of revegetated coal mine overburden dumps: a chronosequence study from dry tropical climate
J. Environ. Manag.
(2017) - et al.
Dynamics of storage and relative availability of soil inorganic nitrogen along revegetation chronosequence in the loess hilly region of China
Soil Till. Res.
(2019) - et al.
Relative availability of inorganic N-pools shifts under land use change: an unexplored variable in soil carbon dynamics
Ecol. Indicat.
(2016) - et al.
Soil microbial community and its interaction with soil carbon and nitrogen dynamics following afforestation in central China
Sci. Total Environ.
(2016)
Farmers' initiative on adaptation to climate change in the Northern Agro-pastoral Ecotone
Int. J. Disaster Risk Reduct.
Vertical distribution and temporal stability of soil water in 21-m profiles under different land uses on the Loess Plateau in China
J. Hydrol.
Response of aggregate associated organic carbon, nitrogen and phosphorous to re-vegetation in agro-pastoral ecotone of northern China
Geoderma
Soil texture determines the distribution of aggregate-associated carbon, nitrogen and phosphorous under two contrasting land use types in the Loess Plateau
Catena
The temperature sensitivity of organic carbon mineralization is affected by exogenous carbon inputs and soil organic carbon content
Eur. J. Biol.
Priming of soil organic matter mineralisation is intrinsically insensitive to temperature
Soil Biol. Biochem.
How do soil organic carbon stocks change after cropland abandonment in Mediterranean humid mountain areas?
Sci. Total Environ.
Effects of aggregates size and glucose addition on soil organic carbon mineralization and Q10 values under wide temperature change conditions
Eur. J. Soil Biol.
Long-term fertilization increases the temperature sensitivity of OC mineralization in soil aggregates of a highland agroecosystem
Geoderma
Soil organic matter quality interpreted thermodynamically
Soil Biol. Biochem.
A warmer climate reduces the bioreactivity of isolated boreal forest soil horizons without increasing the temperature sensitivity of respiratory CO2 loss
Soil Biol. Biochem.
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