Linking sedimentological and spatial analysis to assess the impact of the forestry industry on soil loss: The case of Lanalhue Basin, Chile
Graphical abstract
Introduction
During the last decades, global change has generated a dramatic transformation of the land cover on the planet's surface. Among these effects, the increase in erosion stands out as a particularly concerning issue (Borelli et al., 2017), because soil is considered a non-renewable resource on a human time scale, and because the lost soil increases sedimentation and eutrophication in different bodies of water (Owens 2008). For this reason, a series of efforts has been developed globally to detect and control soil loss (Borrelli et al., 2017) as well as to develop new methodologies and frameworks for prioritizing areas for restoration (Geneletti et al., 2011, Crossman and Bryan, 2006). These methodologies include long-, medium-, and short-term analyses. Long-term studies are based on paleolimnology analysis, which reconstructs past environments by quantifying observed changes over time in factors like sedimentation rates, sedimentology, and biological proxies) (Larocque-Tobler, 2016). The medium-term analysis uses algorithms such as the Universal Soil Loss equation (USLE) to estimate the potential soil loss across a spatial expanse based on a series of hydrometeorological, physiographic, and land-cover factors (Wischmeier and Smith, 1978). This methodology can be applied by using satellite data in combination with edaphic cadasters to generate erosion assessments (Alewell et al., 2019). It is not possible to compare long- and medium-term methods directly, because USLE cannot estimate the total yield of sediment that enters into a lake, since part of it is retained in valleys or creeks. Boyle et al. (2011) discussed the SEDEM model, which was developed to estimate the fraction of soil that is not deposited in the lake, concluding that this method is difficult to apply because it requires high quantity and quality field information (short-term erosion studies), unlike the USLE method. Because of the lack of short−term erosion studies, Boyle et al. (2011) proposed an alternative approach based on the results of Vandenberghe et al. (1998) in Belgian lakes: discard that quantity of retained sediment, especially in the case of small catchments (< ~ 100 km2) because it is a small amount, and use USLE to estimate the sediment deposited in lakes (see Table 1).
One of the main sources of disturbance and soil loss is the replacement of natural land cover by forestry plantations (Grace, 2004, Huber et al., 2010). Chile has been one of the countries most affected by this type of land-cover change, especially in its south-central coastal area (Miranda et al., 2015, Miranda et al., 2017). In Chile, the species used for forestry plantations are mainly exotic; Pinus radiata was the first species to be massively planted, followed by Eucalyptus globulus. Forestry activity has been considered one of the most environmentally harmful activities in Chile since 1974, when the government offered subsidies for private owners to plant exotic species, producing an exponential expansion of plantations (Leyes de Chile, 2019). Industrial plantations use a clear-cutting system in which large stands of plantations are cut at once, leaving soil exposed to dramatic erosion by precipitation (Gayoso and Iroumé, 1995). In addition, the hydrophobic condition of Pinus species hinders water infiltration into soil, affecting water balance (Huber et al., 2010). Erosion is also promoted by the mountainous topography and heavy rain characteristic of south-central Chile (Oyarzun and Peña, 1995). The aim of this study is to estimate the impact of the forestry industry on soil loss by combining sedimentological and USLE methods in a medium-sized lake basin located in central Chile, and to propose priority sites for soil restoration and erosion control. Sedimentology allows us to estimate long-term changes of sedimentation rates before Pinus and Eucalyptus plantations (the background conditions), and comparing these results with the present soil loss obtained from the USLE model allows us to estimate the quantity of soil that is transported from nearby hills into the lake as well as the activity associated with soil loss.
We specifically address the following questions: A) Have sedimentation rates changed during the last 120 years in Lanalhue lake? B) What was the timing of these changes? C) Which of the factors of the USLE analysis had the greatest influence on erosion for each type of land cover? D) What type of land cover and property type has caused the greatest soil loss in the basin? E) Where is it most necessary to implement restoration actions? We propose that sedimentology and USLE models, working together, give us a powerful tool, because sediment analysis tells us the comparative quantity of sediment deposited in the bottom of the lake and its temporal changes through centuries and even decades, and the USLE method gives us information about the land use that produced this sediment, as well as the quantity of sediment in tons per area per year that arrived to the lake. The USLE model also tells us the origin (anthropogenic or not) and the land use that are producing the greatest amount of sediment. USLE models, validated by sedimentology, allow us to propose management actions to control soil loss. We also present a series of methodological advances which could be used to replicate USLE analysis.
Section snippets
Study area
Lanalhue basin is located in the Biobío Administrative Region, southwest of the Nahuelbuta coastal range (73° S, 37° W, Fig. 1). This coastal basin flows into the Pacific Ocean; it is surrounded by mountains composed of metamorphic rocks that rise from 500 to 800 m in the east (with minimum valley elevation of 21 m) and in the west rise up to 1065 m (SERNAGEOMIN, 2003). The average slope is 15° ± 9.9°, with a maximum of 63.3° . The basin has an area of 365.4 km2. The lake is 9 km long and
Sediment sampling and chronology
Fieldwork was carried out during January 2019 (austral summer). Lake bathymetry was explored with an echo sounder (Garmin echoTM100) and sediment cores were collected from four sites along the lake, following the principal streams and variable maximum depths (Licahue, 3 m; Lincuyin, 15 m; Huilquehue, 24 m and La Vaina, 24 m) (Fig. 1 and S1). At each site, four 1 m-long sediment cores were collected using an Uwitec gravity corer. Each core was sliced at 1-cm intervals, except for the La Vaina
Age model and radionuclide data
The age model created by Plum presented a good performance for the period 1960–2019 CE, which is the main temporal focus of this research. However, based on the basal radiocarbon ages from each core, we can extend the chronologies up to 1090 CE for Lincuyin, 330 CE for Huilquehue, 440 CE for Licahue, 1270 CE for La Vaina (Fig. S10, Table S4).
The mean unsupported 210Pb fluxes inferred by the Plum model were 58.7 Bq/m2 yr−1 for Lincuyin, 50.1 Bq/m2 yr−1 for Huilquehue, 22.5 Bq/m2 yr−1 for
Integrated insights from sedimentological analysis
Sedimentological proxies from Lanalhue lake presented here (sediment accumulation rates, organic matter content, and grain size) showed three main depositional phases over the last 120 years. From 1900 to 1950 CE, the lake had very low accumulation rates (<0.15 cm/year) in the four studied cores (Fig. 3). Although the accumulation rates from any core may differ greatly from the historical sedimentation of a lake, we have not found large differences between cores during this time period, as we
Assumptions, limitations and future potential
It has been found that USLE, RUSLE, and WEPP models may overestimate erosion in zones with high erosion (usually related to plots with high slope), and underestimate it in plots with low erosion (Tiwari et al., 2000, Aburto et al. 2010). The documented differences between real plots and models from previous studies suggest that WEPP models generate more uncertainty, while USLE and RUSLE produce more similar results in comparison with field plots (Tiwari et al., 2000). Since the Lanalhue basin
Concluding remarks
Our approach allowed us to estimate and map the dynamics of soil loss on historical (long-term) and recent (middle-term) time frames, helping to understand the trends and impacts of landscape transformations on the basin. The insight obtained from the sedimentological record can extend our understanding of landscape evolution developed from the USLE method previous 1985 CE, and is a useful and novel tool in ecosystem restoration planning. These approaches provided consistent results: the recent
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
We are grateful to Violeta Tolorza for valuable conversations about soil erosion, and to Manuel Malibur for the local information he provided. We thank Manuel, Pedro Peña and Vivianne Claramunt for their field support. This study had the financial support of the Chilean Ministerio de Medio Ambiente FNDR-PRELA 608897-63-LP18 Project, the Instituto de Ecología y Biodiversidad (IEB) AFB 170008, and Fondecyt 1190398, 1201528 Projects. Alberto J. Alaniz was supported by ANID-PFCHA/ Doctorado
References (107)
- et al.
Use and misuse of the K factor equation in soil erosion modeling: An alternative equation for determining USLE nomograph soil erodibility values
Catena
(2014) - et al.
Google Earth Engine: Planetary-scale geospatial analysis for everyone
Remote Sens. Environ.
(2017) - et al.
Different times, same story: Native Forest loss and landscape homogenization in three physiographical areas of south-central of Chile
Appl. Geogr.
(2015) - et al.
Lacustrine turbidites produced by surficial slope sediment remobilization: A mechanism for continuous and sensitive turbidite paleoseismic records
Mar. Geol.
(2017) Sediment behaviour, functions and management in river basins
Sustain. Manage. Sediment Resour.
(2008)- et al.
Improvement to the prediction of the USLE K factor
Journal of Geomorphology
(2014) - et al.
Informe final: Análisis de Testigo Sedimentario en Lago Lanalhue, Provincia de Arauco, Región del Biobío
Licitación Pública Id
(2020) - Abarzúa, A.M., Pichincura, G.A., Jarpa, L., Martel-Cea, A., Sterken, M., Vega, R., Pino Q., M. (2014). Environmental...
- et al.
Hillslope soil erosion and mobility in pine plantations and native deciduous forests in the coastal range of South-Central Chile
Land Degrad Dev.
(2020) - et al.
Terraclimate, a high-resolution global dataset of monthly climate and climatic water balance from 1958–2015
Sci. Data
(2018)
Impacto del manejo de plantaciones sobre el ambiente físico. Evaluación de la erosión producida por actividades forestales productivas
Informe Técnico CONAF. Programa Manejo de Cuencas VIII Región, Concepción
Bayesian Analysis of 210Pb Dating
J. Agric., Biolog. Environ. Statist.
Flexible paleoclimate age-depth models using an autoregressive gamma process
Bayesian Analysis
Water Erosion Prediction Using the Revised Universal Soil Loss Equation (RUSLE) in a GIS Framework, Central Chile
Chil. J. Agric. Res.
Assessment of the impacts of clear-cutting on soil loss by water erosion in Italian forests: first comprehensive monitoring and modeling approach
CATENA
An assessment of the global impact of 21st century land use change on soil erosion
Nat. Commun.
Descriptions of soils, materials, and symbols
Variaciones isotópicas (210Pb, 137Cs) antropogénicas en el registro estratigráfico de un lago de la cordillera de Nahuelbuta, Chile
Revista Geológica de Chile
Effects of historical land use on sediment yield from a lacustrine watershed in central Chile
Earth Surf. Proc. Land.
Petrology of Sedimentary Rocks
A combined approach to establishing the timing and magnitude of anthropogenic nutrient alteration in a mediterranean coastal lake- watershed system
Sci. Rep.
Sustainable use zoning of land resources considering ecological and geological problems in Pearl River Delta Economic Zone
China. Scientific Reports
Situación de impacto ambiental de la red de caminos del fundo Nonguén
Identificación de áreas prioritarias para la restauración de bosques secos
Cited by (5)
High vulnerability of coastal wetlands in Chile at multiple scales derived from climate change, urbanization, and exotic forest plantations
2023, Science of the Total EnvironmentForest hydrology in Chile: Past, present, and future
2023, Journal of HydrologyCitation Excerpt :This higher sediment load was due to the activation of catchment slopes and forest roads. For example, from a sediment core analysis in the Lanalhue lake in central Chile (37° S) Alaniz et al. (2021) found a correlation of the increasing erosion and organic matter content within this lake and the afforestation with exotic plantations within the last 30 years. Tracers have frequently been used to study hydrological processes, biogeochemistry and sediment sources at plot and catchment scale.
Multiscale spatial analysis of headwater vulnerability in South-Central Chile reveals a high threat due to deforestation and climate change
2022, Science of the Total EnvironmentCitation Excerpt :Limit of industrial forestry in the coastal zone by preventing the expansion of exotic plantations near headwaters, as well as requesting the reduction of the size of clear-cut harvest in these zones. This is associated with extensive scientific evidence that links industrial forestry with erosion and water scarcity, thus altering water quality and quantity at basin scales (Alaniz et al., 2021; Lara et al., 2009). Our results present an informing scenario on the current state of vulnerability of headwaters, identifying spatial patterns and drivers at multiple scales.
Importance of Swamp Forest Fragments for the Habitat and Conservation of Vertebrates
2023, Research SquareIndustrial forestry negatively affects small-farms honey production in south-central Chile: evidence from a landscape scale
2023, Journal of Apicultural Research