Erosion and sedimentation effects on soil : organic carbon redistribution in a complex landscape of western Ecuador

M.D. Corre, J.M. Schoorl, F. de Koning, M. López-Ulloa, E. Veldkamp

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Abstract

This study was conducted to evaluate how land-use changes affect the distribution of SOC within a complex tropical landscape through the processes of erosion and sedimentation. The objectives were: (i) to estimate the present SOC storage at a landscape scale using predictors such as slope, elevation, texture, land-use type and landscape position; (ii) to estimate soil redistribution under the present land-use conditions and under different land-use change scenarios using an erosion-sedimentation model; and (iii) to estimate the redistribution of SOC caused by erosion-sedimentation processes and its effect on landscape-scale SOC stocks. Implications for land-use policy options for the study area are also discussed. The study was conducted in the southern part of Manabi province in western Ecuador where 12 sites were selected in each of the three land-use systems (36 sites in total) to represent the two major physiographic soil units. The main agricultural land uses are coffee-agroforestry systems, pastures and upland rice fields. Using a general linear model with backward stepwise elimination, a model was developed for predicting SOC stocks (as the dependent variable) using the following regulatory factors (independent variables): elevation, slope, texture (as continuous variables), land-use type and soil-landform class (as categorical variables). Results showed that the significant variables that explained SOC stocks at the landscape scale were: elevation (P<0.01), texture (sand) (P<0.05), land-use type (LU1 = coffee-agroforestry; LU2 = pasture) (P<0.05), and soil-landform class (SL1 = lowland soils) (P<0.01), as reflected in the regression model. The highest SOC stocks (in the south-east corner of the area) were found in lowland soils on river valleys, river terraces and lower hills, whereas lower values were found in upland soils on higher landscape positions (north-west corner of the area). SOC stocks in the top 25 cm depth ranged from 30-87 Mg C ha-1 and the area-weighted mean was 63.6 Mg C ha-1. The SOC map illustrates that the actual SOC stocks were strongly related to topography and topography-related soil textural classes, suggesting that topography-driven water erosion and sedimentation processes play an important role in this landscape. Soil erosion losses and sedimentation gains showed stark contrasts among the four land-use change scenarios. SOC redistribution in the landscape, caused by land-use change effects on erosion and sedimentation, showed the highest impact in clay soil zones on depositional lower landscape positions and in lowland soils on river terraces, whereas the lowest impact was found in sand and loam soils on upper landscape positions.
Original languageEnglish
Title of host publicationLand-use change impacts on soil processes : Tropical and savannah ecosystems
EditorsF.O. Brearley, A.D. Thomas
Place of PublicationOxfordshire, UK
PublisherCAB International
Pages108-121
Number of pages200
ISBN (Print)9781780642109
DOIs
Publication statusPublished - 2015

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    Corre, M. D., Schoorl, J. M., de Koning, F., López-Ulloa, M., & Veldkamp, E. (2015). Erosion and sedimentation effects on soil : organic carbon redistribution in a complex landscape of western Ecuador. In F. O. Brearley, & A. D. Thomas (Eds.), Land-use change impacts on soil processes : Tropical and savannah ecosystems (pp. 108-121). CAB International. https://doi.org/10.1079/9781780642109.0108