Subproject 6: Soil properties / Soil erosion
Mechanisms of soil erosion as a function of species richness and species composition in subtropical forests
PI: Thomas Scholten, Prof. Dr. rer. nat. (University of Tübingen)
Co-PI: Peter Kühn, Dr. rer. nat. (University of Tübingen), Thorsten Behrens, Dr. rer. nat. (University of Tübingen)
Summary
This project seeks to investigate the relationship between biodiversity and soil erosion. Two process systems will be analysed, (a) modification of kinetic energy of precipitation by its pass through the tree canopy and the shrub layer, and (b) connection between surface runoff, sediment transport and changing intrinsic soil properties as a function of biodiversity gradients. Main factors controlling mechanisms of soil erosion under forest are vegetation, soil cover by litter, intrinsic soil resistance against erosion and the given micro-relief of the soil surface. Main experimental components are (a) measurements of the kinetic energy of rainfall with disdrometers and splash cups under different tree species varying in height and architecture, (b) measurements of surface water flow and sediment on runoff plots at different levels of species richness and species composition, and (c) geomorphometric measurement of changes of soil surface micro-elevation and -form in relation to runoff routing. In addition, this project will also be responsible for spatial and pedological aspects of soil genesis, substrate characteristics, landscape development, and land use history. Soil properties analysed at the plot level like soil texture will serve as baseline data for the whole experiment. Finally, the soil erosion project will contribute substantially to the interpretation of soil-related data sets and the synthesis of results on soil-plant interactions, and will help with the high-resolution DEM from laser scanning and photogrammetry. The Chinese partner project concentrates on detection of dynamics in aggregate stability and organic matter composition in soils related to changes in stand canopy, functional traits and species composition, and on the effect of LAI of forests on soil erosion in relation to biodiversity.
Objectives
The main objective is to answer the question how close biodiversity is coupled to soil erosion by water in forest ecosystems. The following hypotheses will be tested:
1. Subtropical forests reduce soil erosion significantly. Erosion control depends on the level of biodiversity at different succession stages. Modification of rain drop energy is most significant in plots with the highest diversity of tree and shrub species.
2. During the succession, different mechanisms of erosion control based on changes in kinetic raindrop energy are activated depending on the dynamics of tree and shrub growth as well as soil surface cover by litter.
3. Intrinsic properties controlling the erodibility of a soil (e.g. texture, stone content, aggregation, infiltrability) interact with species richness and composition. Vegetation cover superimposes the effect of abiotic soil properties so that soil erosion control becomes a function of biodiversity.
4. Combinations of representative sampling schemes and supervised data mining techniques using topography, soil and biodiversity as predictors allow the extrapolation of biodiversity related susceptibility to soil erosion.