Modelling the effects of above and belowground biomass pools on erosion dynamics

Abstract

Despite the scientific consensus that vegetation modifies erosion/deposition processes, traditional erosion and landform evolution models often include a simplified representation of vegetation dynamics, which does not consider the influence of the various biomass pools on erosion mechanisms. In this paper, we present a new modelling framework that couples dynamic modules of hydrology, vegetation, biomass pools and landform evolution/erosion processes. We analyse the effect of above and belowground biomass pools (leaves, roots, litter and soil carbon) changes in erosion rates by considering: (1) the effect of root biomass on soil erodibility, (2) the effect of leaf cover on soil diffusivity, (3) the effect of litter on flow resistance, and (4) the effect of soil carbon on soil water retention. We implement the model using daily data for an open-forest vegetation and ran different idealized experiments for a period of 100 years. The objectives of the experiments are to understand the combined effects of biomass pool dynamics and climatic seasonality on erosion patterns, and to compare results including the effects of various biomass pools on erosion versus those obtained using simplified formulations (i.e., bare soil, constant vegetation). Our results indicate that the erosion protection effects of the individual biomass pools are not simultaneous, with different biomass pools providing protection at different times of the year. We also find that simplified vegetation formulations (e.g. constant vegetation) can significantly under/overestimate erosion when compared with the fully dynamic biomass pools formulation. These findings highlight the importance of including a detailed representation of dynamic vegetation and biomass pools in models, to capture the feedbacks between erosion and vegetation processes and better understand and predict erosion/deposition processes.