Influence of orographic precipitation on coevolving landforms and vegetation in semi-arid ecosystems

Topography affects the intensity and spatial distribution of precipitation due to orographic lifting mechanisms and, in turn, influences the prevailing climate and vegetation distribution. Previous modelling studies on the impact of orographic precipitation on landform evolution have considered bare soil conditions. However, research on the effect of changes in precipitation regimes induced by elevation gradients (particularly in aspect-controlled semi-arid ecosystems) on landform patterns, trying to understand feedbacks and consequences for coevolving vegetation, has been limited. In this study, the Channel-Hillslope Integrated Landscape Development (CHILD) landscape evolution model coupled with the vegetation dynamics Bucket Grassland Model (BGM) is used to analyse the coevolution of semi-arid landform-vegetation ecosystems. The CHILD+BGM model is run under different combinations of precipitation and solar radiation settings. Three precipitation settings, including uniform, elevation control, and orographic control on precipitation, are considered in combination with spatially uniform and spatially varied radiation settings. Based on the results, elevation control, aspect, and drainage network are identified as the major drivers of the distribution of vegetation cover on the landscapes. Further, the combination of orographic precipitation and spatially varied solar radiation created the highest asymmetry in the landscape and divide migration due to the emergence of gentler slopes on the windward than the leeward sides of the domain. The modelling outcomes from this study indicate that aspect control of solar radiation in combination with orographic precipitation plays a key role in the generation of topographic asymmetry in semi-arid ecosystems.