Dynamics of desert-shrub populations in regulating soil transport based on plant-size scaling relevant to climate-change timescales
Fathel, Siobhan L.
Desert vegetation in the Southwestern United States influences sediment transport. Specifically, rainsplash processes create mounds beneath shrubs which regulate the sediment flux on hillslopes. In turn, complex plant community dynamics make it difficult to predict changes in transport rates over climate-change timescales. Southwestern climate predictions suggest changes in precipitation, which affect desert shrub populations and sediment transport rates. We use a coupled, physically based model of shrub population dynamics and sediment transport to understand the implications of arid-region climate change and compare ‘normal’ precipitation to precipitation scenarios influenced by climate change. Using this model, we track changes in shrub populations and resulting fluctuations in transport rates. In particular, we track changes in the vegetation, measured in terms of biomass, using the validated WBE scaling model, and relate it to sediment transport rates. This allows for biomass calculations from structural measurements defined in the coupled model. Furthermore, simulated values from the model confirm the idea that increasing amounts of biomass, for two analyzed shrub species, indeed lead to decreasing sediment flux values. This correlation opens an opportunity to use biomass as a common currency to describe sediment flux. Variations in shrub morphology between species leads to differences in shrub response to climate change, particularly aridification. This work provides an opportunity for large scale monitoring, and possibly prediction, of changes in shrub populations and associated sediment transport on Southwestern desert hillslopes when considering shrub sensitivity to fluctuations in precipitation.