Life and landscapes down under: Modelling the effect of biogeomorphologic feedbacks to investigate human and climate change effects on landscape function.

We study the biogeomorphologic feedbacks between landforms, vegetation, water and soils using a landscape evolution model in response to anthropogenic pressures and climate variability.  We first investigate the impact of seasonal variability of vegetation pools on erosion mechanisms. We use a landscape evolution modelling framework that includes mechanistic representations of hydrology and vegetation, to capture the effect of seasonal rainfall variability on different biomass above and below ground pools and the associated erosion protection. Rainfall leads to both runoff (erosion potential) and vegetation growth (erosion protection), but these two effects are not synchronized. Results for a Eucalyptus savanna landscape in the Northern Territory (Australia) suggest that maximum erosion events tend to occur early during the rainy season when vegetation protection is not strong, and that different pools have varying protection effects and timing through the year. We show that these dynamic effects and feedbacks need to be included to assess climate impacts in restoration and/or mitigation studies.

We then examine the effect of shifts in vegetation structure resulting from anthropogenic activities, which affect water and sediment redistribution in semiarid areas of Australia with sparce vegetation cover.  The study areas have patterned Mulga vegetation composed by mixed herbaceous and woody plant species, that evolve responding to competition and facilitation interactions.  We analyse modelling results from the coupled landform evolution-vegetation model on water redistribution and erosion to investigate how changes in biomass cover that alter the hydrologic response and lead to impacts on ecosystem functioning are linked to loss of resources leading to degraded states (identified from remote sensing data). These results are used to examine the potential impact of varying management strategies and the implications for the productivity of Australian rangelands.