Landform-Water-Vegetation Feedbacks: Exploring Ecosystem Stability and Restoration Potential in Semiarid Hillslopes
Wednesday, 17 December 2014: 1:55 PM
Vegetation dynamics and soil surface processes (e.g. runoff, soil erosion, sedimentation) are tightly coupled in drylands, where vegetation cover is patchy and plant production largely depends on favourable redistribution of water and sediments. At the same time, the amount and spatial distribution of vegetation control hillslope runoff and erosion, and strongly influence the redistribution of water and soil resources in these systems. Large shifts in the structure and organization of vegetation are associated with land degradation, frequently involving nonlinear responses to both human and climatic pressures. The study of landform-water-vegetation feedbacks has, therefore, a critical role for the comprehension of ecosystem stability and restoration potential in arid and semiarid environments. We present a synthesis of field-based, remote-sensed and modelling studies on soil-vegetation patterns in semiarid rangelands of Australia and water-restricted reclaimed mining slopes of Spain. Our results indicate that the organization and stability of vegetation patterns strongly depends on feedbacks with coevolving landforms. Exploration of degradation trends in banded Mulga shrublands of central Australia reveals that human disturbances (e.g. grazing) can strongly alter landform-water-vegetation feedbacks and particularly the way water is spatially redistributed and used by vegetation, resulting in threshold-like responses of ecosystem function. Successful experiences on the restoration of these systems highlight that the management of runoff and sediment flows is decisive to recover vegetation patchiness and landscape function. The study of vegetation-water-landform feedbacks in Mediterranean-dry reclaimed mining slopes of Spain offers additional indications on the restoration of drylands, particularly on the effects of rill and gully erosion on the stability of restored vegetation. The development of rill and gully networks provides very efficient drainage networks for the routing of water and sediments, which drastically reduce the availability of resources for plant production and ultimately can cause irreversible ecosystem changes.