Aeolian processes redistribute sediments and nutrients within arid landscapes with important implications on the composition and structure of vegetation. The interactions among hydrological - aeolian processes and vegetation are known to affect the dynamics of land degradation in these landscapes. The differential rates of soil deposition and erosion by aeolian processes result in differential rates of hydrological processes such as run off and infiltration with implications on the emergence of a patchy distribution of vegetation. Vegetation patterns, in turn, affect the spatial dynamics of sediment transport, soil moisture and nutrients in the system. These processes play a major role in creating a heterogeneous distribution of soil resources and in the conversion of desert grasslands to shrublands with important impacts on regional climate and desertification. Further, the erosion processes interact with disturbances such as fires to affect the redistribution of soil resources in the system. Here it is shown that at the early stages of shrub encroachment, fire can play an important role in the local-scale redistribution of soil resources within the landscape by enhancing local scale soil erosion processes. To this end microtopography measurements, δ15N isotope tracer experiments and post fire erosion monitoring were conducted in a shrub-grass transition zone.
Results/Conclusions
The results indicate that in a landscape covered by a mixture of native grasses and invading shrubs fires change the spatial patterns of soil erosion, favoring the local scale redistribution of soil nutrients from the islands of fertility beneath the burned shrubs to the adjacent bare interspaces. This process of post fire resource homogenization may effectively counteract land degradation at the desert margins.
