The geomorphic signature of bare-nosed wombats (Vombatus ursinus) and cattle (Bos taurus) in an agricultural riparian ecosystem

Riparian agricultural environments in eastern Australia are widely used for cattle grazing, but are also preferred habitat for native, soil-disturbing mammals such as the bare-nosed wombat (Vombatus ursinus). We examined the effects of mound construction by wombats, and track development by cattle and wombats, on soil displacement in a riparian landscape at high and low levels of cattle usage. Splash erosion was measured on mounds and inter-mounds with splashboards, and changes in the profiles of cattle-wombat tracks were assessed using a profilemeter. Twice as much soil was detached by splash erosion from mounds than inter-mounds, irrespective of cattle usage, and about three-times more coarse sand and 40% more fine sand was detached from mounds and inter-mounds at the high cattle sites. Increasing amount of rainfall corresponded with increasing splash erosion, but only on the mounds. The volume of soil displaced from wombat and cattle tracks ranged from 7.9 to 88.8 m3 ha−1 (4.7 to 118.7 t ha−1), but there were no differences in relation to cattle usage. Our results indicate that track development by cattle and wombats and mound construction by wombats may be substantial geomorphic processes given the large mass of soil displaced. Our results suggest that mounding by wombats may be an important process in riparian environments by providing a range of microsites that favour different plant cover densities.