Land-use change from indigenous management to cattle grazing initiates the gullying of alluvial soils in northern Australia

摘要

Catchments in northern Australian have undergone dramatic land-use changes from traditional Aboriginal management to widespread cattle grazing post-European settlement. Quantifying the soil erosion impacts of these changes is essential to the future sustainable management of the soils in these catchments. Rates of gully erosion in alluvial soils were measured using recent GPS surveys and historical air photographs. The results indicated that median erosion rates currently and historically are within the same order of magnitude (0.1 to 1m per year). Historic air photo analysis demonstrated rapid increases in gully area of 2 to 10 times their initial 1949 area. Extrapolation of gully area growth trends backward in time suggested that most gullies initiated between 1880 and 1950. European cattle were introduced into the lower Mitchell catchment in the 1880's, suggesting the contribution of land use intensification to either gully initiation or acceleration. It is hypothesized that intense cattle grazing concentrated in the riparian zones during the dry season decreased perennial vegetation cover along hollows and steep river banks, increasing the potential for gully erosion. Once initiated on steep banks into dispersible sub-soils, alluvial gullies can rapidly progress in consuming and degrading the most productive part of the landscape, the riparian zone.