Soil seed reserves in arid grazing lands of central Australia. Part 1: seed bank and vegetation dynamics

Heavy grazing can cause a long-term reduction in the capacity of vegetation to respond to rain particularly after drought. One potential cause is a lack of soil seed reserves. We found that the size and composition of the germinable seed bank in arid calcareous grazing lands were changed where there had been several decades of heavy grazing, including a period of drought, but not when grazing was lighter, time was shorter and drought was absent. The same was true for the species numbers and composition in the standing herbage. Seed reserves were persistent and ‘moderately similar’ in species composition to the standing herbage at a broad level (Sorenson similarity index 60% and 66%). Similarity was likely to be strongly affected by prevailing seasonal conditions and so should be assessed over several years.