Topsoil handling and storage effects on woodland restoration in Western Australia

An analysis of the effects of topsoil handling and storage methods was unde rtaken to optimize the potential rehabilitation of southwest Western Austra lian Banksia woodland species present before site disturbance. An increase in the depth of topsoil stripped from the Banksia woodland, from 10 to 30 c m, correlated to decreasing seedling recruitment from the soil seedbank by a factor of three following in situ respreading in an area to be restored. There was no significant difference in total seedling recruitment in situ a t two depths of spread, 10 cm and 30 cm. These results concur with an ex si tu trial on the effects of depth of seed burial on seedling recruitment tha t showed most species failed to emerge from depths greater than 2 cm. In si tu stockpiling of the woodland topsoil for 1 or 3 years demonstrated a subs tantial and significant decline in seedling recruitment to 54% and 34% of t he recruitment achieved in fresh topsoil, respectively. Stripping and sprea ding during winter substantially depressed seedling recruitment, compared w ith autumn operations, as did in situ stockpiling followed by spreading in the wet season, or stockpiling in winter followed by spreading in spring. N o loss in total seedling recruitment occurred when replaced topsoil and sub soil were ripped to 80 cm following spreading of topsoil in sites to be res tored. Conclusions from this study are that (1) topsoil provides a useful s ource of seeds for rehabilitation of Banksia woodland communities in the so uthwest of Western Australia, (2) correct handling of the topsoil, stripped and replaced fresh and dry (autumn direct return) to the maximum depths of 10 cm, can be used to optimize revegetation of species-rich plant communit ies with this type of seedbank, and (3) ripping of topsoil and subsoil to e ase compaction of newly restored soils does not diminish the recruitment po tential of the soil seedbank in the replaced topsoil.