Resilience of a native soil seed bank in a floodplain lake subjected to cropping, grazing and extended drought

Abstract

Ephemeral floodplain lakes are an integral component of inland wetland ecosystems and experience highly variable hydrology and prolonged dry periods. Although wetland soil seed banks are highly resilient to drought and floods, anthropogenic land use may add an additional stress. Understanding the recovery potential of wetland soil seed banks to different historical land uses helps manage and prioritise environmental water. In this study we explored the resilience of the wetland plant community in an ephemeral floodplain lake (Ita Lake, NSW, Australia). We collected soil samples during an extended dry phase (10 years) from two distinct zones within the lake, one of which was subjected to historical grazing and the other to lakebed ploughing and cropping. The samples were inundated under multiple inundation regimes to assess soil seed bank response. We found that the soil seed bank was viable, indicating a level of resilience not previously recorded for some plant species, namely Ricciocarpus natans, Chara spp., Nitella spp., Alternanthera denticulata and Eleocharis acuta. Although the results highlight the resilience of ephemeral wetland plant communities, intensive land uses such as ploughing and cropping will limit the availability of seeds to germinate, and the inundation regime will influence species composition and the subsequent likelihood of restoration.