Temporal changes in threatened ephemeral claypans over annual and decadal timescales in south-west Australia

Abstract

The vegetation of the ephemeral claypans of south-west Australia were first described over 100 years ago. Since then they have been almost totally cleared for agriculture and urban development and are currently listed as critically endangered. These claypans have many similarities with ephemeral wetlands found in other Mediterranean climate regions with significant species turnover both within and between claypans and fine scale patterning highly correlated with micro-topography. Although annual variation in species composition was apparent there was also a consistent trend of increasing exotic taxa richness due to higher recruitment rates. This increasing exotic richness is of note, as the major threat to these communities is the invasion by a small number South African taxa, which can establish dense monocultures across these wetlands. Over the last two decades these invasive taxa have spread into 37% of the previously non-invaded quadrats. As remnant size was not a good predictor of their occurrence all remnants should be considered vulnerable. Management of these invasive taxa will be the major conservation issue in these threatened wetlands into the future.