Phreatophytic Vegetation Response to Climatic and Abstraction-Induced Groundwater Drawdown: Examples of Long-Term Spatial and Temporal Variability in Community Response
Faculty of Computing, Health and Science
School of Natural Sciences
The influence of climatic drought and groundwater abstraction on phreatophytic vegetation dynamicswas investigated in the southwest of Western Australia.Twocontrasting examples of long-term phreatophytic plant community response to reduced water availability are presented. Multivariate analysis of vegetation and hydrological parameters determined depth to watertable as the dominant biophysical driver of floristic spatial and temporal patterns. Under lower rates of watertable drawdown (9cmyear−1), a progressive change in floristic composition was observed over a 33-year period. The abundance of species with a preference for wetter siteswassignificantly reduced, whereas that ofmoredrought-tolerant species increased. Higher rates of drawdown (50cmyear−1) where groundwater abstraction exacerbated climatic drought resulted in a threshold response in vegetation and 33% dissimilarity to pre-abstraction floristics in 12 years. In the context of an ecohydrological state and transition conceptual model, it is suggested higher rates of groundwater drawdown result in a threshold breach and subsequent transition to an alternative ecohydrological state, whilst lower rates result in a progressive floristic transition.