Integrating hydrology and land use to understand the ecology of floodplain wetlands in the Condamine Catchment, southern Queensland, Australia

Floodplain ecosystems support an abundant and diverse range of species. However, in many agricultural landscapes, hydrological and land use changes have caused a decline in the extent and condition of wetlands. There are numerous hydrological based concepts which have helped provide a basis for understanding, predicting and managing the ecological impacts of hydrological changes on floodplain systems. However, while hydrology focused concepts have proved highly informative, they have also lead to much research being exclusively focused on the independent effects of hydrological factors (e.g. reductions in stream flow and flood events). This may limit the ecological understanding and management in three important ways. Firstly, as most studies are carried out in floodplains of large perennial rivers, many current concepts neglect smaller non-flowing habitats, such as floodplain wetlands. Secondly, as research is often exclusively focused on hydrological factors it may not adequately consider the additional impacts of other drivers, such as land use factors. Thirdly, current research gives little consideration to the nature of interactions between different hydrological and land use factors and how they may exacerbate and mitigate effects. To help test these potential limitations, two alternate hypothesis were developed for the ecology of floodplain wetlands. The “hydrology hypothesis” views these systems as being driven exclusively by hydrological factors. In contrast, the “interactive hydrology-land use hypothesis” considers hydrological and land use factors and their interactions as drivers of ecological patterns in floodplain wetlands. These competing hypotheses are not designed to test which factors are of most relative importance, but to ask whether hydrology focused research is limited by not considering land use and interactions. These hypotheses were tested using data from surveys on the dominant tree species, Eucalyptus camaldulensis Dehnh., of floodplain wetlands in the Condamine Catchment, south east Queensland, Australia. The catchment has undergone extensive hydrological and land use alteration to support agricultural production and therefore offers an ideal setting to test these competing hypotheses. The hydrological characteristics (inundation frequency, river connectivity, groundwater depth and rain volume) of 102 modified and 149 ‘natural’ unmodified wetlands across the Condamine Catchment were determined using data derived from satellite imagery and digital elevation models and compared. The hydrology of unmodified and modified wetlands differed significantly (ANOVAs; p