The resilience of a floodplain vegetation landscape

Abstract

Floodplains are complex adaptive ecosystems that provide an array of ecosystem services. Despite the growing focus on resilience as a fundamental feature of floodplain ecosystems, and as an aim in floodplain management, few studies have quantified the resilience of floodplain landscapes over meaningful timescales. This study examines the resilience of floodplain vegetation communities over medium (decadal) and long term (multi-decadal) times scales through an analysis of the spatial organisation of different vegetation communities. The floodplain vegetation landscape is conceived as having two basins of attraction represented by; (1). Natural vegetation, which incorporates two domains of flood dependent (FD) and non-flood dependent (NFD) vegetation communities; and, (2). Cleared vegetation (CL). We examine change in the spatial organisation of vegetation communities on the Yanga floodplain, located on the Murrumbidgee River, Australia, over a forty-year period (1965–2005). Detailed vegetation community maps, constructed from orthorectified aerial photographs for the years 1965, 1973, 1997 and 2005, were used. Substantial changes in the extent and spatial configuration of vegetation communities occurred over the 40-year period. Many changes were bidirectional transitions between FD and NFD vegetation communities, representing transitions in response to variations in flood frequency. However, the predominant unidirectional transition of the FD and NFD vegetation communities were to CL. The dynamic character of the Yanga Floodplain vegetation landscape is shown by 91 detectable transitions among vegetation community types. Despite large areas of the floodplain vegetation landscape having undergone persistent community change, some areas of the floodplain display resilience over the 40-year period. This suggests floodplain vegetation communities are well adapted to substantial changes in environmental conditions as a result of episodic flooding and drying. However, large net changes and an increase in CL, which did not revert back to previous vegetation community types, suggest a transition to a different basin of attraction, and a loss of system resilience.