The response of dryland floodplain vegetation productivity to flooding and drying

• Floodplain vegetation productivity was assessed in dry and wet resource states.
• Significant differences were found between dry and wet resource states.
• Complex response patterns occurred between communities and resource states.
• The response does not fit a boom and bust model of floodplain ecosystem productivity.

Dryland floodplains are characterized by highly variable flooding and drying. This variability plays a key role in the productivity of dryland floodplain vegetation. The Normalized Difference Vegetation Index, a surrogate for vegetation productivity, has been extensively used to examine floodplain vegetation productivity responses to flood inundation but generally focuses on inundation alone, or at a single scale thereby potentially omitting important elements of dryland variability. This study used fine resolution satellite imagery, through sequences of flood and dry resource states, at multiple scales of observation and with consideration of the relative influence of rainfall and flow to examine floodplain vegetation productivity in the dryland floodplain. There were marked differences in floodplain vegetation productivity between wet and dry resource states. Overall, response patterns were complex and varied among vegetation communities and in different resource states. The findings suggest that vegetation productivity in the Narran floodplain does not correspond well with the boom and bust model of floodplain ecosystem productivity. Rather, understanding vegetation productivity in a highly variable floodplain requires an enhanced understanding of the nature of variability in space and time. Conceptual models that can better convey the complexity of vegetation productivity responses to floodplain wetting and drying are suggested.