ORGANIC MATTER DISTRIBUTION IN FLOODPLAINS CAN BE PREDICTED USING SPATIAL AND VEGETATION STRUCTURE DATA

Riparian forest ecosystems play a significant role in the storage of organic carbon. However, the knowledge on the spatial patterns of organic matter distribution which is crucial to the assessment of the C sequestration potential of riparian ecosystems is still lacking. The aim of our study was to identify predictors of organic matter distribution in floodplain soils and vegetation. We analysed the depth distribution of soil horizons to 1 m below the surface, calculated the organic C content and quantified living biomass and woody debris at 67 sampling plots in the Donau-Auen National Park (Austria) along principle spatial gradients (longitudinal, lateral and vertical to river direction). Multiple regression models were fitted using hierarchical partitioning of spatial information, which was supplemented by forest stand parameters as possible predictors of soil C. The concentration of organic C in the subsoil horizons increased significantly with distance to the main channel. In addition, the thickness of soil horizons enriched with organic matter increased downstream which probably indicates the effect of riverbed changes over the last two centuries. Model prediction of soil parameters was improved with the inclusion of vegetation structure variables which are a consequence of local river dynamics. Highly dynamic locations indicated by higher stem numbers, greater understory vegetation cover, lower mean stem diameter and lower canopy cover showed significantly lower concentrations of soil organic C and lower total organic C stocks. We conclude that spatial information and vegetation structure can indicate gradients of geomorphic floodplain dynamic, which is the main driver of organic matter storage. Copyright (C) 2010 John Wiley & Sons, Ltd.