Hydrological prerequisites for optimum habitats of riparian Salix communities - identifying suitable reforestation sites

Question: What are the hydrological requirements for the successful reforestation of riparian Salix communities? Do differences in site conditions between various life stages of woody vegetation types need to be considered? Do interactions between hydrological factors influence distribution patterns? Location: Mid-reaches of the Elbe River, Germany. Methods: Young and old life stages of two different riparian Salix communities were surveyed in 1067 plots of 400 m(2) to determine hydrological growth conditions using habitat distribution models. Models were extrapolated in a Geographic Information System to quantify the extent of potential stands available for reforestation measures. Results: Average water level and water level fluctuations were related to different vegetation types as well as to the age classes of the vegetation types. Differences in hydrological niches of young and old vegetation of the two vegetation types (tree community versus shrub community) could be identified. Moreover, the shrub vegetation was influenced by the interaction of average water level and fluctuations. Comparison of the distribution of current vegetation and suitable habitat revealed that considerable areas of the floodplain were suitable for the reforestation of Salix woodland communities. Conclusions: Hydrological variables explain the distribution patterns of riparian Salix communities in the active floodplain when different life stages, vegetation types and interaction of variables are included in the analyses. This information can be used to recommend suitable sites for Salix plantings in riparian landscapes.