Reduced groundwater recharge under short rotation coppice plantations - may agroforestry help to lessen enhanced water consumption ?

PosterShort rotation coppices (SRC) with mainly poplar and willow trees provide a high potential of energy supply and the substitution of fossil fuels. One shortcoming of SRC is a negative effect on groundwater recharge (GWR), as higher rates of transpiration and interception evaporation of poplar and willow plantations can be expected. Therefore it is very important to measure, analyse, and model the effects of SRC-plantings on the landscape water budgets, which are also main aims of the ongoing and joint research project BEST. To analyse the effects on the water budget a poplar SRC was studied on the plot level by measuring soil hydrological quantities as well as sensitive parameters for hydrological modelling. By using these parameters within the hydrological model WaSim we were able to fit our measured soil water contents. Fig. 1 compares the corresponding annual ground water recharge of the research plot, assuming a constant soil and vegetation cover for poplar SRC as well as for winter wheat and grassland. Especially in succeeding dry years the GWR of the SRC plantation is very low or even missing, compared to winter wheat or grassland. Agroforestry (AF) in form of e.g. an alley cropping system with strips of SRC can be seen as a compromise to balance between woody biomass production and GWR issues. However, further investigations and analyses are needed to study the effects of AF on the water budget. Interactions of trees and crops in AF are quite complex due to the differences in model sensitive parameters like leaf area index, transpiration, root distribution, root depth and effects on microclimate. A positive effect of AF alleviating the negative influence of SRC on GWR can be expected. Especially in regions with low water availability AF in an appropriate amount and design can help to provide woody biomass by not endanger water resources