Transpiration of a hybrid poplar plantation in Saxony (Germany) in response to climate and soil conditions

The aim of this study was to investigate transpiration and its main driving factors on the example of a hybrid poplar plantation with the clone Populus maximowiczii x P. nigra, cv. Max 1 on a site in the hilly loess region of Saxony (Germany). Transpiration was measured using sap flow techniques during the 2007 and 2008 growing season. At the same time, throughfall, soil moisture dynamics and soil physical properties were also measured. Total transpiration rates amounted to 486 mm and 463 mm, respectively, during the 2 years. Maximum daily transpiration rates reached 6.7 mm/day, while an average of 2.2 mm/day for the entire growing season was recorded. The main controlling factors for stand transpiration included the evaporative demand, water availability and soil temperature. The information was implemented into a simple empirical model for the prediction of transpiration. It can be concluded that large-scale establishment of poplar plantations will result in a distinct reduction in groundwater recharge. On the other hand, surface run-off and soil erosion may decrease. Due to limited water availability in the late growing season, the growth potential of the tested clone cannot fully be exploited at many sites in Germany.