The role of interception in the water budget of spruce stands in the Eastern Ore Mountains/Germany

In the Eastern Ore Mountains large areas situated at the ridge are deforest ed mainly due to high levels of atmospheric sulphur dioxide. For the quanti fication of element budgets the water budget of small forested experimental watersheds is recorded, one situated in the upper, the other in the lower mountains. Interception is a major part of forest evapotranspiration in hum id climates due to their low aerodynamic resistances. Interception was meas ured representatively at two spruce sites. It made up 51% of open-field pre cipitation in summer at the lower elevation site but only 28% at the higher site. The absolute figures of interception and its portion of eddy-covaria nce-energy-balance (ECEB)-evapotranspiration (lower site: 44%, higher site: 33%) show the importance of interception for evapotranspiration. ECEB-evap otranspiration was compared to the hydrological difference of precipitation and discharge of bath watersheds. The water budget of the ridge watershed showed a marked difference explained by fog interception as important addit ional water input for fog-rich sites, also seen by the ratios and magnitude of interception loss above. The high atmospheric coupling of spruce forest s could be seen by near-equality of evapotranspiration at both sites despit e an altitudinal gradient of 360 m. All these findings show the importance of proper measurement and modelling of interception for water and element b udget studies of forested watersheds. (C) 1999 Elsevier Science Ltd. All ri ghts reserved.