THE SOLLING ROOF PROJECT - SITE CHARACTERISTICS, EXPERIMENTS AND RESULTS

The results from roof experiments in the Selling forest in central Ger many are reported. A 'clean rain' manipulation study and a drought/rew etting experiment are run side by side in a 60-year-old Norway Spruce (picea abies KARST.) stand. The results are presented in an integrated , interdisciplinary manner and comprise soil water chemistry, root gro wth, and aboveground stand response. In the clean rain experiment with strong input reduction of S and N a temporal response sequence of soi l water chemistry --> root growth --> above-ground reaction occurs. Ni trate leaching is efficiently turned down to very low levels on rather short-term (1-2 yr after start of manipulation). In the drought/rewet ting experiment the effects of induced drought stress are strongest an d quickest on the above-ground parameters of the spruce stand. Growth and photosynthetic capacity are reduced, while fine root growth reacts indifferently. It may be concluded from the results that: in spruce f orests on acid soil atmospheric element input largely controls soil so lution chemistry and output; N saturation may be reversed in such ecos ystem types by strict air pollution control measures and that spruce f orests exhibit a time-lagged response to a changing chemical environme nt, but rapid responses to drought stress. (C) 1998 Elsevier Science B .V.