The Solling roof project — site characteristics, experiments and results

Abstract

The results from roof experiments in the Solling forest in central Germany are reported. A ‘clean rain’ manipulation study and a drought/rewetting 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 growth, and aboveground stand response. In the clean rain experiment with strong input reduction of S and N a temporal response sequence of soil water chemistry → root growth → above-ground reaction occurs. Nitrate leaching is efficiently turned down to very low levels on rather short-term (1–2 yr after start of manipulation). In the drought/rewetting experiment the effects of induced drought stress are strongest and 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 forests on acid soil atmospheric element input largely controls soil solution chemistry and output; N saturation may be reversed in such ecosystem types by strict air pollution control measures and that spruce forests exhibit a time-lagged response to a changing chemical environment, but rapid responses to drought stress.