The Höglwald field experiments – aims, concept and basic data

An outline is given of the aims and the concept of the interdisciplinary research work exerted at the Hoglwald, an experimental field station in Southern Germany. The Hoglwald lies in the temperate suboceanic broadleaf zone. Under natural conditions beech would prevail. The soils are mostly developed as Typic Hapludalfs, weakly aquic in the argillic horizon and strongly acidified in the topsoil. The investigations performed in stands of Norway spruce (Picea abies L. Karst) and European beech (Fagus sylvatica L.) were initiated in 1982/83. The main aims are (1) to test experimentally the soil acidification hypothesis predicting root damage by aluminium toxicity, (2) to study the effects of compensatory liming with and without artificially increased acid input, (3) to investigate comprehensively nitrogen cycling and turnover including studies about (a) N-gas fluxes, (b) root reactions to excess N-supply, (c) N-assimilation in the canopy, (d) effects of experimentally increased N-input on trees, soil and seepage water chemistry, and (e) N-turnover under natural and experimentally produced drought periods. Part of these investigations were also performed in a mixed stand of spruce and beech to show possible interactions of both species.