Growth and fructification of a norway spruce (Picea abies L. Karst) forest ecosystem under changed nutrient and water input

Abstract

In the mountainous region of a low mountain range (Solling mountains) an ecosystem manipulation experiment with roof constructions underneath the canopy of a 60-year old Norway spruce stand is run since 1991. The responses to artificially prepared, "pre-industrial" through fall and to extended summer droughts with intensive rewetting are investigated in two parallel roof experiments and evaluated against a roof control and an ambient control plot. After long terms of drought distinct reactions of the trees were visible in growth. The reactions of height-increment were more distinct than the effects on diameter-increment. Furthermore, the trees of the dominating social classes (Kraft I and II) reacted more on low water-supply than the dominated trees. So it is probable that a long lasting stress by drought effects changes the stand structure, too: the vertical structure of a stand would get more homogeneous and the diversity in the stand structure would decrease. Reduced input of sulphur and nitrogen did not show any distinct growth reactions within the 9-year observation period.