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Development prognosis of forest ecosystems in the light of hierarchy theory

Ulrich, Bernhard
Forstwissenschaftliches Centralblatt 1999 v.118 no.1-6 pp. 118-126
base saturation, canopy, defoliation, forest ecosystems, forest soils, monitoring, nitrogen, nutrients, risk, soil depth, space and time, stand development, trees, Germany
Forest ecosystems are characterized by a hierarchy of their processes, differentiated according to a space and time scale. Thus, the hierarchy theory can be applied, which allows conclusions about self-organization, stability conditions, and the reaction to disturbances. Process patterns allow to judge whether a process is undisturbed or disturbed. This is demonstrated by growth patterns in the root, stem and canopy domain. Defoliation indicates that disturbances have reached the level of the whole tree. The monitoring of defoliation should be continued as an indicator for destabilization. Base saturation is a pattern for the storage and buffer function of the soil in respect to nutrients and acid load. On more than half of the forest soils in Germany base saturation is too low even at greater soil depth. This, together with elevated nitrogen deposition, is taken as criterion for risks in respect to stand development and regeneration. Measures for the stabilization of forest ecosystems are mentioned.