Wie viel Totholz braucht der Wald? | Dead wood in managed forests: how much is enough?

Abstract

Dead wood is of paramount importance for forest biodiversity. For this reason it was adopted as an indicator for sustainable forest management by the Ministerial Conference on the protection of forests in Europe. This paper aims to answer the question of how much dead wood is necessary for the maintenance of biodiversity in sub-alpine spruce forest ecosystems. For this purpose we studied the habitat preferences of the three-toed woodpecker, a bird species that depends heavily on dead trees. Previous ecological studies had already demonstrated that this woodpecker is an indicator of spruce forests with a high degree of naturalness and biodiversity. Our field study in Swiss sub-Alpine spruce and Swedish boreal forests showed that, below a threshold level of about 20 m3 standing dead trees per ha, the probability of finding these woodpeckers drastically decreases. Similar results were obtained using a bioenergetic model, which calculated the energy requirements of this insectivorous woodpecker. Based on the results, our recommendation is to ensure a scattering of dead-wood rich areas in forest landscapes. Each area should cover about one square kilometre and have a mean of 5% of standing dead trees (≥ 18 m3 ha–1), and a total of approx. 9% of dead wood(≥ 33 m3 ha–1 standing and fallen).