Impacts of forest management on the carbon budget of European beech (Fagus sylvatica) forests

Forests cover about 31% of European land area (excluding CIS countries). Except for some protected or inaccessible areas, all of these forests are used by humans. The influence of different silvicultural treatments on timber production and the amount of carbon ill tree biomass is well known. In contrast, data on the impacts of forest management, particularly of moderate silvicultural practices in hardwood forestry, on the amount of organic carbon in the mineral soil (SOC) are very limited. A case study on differently managed European beech (Fagus sylvatica) forests in Germany showed that the successive removal of trees in a shelterwood system and a selection system reduces the amount of carbon stored in tree biomass on average by about 30% compared to an unmanaged forest. Biomass carbon at the even-aged stands of the shelterwood system showed a clear age-related maximum curve (maximum at a stand age of about 100 years: 230 tC ha(-1)). Leaf litter resting on the mineral soil at the end of September before litter fall began (0.8-2.8 tC ha(-1)) was mainly affected by annual leaf litter fall of the previous year and the basal area (R-2= 0.67). Excluding the effect of variations in the clay content and the C:N ratio via statistical analysis soil organic carbon in the upper mineral soil (0-15 cm soil depth, SOC0-15) did not correlate with stand age, and mean SOC0-15 of the study sites or silvicultural systems (ranging -between 40 and 48 tC ha(-1)) did not differ significantly. These results indicate that the effects of disturbances due to shelterwood cuttings or selection cuttings on SOC0-15 are small compared to the high small-scaled variability of soils, the favourable growing conditions at the Hainichi-Dun region that allow for a rapid canopy closure after tree harvesting, and potential long-term effects of historical forest use. However, there was a trend to lower mean SOC0-15 at the managed sites (42 tC ha(-1)) as compared to the Linmanaged site (48 tC ha(-1)). This trend may represent a Cumulative effect of the cessation of timber use at the unmanaged forest for the last 35 years. The impacts of the investigated moderate silvicultural practices on the carbon budget of European beech forests were lower than those reported for clear cuttings in temperate forests. A major challenge of future research is to quantity the long-term effects of historical forest use on the Current amount of SOC and to separate them from the effects of recent forest management. A crucial precondition for these investigations is the establishment of representative long-term, managed and unmanaged study sites. [References: 124