Verändertes Klima - veränderte Vegetation : Das Wildbachsystem

1998

7 Abb., 51 Lit. Ang.

Unselbständiges Werk

8632

200096737

Two different simulation models were applied to evaluate potential climate-induced longterm changes in the species composition of mountain forests in Central Europe and its potential impacts on landslide hazards. The first approach is a static equilibrium model that allows estimation of the potential natural forest community on any point of the study area (ca. 40'000 km¬) in a 250 m-grid. The second model in a dynamic forest succession model that has been used to generate the development of individual species biomass through time on scattered locations. Both models agree that under temperature increase beech dominated communities in the collinesubmontane belt might be replaced by oakhornbeam communities. In the high montante and subalpine belt the dominance of needle trees will be seriously threatened by an invasion of deciduous species from today's low montane and submontane belt. Under moderate warming (increase of the mean annual temperature between 1,0° C and 1,4° C or increase of July temperature by 1,5° C, depending on model version), 30 to 55 % of the Swiss forest inventory points (FIP) in a 1 km-grid show a change in the potential natural vegetation type (number of vegetation types that were distinguished based on floristic affinities = 15). The range of the percentage values depends on the model version used. Under strong warming (increase of the mean annual temperature between 2,0° C and 2,8° C or increase of July temperature by 3,0° C, depending on model version applied), 55 to 89 % of all FIP considered change the potential natural vegetation unit. A comparison between the potential natural distribution of dominant tree species and the actual distribution (based on FIP data) shows that under current climate conditions approximately 25 to 30 % (depending on the model version) of all FIP are considered as badly adapted in terms of species composition, i.e. less than 20 % of the actual basal area consists of tree species that are expected as dominating taxa under natural conditions. This result holds for trees with a DBHß 12 cm. Moderate warming increases the percentage of badly adapted FIP by 5 to 10 %, whereas strong warming leads to a 10 to 30 % increase of all FIP considered. Concerning landslide hazards, the study shows that under warmer and wetter conditions forest communities that are strongly associated with landslide phenomena slightly increase in area. Under warmer conditions and no increase of precipitation the area of forest communities that are strongly associated with landslide phenomena decreases considerably.