Vplyv klimatických zmien na vývoj lesných ekosystémov hornej hranice lesa
Analyses of dynamic changes of natural ecosystems of the upper three line using the Forest Gap Model was applied to predict effects of climate changes after doubling the concentration of carbon dioxide (CO2). The Forest Gap Models belong into the group of dynamic models that are able to calculate varied parameters of forest trees in time series. The models are based on simulations of natural regeneration, growth, mortality of each tree in the studied ecosystem. To simulate effects of double increased concentration of carbon dioxide expected in the year 2070, the regional models of climate change (regional interpretation of the values of climatic elements based on general atmospheric circulation models) from the territory of the Slovak Republic were applied. The values the regional models of climate change were also derived from the Canadian Climate Centre Model (CCCM). The following input parameters of individual forest trees were used in the simulation: the maximal age of tree, the maximal tree width (1.3 m), the maximal height, and the parameters of natural tree regenerations. The model includes several response functions that cover environmental effect of individual trees such as the lights requirements, the temperature requirements, and moisture requirements. Characteristics of individual tree species (age, diameter, height) incorporated in the simulation algorithms were collected in the three long term monitoring plots in the nature reserves by the Forestry Research Institute in Zvolen. Two monitoring plots located in the Piľsko (1 250 m a.s.l.), Oravské Beskydy Mts., and in the Vajskovská valley (1 300 m a.s.l.), Nízke Tatry Mts., represented mountain forest ecosystems dominated by Fagus sylvatica, Picea abies, Abies alba, and Sorbus aucuparia. The third monitoring plot dominated by Pinus mugo, Picea abies, and Sorbus aucuparia was also sited in the Vajskovská valley, 1 700 m a.s.l., represented the dwaft pine communities above the upper tree line (subalpine zone). Simulations of the climate change effects on tree species were based on climatic amplitudes of their geographic range. The model simulations were carried out for the current climate conditions (means 1951-80) and for the expected climatic conditions following the model CCCM. The model simulations showed significant changes in the potential forest production and distributional patterns of tree species in each studied site. The computer simulations of the two sites located in the mountain forest zone showed significant increase of relative abundance of Fagus sylvatica and Acer pseudoplatanus, significant decrease or almost absence of relative abundance of Picea abies, and increase of the total biomass production for 17–30 %. The simulations showed the most drastic changes in the subalpine zone. The original dwarft pine community will be dominated by Picea abies, dominance of other tree species will also increase, yet Pinus mugo will decline, and the total biomass production will increase for 200–300 %. The results should be, however,. interpreted carefully since the applied models did not incorporate possible effects of chemical climate change e.g., increased concentration of tropospheric ozone, increased UV-B radiation, immissions, etc.
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