Modeling dynamics of forest ground vegetation diversity under different forest management regimes

摘要

Forest ground vegetation constitutes the largest number of plant species that participate in forest dynamics. Single species or species groups of forest ground vegetation can be used as indicators for site conditions. Ground vegetation has to be accounted in forest simulation modelling if biodiversity dynamics are evaluated to serve the purpose of sustainable forest management. The usual approach is to segregate ground vegetation into plant functional types. However, there are other methods that could be used. In our contribution we propose to split ground vegetation into ecological-coenotic species groups. An application of the ecological-coenotic approach allowed for a forecasting of the dynamics of forest ground vegetation diversity on the basis of forest ecosystem modelling outputs, standard forest inventory data, and regional phytosociological data sets. A new software BioCalc designed for the forecasting of dynamics of forest ground vegetation diversity, and the EFIMOD model of the forest growth and element cycling in the forest-soil system is used for simulating the forest ecosystem parameters under different forest management regimes. An application of the proposed method for a study area, dominated by Pinus sylvestris and Betula sp., situated in the Central European Russia is discussed. Two hundred-year dynamics of ground vegetation composition, forest types and species diversity is analysed under four forest management scenarios: natural development (NAT); selective cuttings (SCU); authorized by Russian legislation clear cuttings (LRU); non-authorized by the legislation but widespread clear cuttings (ILL). The simulation results showed that the total number of forest types is higher in all scenarios with cuttings relative to the NAT scenario. However, the NAT strategy leads to the growth of coniferous-broad-leaved forests close to the climax forest type of the study area. Cuttings hinder the development of climax forest structure due to the low level of deadwood in harvested forests and the absence of species-rich forest units dominated by nitrophilous tall herbs in the understorey. The NAT strategy leads to the highest species diversity in ground vegetation if a free forest development has taken place for rather long time, i.e., more than 100 years in the study area. The sum of species diversity is rather low for SCU, LRU, and ILL scenarios. It is 0.8, 0.7, and 0.6, respectively, in comparison with the NAT scenario. The SCU scenario lead to a simplification of ground vegetation together with a conservation of nemoral and boreal species. Scenarios with clear cuttings (LRU and ILL) maintain piny and meadow groups in ground vegetation. None of the forest management scenario leads to the maintenance of the whole set of ecological-coenotic groups in ground vegetation. Only a spatial combination of different management regimes in the forest area is necessary for the biodiversity restoration and maintenance..