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|ŠUMARSKI LIST 1-2/2013 str. 32 <-- 32 --> PDF|
mountain slope on Vogelsberg in central Germany showed that some genotypes are more frequent at the higher elevated stands than in lower elevated stands and vice versa (Sander et al. 2000).
Beech populations sampled from different sites on Gorjanci Mountains appeared to be genetically different. Genetic differentiation, as expressed by the proportion of alleles not shared between lower and higher elevated population was relatively high for the small geographical region studied (d0 = 6.1 %). For example, the genetic distances of beech populations in Germany (Bavaria) studied using the same analyzing method were reported to range between d0 = 2.6 % and d0 = 10.9 % (Konnert and Henkel 1997). The observed clines at gene loci Aco-B, Idh-A, 6-Pgdh-A and the allelic distances from 13 % to 17 % between sampled stands in Gorjanci Mountains could indicate that gene flow between sampled stands is limited or that specific site conditions in sampled locations demonstrate a possible effect of environmental adaptation to this gene loci.
The structure of the obtained genetic information is the result of the sampled stands’ high adaptation and specialization to specific homogenous environmental conditions in the investigated ecosystems and historical influences of anthropogenic impacts. Under constant environmental conditions, the higher genetic variability within populations means a higher fitness of the population. This situation remains optimal as long as the site conditions are not affected by climate changes and manmade selection to that extent that a process of adaptation to new site conditions is interrupted.
As reported Mátyás et al. (2010) for the beech forests at the xeric limit in Southeast Europe (case Hungary), the very similar pattern might be expected at Gorjanci Mountains where low-elevation beech forests (Hedero-Fagetum forests) might be threatened by the warming more than higher-elevation beech forests (Lamio orvalae-Fagetum forests). In more preserved, less degraded sites of Hedero-Fagetum forest, beech is well developed and has high competitive potential against other tree species. However, at more degraded sites of this forest community, where intensive human influence took place in the past, beech is not so competitive and its growth is less intensive, and the quality of beech stems is not so high. In such degraded sites of Hedero-Fagetum, some species of earlier forest development stages, like Quercus petraea, Q. cerris and Carpinus betulus, are more competitive and more frequent. In such human-degraded forms of this forest community, the coppice forest is more common. In such forest conditions, the lability of forest sites with the dominate Luvisol to moderately dystric Cambisol might have been aggravated by inappropriate forest management in the past, such as litter-raking, and intensive use without any management concept. Due to old settlements at the bottom of Gorjanci Mountains, the forests in the hilly zone have been under human impact. Thus, the relative high share of coppice, litter-raking forest sites planted by non-native tree species and other degraded forests in this area reflect the negative human impacts in the past. The mountain beech forests of Lamio orvalae-Fagetum at Gorjanci Mountains, compared to more degraded sites of Hedero-Fagetum forest, have a stable biocenotic structure. Even after larger clearings, all development stages of the forests can be renewed by beech trees. Due to their more remote and isolated location, the sites of these forests were not transformed into agricultural land (Marinček and Čarni 2002). Beside the genetic potential of beech, the future development of these forests is related to the past and future land use, and to impact of climate changes (Kutnar and Kobler 2011) and other degradation processes (Kutnar et al. 2011). As the ability of forest ecosystems is strongly related to the existence of intrapopulation genetic diversity, even in mixed natural stands, the stability is threatened as soon as the genetic diversity of one of the involved species is threatened; there is a great need for investigations of the genetic basis of forest ecosystems in geographically smaller but heterogeneous areas.
The sampled populations of beech from Vrhovo and Kozarje sites are autochthonous. The observed genotypes were consistent with the expectations under random mating and no restriction in genetic multiplicity was determined. The Kozarje population, from the higher mountainous zone, showed higher genetic diversity than the Vrhovo population from the hilly area. Results of our study verify the existence of genetic differentiation between two local beech populations in Gorjanci Mountains associated with variation of significantly different forest sites, different ecological conditions and different forest-management history. Further studies should be preformed to prove the hypothesis of the interaction between disruptive natural selection and gene flow in development of among population genetic differentiation. Attention to the transfer of beech reproductive material from higher to lower elevations of the Gorjanci Mountains is recommended.
This study took place partially within the framework of research tasks of projects: V4-1140, V4-492, L4-6232 and research programme P4-0107 financed by the Slovenian Research Agency and co-financed by the Ministry for Agriculture and Environment. The authors are grateful to Dr.