Analyse des Vorkommens, der Morphologie und der genetischen Diversität von Biologischen Bodenkrusten extrazonaler Gebirgssteppenstandorte der nördlichen Mongolei

Abstract

At extrazonal mountain steppe sites in the western Khentej in Northern Mongolia there was to be explored the appearance, the morphology and the genetic diversity of Biological Soil Crusts. At the study site the Siberian taiga borders on the Mongolian-Daurian forest steppe; this situation results in a unique intermixture of vegetation sites, such as the dark taiga, the light taiga and forest steppe (Dulamsuren, 2004). Thus the assortment of boreal, temperate and dauric elements the forest steppe is eminently rich in species (Mühlenberg and Samyia, 2002). The habitats of Biological Soil Crusts in the western Khentej are not forested because of a combination of climatic and edaphic factors (Dulamsuren et al., 2005) and are to be divided into the vegetation types Carex amgunensis-, Festuca lenensis-, Pulsatilla ambigua- and the Artemisia frigida-mountain-dry-steppe und Ulmus pumila-open woodland (Dulamsuren, 2004). For this vegetation types there were to be analyzed the requirements between appearance and composition of Biological Soil Crusts and different biotic and abiotic factors. There were found weak correlations between the distance from the ridge of the mountain, the inclination and the exposition and the number of cryptogamic species for the Artemisia frigida-mountain-dry-steppe. For the Artemisia frigida- mountain-dry-steppe and the Artemisia frigida- Pulsatilla ambigua- mountain-dry-steppe there were detected weak negative correlations between the percentaged plant cover and the number of cryptogamic species. A further study analyzed the cover of Biological Soil Crusts on the one hand in relation to the cover of plants generally and on the other hand in relation to the cover of plants of different height- and growth- form classes. The general plant cover was correlated negatively with the cover with Biological Soil Crusts. This was also the case for the relation of cover with grass and the cover with medium herbs (herbal, low radius, up to 30 cms height and not much shading). As the results vary in a high degree, there is assumed another not regarded and unknown factor for the appearance and the composition of Biological Soil Crusts. Furthermore the variation in genetic diversity of Biological Soil crusts, especially of Bacteria and Archaea of two different sites with a diverging degree of disturbance was to be shown. For this there were constructed site-gene banks of bacterial 16S-rDNA; the archeal diversity was shown by DGGE (denaturating gradient gel electrophoresis). From the 10S-rDNA- sequence data there could be deduced phylogenetic trees and a classification by comparing with RDP-II-data could be accomplished. Both sites differ forasmuch as at both there indeed predominate Proteobacteria, but at the less disturbed site the Cyanobacteria formed the second largest group, while at the more disturbed site these were the Bacteroidetes. At both sites the third group were Acidobacteria. At the more disturbed site there occured additionally to the phyla Firmicutes, Gemmatimonadetes and Planctomycetes and the class Deltaproteobacteria found at both sites, while at the less disturbed site there occured additionally only one species of Nitrospira. DOTUR analysis showed that both sites were exhausted on species level to about 35 % and on the level of the phylum to 78-92 %. Rarefaction analysis showed that the bacterial diversity on the level of the phylum was in both cases near saturation, while the bacterial diversity on species level was not bailed. The Shannon-Wiener-Index for biodiversity was for the less disturbed site and at the distance of 3 % (species) 3,93 and at the distance of 20 % (phylum) it was 2,12. For the more disturbed site it was at a distance from 3 % 4,39 and at the distance of 20 % 2,64.