Soils as Habitats for Microorganisms
It is more than a small step into the living sphere of microorganisms. They have special demands for their living space, like plants for their rooting space. The supply of heat, water, soil gases, organic matter and inorganic nutrients presents the genera
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16.1 Introduction It is more than a small step into the living sphere of microorganisms. They have special demands for their living space, like plants for their rooting space. The supply of heat, water, soil gases, organic matter and inorganic nutrients presents the general framework. The range of their homes and their activities at the micro-scale is dominated much more directly by physical and chemical laws. Transport mechanisms of dissolved organic and inorganic nutrients as well as gases primarily follow the forces of diffusion rather than active transport mechanisms. Originally, physically driven movements, e.g. cryoturbation, become more important than biomechanical activities, e.g. bioturbation. This holds especially true for the polar soils, where only few micro-arthropods and nematodes can be busy at this job (Block 1984). Thus, we shift from animal-mediated transport of material and breakdown of structural matter and approach an environment of chemical processes driven by physical processes, mainly temperature. This applies to the final degradation of organic matter by enzymes as well as for the chemical weathering processes. Antarctic coastal terrestrial environments are only small in extent. Broad classifications into ‘dry, mesic and wet’, as used in the Arctic, can only just be adopted – except for the large areas of the Dry Valleys.Very different areas can be found close to each other, and thus very different conditions for plants and soil-dwelling organisms. We might ask what are the necessary, essential or even indispensable conditions for sustaining microbial life in soils, and what are the conditions to which the organisms have to respond?
16.2 The Microbial Environment The microbial environment, however, should not only be described as a space which limits life processes, but also as a habitat which promotes different life strategies. Physical and chemical variations lead to many niches and individual habitats. This variability over space has made field measurements extremely variable and has long been recognised as one of the main nuisances Ecological Studies, Vol. 154 L. Beyer and M. Bölter (eds.) Geoecology of Antarctic Ice-Free Coastal Landscapes © Springer-Verlag Berlin Heidelberg 2002
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M. Bölter and H.-P. Blume
of environmental research (Addicott et al. 1987; Smiles 1988; White 1995). The arrangements in space can be accomplished by strong variability of nutrients and their individual concentrations, leading to numerous gradients. Although this variability might be regarded as a disturbance factor in environmental descriptions, it is the result of the physical, chemical and biological processes. Nevertheless, the Antarctic soil environment – without bioturbating animals – is basically a rather conservative environment and tends to reduce strong physical shifts. This is, however, a matter of scale and the abundance of organisms which determine its statistical distribution. Much of the pattern of distribution is due to reproductive phenomena, i.e. the formation of microcolonies and -co
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