chapter_30 - Soil as an Environment for Microorganisms...

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1 1 Chapter 30 Microorganisms in Terrestrial Environments 2 Soil as an Environment for Microorganisms dominated by inorganic geological material modified by organisms to form soils in ideal soils, microorganisms in close contact with oxygen rainfall and irrigation alter ideal state “mini” aquatic environments water-logged soil CO 2 , CO and concentrations of other gases altered 3 Figure 30.1 4
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2 5 Microorganisms in the Soil Environment peds – aggregated soil particles Figure 30.2 6 Microbial populations in soils numbers can be very high only small portion have been cultured microbes are constantly being added to soil most do not survive make important contributions to biogeochemical cycling gram-positive bacteria are important members of soil communities 7 8 Geosmin produced by filamentous actinomycetes gives soils characteristic earthy odor
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3 9 Organic matter transformations soil insects and animals carry out decomposition and physical reduction increases surface area and makes nutrients more available to bacteria and fungi microbes some prefer easily available substrates; others prefer more resistant substrates differ in terms of required substrate concentration 10 Transformations… microbivory use of microorganisms as a food source microbial loop carried out by soil protozoa results in increased rates of nitrogen and phosphorus mineralization many organisms release hydrolytic enzymes into soil 11 Microorganisms and the Formation of Different Soils newly exposed geological materials weathering pioneer colonizers (e.g., cyanobacteria) succession of organisms soils of different types 12 Tropical and Temperate Region Soils Soil fertility impacted by relative rates of primary production and decomposition these impacted by temperature and rainfall slash-and-burn agriculture cutting and burning of vegetation, followed by agricultural use in tropical regions can cause almost irreversible degradation of soil
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4 13 Figure 30.3 14 Cold Moist Area Soils low levels of both primary production and decomposition many nutrients immobilized in accumulated organic matter bogs can be formed very sensitive to disturbance and pollution 15 Deserts Soils desert crusts
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This note was uploaded on 01/11/2009 for the course BICS 300 taught by Professor Dr.d.w.smith during the Spring '07 term at University of Dundee.

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chapter_30 - Soil as an Environment for Microorganisms...

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