soilandwaterS09s

soilandwaterS09s - SA1 Terrestrial and Aquatic Environments...

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Terrestrial and Aquatic Environments as Microbial Habitats Terrestrial and Aquatic Environments as Microbial Habitats Soils Soils : may be organic (rare) or (commonly) inorganic soil formation: a complex process; requires many years (i.e., 1000s) to reach mature soil profile microbial activities contribute (metabolic products, e.g. organic acids, CO 2 ), as do other physical and chemical processes (e.g., freeze-thaw, wind and water erosion, dissolution by dilute acids) animals (e.g., worms) living in the soil also contribute to soil structure and fertility by mixing and aerating upper layers SA1 (chpt 23, 24 12 th ; chpt 19 11 th )
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SA1a O A B clay-rich soil, Carbondale Illinois mature soil profile (Fig 23.10)
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microenvironments within a soil aggregate clay, mineral, organic matter surfaces air-filled, water-filled pore space determinants of microbial activity in soil water availability → affects O 2 availability SA2 (Fig 23.11)
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Plants Plants : greatly influence soil habitat, as well as serving as potential habitat rhizosphere = soil that surrounds plant roots • an environment that is significantly different from bulk soil environment → “ rhizosphere effect bacterial physiological group rhizosphere soil (number/g) control soil (number/g) approx R:S ratio ammonifiers 5 x 10 8 4 x 10 6 125:1 gas-producing anaerobes 3.9 x 10 5 3 x 10 4 13:1 anaerobes 1.2 x 10 7 6 x 10 6 2:1 denitrifiers 1.26 x 10 8 1 x 10 5 1260:1 aerobic cellulose-degraders 7 x 10 5 1 x 10 5 7:1 anaerobic cellulose degraders 9 x 10 3 3 x 10 3 3:1 endospore formers 9.3 x 10 5 5.75 x 10 5 1:1 (modified from Prescott et al. 1996)
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soilandwaterS09s - SA1 Terrestrial and Aquatic Environments...

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