MBIO 3280 Lecture Notes - Lecture 20: Vadose Zone, Loam, Aquifer
1 Nov 2017
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Document Summary
Porosity: allows movement of air, water and microbes, distances between particles can be um to mm. Moisture (water content: most important variable, affects physical structure, chemical composition, gas diffusion, microbial survival and activity, microbes adapt to intermittent dryness (spores, cysts) Texture: clay, pores are smallest in soil, silt, medium pore size, ex. Surface area of soil particles increases water absorption substratum for microbial growth. But, clay is negatively charged (decreases the attachment and growth of microbes) Most soils are mineral soils: weathering of rocks limited in organic carbon. Organic soils (bogs and marshes) are abundant in organic carbon from sedimenting plant matter. Humic material (humus: decaying plant material becomes unrecognizable, easily degraded compounds are gone, variable chemical composition, complex, highly cross-linked polymers, spongy structure that absorbs water, ions, organics. O2 supply limited in water, wet soils are therefore more anaerobic.
