How does the moisture content of the soil affect biological activity ?
The majority of soil organisms are aerobic, meaning they require oxygen to live, and all require moisture. As the water content increases, water replaces air in soil pores. Above a certain water content organisms consume the oxygen in soil pores faster than air can diffuse from the soil surface. The organisms that depend on air either suffocate or go dormant and microbes adapted to live in the absence of oxygen (anerobic microbes 3) become active. The anaerobes remain the dominant active community until the soil moisture level decreases sufficiently for air to diffuse into the soil depths, bringing back to life the dormant aerobic microbes.
