FIGURE 4.6. Daily estimates of numbers of bacteria, amoebae, and flagellates in the humus layer of a pine forest after rain (from Clarholm, 1994).

Further information on protozoan feeding activities and their impacts on other organisms and ecosystem function are given in Griffiths (1994), Zwart et al. (1994), Poussard et al. (1994), and Bamforth (1997). Bonkowski et al. (2000) suggest that protozoa, and the bacteria they feed upon in the rhizosphere, produce plant-growth-promoting compounds that stimulate plant growth above and beyond the amounts of nitrogen mineralized in the rhizosphere. This is an interesting area of new process-oriented research, and we can expect further developments in the near future.

Protozoa and other microfauna are quite sensitive to environmental insults, and changes in the distribution and activities are diagnostic of changes in soil health (Gupta and Yeates, 1997). We address the issue of soil health more extensively in Chapter 8.

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