Population estimates of fungi, bacteria, and actinomycetes in desert soil were determined with respect to soil depth and distance from shrubs. In general the highest numbers of microbes were found at the shrub base; the lowest numbers were found in the interspaces. While the total number of organisms usually declined in deeper soil, the relative importance of the actinomycetes increased. These population trends are attributed to substrate availability and utilization and interspecific interactions.
As the soils became drier and warmer the total number of microorganisms decreased. Mold populations remained at about the same level during the study. While the numbers of both bacteria and actinomycetes declined, the relative importance of the actinomycetes increased.
Vollmer, A. T.; Au, F.; and Bamberg, S. A.
"Observations on the distribution of microorganisms in desert soil,"
Great Basin Naturalist: Vol. 37
, Article 8.
Available at: http://scholarsarchive.byu.edu/gbn/vol37/iss1/8