Chronosequences of sites withdrawn from grazing for 0, 11, and 16 years were sampled by Kieft, in a grassland (Bouteloua spp.) area and a shrubland (Atriplex canescens) area on and near the Sevilleta National Wildlife Refuge in central New Mexico. Although Kieft hypothesized that individual values of the soil C triangle would increase and that the ratios would decrease with time since grazing, differences in microbial parameters between sites located along the chronosequences were generally not significant. Grazing did not appear to have a major effect on microbial biomass and activity on these grassland and shrubland chronosequences. Unfortunately, this does little to resolve the controversy regarding the effects of grazing on plants and soil microorganisms, since Kieft found neither increase nor decrease in soil microbial processes on the grazed sites. The plant-canopy effect on soil microorganisms was very consistent and was reflected in the individual soil C parameters (organic C, microbial C, basal respiration rate) as well as in the microbial: organic C ration and the metabolic quotient.
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