| The overall goal of this research was to determine the scale dependency and landscape patterns of microbial community dynamics. Initial studies evaluated whether soil acidification, a widespread, chronic disturbance and forest thinning, an acute disturbance, produced interactive effects capable of producing ecosystem level changes. Although, interactive effects were detected, failure to account for spatial distribution of microbes in soil probably decreased the ability to model biomass. Further studies focused on the importance of scale and spatial distribution in evaluating microbial communities.; N mineralization, nitrification, bacterial and fungal biomass, pH, organic C and moisture were examined in four hardwood forests in southern Ohio. Analysis of variance revealed significant differences in N mineralization parameters, microbial abundance and soil chemistry at landscape (among forests), local (among contiguous watersheds within forests), topographic (along gradients of moisture within watersheds) and individual tree (upslope and downslope of individual trees) scales. At the regional scale N mineralization, nitrification, NO{dollar}sb3sp-{dollar} pool size, bacterial abundance, fungal to bacterial biomass ratio, and organic C varied significantly. At the topographic scale, microbial abundance and most N mineralization parameters varied significantly, while fungal abundance, organic C and inorganic N pool sizes varied at the local scale. Causal analysis of microbial parameters performed independent of scale revealed that scaling-up models of nitrification from plot to region should be straightforward, whereas scaling-up N mineralization will require incorporation of independent scaling paradigms at three (or more) spatial scales. Causal analysis of microbial abundance independent of scale also revealed that strong models of bacterial abundance and organic C could be produced by scaling-up results from sampling points to the region, whereas this was not possible for fungal abundance and F:B ratio due to poor resolution at the local scale. Overall, these results suggest that microbial communities in forest soils are spatially structured at a number of scales and this must be accounted for in order to produce accurate models of belowground function and detect fine scale changes as a result of natural or anthropogenic disturbance. |
