Spatial distribution of fungal and bacterial biomass in southern Ohio hardwood forest soils: scale dependency and landscape patterns

The scale dependency and landscape patterns of fungal and bacterial biomass, soil pH, organic C and moisture were examined in four hardwood forests in southern Ohio. Analysis of variance revealed significant differences in microbial biomass and soil chemistry among four forests (regional scale), among three contiguous watersheds within each forest (local scale), along gradients of moisture within watersheds (topographic scale) and upslope and downslope of individual red oaks (individual tree scale). Fungal and bacterial biomass varied significantly along gradients of moisture within watersheds while only bacterial biomass varied among sites and fungal biomass among watersheds. Fungal-to-bacterial biomass (F-to-B) ratio varied only among forests. Soil chemical properties varied at all scales examined except among watersheds. Hierarchical modeling of microbial patterns independent of scale revealed that while bacterial biomass and organic C are constrained by soil moisture present at the time of sampling and soil chemistry, fungal biomass is constrained by measures of long-term moisture patterns and soil texture. The resultant models also revealed that strong scale-independent models of bacterial biomass and organic C could be produced by scaling-up results from sampling points to the region, whereas this was not possible for fungal biomass and F-to-B ratio due to poor resolution at the local scale.