Spatial distribution of fungal and bacterial biomass in southern Ohio hardwood forest soils: fine scale variability and microscale patterns

Fine scale variations and microscale spatial patterns of fungal biomass, bacterial biomass and soil properties were examined in a hardwood forest in southern Ohio. Two 0.5×2.0 m macroplots and four 10×10 cm microplots were established 0.25 m upslope and downslope of the base of a red oak (Quercus rubra) tree in a mixed oak forest in southeastern Ohio. These plots were sampled in a regular grid pattern for bacterial and fungal biomass, organic C, pH and moisture. Semivariance analysis was used to determine the degree of spatial autocorrelation among the samples from each plot. Significant linear/sill models for microbial and soil variables were produced for the two macroplots and the majority of the microplots. The proportion of variation accounted for by spatial pattern ranged from 0 to 100% for microbial variables, depending on location and variable. Patterns of variation for all variables measured in all plots were mapped using kriging. From the semivariance analysis, the kriged maps and path analysis, it became apparent that the spatial patterns of microbial biomass and organic C were condensed upslope of the tree base and expanded downslope below the tree base. Overall, the results indicate that considerable spatial variability in fungal and bacterial biomass exists at the 1–10 cm scale, and that this variability can be adequately managed by sampling in a pattern which takes into account both random and non-random (spatial) components of variation.