Response of microbial processes and fungal community structure to vegetation management in mixedwood forest soils

Previous research to determine the impacts of harvesting and site preparati on on microbial processes and decomposer fungi in mixedwood forests indicat ed that effects were minimal. As an extension to this research, the present study was conducted to evaluate if microbial precesses and decomposer fung i were sensitive to manual or chemical vegetation management in addition; t o harvesting and site preparation. The impact of vegetation management on m icrobial processes and decomposer fungi was examined in organic and mineral soil from harvested sites in northwestern Ontario. Three vegetation manage ment treatments were applied to three clear-cut and prepared sites 2 years prior to the initiation of the study. Four treatments were established with in each site: (i) harvested (control), (ii) glyphosate herbicide (Vision(R) ), (iii) triclopyr herbicide (Release(R)), and (iv) manually operated brush saws. The objective of the study was to determine the response of basal res piration, microbial biomass C, metabolic quotients (qCO(2)), microbial carb on : soil organic carbon ratio (C-mic/C-org), nitrogen mineralization, and fungal community structure to vegetation management by chemical and manual means. Relative to the harvested control, vegetation management had no sign ificant impact on fungal community structure as evidenced through rank abun dance curves and indices of fungal community richness, diversity, evenness, or dominance. Although the abundances of the majority of fungal species we re not impacted by vegetation management, herbicide and brushsaw use decrea sed the isolation frequencies of Mortierella vinacea (Dixon-Stewart) and Pa ecilomyces carneus (Duche and Helm) Brown and Smith, respectively. Occurren ce of Paecilomyces carneus was significantly greater in the organic soil th an in the mineral soil of the harvested control, but this difference was no t detectable in the blocks that had undergone vegetation management. Two ye ars after vegetation management was imposed there were no detectable effect s on basal respiration, microbial biomass C, qCO(2), CmicCorg, or nitrogen mineralization in either the organic or mineral soil layers compared with m easurements made in the harvested control plots.