Aspen Bibliography

Soil Microbial Community Response to Silvicultural Intervention in Coniferous Plantation Ecosystems

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Ecological Applications





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Five years after planting and initial treatment, we examined the response of a microbial community to three intensive silvicultural practices: soil surface modification (scarification), fertilization, and control of competing vegetation by herbicide. We correlated microbial response with changes in environmental conditions following treatment, including soil temperature and moisture, total and available nutrients in soil, and light intensity in the tree canopy. The microbial biomass C (2.1—5.3 mg/g in the F/H horizon and 0.14—0.62 mg/g in the surface mineral soil) as determined by the fumigation—extraction method was reduced by vegetation control and fertilization. The ratio of microbial to total organic carbon (Cmic/Corg) was also reduced by vegetation control, and tended to increase in the new organic horizon developed during the 5 yr after soil surface scarification. Microbial biomass N (0.15—0.40 mg/g in the F/H horizon and 0.014 to 0.057 mg/g in the mineral soil) was not affected by the treatments. The microbial community structure (relative volumes of bacteria and fungi) was evaluated on glass slides placed in the litter bags of pine and aspen litter. The treatment effects on the relative volumes of microorganisms on slides were similar to effects noted for microbial biomass C in the soil. Five years of vegetation succession resulted in conservative N cycling and N limitation of the plant community in control plots. In response to silvicultural treatments this state may either remain relatively unchanged after fertilization, the N limitation may be increased (scarification), or apparent C limitation induced (vegetation control). Reducing the nutrient pool by scarification caused an apparent nutrient limitation, and the microbial community tended to widen the C/N ratio. Increasing the nutrient pool by fertilization or vegetation control tended to narrow the C/N ratio of microbial biomass.