Impact of forest harvesting on soil microbial communities and nutrient cycling in forest soils of the Boreal Plain, Alberta
Canada’s Boreal forest covers 35% of the landmass, much of which is managed by the natural resources industry. As the largest exporter of wood products globally, the Canadian forestry industry relies on sustainable productivity of the soil. Microbial communities and bioavailability of nutrients are critical components of the sustainability of continuously harvested lands, thus assessing their response to harvesting was the overarching objective of this study. Microbial community biomass and composition was assessed using phospholipid fatty acid (PLFA) analysis and DNA fingerprinting of the bacterial community and ammonia oxidizing bacteria (AOB). In situ nutrient availability and chemical soil parameters were also measured here. Six cutblocks similar to each other except for their age since harvesting were sampled in the summer of 2009 and 2010 in both the forest floor and mineral Ae horizons of Orthic Gray Luvisols of central Alberta in the Boreal Plain ecozone. Microbial communities of these forest soils were generally resilient and adaptable to harvest disturbance over the first ~20 years post harvest. Soil moisture content emerged as a strong influence on microbial biomass, potentially interacting with the affect of the harvesting activities. There was a flush of nutrients in the first growing season after clear cutting, followed by a consistent decline over time. The AOB community composition changed in parallel with changes in N availability, suggesting that N bioavailability may be directly linked to AOB community structure. This research contributes to the knowledge that forest harvesting does not necessarily alter the soil ecosystem in a detrimental way. The microbial community adapted to the relatively minor changes imposed by harvesting, as seen by the shift in community composition yet consistency of the total microbial biomass.
microbial, soil microbiology, forest soil, nutrient availability
Master of Science (M.Sc.)
Van Rees, Ken;Si, Bing;Putz, Gordon