Does intensified boreal forest harvesting impact soil microbial community structure and function?

Abstract

Intensified biomass harvesting in northern forests could potentially negatively impact soils. This study measured microbial community structure and function to assess the impacts of intensified biomass removal on soil from a managed northern jack pine (Pinus banksiana Lamb.) forest in Ontario, Canada. Four clear-cut harvesting removal intensities were compared with uncut controls and mature, fire-regenerated forest reference plots: stem-only removal, full-tree biomass removal, full-tree biomass with stump removal, and full-tree biomass with stump removal and soil blading that eliminated all aboveground and much belowground organic matter. A nearby recently burned forest site, representing common natural disturbance in the region, was also studied. Within the first two years after harvesting, there were significant differences in community structure and degradation of various C compounds among all harvested and unharvested sites, but little difference in communities across the different harvest intensities. Communities within the fire site were not comparable with those of harvested treatments, indicating that clear-cut logging may not initially produce an ecologically comparable disturbance with that of fire, although this conclusion is based on only one fire disturbance site. In the two years after harvesting, an important time for seedling establishment in managed forest systems, it appears that intensification of harvesting does not further disrupt microbial community structure and functioning beyond impacts from current harvest practices.

Direct and Indirect Effects of Forest Anthropogenic Disturbance on Above and Below Ground Communities and Litter Decomposition

“…Consistent with Chen and Wise (1999), we also found carnivorous spiders and ground beetles to increase with prey availability. The lower abundance of fungivorous mesofauna and rove beetles may also result from the microbial biomass decline observed in disturbance treatments (Smenderovac et al, 2017). In contrast, our analysis suggests that negative effects of increasing predators on their prey in disturbance treatments were not significant.…”

“…Increasing soil temperature typically increases litter decomposition rate (Anderson, 1991;Hobbie, 1996;Fierer et al, 2005), but higher temperature can also lower moisture which is likely to decrease microbial activity and therefore decomposition (Schimel et al, 1999;Wan et al, 2007;Butenschoen et al, 2011). Working in the same sites used in this study, Smenderovac et al (2017) documented lower microbial biomass in the disturbance treatments compared to the mature forest. We effectively found lower litter mass loss in these treatments.…”

“…This experimental site was designed to conduct collaborative research (Aubin et al, submitted). Several researchers are investigating environmental and species responses to forest disturbance intensity, providing an opportunity for integrative multitrophic analyses (Boisvert-Marsh et al, 2016;Webster et al, 2016;Smenderovac et al, 2017;Venier et al, 2017;Rousseau et al, 2018).…”

Forest soil biotic communities show few responses to wood ash applications at multiple sites across Canada

“…As there was also little evidence of changes to soil quality or pH in these sites, the lack of community response to ash addition is likely because the changes to soil characteristics were minor to non-detectable 18 . It has been demonstrated that harvesting can cause detectable community changes 17 . While the quantities of wood ash added in this study are considered reasonable operational amount, they might have been insufficient to mitigate stresses (e.g., calcium and magnesium depletion, high acidity) and create further community shifts.…”

“…Soil arthropod, bacterial and fungal communities are known to be responsive to differences in moisture, pH and calcium levels 16 . While harvest disturbance alters moisture, pH and calcium which results in stark changes to microbial community composition from uncut forest systems, increases to harvesting intensity can be small and undetectable 17 . The effects of wood ash amendment are likely also small; a recent study of sites across Canada showed inconsistent responses in soil quality metrics due to wood ash amendment 18 .…”