Effects of slash harvest on bryophytes and vascular plants in southern boreal forest clear-cuts

Authors


M. Åström, Landscape Ecology Group, Department of Ecology and Environmental Science, Umeå University, SE-901 87, Umeå, Sweden (fax + 46 90 7867860; e-mail marcus.astrom@emg.umu.se).

Summary

  • 1Slash harvesting from forests to provide bioenergy reduces the amount of woody debris in the managed forest landscape and changes the physical and chemical environment in clear-cuts. We examined previously unstudied effects of commercial (i.e. non-experimental) slash harvest on species composition and richness of liverworts, mosses and vascular plants. The results call for modification of commercial slash harvest practices.
  • 2Differences between conventionally harvested (i.e. slash left) and slash-harvested stands were investigated 5–10 years after clear-cutting through analysis of 28 paired stands, with one 0·1-ha plot divided into five 0·02-ha subplots in each stand.
  • 3The species composition of mosses and liverworts in 0·1-ha plots was significantly affected by slash harvest, whereas the composition of vascular plant species was not.
  • 4The species richness of liverworts was significantly reduced by slash harvest in plots of both sizes, whereas moss richness was reduced only in 0·02-ha plots. The loss of liverwort species was largest, with approximately one-third of the species disappearing. The species richness of vascular plants was not significantly affected by slash harvest in either plot size.
  • 5Slash harvest reduced species richness of forest bryophytes and of bryophytes typically growing on organic substrates in open habitats. Species richness of non-forest bryophytes on inorganic substrates remained unchanged.
  • 6Synthesis and applications. Our results show that slash harvest reduces shelter and woody substrates, which changes species composition and reduces species richness of liverworts and mosses in clear-cuts. Increased mechanical disturbance that removes remnant vegetation and exposes mineral soil may also play a role. In order to conserve bryophytes, we advocate mitigation of adverse ecological effects through enhanced environmental care within slash-harvested stands. Leaving more tree clusters, and creating and protecting large woody debris would be especially important in these stands, and would also improve the habitat for other organisms.

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