Forest harvest makes many changes in a forest stand. It affects microclimate, existing vegetation in terms of composition and abundance, and coarse woody debris (CWD) volume and quality. Alteration of these forest attributes during harvest can lead to local species loss. Partial harvest has been hypothesized to reduce these impacts. Initial post-harvest studies indicated the ability of partial harvest to attenuate harvest impacts on CWD volume and quality and to encourage the development of microhabiat conditions similar to old growth forests. However, long term studies are needed to determine actual effects. 15 years after harvest disturbance and 8 years after the initial study, we investigated the impacts of partial harvest on forest microhabitats (CWD characteristics and microclimatic conditions) using epixylic bryophytes as indicator species. Unharvested control, partial harvest, and total harvest were used as a gradient to represent the different levels of harvesting impacts on forest microhabitat conditions. Epixylic bryophytes (composition and richness) and CWD characteristics were examined in 30 permanent plots located in the boreal black spruce –feathermoss forests of northwestern Quebec, Canada. Microclimatic variables and stand characteristics (canopy openness and stem density) were also measured to explain the relationships between epixylic bryophyte and their microhabitat.
Results/Conclusions
High epixylic species richness was found in the control and partial harvest but not in the total harvest. These differences were due to the effect of harvest on CWD decay stage and canopy openness. Less CWD in early decay stages were found in total harvest and some decay stages were completely absent. In contrast, all decay stages were present in unharvested control and partial harvest. Decay class volumes were similar in both harvesting treatments except in decay class 2 where volumes were higher in unharvested control than in partial cut. Also, greater canopy openness in total harvest resulted in less humidity which resulted in low epixylic species richness. In conclusion, this study confirms the results of the initial post-harvest study and indicates that residual stands after partial harvest provide a good microclimate and ensure a continual supply of suitable substrates for epixylic bryophytes over 12 years post-harvest. Consequently, partial cuts maintained high species richness communities, which was not the case with a traditional total harvest and they therefore offer an effective strategy for biodiversity conservation in managed forest landscapes.