Functional trait analysis of the impact of a gradient of forest management on understory plants: Multi-scale approach comparing Canada vs Finland

Background/Question/Methods

It has been recognized that protected areas alone cannot maintain biodiversity and that we must also create conditions appropriate for plants and wildlife in managed landscapes. This project compares the impact of different historical forest management intensities at the stand and landscape level on functional traits of understory plants. To do this, a gradient in intensity of forest management, spanning from unmanaged (disturbed only by natural perturbations) and managed forests in Canada (partial cuts, clear cuts and plantations) to managed forests in Finland (plantations) were analysed on the basis of functional traits of understory species present. A total of ten sites in each category were sampled. The trait approach is much less sensitive than the species approach which means that a significant difference is the result of a strong environmental pressure.

Results/Conclusions

Overall, in the herbaceous layer in Finland there was a predominance of species that share features generally associated with early successional species, even 30 to 50 years after cutting. For example, thelophytes and species dispersal by epizoochory were more present in forest plantations of Finland. In contrast, species with traits associated with closed forests were significantly less present. No differences in occurrence of functional trait were observed between natural and managed forests in Canada. The sites in Canada do not show significant differences in terms of forest and agricultural covert at the landscape scale compared to Finland where there were significantly more agricultural covert and less forest covert. Also volume of dead wood was more abundant in natural forest of Canada (123 m³/ha) compared to managed forest of Canada (66 m³/ha ) and Finland (24 m³/ha).  In addition, sites in Finland were globally less rich in cations (Na, K and Ca) and with a higher density. These results suggest that intensive forestry done over a long period of time and over a large landscape could negatively impact understory plant diversity.