Limited Impacts of Extensive Human Land Use on Dominance, Specialization, and Biotic Homogenization in Boreal Plant Communities

Stephen Mayor
Stan Boutin
Fangliang He
James Cahill
Page Length

Rank species occupancy curves revealed high species dominance regardless of  disturbance: within any disturbance class a few species occupied nearly every site and  most species were found in a low proportion of sites. However, species were more  widespread and displayed more even occupancy in intermediately disturbed communities than among communities of either  low or high disturbance. We defined specialists and generalists based on turnover in co-occupants and thereby assessed impacts of human disturbance on specialization of species and community homogenization. Generalists were not disproportionately  found at higher disturbance sites, and did not occupy more sites. Communities with  greater human disturbance were not more functionally homogeneous; they did not harbor communities with more generalists.

We unexpectedly did not observe strong linkages between species  specialism/generalism and disturbance, nor between community homogenization and disturbance. These results contrast previous findings in more species rich, complex or spatially heterogeneous systems and ecological models. We suggest that broad occupancy-based intercommunity patterns are insensitive to human land use extent in boreal vascular plants, perhaps because of ubiquity of generalists, low species richness, and history of natural disturbance. The poor sensitivity of these metrics to disturbance presents challenges for monitoring and managing impacts to biodiversity in this region.