Canopy gaps are hotspots for bees and rare plants in an oak savannah-woodland system in southern Ontario

Abstract

Prairies and savannahs have suffered significant declines in North America since European settlement due to both loss of habitat and the suppression of fire. In the oak savannahs of Pinery Provincial Park, prescribed burns were introduced in the 1980s to reopen the canopy and restore savannah habitat. However, the success of these measures has not been quantified. Plant and bee community composition were measured in areas of the park under varying fire regimes to determine how prescribed burns were affecting habitat structure, and how both management and habitat structure influence the bee community in terms of abundance and diversity. It was found that the greatest bee abundance and richness, proportion of savannah species, and rare plant abundance were in areas with more open canopy. Though these areas are hotspots for diversity, they made up only 14% of the plots sampled. Further, the average canopy cover for areas that are being managed with prescribed burns is 67%, much higher than the defined savannah canopy cover of 10-35%. If management goals are to increase habitat for rare plants, savannah plants, and native bee pollinators, then more intense management (possibly mechanical removal of trees, more intense/frequent burns) will be necessary.