Canadian Forest Service Publications
Functional responses and resilence of boreal forest ecosystem after reduction of deer density. 2014. Bachand, M.; Pellerin, S.; Moretti, M.; Aubin, I.; Tremblay, J.-P.; Coté, S.D.; Polin, M. PLoS ONE 9(2):e90437-e90437.
Issued by: Great Lakes Forestry Centre
Catalog ID: 35652
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The functional trait-based approach is increasingly used to predict responses of ecological communities to disturbances, but most studies target a single taxonomic group. Here, we assessed the resilience of a forest ecosystem to an overabundant herbivore population by assessing changes in 19 functional traits for plant, 13 traits for ground beetle and 16 traits for songbird communities after six years of controlled browsing on Anticosti Island (Quebec, Canada). Our results indicated that plants were more responsive to 6 years of reduced browsing pressure than ground beetles and songbirds. However, co-inertia analysis revealed that ground beetle communities responded in a similar way than plant communities with stronger relationships between plant and ground beetle traits at reduced deer density, a pattern not detected between plant and songbird. High deer density favored plants species that reproduce vegetatively and with abiotic pollination and seed dispersal, traits implying little interaction with animal. On the other hand, traits found at reduced deer density mostly involved trophic interaction. For example, plants in this treatment had fleshy fruits and large seeds dispersed by birds or other animals whereas ground beetle species were carnivorous. Overall, our results suggest that plant communities recovered some functional components to overabundant herbivore populations, since most traits associated with undisturbed forests were reestablished after six years of deer reduction. The re-establishment of functional plant communities with traits involving trophic interaction induces changes in the ground-beetle trait community, but forest structure remains likely insufficiently heterogeneous to shift the songbird trait community within six years.
Plain Language Summary
The functional trait approach has been developed to better understand plant communities by simplifying each species into a suite of characteristics that matter for ecosystem processes. Using this technique, we investigate the resilience of forest plant and animal communities exposed to over-browsing by deer. Taking advantage of a long-term experimental site on Anticosti Island (Quebec), we take an integrative look at the bird, beetle and plant communities using innovative statistical techniques. We find that plant communities are functionally resilient to over-abundant herbivore populations. We also find functional changes in the beetle community composition that parallel the recovery of the plant community, although none were apparent for birds. This study represents a ground-breaking effort to assess ecosystem resilience to over-browsing with such integrative techniques. The technique that was used shows promise in the study of ecosystem capacity to recover from major disturbances.