Abstract
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.
Highlights
Predicting the response of communities to environmental changes is a fundamental issue in ecosystem ecology
Plant Traits According to indicator traits analysis (ITA) and pRDA, seven plant traits were mainly associated with high deer density, especially in situ density, whether in cut-over areas or uncut forests or both (Figs 2 and 3)
Species with fleshy fruits and large seeds dispersed by birds or by epizoochory were indicator of reduced deer density (RDD)
Summary
Predicting the response of communities to environmental changes is a fundamental issue in ecosystem ecology. There has been a growing interest in the use of functional traits to identify the mechanisms that underlie community changes and determine ecosystem functioning [1,2]. Most studies using a functional trait-based approach have focused on a single taxonomic group (for example, [6,7]). There are growing expectations that extending the trait concept to multiple taxonomic groups will improve our ability to understand the complex dynamic of ecosystems and identify mechanisms that drive biotic control over ecosystem functions [8,9,10,11]. We examine the effect of reducing large herbivore browsing pressure on community-level functional response and effect traits using a multiple taxonomic groups approach. Ground beetles and songbirds, each taxon with different mobility capacity and type of resources uses, characteristics expected to strongly influence response to environmental changes
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