Sustained functional composition of pollinators in restored pastures despite slow functional restoration of plants.

Marie Winsa,Erik Öckinger,Ignasi Bartomeus,Riccardo Bommarco,Stuart P M Roberts,Johanna Wärnsberg,Regina Lindborg

doi:10.1002/ece3.2924

Abstract

Habitat restoration is a key measure to counteract negative impacts on biodiversity from habitat loss and fragmentation. To assess success in restoring not only biodiversity, but also functionality of communities, we should take into account the re‐assembly of species trait composition across taxa. Attaining such functional restoration would depend on the landscape context, vegetation structure, and time since restoration. We assessed how trait composition of plant and pollinator (bee and hoverfly) communities differ between abandoned, restored (formerly abandoned) or continuously grazed (intact) semi‐natural pastures. In restored pastures, we also explored trait composition in relation to landscape context, vegetation structure, and pasture management history. Abandoned pastures differed from intact and restored pastures in trait composition of plant communities, and as expected, had lower abundances of species with traits associated with grazing adaptations. Further, plant trait composition in restored pastures became increasingly similar to that in intact pastures with increasing time since restoration. On the contrary, the trait composition of pollinator communities in both abandoned and restored pastures remained similar to intact pastures. The trait composition for both bees and hoverflies was influenced by flower abundance and, for bees, by connectivity to other intact grasslands in the landscape. The divergent responses across organism groups appeared to be mainly related to the limited dispersal ability and long individual life span in plants, the high mobility of pollinators, and the dependency of semi‐natural habitat for bees. Our results, encompassing restoration effects on trait composition for multiple taxa along a gradient in both time (time since restoration) and space (connectivity), reveal how interacting communities of plants and pollinators are shaped by different trait–environmental relationships. Complete functional restoration of pastures needs for more detailed assessments of both plants dispersal in time and of resources available within pollinator dispersal range.

Highlights

Habitat restoration aims to counteract the negative effects of habitat loss and land-u se change on biodiversity (Bakker & Berendse, 1999)
Plant trait composition in restored semi-natural pastures was more similar to the composition in continuously grazed pastures than that in abandoned sites, indicating that plant communities in formerly abandoned semi-natural pastures have a good chance to recover in terms of functionality after restoration
Part of the variation in plant trait composition in restored sites, at least for flowering plants, was explained by the time since restoration, with older restored pastures being more similar to continuous pastures than recently restored pastures

Summary

| INTRODUCTION

Habitat restoration aims to counteract the negative effects of habitat loss and land-u se change on biodiversity (Bakker & Berendse, 1999). To advance current research on biodiversity and ecosystem functioning, an analysis of abundance-based trait composition of communities is a promising approach (Gagic et al, 2015) Species traits determine both how species are affected by environmental change (i.e., response traits; Lindborg et al, 2012; Öckinger et al, 2010; Williams et al, 2010) and species functional role in the ecosystem (i.e., effect traits; Lavorel & Garnier, 2002; Violle et al, 2007). Temperate semi-natural grasslands harbor species-rich plant communities (Wilson, Peet, Dengler, & Pärtel, 2012) and act as source habitat for many pollinator species (Öckinger & Smith, 2007) This habitat type has declined drastically, both globally and in many parts of Europe during the 20th century (e.g., Hoekstra, Boucher, Ricketts, & Roberts, 2005). We hypothesized that the trait composition in restored pastures is intermediate between abandoned and intact pastures, but become more similar to intact pastures with increasing time since restoration, and that this recovery is facilitated by increasing connectivity to other intact semi-natural grasslands (Figure 1)

| METHODS

Abandoned Continuous Restored

Findings

| DISCUSSION