Functional shifts in bird communities from semi-natural oak forests to conifer plantations are not consistent across Europe

Abstract

While the area of plantation forest increased globally between 2010 and 2015, more than twice the area of natural forests was lost over the same period (6.5 million ha natural forest lost per year versus 3.2 million ha plantation gained per year). Consequently, there is an increasing need to understand how plantation land use affects biodiversity. The relative conservation value of plantation forests is context dependent, being influenced by previous land use, management regimes and landscape composition. What is less well understood, and of importance to conservation management, is the consistency of diversity patterns across regions, and the degree to which useful generalisations can be provided within and among bioregions. Here, we analyse forest birds in Ireland, France and Portugal, representing distinct regions across the Atlantic biogeographic area of Europe. We compared taxonomic, functional and phylogenetic diversity of bird communities among conifer plantations and semi-natural oak forests, and assessed correlations between species traits and forest type across these regions. Although bird composition (assessed with NMDS ordination) differed consistently between plantation and oak forests across all three regions, species richness and Shannon diversity did not show a consistent pattern. In Ireland and France, metrics of taxonomic diversity (richness and Shannon diversity), functional diversity, functional dispersion and phylogenetic diversity were greater in oak forests than plantations. However, in Portugal taxonomic and phylogenetic diversity did not differ significantly between forest types, while functional diversity and dispersion were statistically significantly greater in plantations. No single bird trait-forest type association correlated in a consistent direction across the three study regions. Trait associations for the French bird communities appeared intermediate between those in Ireland and Portugal, and when trait correlations were significant in both Ireland and Portugal, the direction of the correlation was always opposite. The variation in response of bird communities to conifer plantations indicates that care is needed when generalising patterns of community diversity and assembly mechanisms across regions.

Tree mixtures mediate negative effects of introduced tree species on bird taxonomic and functional diversity

“…Similar relationships have been discussed in studies of other non-native tree species (e.g. Hanzelka & Reif, 2016), and Pedley et al (2019) showed that conifer admixture negatively affects bird diversity particularly when these conifers are not part of the natural species composition of a region.…”

Trait‐habitat associations explain novel bird assemblages mixing native and alien species across New Zealand landscapes

“…However, diet, body size and territoriality also range amongst the traits that explain the winner/loser dynamics observed in European and Nearctic bird assemblages (Baiser & Lockwood, 2011; Devictor et al., 2008; Newbold et al., 2018). Species that cope well with anthropogenization in their area of origin are common in landscapes dominated by exotic plantations in New Zealand (e.g., greenfinch [ Carduelis chloris ], chaffinch [ Fringilla coelebs ] and goldfinch [ Carduelis carduelis ]), as also observed in European plantation forests (Pedley et al., 2019). This similarity suggests that trait‐based winner/loser dynamics could also have confined ecologically specialized native species in their native habitats, while generalism would have permitted some alien colonizers to invade novel man‐created landscapes, which remained largely free of competition from native species (Cardador & Blackburn, 2019).…”

Endangered lowland oak forest steppe remnants keep unique bird species richness in Central Hungary

“…We found that pine plantations were one of the poorest habitats for birds of this plantation matrix, largely because of their inability to decompose leaf litter, their poor under-and midstorey levels, and among other factors, the resin of pines inhibits cavity formation in living trees (Conner et al 2001). Coniferous stands, hybrid poplar and black locust plantations in our study also harboured lower total abundance, diversity, and species richness relative to old oak remnants, with most consisting of habitat generalists such as common chaffinch (Graham et al 2014) and species that prefer open forests such as Eurasian golden oriole, spotted flycatcher, and tree pipit (Pedley et al 2019). Pine plantations also provide nesting habitat for specialists of coniferous forests such as coal tits (Sweeney et al 2010a;Winkler and Erdő 2012).…”