Are woodland creation schemes providing suitable resources for biodiversity? Woodland moths as a case study

Abstract

Woodland, like many habitats throughout the world, has been severely affected by habitat loss and fragmentation. Woodland restoration programmes aimed at reversing habitat loss have been in place in many countries over the last 100years. In particular, agri-environment schemes (AES) to increase the amount and quality of woodland on agricultural land have operated in Europe and Australia for decades (nearly 30years in the United Kingdom). However, to date there has been very little assessment of their value to biodiversity. We assessed the potential benefits to biodiversity of woodlands planted during 1988–1991 under a woodland grant scheme (WGS in Scotland), according to local and landscape-level habitat characteristics. Specifically, we (1) performed a linear discriminant analysis to compare the characteristics of 24 WGS sites to those of more mature semi-natural woodlands (34 sites >60years old), and (2) used existing information on the influence of woodland characteristics on a biologically diverse group (i.e. moths) to quantify the benefits of WGS sites to biodiversity. The creation of new WGS patches increased woodland extent and connectivity in the landscape; however, planting that took place adjacent to previously existing woodland did not usually increase connectivity. WGS sites were mainly composed by broadleaved native tree species, but non-native species were also present. In general, WGS sites had lower tree species richness, proportion of native trees, tree basal area and amount of understory, and higher tree densities and canopy cover than more mature semi-natural woodlands. Overall, WGS sites were predicted to have lower moth abundance and species richness than older semi-natural woodlands. However, the magnitude of these differences depended on the habitat specificity and dispersal abilities of different moth groups, suggesting that WGS sites are better at providing suitable resources for generalist species and for species less limited by dispersal. Our findings have important implications for the way in which current woodland creation and management schemes operate in many countries and suggest that: (1) the creation of new woodlands should focus on planting native species, (2) woodland creation schemes are likely to be more beneficial for biodiversity if certain management practices (e.g. thinning to enhance structural diversity and accelerate the transition to later successional stages) accompany the provision of these grants, and (3) spatially-targeted woodland creation would further increase the contribution of AES woodlands to enhance biodiversity

Insect herbivory and avian insectivory in novel native oak forests: divergent effects of stand size and connectivity

“…We have two possible, non-exclusive explanations for this phenomenon: (i) colonization rates of chewers and skeletonizers could generally be so high in our study system that even the smallest forest stands will be effectively reached (and, if necessary, re-colonized) when a certain threshold abundance of suitable habitats and associated herbivore source populations exist in the landscape (Fahrig, 2013). This hypothesis is supported by the fact that novel established forest stands are very rapidly colonised by woodland generalist species (Fuentes-Montemayor et al, 2015;Fuller et al, 2018). Second, (ii) insect herbivory tends to be favoured by edge effects (De Carvalho Guimarães et al, 2014), especially when it involves generalist species (Bagchi et al, 2018).…”

“…Typical breeding season territories of the most frequently recorded bird species actually exceed the size of our smallest stands (Hinsley et al, 1995) and only the largest stands could regularly sustain more than one territory of the same species. These large stands should also provide the broadest range of tree ages and vegetation structures to different species, although it certainly is still inferior to that of mature forests (Fuentes-Montemayor et al, 2015). Habitat diversity and quality might then also be behind our rather surprising finding that bird abundance (although not species richness) tended to decrease with increasing stand connectivity (Fig.…”

“…Such stands share certain characteristics that set them apart from those created by fragmentation: (i) they typically are quite small-sizedeven smaller than the smallest fragments of remnant forest; (ii) they are dominated by young trees, resulting in a reduced amount and range of habitats available to forest-dwelling species (Franklin, 1988;Fuller et al, 2018); and (iii) all their species necessarily originate from colonization events over a limited period of time, implying that these systems are triggered by immigration credit instead of extinction debt (Jackson and Sax, 2010). Recent studies on insect and bird species richness along chronosequences of novel native forest development have shown that these are rapidly colonized by woodland generalists whereas specialists can still remain absent even 150 years after forest establishment (Fuentes-Montemayor et al, 2015;Fuller et al, 2018;Whytock et al, 2018). These studies also revealed that local stand characteristics are relatively more important than landscape characteristics for successful colonization by insects and birds.…”

Local‐scale attributes determine the suitability of woodland creation sites for Diptera

“…This is also likely to benefit a range of other taxa and those reliant on woodland insects as a food source. Many existing woodlands in the UK are planted on private lands using government grants and are subsequently abandoned or have little management input (Fuentes‐Montemayor et al., ; Lawrence & Dandy, ). Active woodland management could be encouraged, such as thinning woodlands once they are established to allow trees to grow and natural regeneration to occur, and maintaining open spaces within glades or rides.…”

“…Woodland is the term commonly used in the UK to describe any forested area; for convenience, we use this term hereafter in the paper. However, many of these newly created areas of native broadleaf woodland are small, isolated from existing woodlands and surrounded by urban or agricultural land (Fuentes‐Montemayor, Peredo‐Alvarez, Watts, & Park, ; Quine & Watts, ). This potentially inhibits dispersal of woodland species across the landscape (Villard & Metzger, ) and reduces the value of created woodlands as a resource for biodiversity.…”