Moth Responses to Forest-To-Bog Restoration
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Moth responses to forest-to-bog restoration A. Pravia1,2, R. Andersen1, R.R.E. Artz2, K. Boyd1, N.R. Cowie3, N.A. Littlewood2,4 1 Environmental Research Institute, University of the Highlands and Islands, Thurso, UK 2 James Hutton Institute, Craigiebuckler, Aberdeen, UK 3 RSPB Scotland, Edinburgh, UK 4 Department of Rural Land Use, SRUC North Faculty, SRUC Aberdeen, Bucksburn, Aberdeen, UK _______________________________________________________________________________________ SUMMARY The responses of peatland invertebrates to land use changes and associated effects of peatland degradation are not well known, particularly for diverse and species-rich taxa such as moths. We investigated broad patterns of distribution in moth communities during the restoration of formerly afforested blanket bog, as well as their degree of habitat affinity (tyrphophilia). Thus, we examined the response of moth communities to peatland management across a restoration chronosequence and used information about species traits to explain the species’ responses to restoration (trait syndromes). A clear shift towards open habitat moth species and away from specialist forest species took place following tree felling, and the moth communities of restoration treatments resembled the bog community within a few years following onset of restoration. Interestingly, species traditionally considered tyrphobionts (bog specialists) were not restricted to core bog habitats. Trait syndromes were identified for each treatment, highlighting the importance of phylogenetic, phenological and ecological performance traits linked mainly to species microhabitat selection, resource use and dispersal capability. The restoration of afforested blanket bog opens up the habitat for the recolonisation of bog- inhabiting moth species, mediated by species functional traits. However, a better understanding of moth functional traits, especially linked to moth ecology (including habitat preferences), is needed to aid understanding of the relationship between restoration trajectory, species traits and blanket bog habitat. KEY WORDS: afforestation, blanket bog, functional traits, Lepidoptera, peatland _______________________________________________________________________________________ INTRODUCTION and the tyrphophilia of many peatland species is not well known. Peatland fauna can display varying degrees of Tyrphobiont insects can face constraints that may affinity with bog habitats (Peus 1928, Spitzer & be associated with stable habitats, such as having Danks 2006). Tyrphobionts are specialised species poor dispersal ability (e.g. the carabid beetle Agonum that are found only in core peatland habitat while ericeti; de Vries & den Boer 1990). Thus, land-use tyrphophiles are found mainly in core peatland but changes and associated effects of peatland also in adjacent habitats. Tyrphoneutrals, on the other degradation, such as drainage and habitat hand, show varying degrees of affinity with peatland fragmentation, may lead to replacement of these but are often also found in other types of habitats species (Vepsäläinen et al. 2000). Despite the often (Mikkola & Spitzer 1983, Spitzer et al. 1999). species-poor nature of peat bog faunas (Desrochers However, the same species can display geographical & van Duinen 2006, Batzer & Boix 2016), insects differences in bog affinity (Spitzer & Danks 2006), tend to be the most abundant and well-adapted animal particularly when latitude and altitude are taken into inhabitants of bog, with more tyrphobiont species account (Mikkola & Spitzer 1983). There is evidence observed in some flying insect groups (such as that, in central and eastern Europe, anthropogenic butterflies) than amongst predominantly non-flying influence may reduce the abundances of tyrphobionts insects (Spitzer & Danks 2006). Amongst flying in favour of tyrphophile and tyrphoneutral species, insects, fewer macro moth species are associated with with tyrphobiont species utilising bog remnants as blanket bog habitats than with other British habitats refugia (Spitzer et al. 1999, Spitzer & Danks 2006). (e.g. Waring & Townsend 2009). Moth assemblages To date, however, such studies are lacking in the UK specifically associated with bogs in Europe are Mires and Peat, Volume 26 (2020), Article 27, 19 pp., http://www.mires-and-peat.net/, ISSN 1819-754X International Mire Conservation Group and International Peatland Society, DOI: 10.19189/MaP.2019.OMB.StA.1787 1 A. Pravia et al. MOTH RESPONSES TO FOREST-TO-BOG RESTORATION composed of a large proportion of tyrphobiont and 1) quantify changes in moth communities across a tyrphophile species with a relatively high proportion restoration chronosequence; and 2) identify key being stenotopic, i.e. able to tolerate a only narrow trait - habitat associations (trait syndromes). We range of environmental change (Bezděk et al. 2006). hypothesised that: 1) moth communities will exhibit Such strong habitat affinity facilitates the use of a non-linear temporal restoration trajectory, with a moths as indicators of peatland quality (Spitzer & reduction of closed-habitat species and an increase of Jaroš 1993, Spitzer et al. 1999, Dapkus 2000) and open-habitat species, as trees are felled and habitat stability (Bezděk et al. 2006), and thus vegetation succession progresses; 2) regardless of the potentially as targets by which to assess progress trajectory observed, tyrphobiont species will occur towards a desired state following restoration only in undamaged blanket bog habitats; and 3) moth intervention. assemblages associated with different successional In the UK, where moth populations have been stages will consist of species exhibiting trait systematically monitored since 1968, alarming syndromes related to habitat preference (degree of declines in overall abundances have been identified habitat openness) and types of vegetation available, in the southern half of the country, even within as moths are intimately linked to host foodplants. common and widespread species (Fox 2013). However, in the north of the UK, almost as many species have shown an increase in abundance as have METHODS decreased between 1968 and 2002 (Conrad et al. 2006). More recent research on Scottish moth data Study site has revealed signs of both abundance declines and This research took place at RSPB (Royal Society for range expansions (Dennis et al. 2019). Overall, the Protection of Birds) Forsinard Flows, a 154 km2 though, severely declining trends in moth National Nature Reserve (NNR) in the heart of the populations have been observed in recent decades, Flow Country (latitude 58.357, longitude -3.897), primarily driven by land-use changes resulting in northern Scotland, UK. Following extensive planting habitat fragmentation, degradation and loss as well as of Sitka spruce (Picea sitchensis) and lodgepole pine by climate change (Fox 2013, Fox et al. 2014). (Pinus contorta) (both non-native conifers) in the Studies of moth abundance and diversity have been 1980s, restoration efforts since 1997 have created a conducted primarily in grasslands, agricultural land chronosequence of restoration areas amongst residual and broadleaf woodlands, with few investigating the open unmodified blanket bog and remaining forestry effects of widespread coniferous plantation which is plantations on peat (Wilkie & Mayhew 2003, one of the main degrading agents for Scottish blanket Hancock et al. 2018). Briefly, the restoration bogs (Warren 2000). For the UK, a single study management involved various combinations of outlines negative effects of extensive conifer planting mechanical tree felling and harvesting, coupled with on moth populations, acting through changes to the drain blocking (‘fell-to-waste’ management). habitat and loss of food resources (Ramchunder et al. 2009). Elsewhere, there is evidence that timber Study design extraction may disrupt moth communities in native A chronosequence of restoration stages was sampled, forests in the United States (e.g. Summerville & Crist encompassing a total of 13 restoration age classes 2002, Summerville 2014). In commercially managed (years since tree-felling) across the study area in a non-native conifer plantations, clear-felling space-for-time substitution, as well as the established practices, as opposed to continuous forest cover, have forest (starting state) and open blanket bog (target demonstrable negative effects on moth species state) (Table 1). During the study period, restoration richness, abundance and diversity (Kirkpatrick progressed to include further management actions 2016). To the best of our knowledge, however, there such as brash crushing and furrow blocking in some is a lack of studies investigating moth responses to felled areas. Due to these ongoing reserve felling of non-native conifer plantations on peatlands management works, the same sites could not all be and formerly afforested peat bogs and, especially, re-sampled each year, reducing the pool of sites concomitant recovery of peatland-associated moth available over the course of this study. Thus, the fauna. overall number of trapping nights per restoration age In this study we investigated broad patterns class varied. When interpreting the results, the age among moth communities in response to the classes were aggregated into two categories: younger restoration of a formerly afforested blanket bog, and restoration (R3–R9, the number indicating years the degree of habitat affinity (tyrphophilia) displayed since tree felling at time of sampling, 38 replicates); by moth species.