Bat exploitation of Sitka Spruce plantations: Impacts of management on bats and nocturnal invertebrates

Plantations are widespread throughout temperate regions, and the area of plantation land cover is predicted to get larger in the future. Interest in ensuring sustainable plantation management is also growing, as it is increasingly recognised that productive areas should play a role in biodiversity conservation. Plantation landscapes can comprise the majority of forested cover in some countries, but taxon-specific guidance can be lacking, due to plantations often being under surveyed. Therefore, despite substantial incentives existing to ensure that plantations meet various ecological criteria, plantation managers lack the information necessary to implement effective management plans. Many bat species have undergone widespread declines in recent decades, attributed to habitat loss and fragmentation, particularly of forested habitat. In many temperate countries, historical deforestation has resulted in very low native tree cover, and subsequently, considerable replanting with non-native commercial coniferous plantations has taken place. Species specific habitat surveys have often demonstrated avoidance of conifer plantations by bats, which has been attributed to a lack of roosts and low invertebrate prey abundance. Furthermore, widespread lepidopteran declines have been partly attributed to afforestation with non-native conifer, but moth associations with commercial coniferous plantations are usually only studied for pest species. Bats present a particular challenge in plantation landscapes; tree cover is important to many species to a greater or lesser extent, and in the United Kingdom, destruction of a roost site is illegal, regardless of whether it was deliberate or accidental. However, the extent to which bats associate with non-native commercial plantations is relatively unexplored. This is the first study to explicitly test bat associations with Picea sitchensis plantations (using acoustic detectors, trapping and radio tracking), and shows that, contrary to expectations, they may be an important habitat for breeding populations of Pipistrellus spp., particularly P. pygmaeus. High levels of activity were recorded for both P. pygmaeus and P. pipistrellus, despite little difference in dipteran abundance between different stand types, both species preferentially foraged in felled or less dense stands. This suggests that bats preferentially forage in areas with less acoustic and physical clutter, which will increase foraging efficiency. The impacts of felling in non-native commercial coniferous plantations on foraging activity was tested, for the first time, using a Before – After – Control – Impact experimental design. Bat activity (specifically P. pipistrellus and Nyctalus) increased after felling, particularly in smaller stands. In contrast felling had significant, negative impacts on moth abundance, species richness and diversity, and these effects remain after constraining for functional trait similarity. Reductions in richness and diversity in response to felling were similarly large for both rare and abundant species. Therefore, while bats may benefit from clear fell practices, albeit as long as the size of patches is small, moth populations could benefit from a shift towards other forestry methods, iv such as continuous cover forestry. These results also have implications for the recent, but increasing practice of siting wind turbines in commercial coniferous plantations, as pre-installation preparation involves clearing small patches of forest which may attract foraging bats; post felling monitoring should be carried out to examine potential impacts on bat populations. The presence of broadleaf trees in and around plantations significantly increased moth richness, mostly through increased occurrence of rare species. Broadleaf woodlands (defined as land spanning more than 0.5 ha, with trees higher than 5m and a combined cover of shrubs, bushes and trees above 10%), also had higher functional redundancy than plantation sites. For a diverse moth population to persist in plantation landscapes, preserving remnant patches of broadleaf trees is essential. There was little difference in bat activity between broadleaf woodlands and plantation sites. However, bat abundance, particularly that of reproductively active females, was greater in broadleaf sites compared to plantations. This was particularly true for Myotis and Nyctalus spp., very few of which were trapped in commercial plantations. Therefore, although reproductively active female Myotis bats are present in the surrounding landscape, they do not appear to associate with plantations themselves. This may reflect a lack of roost availability; both P. pygmaeus and P. pipistrellus preferentially form large maternity colonies in buildings, but for Myotis and Nyctalus spp. which roost switch regularly and often use trees, it is unlikely many suitable roosts exist within the plantations themselves. Many substantial P. pygmaeus maternity colonies were identified in and around Galloway forest, with some holding more than 500 individuals. All maternity colonies were in buildings, and most inhabited (and one uninhabited) buildings within the plantation contained a roost. Although females occasionally used old or dead deciduous trees as temporary roosts, there was no evidence of roosting in crop trees such as P. sitchensis. During this study, the Forestry Commission installed 36 bat boxes; within 6 months over 90% had been used, with a number of harems found inside. This fast uptake compared with bat use of boxes in other locations reflects the paucity of appropriate structures for either roost or harem use in commercial plantations. Twelve bats were captured while foraging, tagged with small radio transmitters, and followed for between 2 and 6 nights during 2014 and 2015. All but one tagged female preferentially foraged within the plantation, with individuals selecting equally riparian habitats and felled stands. Tagged females which roosted furthest from the plantation had the largest home ranges; one individual flew nearly 40km each night to reach foraging areas distant from her roost, suggesting that the food availability within the plantation was sufficient to render such a long journey energetically viable. v These results have important implications for bat populations in and around commercial coniferous plantations. Far from being avoided by bats, plantation landscapes may constitute an important habitat type for both P. pygmaeus and P. pipistrellus, likely due to the high abundance of nematoceran diptera in plantation woodlands. Furthermore, plantation forests support a similar richness of moth species to urban and agricultural woodlands, including a number of declining species of special conservation concern. A list of management recommendations to benefit both bat and moth populations in commercial plantations is presented at the end of this thesis

Negative impacts of felling in exotic spruce plantations on moth diversity mitigated by remnants of deciduous tree cover

Moths are a vital ecosystem component and are currently undergoing extensive and severe declines across multiple species, partly attributed to habitat alteration. Although most remaining forest cover in Europe consists of intensively managed plantation woodlands, no studies have examined the influence of management practices on moth communities within plantations. Here, we aimed to determine: (1) how species richness, abundance, diversity of macro and micro moths in commercial conifer plantations respond to management at multiple spatial scales; (2) what the impacts of forest management practices on moth diversity are, and (3) how priority Biodiversity Action Plan (BAP) species respond to management. BAP species were selected as they represent formerly widespread and common species, which have undergone substantial declines in the UK and Europe. We assessed moth communities in three conifer plantations in Northern England and Scotland by light trapping, combining local (e.g. age of planting) and landscape level (e.g. proximity to felled areas) characteristics to evaluate the impacts of forest management on moths. We found no relationship between local factors and moth richness, abundance and diversity but the amount of clear felling in the surrounding landscape had a strongly negative correlation. In contrast, the amount and proximity of broadleaf cover in the surrounding landscape positively influenced macro moth richness and abundance. For six BAP species, abundances were lower close to felled areas but increased with the size of adjacent broadleaf patches. We conclude that clear felling negatively affects moths, probably through alteration of habitats, the loss of larval host plants, and by limiting dispersal. A shift to continuous cover and maintaining broadleaf tree cover within plantations will greatly enhance their value for moth communities

The metric matters when assessing diversity: Assessing lepidopteran species richness and diversity in two habitats under different disturbance regimes

How we measure diversity can have important implications for understanding the impacts of anthropogenic pressure on ecosystem processes and functioning. Functional diversity quantifies the range and relative abundance of functional traits within a given community and, as such, may provide a more mechanistic understanding of ecosystems. Here, we use a novel approach to examine how lepidopteran richness and diversity, weighted by species abundance, differ between habitats under different disturbance regimes (highly disturbed non‐native plantations and less disturbed broadleaf woodlands), both with and without constraining by similarity due to shared taxonomy or functional traits. Comparisons of diversity between the two habitats differed according to which metric was being used; while species richness was 58% greater in broadleaf woodlands, after accounting for species similarity due to shared functional traits, there was little difference between woodland types under two different disturbance regimes. Functional diversity varied within the landscape but was similar in paired broadleaf and plantation sites, suggesting that landscape rather than local factors drive biotic homogenization in plantation dominated landscapes. The higher richness in broadleaf sites appears to be driven by rare species, which share functional traits with more common species. Moth populations in disturbed, plantation sites represent a reduced subset of moth species compared to broadleaf sites, and may be more vulnerable to disturbance pressures such as clear‐felling operations due to low community resilience

Responses of bats to clear fell harvesting in Sitka Spruce plantations, and implications for wind turbine installation

Commercial coniferous plantations are often assumed to be poor habitats for bats. As a result, the impact of forest management practices on bats, such as clear felling, has received little attention, particularly in Europe. However, there is growing evidence from multiple regions that bats do make use of plantation landscapes, and as interest in siting onshore wind turbines in upland conifer plantations grows, there is an urgent need to examine whether felling prior to turbine installation is likely to put foraging bats at risk of collision. In the first study of its kind, we use a “before – after – control – impact” study to explore the short-term impacts of clear fell harvest on bat activity in commercial plantations. Thirty-one mature stands of Sitka Spruce were surveyed using acoustic detectors in three large, upland Sitka Spruce plantations in Britain. Eleven stands were felled between 2013 and 2015, and 26 of the original 31 stands were resurveyed in 2015. The change in total bat activity and species- or genus-specific bat activity was modelled before and after felling occurred at both felled and control stands using generalised linear models. There was no change in overall bat activity at felled sites compared to control sites, but activity ofNyctalusspecies was 23 times higher following felling. TotalPipistrellus spp.activity doubled at felled sites post-harvesting, although this was mainly driven by increased activity at a few felled sites. WhenP. pygmaeusandP. pipistrelluswere considered separately, activity increased slightly but non-significantly. The size of the felled area influenced activity (for bats overall andPipistrellus spp.), with 90% higher activity in smaller felled stands (less than 5ha−1) compared to larger felled stands (greater than 30ha−1). ForP. pipistrellus, activity in felled areas decreased with the duration since harvesting; the greatest activity occurred in stands felled within two months compared to those harvested more than 16months previously. Higher activity for some groups following felling may occur due to the creation of more edge habitat, which is preferred by bothPipistrellusspecies we recorded. An increase in activity following the small-scale felling (‘key-holing’) required for the installation of turbines could put foraging bats at risk from collisions with turbines. Further investigation of the influence of both size of clear fell patch, timing of felling and changes in invertebrate abundance due to felling are required to establish the potential risk of key-holing and turbine installation to foraging bats

Flexible foraging strategies in Pipistrellus pygmaeus in response to abundant but ephemeral prey

There is growing recognition that with sympathetic management, plantation forests may contain more biodiversity than previously thought. However, the extent to which they may support bat populations is contentious. Many studies have demonstrated active avoidance of coniferous plantations and attributed this to the lack of available roost sites and low invertebrate density. In contrast, other work , carried out in plantation dominated landscapes have shown that certain bat species are able to exploit these areas. However, the extent to which bats use plantations for roosting and foraging, or simply move through the plantation matrix to access more favourable sites is unclear. We radio tracked female Pipistrellus pygmaeus over two summers to establish the extent to which individual bats use Sitka Spruce plantations in southern Scotland for foraging and roosting and assess the implications for felling operations on bats. Maternity roosts identified (n=17) were in all in buildings and most were large (> 500 individuals). We found no evidence of bats roosting in mature Sitka Spruce crop trees, although several bats used roosts in old or dead beech and oak trees as an alternative to their main maternity roost. Home ranges were much larger (mean 9.6 ± 3.12 km2) than those reported from other studies ((0.6 – 1.6 km2), and it is likely that roost availability rather than food abundance constrains P. pygmaeus use of Sitka Spruce plantations. At the landscape scale, most individuals selected coniferous habitats over other habitat types, covering large distances to access plantation areas, whilst at a local scale bats used forest tracks to access water, felled stands or patches of broadleaf cover within the plantation. Sitka Spruce plantations support a high abundance of Culicoides impuctatus, the Highland midge which may act as a reliable and plentiful food source for females during lactation, an energetically expensive period. The use of felled stands for foraging by bats has implications for forest management as wind turbines, following small-scale felling operations, are increasingly being installed in plantations; wind turbines have been associated with high bat mortality in some countries. Decisions about siting wind turbines in upland plantations should consider the likelihood of increased bat activity post felling

Bat use of commercial coniferous plantations at multiple spatial scales: Management and conservation implications

Commercial plantations are primarily managed for timber production, and are frequently considered poor for biodiversity, particularly for mammalian species. Bats, which constitute one fifth of mammal species worldwide, have undergone large declines throughout Europe, most likely due to widespread habitat loss and degradation. Bat use of modified landscapes such as urban or agricultural environments has been relatively well studied, however, intensively managed plantations have received less attention, particularly in Europe. We assessed three of the largest, most intensively managed plantations in the UK for the occurrence of bats, activity levels and relative abundance in response to environmental characteristics at multiple spatial scales, using an information theoretic approach. We recorded or captured nine species;Pipistrellus pipistrellusandP.pygmaeuswere the most commonly recorded species on acoustic detectors and femaleP.pygmaeuswere the most commonly captured. The influence of environmental characteristics on bat activity varied by species or genus, although all bat species avoided dense stands. Occurrence and activity of clutter and edge adapted species were associated with lower stand densities and more heterogeneous landscapes whereas open adapted bats were more likely to be recorded at felled stands and less likely in areas that were predominantly mature conifer woodland. In addition, despite morphological similarities,P.pipstrellusandP.pygmaeuswere found foraging in different parts of the plantation. This study demonstrates that with sympathetic management, non-native conifer plantations may have an important role in maintaining and supporting bat populations, particularly forPipistrellusspp

A global model of the response of tropical and sub-tropical forest biodiversity to anthropogenic pressures

Habitat loss and degradation, driven largely by agricultural expansion and intensification, present the greatest immediate threat to biodiversity. Tropical forests harbour among the highest levels of terrestrial species diversity and are likely to experience rapid land-use change in the coming decades. Synthetic analyses of observed responses of species are useful for quantifying how land use affects biodiversity and for predicting outcomes under land-use scenarios. Previous applications of this approach have typically focused on individual taxonomic groups, analysing the average response of the whole community to changes in land use. Here, we incorporate quantitative remotely sensed data about habitats in, to our knowledge, the first worldwide synthetic analysis of how individual species in four major taxonomic groups—invertebrates, ‘herptiles’ (reptiles and amphibians), mammals and birds—respond to multiple human pressures in tropical and sub-tropical forests. We show significant independent impacts of land use, human vegetation offtake, forest cover and human population density on both occurrence and abundance of species, highlighting the value of analysing multiple explanatory variables simultaneously. Responses differ among the four groups considered, and—within birds and mammals—between habitat specialists and habitat generalists and between narrow-ranged and wide-ranged species

The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project

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The PREDICTS database: a global database of how local terrestrial biodiversity responds to human impacts

Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species. Existing global databases of species’ threat status or population time series are dominated by charismatic species. The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project – and avert – future declines. We describe and assess a new database of more than 1.6 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world. The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadiverse countries. The database contains more than 1% of the total number of all species described, and more than 1% of the described species within many taxonomic groups – including flowering plants, gymnosperms, birds, mammals, reptiles, amphibians, beetles, lepidopterans and hymenopterans. The dataset, which is still being added to, is therefore already considerably larger and more representative than those used by previous quantitative models of biodiversity trends and responses. The database is being assembled as part of the PREDICTS project (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems – www.predicts.org.uk). We make site-level summary data available alongside this article. The full database will be publicly available in 2015