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Forests provide critical habitats for pollinating insects, including forest-dependent and habitat generalist species, yet it is unknown how these assemblages are shaped by overstory tree composition. We sampled bees in closed canopy plots in the southeastern United States representing a continuum of forest age and tree composition, from younger conifer-dominated forests to older forests dominated by deciduous broadleaf trees. Species-specific responses of bees to forest composition, and the influence of their traits on responses, were estimated using a joint species distribution model. Additionally, we investigated species richness trends of nesting, sociality, and phenological trait groups. Forest composition greatly influenced bee species occurrence: 48 % of species had positive relationships with the diversity of insect-pollinated broadleaf trees and 46 % had negative relationships with the proportion of conifer basal area. Bee species with early phenological activity drove these responses and richness patterns supported these trends. Our results indicate that phenology is an important factor determining bee species' forest dependency and sensitivity to forest composition in this region. We conclude that diverse broadleaf forests are crucial to maintaining bee diversity by providing floral resources that support forest-dependent species even in closed canopy conditions. Conifer forests can also provide valuable habitat to bee pollinators when restored to open canopy conditions. However, because no traits are indicative of conifer forest dependency and bee species respond to understory flora rather than tree attributes, open conifer forests may more strongly favor habitat generalists than forest specialists. • 48 % of bee species had positive relationships with insect-pollinated tree diversity. • 46 % of bee species had negative relationships with the proportion of conifer trees. • Bees species responding to tree composition had early phenological activity. [ABSTRACT FROM AUTHOR]

The effects of prescribed fire on forest pollinator communities are complex and incompletely understood. One of the least-studied questions concerns how these organisms are affected by the size, or spatial scale, of fire. We sought to address this by sampling bees (Hymenoptera: Apoidea), butterflies (Lepidoptera), and hover flies (Diptera: Syrphidae) at different distances along 500 m transects into forests burned every three years in the southeastern United States. We found combined pollinator richness to decline significantly with distance, being about 23.9 % lower near the centers of burn units than near the edges, and this did not change with time since fire. These patterns held true when small and large pollinators were analyzed separately, as well as for the richness of bees and butterflies (but not hover flies), and regardless of bee nesting guild. We found no relationship between the abundance of all pollinators and distance. However, the abundance of small pollinators decreased with distance whereas that of large pollinators increased. A competing model provided no support for the alternative hypothesis that the observed effects of distance can be explained by the length of road edges nearby as opposed to distance from unburned habitat. The richness and abundance of all pollinators combined and most taxonomic groups and species analyzed separately increased with increasing canopy openness as well as with increasing plant richness. Although pollinator richness declined with distance into large burns and small species appear to be particularly sensitive, we also found the richness and abundance of pollinators to decrease with time since fire. Our results show that fire can improve local conditions for pollinators but that unburned habitats serve as important refugia or sources of flowers following fire, underscoring the importance of pyrodiversity in managed landscapes. • Pollinator richness declines with distance into large burn units. • Small species are more sensitive than large species. • Effects persist even several years since the last fire. • Pollinator richness and abundance decrease with time since the last fire. [ABSTRACT FROM AUTHOR]

• Species' traits influenced their responses to forest age, landscape forest cover, and deadwood. • Community trait composition was influenced by forest age, landscape forest cover, and deadwood. • Large-bodied species benefitted from old forests and high amounts of forest cover in the landscape. Many forests throughout the world consist of regenerating mature stands. Although these forests differ in many respects from old-growth (with a history of minimal human disturbance), they typically develop similar structural attributes over time. As a result, older mature forests may be of particular conservation value if they contain resources and microhabitats benefitting saproxylic (deadwood dependent) species. Species' response to forest age may be driven by traits that relate to ecological functions or habitat preferences, such that species with less compatible traits for a local forest environment are "filtered" out. Thus, forest age may influence species' distributions and the trait composition of assembled communities. The Piedmont region of the southeastern United States has experienced widespread forest regrowth over the past century due to agricultural abandonment. Today's landscapes are largely characterized by mature forests that are becoming increasingly fragmented by suburbanization. Here, we assessed the filtering effects of forest age, landscape forest cover (LFC), and deadwood volume on saproxylic beetles in northeastern Georgia. Using historic aerial imagery to distinguish forest age (young = regrown after 1938; old = mature in 1938), we sampled beetles in mature forests of both age classes occurring along an LFC gradient. We measured five traits with hypothesized functional roles (body length, body width, body roundness, antenna length, eye length) for the 472 species captured. Using a joint species distribution model (JSDM), we tested trait-niche relationships (i.e., how traits influence species' responses) and estimated community trait composition (mean and dispersion of trait values) along gradients of environmental filters. We found that forest age is a filter for several traits (six supported relationships with > 95 % posterior probability), but LFC and deadwood volume were less strongly related to fewer traits. Most notably, large species (typically having lower population sizes and requiring stable larval habitat) were filtered from young mature forests and low LFC. Thus, old mature forests with high LFC showed higher mean and dispersion of beetle body length. Sensory traits also showed responses, likely reflecting adult life under bark (eye length) or ability to detect resources or mates (antenna length). Body width and roundness showed inconsistent responses with regard to indicated functional roles. Our results show that forest age is a strong filter on saproxylic beetle communities in the southeastern United States. Old mature forests, despite their scarcity in the region, are important for species requiring habitat stability and for maintaining communities with diverse trait composition. [ABSTRACT FROM AUTHOR]

Highlights • Downed wood volume is not consistently higher in old-growth vs. secondary longleaf pine forests. • Old-growth longleaf pine forests have among the lowest wood volumes of any old-growth forest. • Fire- and decay-resistant heartwood appears to be an indicator of old-growth conditions. Abstract Few efforts have been made to quantify the amount and variety of deadwood in frequently burned ecosystems, particularly the longleaf pine (Pinus palustris Mill.) ecosystem of the southeastern United States. Moreover, comparisons of coarse woody debris between old-growth and secondary longleaf pine forests are lacking despite the widely recognized value of deadwood to biodiversity in many forest types. We measured standing and fallen deadwood in three old-growth and four mature (100–125 years-old) secondary forests in two landscapes characterized by either sandy or clayey soils within the historic range of P. palustris. Downed coarse woody debris volume was variable at the old-growth locations, ranging from 2.51 ± 0.79 to 29.10 ± 14.55 m3 per ha, which includes perhaps the lowest values ever reported from any old-growth forest. Factors likely contributing to these low volumes include frequent fire, the low basal area characteristic of this forest type, subtropical climatic conditions of the southeastern Coastal Plain, and large termite populations. The high variability observed among the three old-growth locations probably reflect interactions between fire and other disturbances (e.g., wind damage). The old-growth location on sandy soils had significantly higher coarse woody debris volume and deadwood variety (e.g., diameter increments, posture, tree genera and decay classes) than secondary forests sampled nearby. Highly resinous heartwood is a significant indicator of old-growth conditions relative to secondary locations, appearing to accumulate as a persistent fraction of the deadwood pool over time. [ABSTRACT FROM AUTHOR]

Old forests are valuable for biodiversity conservation because they provide uninterrupted forest cover over time and late-successional habitat, promoting low-mobility and late-successional species. However, forest age may be less important in highly forested landscapes because dispersal limitation is reduced. We investigated how species richness and community composition of saproxylic beetles (Coleoptera) are influenced by forest age and the surrounding landscape in the southeastern United States (Georgia). Forests in this region are highly fragmented and dominated by early-successional stands. We sampled beetles in 20 old forests (mature in 1938) and 20 young forests (originating after 1938), located along a landscape forest cover (LFC) gradient. Old and young forests were structurally similar but tree communities differed along a Quercus (old) to Pinus (young) gradient. Regional diversity of saproxylic beetles was higher in old forests, and high species turnover between forest age groups suggests they both help to maintain regional biodiversity. Two models of local richness had near equal merit: one showed higher richness in old forests regardless of LFC, while the other showed higher richness in old forests at high LFC. Contrary to expectations, neither model supports old forests losing importance in highly forested landscapes. Higher richness in old forests is likely due to temporal stability and late-successional habitat, promoting low-mobility and specialist species. Because the land area of young forests exceeds that of old forests, old forests are disproportionately important for saproxylic biodiversity in the region. • Old forests are important for saproxylic beetles even in highly forested landscapes. • Old forests support more saproxylic beetle species than young forests. • Saproxylic beetle community composition changed with age, driven by tree species. [ABSTRACT FROM AUTHOR]

Insects play a key role in the regulation and dynamics of many ecosystem services (ES). However, this role is often assumed, with limited or no experimental quantification of its real value. We examined publication trends in the research on ES provided by insects, ascertaining which ES and taxa have been more intensively investigated, and which methodologies have been used, with particular emphasis on experimental approaches. We first performed a systematic literature search to identify which ES have been attributed to insects. Then we classified the references retrieved according to the ES, taxonomic group and ecosystem studied, as well as to the method applied to quantify each ES (in four categories: no quantification, proxies, direct quantification and experiments). Pollination, biological control, food provisioning, and recycling organic matter are the most studied ES. However, the majority of papers do not specify the ES under consideration, and from those that do, most do not quantify the ES provided. From the rest, a large number of publications use proxies as indicators for ES, assuming or inferring their provision through indirect measurements such as species abundances, species density, species richness, diversity indices, or the number of functional groups. Pollinators, predators, parasitoids, herbivores, and decomposers are the most commonly studied functional groups, while Hymenoptera, Coleoptera, and Diptera are the most studied taxa. Experimental studies are relatively scarce and they mainly focus on biological control, pollination, and decomposition performed in agroecosystems. These results suggest that our current knowledge on the ES provided by insects is relatively scarce and biased, and show gaps in the least-studied functional and taxonomic groups. An ambitious research agenda to improve the empirical and experimental evidence of the role played by insects in ES provision is essential to fully assess synergies between functional ecology, community ecology, and biodiversity conservation under current global changes. [ABSTRACT FROM AUTHOR]

Wood properties and microbial community characteristics were compared between loblolly pine ( Pinus taeda L.) logs protected or unprotected from termites (Blattodea: Rhinotermitidae: Reticulitermes spp.) and other arthropods for two years in seasonally flooded and unflooded forests in the southeastern United States. Significant compositional differences were observed between treatments and between flood patterns for both bacterial and fungal communities. Bacteria were 8–9-fold more abundant in unprotected logs compared to protected logs in both flooded and unflooded forests, with the greatest abundance seen in unprotected and unflooded logs. Wood nitrogen and lignin contents were unaffected by treatment, flood pattern or levels of termite damage visible in unprotected logs. We conclude that termites alter the composition of both bacterial and fungal communities and thus have the potential to indirectly affect wood decomposition and related processes through interactions with the microbial community. [ABSTRACT FROM AUTHOR]

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Abstract: Large-scale manipulations of dead wood in mature Pinus taeda L. stands in the southeastern United States included a major one-time input of logs (fivefold increase in log volume) created by felling trees onsite, annual removals of all dead wood above ⩾10cm in diameter and ⩾60cm in length, and a reference in which no manipulations took place. We returned over a decade later to determine how these treatments affected tree growth using increment cores. There were no significant differences in tree density, basal area or tree diameters among treatments at the time of sampling. Although tree growth was consistently higher in the log-input plots and lower in the removal plots, this was true even during the 5year period before the experiment began. When growth data from this initial period were included in the model as a covariate, no differences in post-treatment tree growth were detected. It is possible that treatment effects will become apparent after more time has passed, however. [Copyright &y& Elsevier]

Abstract: Because leaf litter occurs at the interface between the soil and atmosphere, the invertebrates inhabiting it represent important linkages between above- and below-ground food webs. The responses of these organisms to forest disturbance brought about by invasive species should therefore have far-reaching ecological effects. The purpose of this study was to explore how canopy gap formation (gap fraction 1–10%) and fallen ash trees (“logs”) resulting from extensive (>99%) ash tree mortality caused by the invasive emerald ash borer (EAB) affect the distributions of litter-dwelling arthropods and earthworms. These organisms did not vary in abundance across the gap fraction range studied but, as predicted from the literature, many taxa (e.g., Aranea, Coleoptera, Collembola, Diplopoda, Isopoda, Opiliones and exotic earthworms) were more abundant next to logs than away from them. Contrary to expectations, arthropods did not become more concentrated next to logs as canopy openness increased, with isopods exhibiting the opposite response. These results suggest litter-dwelling arthropods in EAB-infested forests are favored by inputs of ash wood to the forest floor but are largely unaffected by increases in canopy openness, at least across the gap fraction range studied. [Copyright &y& Elsevier]

Abstract: Studies on the vertical distribution patterns of arthropods in temperate deciduous forests reveal highly stratified (i.e., unevenly vertically distributed) communities. These patterns are determined by multiple factors acting simultaneously, including: (1) time (forest age, season, time of day); (2) forest structure (height, vertical foliage complexity, plant surface textures, tree cavities); (3) plant community composition (plant diversity, invasive species); (4) climatic gradients (light exposure, temperature, wind speed, humidity); (5) resource availability (foliage, sugars, wood, epiphytes, carrion, dung, prey, hosts, mates); (6) inter-specific interactions (predation, interference, competition) and (7) logistics (dispersal abilities, proximity to emergence sites, open flight zones). Several recommendations can be made with respect to incorporating canopy habitats and resources into management plans in order to maintain diverse forest arthropod communities. Efforts should be made to maintain diverse plant communities, for instance, including eliminating or controlling invasive plant competitors. Protecting large diameter trees and snags is also important, especially for a wide variety of canopy arthropod taxa associated with standing or suspended dead wood, tree cavities and epiphytes. Finally, it is essential to ensure adequate spatial and temporal continuity in the availability of these and other key resources. Although how to best achieve this last objective remains an active area of research, it may be preferable to retain clusters of trees as opposed to isolated individuals. [Copyright &y& Elsevier]

Abstract: Saproxylic beetles are highly sensitive to forest management practices that reduce the abundance and variety of dead wood. However, this diverse fauna continues to receive little attention in the southeastern United States even though this region supports some of the most diverse, productive and intensively managed forests in North America. In this replicated three-way factorial experiment, we investigated the habitat associations of saproxylic beetles on the coastal plain of South Carolina. The factors of interest were forest type (upland pine-dominated vs. bottomland hardwood), tree species (Quercus nigra L., Pinus taeda L. and Liquidambar styraciflua L.) and wood posture (standing and downed dead wood, i.e., snags and logs). Wood samples were taken at four positions along each log and snag (lower bole, middle bole, upper bole and crown) ∼11 months after the trees were killed and placed in rearing bags to collect emerging beetles. Overall, 33,457 specimens from 52 families and ≥250 species emerged. Based on an analysis of covariance, with surface area and bark coverage as covariates, saproxylic beetle species richness differed significantly between forest types as well as between wood postures. There were no significant interactions. Species richness was significantly higher in the upland pine-dominated stand than the bottomland hardwood forest, possibly due to higher light exposure and temperature in upland forests. Although L. styraciflua yielded more beetle species (152) than either Q. nigra (122) or P. taeda (125), there were no significant differences in species richness among tree species. There were also no relationships evident between relative tree abundance and observed or expected beetle species richness. Significantly more beetle species emerged from logs than from snags. However snags had a distinct fauna including several potential canopy specialists. Our results suggest that conservation practices that retain or create entire snags as opposed to high stumps or logs alone will most greatly benefit saproxylic beetles in southeastern forests. [Copyright &y& Elsevier]

Malaise traps were used to sample beetles in artificial canopy gaps of different size (0.13 ha, 0.26 ha, and 0.50 ha) and age in a South Carolina bottomland hardwood forest. Traps were placed at the center, edge, and in the surrounding forest of each gap. Young gaps (∼1 year) had large amounts of coarse woody debris compared to the surrounding forest, while older gaps (∼6 years) had virtually none. The total abundance and diversity of wood-dwelling beetles (Buprestidae, Cerambycidae, Brentidae, Bostrichidae, and Curculionidae (Scolytinae and Platypodinae)) was higher in the center of young gaps than in the center of old gaps. The abundance was higher in the center of young gaps than in the surrounding forest, while the forest surrounding old gaps and the edge of old gaps had a higher abundance and diversity of wood-dwelling beetles than did the center of old gaps. There was no difference in wood-dwelling beetle abundance between gaps of different size, but diversity was lower in 0.13 ha old gaps than in 0.26 ha or 0.50 ha old gaps. We suspect that gap size has more of an effect on woodborer abundance than indicated here because malaise traps sample a limited area. The predaceous beetle family Cleridae showed a very similar trend to that of the woodborers. Coarse woody debris is an important resource for many organisms, and our results lend further support to forest management practices that preserve coarse woody debris created during timber removal. [Copyright &y& Elsevier]

• Wood exposed to termites decomposed significantly faster than that excluded. • Termites can exceed microbes in importance to wood decomposition. • The role of termites and microbes to wood decompose depended on soil contact types. • Wood in direct contact with the soil decomposed 1.4 times as fast as wood separated. Deadwood contains a sizeable proportion of total forest C, and its decomposition transfers organic C to the atmosphere, other organisms and soils. Microbes have traditionally been thought to be the primary drivers of wood decomposition worldwide, but few studies have tested the relative importance of termites to this process. The aim of this study was to compare the relative contributions of microbes and termites to wood (Cinnamomum camphora) decomposition by conducting a field experiment of termite access (with and without termite exclusion) and soil contact (with and without soil contact) treatments in subtropical China. After a two-year period, termites were responsible for an estimated 55.7% and 48.9% of observed wood loss from wood blocks with and without soil contact, respectively. Wood in direct contact with the soil decomposed 1.4 times as fast as wood separated from the soil. Our results show that termites can exceed microbes in importance to wood decomposition in subtropical forests and highlight the importance of soil contact in determining decay rates. [ABSTRACT FROM AUTHOR]

Restoring dead-wood amounts in forests is an increasingly and successfully applied conservation measure to counteract negative effects of intensive logging on biodiversity of saproxylic taxa. By contrast, if and how dead-wood addition benefits the vast number of non-saproxylic forest taxa, and how this varies with contextual factors like canopy openness, remains poorly understood. To enhance dead-wood addition strategies, it is thus important to understand how dead wood affects entire forests communities, not just saproxylic taxa. To untangle effects of dead-wood addition and canopy openness on non-saproxylic epigeal arthropods, we exposed different amounts of logs and branches on 190 0.1-ha plots located in sunny or shady mixed montane forests and sampled epigeal arthropods over three years. Canopy openness was a major driver of species assemblage composition and clearly mediated the effects of dead wood on epigeal beetles, spiders/harvestmen and springtails. Most species groups responded positively to the addition of dead wood. All groups decreased in number with increasing distance to dead wood. Dead wood affected taxa of both lower and higher trophic levels directly and taxa of higher trophic levels benefitted also indirectly owing to bottom-up effects. Our results indicate that increasing the amount of dead wood for conservation of saproxylic taxa benefits also non-saproxylic epigeal arthropods and thus, a larger number of forest species than commonly assumed. Because of the strong effects of canopy openness, similar to those found for saproxylic taxa, dead wood in both sunny and shady forest stands is needed. [ABSTRACT FROM AUTHOR]

The importance of dead wood for biodiversity is widely recognized but strategies for conservation exist only in some regions worldwide. Most strategies combine knowledge from observational and experimental studies but remain preliminary as many facets of the complex relationships are unstudied. In this first global review of 79 experimental studies addressing biodiversity patterns in dead wood, we identify major knowledge gaps and aim to foster collaboration among researchers by providing a map of previous and ongoing experiments. We show that research has focused primarily on temperate and boreal forests, where results have helped in developing evidence-based conservation strategies, whereas comparatively few such efforts have been made in subtropical or tropical zones. Most studies have been limited to early stages of wood decomposition and many diverse and functionally important saproxylic taxa, e.g., fungi, flies and termites, remain under-represented. Our meta-analysis confirms the benefits of dead-wood addition for biodiversity, particularly for saproxylic taxa, but shows that responses of non-saproxylic taxa are heterogeneous. Our analysis indicates that global conservation of organisms associated with dead wood would benefit most by prioritizing research in the tropics and other neglected regions, focusing on advanced stages of wood decomposition and assessing a wider range of taxa. By using existing experimental set-ups to study advanced decay stages and additional taxa, results could be obtained more quickly and with less effort compared to initiating new experiments. [ABSTRACT FROM AUTHOR]