Article

The Impact of Prescribed Burning on Native Bee Communities (Hymenoptera: Apoidea: Anthophila) in Longleaf Pine Savannas in the North Carolina Sandhills

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Abstract

Prescribed burning is a common silvicultural practice used in the management of longleaf pine (Pinus palustris Mill., Pinales: Pinaceae) savannas to reduce hardwood encroachment and ground cover and to maintain biodiversity. We investigated the response of the native bee community (Hymenoptera: Apoidea: Anthophila) in the Sandhills of North Carolina to prescribed burning on a 3-yr rotation over two consecutive years (2012 and 2013). We deployed bee bowl traps in sites that had been burned the year of sampling, 1 yr before, 2 yr before, and in unburned controls. In total, 2,276 bees of 109 species were captured. Bee abundance declined with time since fire, with 2.3 times more bees captured in the most recently burned sites than in unburned controls. Bee diversity also declined with time since fire, with 2.1 times more species captured in the most recently burned sites than in controls. Bee community composition also responded to fire; we present evidence that this response was mediated in part by the effect of fire on the amount of bare ground and canopy cover. Bees nesting aboveground were unaffected by fire, contrary to our expectation that fire would destroy the wood and stems in which these species nest. Our results indicate that prescribed burning is a silvicultural practice consistent with pollinator conservation in longleaf pine ecosystems of the North Carolina sandhills.

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... Still other studies have reported no or little short-term impacts of fire on general arthropod abundance or biomass for several nocturnal insect orders (Armitage and Ober 2012), beetles (Chitwood et al. 2017), or hymenopterans (Chitwood et al. 2017) in the LLPE. In general, however, the majority of LLPE studies indicate that more frequent fires result in higher species richness for bees (Breland 2015, Moylett et al. 2020, saproxylic insects (Campbell et al. 2008), and arthropods at large (Provencher et al. 2003, O'Brien 2017. ...
... Fire plays the most critical role at this level of the longleaf pine forest, regulating plant diversity, arthropod diversity, and multi-trophic interactions between plants, herbivores, and parasitoids (Dell et al. 2019). More frequent fires result in higher species richness for bees (Breland 2015, Moylett et al. 2020. Some studies show an increase in abundance following a burn such as with orthopterans (Provencher et al. 1998a, Kerstyn and Stiling 1999, Bellanceau 2007, halictid bees (Campbell 2005), dance flies (Diptera: Empididae) (Provencher et al. 1998a), and planthoppers (Hemiptera: Cicadellidae, Flatidae) (Provencher et al. 1998a). ...
... Many of them are polylectic (pollinating several plant species; Folkerts et al. 1993, which creates a complex and intricate web of interactions. Bees (Hymenoptera: Anthophila) have dominated the field of LLPE pollinator research, likely due to their status as the most efficient pollinators (Moylett et al. 2020), but other taxa have been examined as well. Rare plants may depend on arthropod pollination in the LLPE (Pitts-Singer et al. 2002). ...
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The longleaf pine Pinus palustris Miller (Pinales: Pinaceae) ecosystem once covered as many as 37 million hectares across the southeastern United States. Through fire suppression, development, and conversion to other plantation pines, this coverage has dwindled to fewer than 2 million hectares. A recent focus on the restoration of this ecosystem has revealed its complex and biologically diverse nature. Arthropods of the longleaf pine ecosystem are incredibly numerous and diverse—functionally and taxonomically. To provide clarity on what is known about the species and their functional roles in longleaf pine forests, we thoroughly searched the literature and found nearly 500 references. In the end, we tabulated 51 orders 477 families, 1,949 genera, and 3,032 arthropod species as having been stated in the scientific literature to occur in longleaf pine ecosystems. The body of research we drew from is rich and varied but far from comprehensive. Most work deals with land management objective associated taxa such as pests of pine, pests of—and food for—wildlife (red-cockaded woodpecker, northern bobwhite quail, gopher tortoise, pocket gopher, etc.), and pollinators of the diverse plant understory associated with longleaf pine. We explored the complex role frequent fire (critical in longleaf pine management) plays in determining the arthropod community in longleaf pine, including its importance to rare and threatened species. We examined known patterns of abundance and occurrence of key functional groups of longleaf pine-associated arthropods. Finally, we identified some critical gaps in knowledge and provide suggestions for future research into this incredibly diverse ecosystem.
... Defined broadly as ecosystems dominated by trees, forests comprise over 30% of global land cover (World Bank, 2021) and often support diverse pollinator communities (Hanula et al., 2016). Open forest conditions maintained by fire or created through management activities such as thinning have been shown to boost the availability of floral resources (Moylett et al., 2019) and increase populations of bees, butterflies, and other flower-visiting insects (Hanula et al., 2016;Galbraith et al., 2019). Forests are also likely to provide an abundance of nesting resources that may be unavailable or scarce in other land use types (Kim et al., 2006). ...
... First, frequent burns are known to result in more open conditions and this may favour ground-nesting bees by increasing the amount of bare soil available and reducing soil moisture (Pane & Harmon-Threatt, 2017). It is also possible that bees nest more readily in frequently burned areas due to an increased availability of floral resources as frequent fires are well known to increase the amount and variety of floral resources within our study region (Platt et al., 1988;Hiers et al., 2000;Moylett et al., 2019). Because female bees are central-place foragers, meaning their activities are centred around their nest (Danforth et al., 2019), it would be reasonable for them to establish nests in areas with an abundance of flowers. ...
... Our results show frequent fire regimes improve nesting habitat for ground-nesting bees in southeastern U.S. forests. These findings nicely complement the results from past studies demonstrating the benefits of fire to floral resources and foraging bee numbers (Moylett et al., 2019). Although there were no major differences in bee communities between annually and biennially burned plots, significantly more individuals were captured in plots burned annually than in those burned triennially. ...
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• Although most efforts to improve habitat for bees and other pollinators focus on floral resources, it is also important to consider the availability and suitability of nesting habitats in relation to various management activities. • We used soil emergence traps to compare the number of ground‐nesting bees among treatments in a long‐term fire frequency study in Florida. We regularly moved the traps, a strategy that appears to greatly improve the efficacy of this sampling approach. The experiment consisted of forested plots that have been burned annually, biennially or triennially for the past six decades as well as unburned reference plots. • Bee abundance was significantly lower in the unburned plots than in any of the burn treatments and was higher in annual plots than triennial plots. Bee richness was significantly higher in plots burned annually than in unburned plots. Bee Shannon's diversity was significantly higher in plots burned biennially or triennially than in unuburned plots. Evenness was significantly lower in annually burned plots than in any of the other treatments. • Indicator species analysis found six bee species to be significantly associated with one or more burn treatments. Four of them were strongly associated with plots burned annually or biennially while two species were significantly associated with plots burned biennially or triennially. None was significantly associated with unburned plots. • Our findings suggest that frequent fires generally improve habitat for ground‐nesting bees in southeastern U.S. forests and that tolerances for particular burn frequencies vary by species.
... Studies of the effects of controlled burns on arthropod taxa have classified unburned groups as those as many as 30-75 years post burn (Andersen et al. 2014, Atchinson et al. 2018, Hanula and Wade 2003, Moretti et al. 2009, Moylett 2014. Table 1. ...
... Even the community collected at the site unburned for 8 years was only marginally different from the others, and still lacked obvious evidence of any indicator species that had clearly benefitted or suffered from the extended absence of fire. Our results are generally consistent with those reported earlier by Breland (2015) and Moylett (2014), where bee communities in Longleaf Pine savannas showed either modest positive or no increase in diversity, depending on the measure used, in sites recently burned versus those either 1 or 2 years post burn. In fact, bee diversity in recently burned sites was only significantly higher when compared against control sites that were 50 years post burn (Moylett 2014). ...
... Our results are generally consistent with those reported earlier by Breland (2015) and Moylett (2014), where bee communities in Longleaf Pine savannas showed either modest positive or no increase in diversity, depending on the measure used, in sites recently burned versus those either 1 or 2 years post burn. In fact, bee diversity in recently burned sites was only significantly higher when compared against control sites that were 50 years post burn (Moylett 2014). ...
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Controlled burning is an essential tool for restoration and management of Pinus palustris (Longleaf Pine) habitats, yet effects of controlled burning on insect species, including pollinators, are rarely considered in conservation planning. We used blue vane traps to sample native bees (Hymenoptera: Apoidea) at recently burned and unburned sites in 2 Longleaf Pine upland forests in Mississippi and Louisiana. Our objective was to quantify short-term effects of controlled burns given fire-return intervals of 1-2 years are now regularly employed to manage Longleaf Pine woodlands. We sampled during 2016 and 2017 and collected 1777 native bees, representing 43 species. Recent fire was found to have no clear effect on species composition, richness, or community structure. Overall, bee communities from burned and unburned sites were similar. Even the community collected from a site that had remained unburned for 8 years was only marginally different from the others. These results suggest that native bee communities may be resilient to low intensity burns.
... Prescribed burns are thought to mimic wildfires and positively influence pollinators by creating early seral stage habitats with abundant floral resources, coarse woody debris, and bare ground (Carbone et al. 2019;Potts et al. 2003; Simanonok and Burkle 2019), but we observed an equivalent number of positive and neutral effects, suggesting that prescribed burns frequently have no effect on pollinators in some circumstances or ecosystems. Bee abundance increased following burns in longleaf pine savannas (Moylett et al. 2020;Ulyshen et al. 2021), southern Appalachian hardwood forests ( , but see (Campbell et al. 2007)), and tallgrass prairies, along with increasing butterfly richness and diversity in upland forest and riparian habitats (Huntzinger 2003), abundance in oak pine woodlands (Rudolph et al. 2006), and tallgrass prairies (Panzer and Schwartz 2000). Prescribed burns also increased pollinator visitation rates to plants in southeastern oldfields (Van Nuland et al. 2013), and pollination services to the netted pawpaw (Asimina reticulata) in Florida scrubland (Barton and Menges 2018). ...
... For instance, bee abundance and richness were not affected by prescribed burns in midwestern oak savannas (Lettow et al. 2018) or pinyon-juniper woodlands (Nyoka 2010) and had no effects on butterflies in Appalachian hardwood forests (Campbell et al. 2007. Burning during the growing season (spring and summer) in tallgrass prairies (Decker and Harmon-Threatt 2019), and burning in three to six year intervals in southern Appalachian hardwood forests ) and longleaf pine savannas (Moylett et al. 2020;Ulyshen et al. 2021) appear to benefit pollinator communities in these habitat types. ...
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Public lands face growing demands to provide ecosystem services, while protecting species of conservation concern, like insect pollinators. Insect pollinators are critical for the maintenance of biodiversity and ecosystem function, but it is unclear how management of public lands influence pollinator conservation. We found 63 studies investigating the effects of prescribed burning, logging, grazing, invasive species removal, revegetation with wildflower mixes, and hosting commercial pollinators, on native insect pollinators on natural and semi-natural ecosystems in the US and summarized the results across taxa and habitat types. Manual removal of invasive shrubs and revegetation with wildflower mixes had consistently positive effects on pollinators. Grazing had neutral effects on pollinators in the Great Plains, but negative effects elsewhere. Prescribed burning had neutral or positive effects for bees depending on the habitat type, with occasional negative effects on butterflies. Logging had neutral to positive effects that were more uniform across ecosystems and taxa than burning. Burning combined with logging benefited pollinators, even when burning or logging alone had no effects. Although poorly studied, hosting commercial pollinators may negatively affect wild bees through pathogen transmission and competition for floral resources. Despite the rapid accumulation of information on factors contributing to pollinator declines, the effects of management actions on pollinators remain understudied for many taxa and habitat types in the US. Improving our understanding of the effects of public land management on pollinators is essential to conserve ecosystem health and services required by society.
... Less-frequent fires result in the displacement of herbaceous plants by shrubs and an absence of fire results in closed hardwood-dominated forests. Although previous studies reported positive responses of bees to prescribed fire in the region, presumably due to increases in floral resource availability following burns (Moylett et al. 2019), as in most regions, the importance of burn heterogeneity to pollinators remains largely unexamined in the southeastern US. ...
... Moreover, the species that responded most positively to high burn diversity and was most sensitive to high burn frequency (A sumptuosa) is a ground-nester. Although aboveground nesting species were more sensitive to fire than ground-nesting species in previous studies (Williams et al. 2010), the frequent low-intensity prescribed fires typical of the southeastern US may pose less of a threat to this fauna (Moylett et al. 2019). ...
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Fire is a key determinant of vegetation structure and composition in ecosystems worldwide and is therefore an important management tool. The “pyrodiversity hypothesis”, which postulates that biodiversity will increase as fire diversity increases, remains largely untested for pollinators, a group of high conservation concern. We tested the relationship between pollinator diversity and pyrodiversity based on a decade of burn history in Florida, as well as testing other parameters, including burn frequency, the percentage of area burned during the year of sampling, canopy openness, and various plant metrics. Both bees and butterflies responded positively to pyrodiversity and to the percentage of area burned during the year of sampling. In addition, our results indicate that pollinators, especially butterflies, may be sensitive to high burn frequency. Our findings reveal the important role fire history plays in shaping pollinator communities and demonstrate that increasing burn heterogeneity can benefit this fauna in fire‐managed landscapes.
... In forest systems, higher wildfire intensity has been associated with higher abundance and richness of non-Bombus wild bees (Galbraith et al. 2019) and a combination of shrub removal and prescribed fire has resulted in higher Hymenoptera abundance in the 2 yr following burn (Campbell et al. 2007). Studies in grassland systems generally confirm the positive impact of fire on wild bees, with higher abundance, diversity, and richness found immediately and up to 3 yr after wildfire (DiCarlo et al. 2019) or prescribed fire (Moylett et al. 2020) compared with unburned controls. However, most wild bee taxa examined are composed of small solitary species with different nesting, mating, and foraging life histories from bumble bees. ...
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Despite the importance of bumble bees (genus Bombus Latreille) for their services to natural and agricultural environments, we know little about the relationship between grassland management practices and bumble bee conservation. Prescribed fire is a common grassland maintenance tool, including in areas where endangered and threatened bumble bees are present. Thus, knowledge of the effects of prescribed fire on bumble bees is essential for designing management schemes that protect and bolster their populations. Using nonlethal surveys to record bumble bee species richness, abundance, and community composition, we evaluated the effects of spring controlled burns on summer bumble bee gynes and workers across five sites in southern Wisconsin. In addition, we explored the effects of fire on floral resources by measuring floral genus richness, abundance, ground cover, and proportion of transects containing blooming flowers in adjacent burned and unburned parcels. Prescribed fire had no measurable effects on bumble bee gyne or worker community composition, species richness, or abundance. However, consistent with previous studies prescribed fire increased floral genus richness and ground cover. The disconnect between bumble bee and floral responses to fire highlights some opportunities for improving our understanding of fire’s effects on bumble bee diapause, nest site choice, and foraging.
... It is possible that grazing can better maintain floral diversity over time by increasing the temporal persistence of both forb and legume species in a restored habitat [42], though other studies have found no difference between management strategies over shorter time scales [43]. Generally, some form of spatially and temporally heterogeneous disturbance is beneficial for maintaining a functioning prairie ecosystem [65,85], and either mowing or grazing is preferred over no post-restoration management. Furthermore, utilization of restored areas for livestock grazing or mowing can generate additional benefits to landowners by providing feed; for example, cattle could graze these areas during interspersed growing seasons or alternatively these areas could be partially hayed to produce winter feed. ...
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Purpose of Review We reviewed the common mechanisms through which intensively cropped landscapes are modified to increase wild bee abundance and diversity in North American prairie ecosystems. We categorized these efforts into three main categories: retaining parcels of land identified as important to wild bee communities, augmenting currently cropped areas to increase available resources, and restoring spaces from cropland to pollinator habitat. We discuss considerations that should be included at both the farm and “farm-neighborhood” scale, and review the literature pertaining to the costs and benefits of each strategy. Recent Findings Wild bee conservation has been a topic of much interest in the past decade, with research generally focused at the field scale. Initial studies have focused on providing evidence that restoring, augmenting, and retaining land for wild bees shows the desired effects. Research quantifying the costs associated with each method still has significant knowledge gaps, as does understanding patterns of variability common in natural prairie ecosystems. Summary Retaining, augmenting, and restoring habitat for wild pollinators can create “win-win” scenarios for both wild bees and land-use decision-makers, whereby increased insect abundance has the potential to increase yield. There are considerations to be taken into account at both the farm and farm-neighborhood scale, and we present a framework which can be used to demonstrate the value of non-cropped areas to land-use decision-makers. Rapidly developing technology, such as GPS yield monitoring, has the potential to dramatically increase our power to detect which areas of a field may be ideal candidates for restoration or augmentation efforts.
... Given the wide-ranging importance of promoting pollinators, our work supports the use of overstory tree thinning to increase the diversity and richness of bees in this biodiversity hotspot. The future effects of savanna maintenance through fire on bee communities will require additional study as these restorations mature, though bees may respond positively to fire (Campbell et al. 2007;Campbell-Moylett 2014;Taylor and Catling 2011). This article is protected by copyright. ...
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Longleaf pine savannas are highly threatened, fire‐maintained ecosystems unique to the southeastern United States. Fire suppression and conversion to agriculture has strongly affected this ecosystem, altering overstory canopies, understory plant communities, and animal populations. Tree thinning to reinstate open canopies can benefit understory plant diversity, but effects on animal communities are less well understood. Moreover, agricultural land‐use legacies can have long‐lasting impacts on plant communities, but their effects on animal communities either alone or through interactions with restoration are unclear. Resolving these impacts is important due to the conservation potential of fire suppressed and post‐agricultural longleaf savannas. We evaluated how historical agricultural land use and canopy thinning affect the diversity and abundance of wild bees in longleaf pine savannas. We employed a replicated, large‐scale factorial block experiment in South Carolina, where canopy thinning was applied to longleaf pine savannas that were either post‐agricultural or remnant (no agricultural history). Bees were sampled using elevated bee bowls. In the second growing season after restoration, thinned plots supported a greater bee abundance and bee community richness. Additionally, restored plots had altered wild bee community composition when compared to unthinned plots, indicating that reduction of canopy cover by the thinning treatment best predicted wild bee diversity. Conversely, we found little evidence for differences between sites with or without historical agricultural land use. Some abundant Lasioglossum species were the most sensitive to habitat changes. Our results highlight how restoration practices that reduce canopy cover in fire‐suppressed savannas can have rapid benefits for wild bee communities. This article is protected by copyright. All rights reserved.
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Chapter
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Maximum likelihood or restricted maximum likelihood (REML) estimates of the parameters in linear mixed-effects models can be determined using the lmer function in the lme4 package for R. As for most model-fitting functions in R, the model is described in an lmer call by a formula, in this case including both fixed- and random-effects terms. The formula and data together determine a numerical representation of the model from which the profiled deviance or the profiled REML criterion can be evaluated as a function of some of the model parameters. The appropriate criterion is optimized, using one of the constrained optimization functions in R, to provide the parameter estimates. We describe the structure of the model, the steps in evaluating the profiled deviance or REML criterion, and the structure of classes or types that represents such a model. Sufficient detail is included to allow specialization of these structures by users who wish to write functions to fit specialized linear mixed models, such as models incorporating pedigrees or smoothing splines, that are not easily expressible in the formula language used by lmer.
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Urbanization is a dominant form of land-use change driving species distributions, abundances, and diversity. Previous research has documented the negative impacts of urbanization on the abundance and diversity of many groups of organisms. However, some organisms, such as bees, may benefit from moderate levels of development, depending on how development alters the availability of foraging and nesting resources. To determine how one type of low-intensity human development, suburbanization, affects bee abundance and diversity and the mechanisms involved, we surveyed bees across suburban and natural forests in the Raleigh-Durham area of North Carolina. We sampled for bees using a combination of bee bowls and hand-netting from March through July of 2008 and 2009. We found higher bee abundance in suburban than natural forests, and although observed species richness was greater in suburban than natural forests, there were no significant differences in rarefied richness or evenness estimates in either year. In addition, the effects of suburbanization were similar across bee species of varying ecological and life-history characteristics. At the local scale, bee abundance and species richness were both positively related to the abundance and richness of flowering species within forests, while the proportion of surrounding developed open areas, such as yards and roadsides, was a strong positive predictor of both bee abundance and richness at the landscape scale. These results suggest that open habitats and the availability of floral resources in suburban sites can support abundant and diverse bee communities and underscore the potential for native bee conservation in urban habitats.
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Pollinators serve critical roles for the functioning of terrestrial ecosystems, and have an estimated annual value of over $150 billion for global agriculture. Mounting evidence from agricultural systems reveals that pollinators are declining in many regions of the world, and with a lack of information on whether pollinator communities in natural systems are following similar trends, identifying factors which support pollinator visitation and services are important for ameliorating the effects of the current global pollinator crisis. We investigated how fire affects resource structure and how that variation influences floral pollinator communities by comparing burn versus control treatments in a southeastern USA old-field system. We hypothesized and found a positive relationship between fire and plant density of a native forb, Verbesina alternifolia, as well as a significant difference in floral visitation of V. alternifolia between burn and control treatments. V. alternifolia density was 44% greater and floral visitation was 54% greater in burned treatments relative to control sites. When the density of V. alternifolia was experimentally reduced in the burn sites to equivalent densities observed in control sites, floral visitation in burned sites declined to rates found in control sites. Our results indicate that plant density is a proximal mechanism by which an imposed fire regime can indirectly impact floral visitation, suggesting its usefulness as a tool for management of pollination services. Although concerns surround the negative impacts of management, indirect positive effects may provide an important direction to explore for managing future ecological and conservation issues. Studies examining the interaction among resource concentration, plant apparency, and how fire affects the evolutionary consequences of altered patterns of floral visitation are overdue.
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We cataloged the bee fauna to determine potential pollinators in upland and wet longleaf pine savannas in Louisiana. A total of 122 species of bees were collected from four savanna sites. A regional list of 165 species was produced by adding species collected from nearby savannas in Mississippi. Our Louisiana survey documented range extensions for 23 species, 64 new state records, and two possible new species. Upland savannas contained a higher proportion of range restricted bees. Three species collected at upland sites are typically associated with prairies or grasslands and are potential targets for conservation efforts. Biogeographically, the fauna is eastern or southeastern with 68% of the species ranges extending eastward. Species composition comparisons of the Louisiana savanna fauna with other grassland and sand scrub habitats indicated 45% overlap with Mississippi, 30% with southern Florida, 29% with Indiana/Illinois, and 22% with Minnesota. Based on our Louisiana study and one nearby in Mississippi, longleaf pine savannas on the western edge of the East Gulf Coastal Plain are likely to contain close to 200 species of bees.
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With the growing interest in pollinator conservation, a need has emerged for a simple, unbiased method to reliably sample local bee faunas. One method, pan-trapping, has increased in popularity without critical evaluation of its efficacy and biases. We compared traditional net collecting at flowers and pan trapping concurrently, sampling the local bee fauna of the dominant desert shrub, creosote bush (Larrea tridentata) growing at the Silverbell site of the International Biosphere Program (IBP) nw of Tucson Arizona. Pan-traps on the ground yielded a faunal sample depauperate in many of the more common native bee species on creosote bush, particularly its floral specialists. This pan-trap sample also corresponded poorly with the previous four years' faunal samples at this site, with pairs of neighboring net-sampled sites throughout the Southwest, and with all pairs of bee samples from Larrea across the Upper Sonoran desert. The likely causes of this disparity and the utility of pan trapping for bees in faunal and community studies is discussed.
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Concern over the status of bees has increased the need to inventory bee communities and, consequently, has increased the need to understand effectiveness of different bee sampling methods. We sampled bees using bowl traps and netting at 25 northwest Indiana sites ranging from open grasslands to forests. Assemblages of bees captured in bowl traps and by netting were very similar, but this similarity was driven by similar relative abundances of commonly captured species. Less common species were often not shared between collection methods (bowls, netting) and only about half of the species were shared between methods. About one-quarter of species were more often captured by one of the two collection methods. Rapid accumulation of species was aided by sampling at temporal and habitat extremes. In particular, collecting samples early and late in the adult flight season and in open and forest habitats was effective in capturing the most species with the fewest samples. The number of samples estimated necessary to achieve a complete inventory using bowls and netting together was high. For example, ≈72% of species estimated capturable in bowls were captured among the 3,159 bees collected in bowls in this study, but ≈30,000–35,000 additional bees would need to be collected to achieve a 100% complete inventory. For bowl trapping, increasing the number of sampling dates or sampling sites was more effective than adding more bowls per sampling date in completing the inventory with the fewest specimens collected.
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Bee pollinators are currently recorded with many different sampling methods. However, the relative performances of these methods have not been systematically evaluated and compared. In response to the strong need to record ongoing shifts in pollinator diversity and abundance, global and regional pollinator initiatives must adopt standardized sampling protocols when developing large-scale and long-term monitoring schemes. We systematically evaluated the performance of six sampling methods (observation plots, pan traps, standardized and variable transect walks, trap nests with reed internodes or paper tubes) that are commonly used across a wide range of geographical regions in Europe and in two habitat types (agricultural and seminatural). We focused on bees since they represent the most important pollinator group worldwide. Several characteristics of the methods were considered in order to evaluate their performance in assessing bee diversity: sample coverage, observed species richness, species richness estimators, collector biases (identified by subunit-based rarefaction curves), species composition of the samples, and the indication of overall bee species richness (estimated from combined total samples). The most efficient method in all geographical regions, in both the agricultural and seminatural habitats, was the pan trap method. It had the highest sample coverage, collected the highest number of species, showed negligible collector bias, detected similar species as the transect methods, and was the best indicator of overall bee species richness. The transect methods were also relatively efficient, but they had a significant collector bias. The observation plots showed poor performance. As trap nests are restricted to cavity-nesting bee species, they had a naturally low sample coverage. However, both trap nest types detected additional species that were not recorded by any of the other methods. For large-scale and long-term monitoring schemes with surveyors with different experience levels, we recommend pan traps as the most efficient, unbiased, and cost-effective method for sampling bee diversity. Trap nests with reed internodes could be used as a complementary sampling method to maximize the numbers of collected species. Transect walks are the principal method for detailed studies focusing on plant–pollinator associations. Moreover, they can be used in monitoring schemes after training the surveyors to standardize their collection skills.
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Globally, plant-pollinator communities are subject to a diverse array of perturbations and in many temperate and semi-arid systems fire is a dominant structuring force. We present a novel and highly integrated approach, which quantifies, in parallel, the response to fire of pollinator communities, floral communities and floral reward structure. Mt Carmel, Israel is a recognised bee-flower biodiversity hotspot, and using a chronosequence of habitats with differing post-fire ages, we follow the changes in plant-pollinator community organisation from immediately following a burn until full regeneration of vegetation. Initially, fire has a catastrophic effect on these communities, however, recovery is rapid with a peak in diversity of both flowers and bees in the first 2 years post-fire, followed by a steady decline over the next 50 years. The regeneration of floral communities is closely matched by that of their principal pollinators. At the community level we quantify, per unit area of habitat, key parameters of nectar and pollen forage known to be of importance in structuring pollinator communities. Nectar volume, nectar water content, nectar concentration and the diversity of nectar foraging niches are all greatest immediately following fire with a steady decrease as regeneration proceeds. Temporal changes in energy availability for nectar, pollen, total energy (nectar+pollen) and relative importance of pollen to nectar energy show a similar general decline with site age, however, the pattern is less clear owing to the highly patchy distribution of floral resources. Changes in floral reward structure reflect the general shift from annuals (generally low-reward open access flowers) to perennials (mostly high-reward and restricted access flowers) as post-fire regeneration ensues. The impact of fire on floral communities and their associated rewards have clear implications for pollinator community structure and we discuss this and the role of other disturbance factors on these systems.
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Given bees' central effect on vegetation communities, it is important to understand how and why bee distributions vary across ecological gradients. We examined how plant community composition, plant diversity, nesting suitability, canopy cover, land use, and fire history affected bee distribution across an open-forest gradient in northwest Indiana, USA, a gradient similar to the historic Midwest United States landscape mosaic. When considered with the other predictors, plant community composition was not a significant predictor of bee community composition. Bee abundance was negatively related to canopy cover and positively to recent fire frequency, bee richness was positively related to plant richness and abundance of potential nesting resources, and bee community composition was significantly related to plant richness, soil characteristics potentially related to nesting suitability, and canopy cover. Thus, bee abundance was predicted by a different set of environmental characteristics than was bee species richness, and bee community composition was predicted, in large part, by a combination of the significant predictors of bee abundance and richness. Differences in bee community composition along the woody vegetation gradient were correlated with relative abundance of oligolectic, or diet specialist, bees. Because oligoleges were rarer than diet generalists and were associated with open habitats, their populations may be especially affected by degradation of open habitats. More habitat-specialist bees were documented for open and forest/scrub habitats than for savanna/woodland habitats, consistent with bees responding to habitats of intermediate woody vegetation density, such as savannas, as ecotones rather than as distinct habitat types. Similarity of bee community composition, similarity of bee abundance, and similarity of bee richness between sites were not significantly related to proximity of sites to each other. Nestedness analysis indicated that species composition in species-poor sites was not merely a subset of species composition at richer sites. The lack of significant proximity or nestedness effects suggests that factors at a small spatial scale strongly influence bees' use of sites. The findings indicate that patterns of plant diversity, nesting resource availability, recent fire, and habitat shading, present at the scale of a few hundred meters, are key determinants of bee community patterns in the mosaic open-savanna-forest landscape.
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Prior to fire suppression in the 20th century, the mixed-conifer forests of the Sierra Nevada, California, U.S.A., historically burned in frequent fires that typically occurred during the late summer and early fall. Fire managers have been attempting to restore natural ecosystem processes through prescription burning, and have often favored burning during the fall in order to mimic historical fire regimes. Increasingly, however, prescription burning is also being done during the late spring and early summer in order to expand the window of opportunity for needed fuel reduction burning. The effect of prescribed fires outside of the historical fire season on forest arthropods is not known. The objective of this study was to compare the short-term effects of prescribed fires ignited in the early and late fire season on forest floor arthropods. Arthropod abundance and diversity were assessed using pitfall trapping in replicated burn units in Sequoia National Park, California. Overall, abundance of arthropods was lower in the burn treatments than in the unburned control. However, diversity tended to be greater in the burn treatments. Fire also altered the relative abundances of arthropod feeding guilds. No significant differences in arthropod community structure were found between early and late season burn treatments. Instead, changes in the arthropod community appeared to be driven largely by changes in fuel loading, vegetation, and habitat heterogeneity, all of which differed more between the burned and unburned treatments than between early and late season burn treatments.
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It is important for conservation biologists to understand how well species persist in human-dominated ecosystems because protected areas constitute a small fraction of the Earth's surface and because anthropogenic habitats may offer more opportunities for conservation than has been previously thought. We investigated how an important functional group, pollinators (bees; Hymenoptera: Apiformes), are affected by human land use at the landscape and local scales in southern New Jersey (U.S.A.). We established 40 sites that differed in surrounding landscape cover or local habitat type and collected 2551 bees of 130 species. The natural habitat in this ecosystem is a forested, ericaceous heath. Bee abundance and species richness within forest habitat decreased, not increased, with increasing forest cover in the surrounding landscape. Similarly, bee abundance was greater in agricultural fields and suburban and urban developments than in extensive forests, and the same trend was found for species richness. Particular species groups that might be expected to show greater sensitivity to habitat loss, such as floral specialists and bees of small or large body size, did not show strong positive associations with forest habitat. Nevertheless, 18 of the 130 bee species studied were positively associated with extensive forest. One of these species is a narrow endemic that was last seen in 1939. Our results suggest that at least in this system, moderate anthropogenic land use may be compatible with the conservation of many, but not all, bee species.
Article
Longleaf pine savannas are highly threatened, fire‐maintained ecosystems unique to the southeastern United States. Fire suppression and conversion to agriculture has strongly affected this ecosystem, altering overstory canopies, understory plant communities, and animal populations. Tree thinning to reinstate open canopies can benefit understory plant diversity, but effects on animal communities are less well understood. Moreover, agricultural land‐use legacies can have long‐lasting impacts on plant communities, but their effects on animal communities either alone or through interactions with restoration are unclear. Resolving these impacts is important due to the conservation potential of fire suppressed and post‐agricultural longleaf savannas. We evaluated how historical agricultural land use and canopy thinning affect the diversity and abundance of wild bees in longleaf pine savannas. We employed a replicated, large‐scale factorial block experiment in South Carolina, where canopy thinning was applied to longleaf pine savannas that were either post‐agricultural or remnant (no agricultural history). Bees were sampled using elevated bee bowls. In the second growing season after restoration, thinned plots supported a greater bee abundance and bee community richness. Additionally, restored plots had altered wild bee community composition when compared to unthinned plots, indicating that reduction of canopy cover by the thinning treatment best predicted wild bee diversity. Conversely, we found little evidence for differences between sites with or without historical agricultural land use. Some abundant Lasioglossum species were the most sensitive to habitat changes. Our results highlight how restoration practices that reduce canopy cover in fire‐suppressed savannas can have rapid benefits for wild bee communities. This article is protected by copyright. All rights reserved.
Article
Managed conifer forests in temperate regions are critical for supplying wood products, but little is known about their potential for pollinator conservation. We hosted a workshop for Pacific Northwest managers and biologists to identify perceived information gaps regarding pollinators in managed conifer forests; we also undertook a literature review on this topic to assess gaps in the primary literature. The most important gaps identified by workshop participants were a need for baseline data on pollinators in managed conifer forests, and for determining how forest management influences pollinators. Our literature review found a dearth of pollinator studies in managed conifer forests, which were limited to few regions and a subset of taxa. Given these findings, we developed a research agenda that targets identified knowledge gaps, including the need for documenting fundamental aspects of pollinator ecology in managed conifer forests and testing how pollinators and their habitats are influenced by management activities.
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Hill numbers (or the effective number of species) have been increasingly used to quantify the species/taxonomic diversity of an assemblage. The sample-size- and coverage-based integration of rarefaction (interpolation) and extrapolation (prediction) of Hill numbers represent a unified standardization method for quantifying and comparing species diversity across multiple assemblages. 2.We briefly review the conceptual background of Hill numbers along with two approaches to standardization. We present an R package iNEXT (iNterpolation/EXTrapolation) which provides simple functions to compute and plot the seamless rarefaction and extrapolation sampling curves for the three most widely used members of the Hill number family (species richness, Shannon diversity and Simpson diversity). Two types of biodiversity data are allowed: individual-based abundance data and sampling-unit-based incidence data. 3.Several applications of the iNEXT packages are reviewed: (1) Non-asymptotic analysis: comparison of diversity estimates for equally-large or equally-complete samples. (2) Asymptotic analysis: comparison of estimated asymptotic or true diversities. (3) Assessment of sample completeness (sample coverage) across multiple samples. (4) Comparison of estimated point diversities for a specified sample size or a specified level of sample coverage. 4.Two examples are demonstrated, using the data (one for abundance data and the other for incidence data) included in the package, to illustrate all R functions and graphical displays. This article is protected by copyright. All rights reserved.
Article
We conducted surveys of wild bee diversity at the University of Florida Ordway-Swisher Biological Station (OSBS) in Putnam County, north-central Florida, using colored cups (bee bowls; pan traps) and netting from flowers including Balduina angustifolia (Pursh) Robins and other Asteraceae and the legume Dalea pinnata (J. F. Gmel.) Barneby. The 5462 bees captured comprised 76 species in 29 genera and five families. Megachilidae was the family represented by the most species, whereas Halictidae included the five most numerous species. Notable differences in species composition and abundance from the bee fauna found in adjacent Alachua County included the presence of several rarely collected autumnal species associated with sandhill habitat such as Colletes howardi Swenk, a new state record for Florida, and Trachusa (Heteranthidium) fontemvitae (Schwarz) and its probable cleptoparasite Stelis (Heterostelis) grossa (Mitchell). Males of Florida endemic species Colletes longifacies Stephen and Perdita (Hexaperdita) blatchleyi Timberlake were discovered and are briefly diagnosed, as is a possible new species of Perdita (Cockerellia). In general, the bee fauna of OSBS is quite different from that of sites further south in Florida but shares apparent sandhill specialist species with Southern Pines in North Carolina, a site of historical interest due to extensive surveys by T. B. Mitchell. Striking differences between the bee community and their floral hosts of OSBS from those of relatively well-sampled sites in nearby Alachua County highlight the need to inventory species-level diversity in different landscapes.
Article
Abundance and biomass of selected insect groups were sampled on adjacent burned and unburned sand prairie for 3 years following a single spring burn. The abundance of all insects combined was significantly lower on the burned site than on the unburned site in the 1st yr postburn but not in subsequent years of the study. Of the selected insect groups, ants were significantly (P < 0.05) more abundant on the burned site than the unburned site for the 1st yr after the fire but not during the 2nd or 3rd. However, for Homoptera the pattern of abundance on burned and unburned sites was reversed. No significant differences in numbers of grasshoppers occurred between burned and unburned sites for any year. However, grasshopper biomass was significantly greater on the unburned site than on the burned site 1 yr postburn but not 2 or 3. Of the two most abundant grasshoppers, Conocephalus strictus was more abundant on the burned site than the unburned site for the 1st and 2nd yr after the burn but not the 3rd, whereas, for Melanoplus flavidus, the pattern of abundance was reversed on burned and unburned sites. The results indicate that while there were varied responses of these insects to fire, none experienced a severe decline in abundance following fire, suggesting they are adapted to habitats experiencing periodic burning.
Article
Twenty years of prescribed burning at different seasons and different frequencies altered the condition of shrub and herbaceous vegetation in the Lower Coastal Plain of South Carolina. The six treatments consisted of annual winter, annual summer, periodic winter, periodic summer, and biennial summer burning, and a no-burn control. Percentage of ground cover increased with most burning treatments, and herbage yields increased with all burning treatments. Annual summer burning eliminated most shrubs; however, dense stands of sprouting shrubs persisted on the periodic summer and on both the annual and periodic winter treatments. The number of herbaceous species and the density of herbaceous plants increased with burning, especially on the annual and biennial summer treatments where grasses became the dominant plants. Most of these changes appear beneficial for wildlife or grazing.
Conference Paper
The interest in the status of North American bees (Hymenoptera: Anthophila) and how they are impacted by land-use has grown over the past quarter-century. Historically, very few North American bee populations have been monitored; only a limited number of quantitative studies on native populations have been completed, leaving ecologists with insufficient baseline data with which to compare current population trends. In an effort to better inform land management decisions and conservation efforts we must investigate how changes across ecological gradients caused by human mediated disturbance influence community composition. In this study we seek to identify how native bee communities in the longleaf pine savannas in the Sandhills ecoregion are impacted by the presence of prescribed burning and if there is any significant effect of time within the 3 year burn rotation.
Article
Disturbance is an important component of many ecosystems, and variations in disturbance regime can affect ecosystem and community structure and functioning. The “intermediate disturbance hypothesis” suggests that species diversity should be highest at moderate levels of disturbance. However, disturbance is also known to increase the invasibility of communities. Disturbance therefore poses an important problem for conservation management, Here, we review the effects of disturbances such as fire grazing, soil disturbance and nutrient addition on plant species diversity and invasion with particular emphasis on grassland vegetation. Individual components of the disturbance regime can have marked effects on species diversity, but it is often modifications of the existing regime that have the largest influence. Similarly, disturbance can enhance invasion of natural communities, but frequently it is the interaction between different disturbances that has the largest effect. The natural disturbance regime is now unlikely to persist within conservation areas since fragmentation and human intervention have usually modified physical and biotic conditions. Active management decisions must now be made on what disturbance regime is required and this requires decisions on what species are to be encouraged or discouraged.
Article
Periodic wildfire defines plant community composition and dynamics in many of the world’s semi-arid biomes, whose climates and floras also favor wild bee diversity. Invasive flammable grasses, deforestation, historical fire suppression and human ignition are increasing fire frequency and intensifying its severity, as well as introducing fire to previously fireproof biomes. In many of these habitats, bees are key pollinators. Many, often most of the solitary bee species and individuals in these biomes nest underground (so-called “mining” bees). To evaluate their susceptibility to fire, we tested heat tolerances of bees’ four life stages using an experimental design that mimicked heat conduction dynamics of natural soils. All life stages survived heating of up to 45°C for 27min, but none survived heating at 54°C for 9min; the pupal stage survived best. At near-lethal temperatures, more prolonged heating caused more mortality. These data were related to published studies of heat penetration depths in soil during fire and an exhaustive compilation of published nesting depths reported for mining bees. We conclude that a small fraction (9%) of the shallowest-nesting mining bee species is likely to die from soil heating by wildfire. Among these, ground-nesting megachilids (Osmia, Megachile) will be most vulnerable, owing to their shallow horizontal nests. Because mining bees prevail in most biomes of the temperate zone, any vegetation rehabilitation efforts should therefore expect that bee communities will largely survive the immediate effects of wildfire, and therefore will need pollen and nectar resources in the year(s) after fire.
Article
The use of both linear and generalized linear mixed-effects models (LMMs and GLMMs) has become popular not only in social and medical sciences, but also in biological sciences, especially in the field of ecology and evolution. Information criteria, such as Akaike Information Criterion (AIC), are usually presented as model comparison tools for mixed-effects models. The presentation of variance explained' (R2) as a relevant summarizing statistic of mixed-effects models, however, is rare, even though R2 is routinely reported for linear models (LMs) and also generalized linear models (GLMs). R2 has the extremely useful property of providing an absolute value for the goodness-of-fit of a model, which cannot be given by the information criteria. As a summary statistic that describes the amount of variance explained, R2 can also be a quantity of biological interest. One reason for the under-appreciation of R2 for mixed-effects models lies in the fact that R2 can be defined in a number of ways. Furthermore, most definitions of R2 for mixed-effects have theoretical problems (e.g. decreased or negative R2 values in larger models) and/or their use is hindered by practical difficulties (e.g. implementation). Here, we make a case for the importance of reporting R2 for mixed-effects models. We first provide the common definitions of R2 for LMs and GLMs and discuss the key problems associated with calculating R2 for mixed-effects models. We then recommend a general and simple method for calculating two types of R2 (marginal and conditional R2) for both LMMs and GLMMs, which are less susceptible to common problems. This method is illustrated by examples and can be widely employed by researchers in any fields of research, regardless of software packages used for fitting mixed-effects models. The proposed method has the potential to facilitate the presentation of R2 for a wide range of circumstances.
Article
1. Pan traps or water traps have been used widely to sample agricultural insect pests, but no formal studies have assessed the utility of these traps as sampling devices for bees. 2. Coloured pan traps, used as flower models, can efficiently and selectively sample an oligolectic bee, Andrena (Hesperandrena) limnanthis, and other bees associated with white-flowered Limnanthes douglasii rosea. 3. Females and males of A. limnanthis unexpectedly exhibit different colour preferences. Females are strongly attracted to white and blue traps, but discriminate against yellow traps. Males prefer white traps over blue and yellow traps. Consequently, blue traps are selective for females only, while white traps are selective for both sexes. 4. Non-A. limnanthis bees were caught in significantly greater numbers in yellow than in blue or white traps. These bees included generalists, as well as specialists that are oligolectic on mostly yellow-flowered species. 5. Colour of traps had a significant effect on the numbers of A. limnanthis females and males, and non-A. limnanthis bees caught in traps. These results indicate that quantitative sampling of bees by pan trap methods can be highly sensitive to trap colour.
Article
Species richness is a fundamental measurement of community and regional diversity, and it underlies many ecological models and conservation strategies. In spite of its importance, ecologists have not always appreciated the effects of abundance and sampling effort on richness measures and comparisons. We survey a series of common pitfalls in quantifying and comparing taxon richness. These pitfalls can be largely avoided by using accumulation and rarefaction curves, which may be based on either individuals or samples. These taxon sampling curves contain the basic information for valid richness comparisons, including category–subcategory ratios (species-to-genus and species-to-individual ratios). Rarefaction methods – both sample-based and individual-based – allow for meaningful standardization and comparison of datasets. Standardizing data sets by area or sampling effort may produce very different results compared to standardizing by number of individuals collected, and it is not always clear which measure of diversity is more appropriate. Asymptotic richness estimators provide lower-bound estimates for taxon-rich groups such as tropical arthropods, in which observed richness rarely reaches an asymptote, despite intensive sampling. Recent examples of diversity studies of tropical trees, stream invertebrates, and herbaceous plants emphasize the importance of carefully quantifying species richness using taxon sampling curves.
Article
1. Bowl and pan traps are now commonly used to capture bees (Hymenoptera: Apiformes) for research and surveys. 2. Studies of how arrangement and spacing of bowl traps affect captures of bees are needed to increase the efficiency of this capture technique. 3. We present results from seven studies of bowl traps placed in trapping webs, grids, and transects in four North American ecoregions (Mid-Atlantic, Coastal California, Chihuahuan Desert, and Columbia Plateau). 4. Over 6000 specimens from 31 bee genera were captured and analysed across the studies. 5. Based on the results from trapping webs and distance tests, the per bowl capture rate of bees does not plateau until bowls are spaced 3–5 m apart. 6. Minor clumping of bee captures within transects was detected, with 26 of 56 transects having index of dispersion values that conform to a clumped distribution and 39 transects having positive Green’s index values, 13 with zero, and only four negative. However, degree of clumping was slight with an average value of only 0.06 (the index ranges from −1 to 1) with only five values >0.15. Similarly, runs tests were significant for only 5.9% of the transects. 7. Results indicate that (i) capture rates are unaffected by short distances between bowls within transects and (ii) that bowls and transects should be dispersed throughout a study site.
Chapter
In this chapter, we discuss reintroduction, via translocation, of native fauna into longleaf pine forests.
Chapter
From Virginia to Texas, much of the coastal plain landscape was once covered by a “vast forest of the most stately pine trees that can be imagined … ”(Bartram 1791 [1955]). Longleaf pine could be found from sea level, on the margins of brackish marshes, to around 2000 feet on the Talladega National Forest in Alabama (Harper 1905; Stowe et al. 2002). The spectacular failure of the primeval longleaf pine forest (Fig. 1) to reproduce itself after exploitation is a milestone event in the natural history of the eastern United States, even greater in scale and impact than the elimination of chestnut (Castanea dentata) from Appalachian forests by blight. This chapter discusses presettlement extent and summarizes major events in the decline of the longleaf pine ecosystem and its displacement from more than 97% of the lands it once occupied.
Article
The longleaf pine-grassland (Pinus palustris-Poaceae) ecosystem occupied over 30 million ha in the southeastern United States at the time of European discovery. Frequent low- to moderate-intensity surface fires ignited by both lightning and native Americans sustained open diverse stands in a fire climax and prevented succession to mixed hardwood forests. Disruption of pre-historical and historical fire regimes, coupled with land conversion, urbanization, and other factors, is responsible for the rapid decline of the ecosystem. Today only about 1.2 million ha remain, much in isolated fragments. Primarily because of habitat loss, many animal and plant species associated with longleaf forests are now rare or in decline. Restoration ecologists and managers face a daunting challenge—recreating an ecosystem, in the face of chronic cumulative stress from human activities, that varied widely over temporal and spatial scales. Key restoration factors include: (1) development of a general understanding of the historical condition of the longleaf ecosystem, especially unusual or unique communities and habitats embedded in the general fabric of the larger ecosystem, (2) initiation and expansion of a fire regime, where feasible, similar to that which historically shaped the ecosystem, (3) maintenance/enhancement of herbaceous diversity, (4) continued research on habitat requirements and distribution of rare species, and (5) encouragement of a multi-owner partnership approach to promote conservation across the landscape. Landowners and the public must be educated about the values of the longleaf pine-grassland ecosystem and develop a conservation ethic that considers aesthetics, wildlife, and biodiversity, in addition to economics, if the ecosystem is to be restored. Most forestry practices used to manage and restore longleaf forests are of low short-term risk to rare species in this ecosystem. The benefits of active management usually far outweigh the long-term risks associated with no management.
Article
The importance of lightning as an ignition source for the fire adapted longleaf pine (Pinus palustris) ecosystem is widely recognized. Lightning also impacts this system on a smaller scale by causing individual tree mortality. The objective of this study was to determine mortality due to lightning and other agents in longleaf stands on the Ocala National Forest in central Florida and to quantify lightning ignited fire. Mortality from lightning was also tracked in longleaf stands on the Savannah River Site in South Carolina. Lightning killed more trees than any other agent with a mean mortality of nearly 1 tree/3 ha/yr in Florida and 1 tree/8 ha/yr in South Carolina. The probability of a tree being struck by lightning increased as a function of tree height at both sites, i.e. lightning preferentially removed the largest trees from the stand. In addition lightning strikes were clumped within stands, sometimes killed multiple trees with a single strike, and often hit trees on the edge of existing gaps. The combination of these processes means gaps suitable for regeneration within longleaf stands are created quite rapidly. This information provides guidelines for the development of selection harvest systems based on this natural disturbance. Although lightning activity was greatest during the summer months in Florida and most fires occurred in June, the probability of a strike causing a fire was highest in February to May.
Article
Four combinations of season and frequency of burning were applied in Coastal Plain loblolly pine stands over a 43-year period. Overstory species composition and growth were unaffected by treatment. Above-ground portions of small hardwoods (less than 12.5 cm d.b.h.) were killed and replaced by numerous sprouts under periodic summer, periodic winter, and annual winter burning regimes. With annual summer burning, small hardwoods and shrubs were killed and replaced by vegetation typical of grassland communities. Grasses and forbs also dominated the understory of annual winter burns but numerous hardwood sprouts survived. Study results emphasize that frequent burning over a long period is needed to create and maintain the pine-grassland community observed by the first European settlers of the southeast.
Article
Treatments to restore understory plant communities of mature (50–80-year old) longleaf pine (Pinus palustris Mill.) and reduce risks of wildfire were applied to 10 ha plots that had a substantial shrub layer due to lack of fire. Plots were located in the Coastal Plain of Alabama and treatments consisted of: (1) untreated control, (2) growing season prescribed burn, (3) thin only, (4) thin plus growing season burn, and (5) herbicide plus growing season burn. Thin plus burn plots had significantly higher tree mortality compared to burn only and control plots and, overall, fire was the primary cause of tree death. Most tree mortality occurred within 1-year of treatment. From 2002 to 2004, we captured 75,598 Coleoptera in multiple funnel traps comprising 17 families and 130 species. Abundance of all Coleoptera combined was not different among treatments. Species richness was significantly higher on thin plus burn plots compared to thin only and control plots. Scolytinae (Coleoptera: Curculionidae) were more abundant on thin plus burn plots compared to control plots in fall 2002 but in fall 2003 they were more abundant on thin plus burn, thin only, and herbicide plus burn compared to controls. Among Scolytinae, Dendroctonus terebrans (Olivier), Xyleborinus saxeseni (Ratzeburg), Xyleborus sp. 3, and Hylastes tenuis (Eichhoff), showed varying responses to the treatments. Other Curculionidae were significantly more abundant on thin only and herbicide plus burn plots compared to all other treatments in spring 2003 and in spring 2004 they were more abundant on herbicide plus burn plots compared to thin plus burn treatments. Among Cerambycidae, Xylotrechus sagittatus (Germar) was higher in abundance in fall 2003 on thin plus burn plots compared to all other treatments except herbicide plus burn plots. Within the predator complex, Trogositidae were higher on thin plus burn plots compared to all other treatments except thin only plots in spring 2003, and Cleridae abundance was higher in spring 2004 on burn only plots compared to all other treatments. Linear regression analyses of dead trees per plot versus various Coleoptera showed captures of Buprestidae, Cerambycidae, Trogositidae, Acanthocinus nodosus (Fabricius), Temnochila virescens (Fabricius), and X. saxeseni increased with increasing number of dead trees. Our results show that the restoration treatments tested did not cause increased bark beetle-related tree mortality and they did not negatively affect populations of early successional saproxylic beetle fauna.
Article
Pollination by insects in forests is an extremely important process that should be conserved. Not only do pollinating insects help to maintain a diversity of plants within forests, but they also aid in pollinating crops found near forested land. Currently, the effects of various forest management practices on floral visiting insect abundance or diversity is unknown, so we investigated how prescribed burning, mechanical shrub control, and combination of the two affected abundance of floral visiting insects. We caught 7921 floral visitors from four orders and 21 families. Hymenoptera was the most abundant and diverse order, with Halictidae being the most abundant family. A total of 45 species of Hymenoptera representing six families were captured. We caught seven families and 35 species of Lepidoptera, six families and 33 species of Coleoptera, and two families and 13 species of Diptera. Most floral visitors were captured in the mechanical shrub control plus prescribed burn treatments, while lower numbers were caught on the mechanical shrub control only, prescribed burn only and control treatments. Overall species richness was also higher on mechanical plus burn treatments. Total pollinator abundance and the abundance of most orders and families was correlated with decreased tree basal area and increased percent herbaceous plant cover. Our study shows that floral visitors increased in abundance and species richness most from forest disturbance that reduced the density of overstory trees and increased the amount of herbaceous plant growth.
Article
The ability to predict the responses of ecological communities and individual species to human-induced environmental change remains a key issue for ecologists and conservation managers alike. Responses are often variable among species within groups making general predictions difficult. One option is to include ecological trait information that might help to disentangle patterns of response and also provide greater understanding of how particular traits link whole clades to their environment. Although this “trait-guild” approach has been used for single disturbances, the importance of particular traits on general responses to multiple disturbances has not been explored. We used a mixed model analysis of 19 data sets from throughout the world to test the effect of ecological and life-history traits on the responses of bee species to different types of anthropogenic environmental change. These changes included habitat loss, fragmentation, agricultural intensification, pesticides and fire. Individual traits significantly affected bee species responses to different disturbances and several traits were broadly predictive among multiple disturbances. The location of nests – above vs. below ground – significantly affected response to habitat loss, agricultural intensification, tillage regime (within agriculture) and fire. Species that nested above ground were on average more negatively affected by isolation from natural habitat and intensive agricultural land use than were species nesting below ground. In contrast below-ground-nesting species were more negatively affected by tilling than were above-ground nesters. The response of different nesting guilds to fire depended on the time since the burn. Social bee species were more strongly affected by isolation from natural habitat and pesticides than were solitary bee species. Surprisingly, body size did not consistently affect species responses, despite its importance in determining many aspects of individuals’ interaction with their environment. Although synergistic interactions among traits remain to be explored, individual traits can be useful in predicting and understanding responses of related species to global change.
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NOTE: This is not a book, contrary to what ResearchGate claims. This is a software application and User's Guide. The current version is Version 9. The citations here are incomplete, since each version has its own citations. EstimateS currently has more than 4000 citations in the peer-reviewed literature. For the full list, go to GoogleScholar: http://bit.ly/11YdUlg .
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1. Valuable insights into mechanisms of community responses to environmental change can be gained by analysing in tandem the variation in functional and taxonomic composition along environmental gradients. 2. We assess the changes in species and functional trait composition (i.e. dominant traits and functional diversity) of diverse bee communities in contrasting fire-driven systems in two climatic regions: Mediterranean (scrub habitats in Israel) and temperate (chestnut forests in southern Switzerland). 3. In both climatic regions, there were shifts in species diversity and composition related to post-fire age. In the temperate region, functional composition responded markedly to fire; however, in the Mediterranean, the taxonomic response to fire was not matched by functional replacement. 4. These results suggest that greater functional stability to fire in the Mediterranean is achieved by replacement of functionally similar species (i.e. functional redundancy) which dominate under different environmental conditions in the heterogeneous landscapes of the region. In contrast, the greater functional response in the temperate region was attributed to a more rapid post-fire vegetation recovery and shorter time-window when favourable habitat was available relative to the Mediterranean. 5. Bee traits can be used to predict the functional responses of bee communities to environmental changes in habitats of conservation importance in different regions with distinct disturbance regimes. However, predictions cannot be generalized from one climatic region to another where distinct habitat configurations occur.
  • Boyer
Discover life bee species guide and world checklist
  • J S Ascher
  • J Pickering