Eastern Deciduous Forest Research Articles

Regional Variability of Chestnut (Castanea sativa) Tolerance Toward Blight Disease

Since its introduction into Europe in the first half of the 20th century, Cryphonectria parasitica has been gradually spreading across the natural range of the sweet chestnut (Castanea sativa Mill.), infecting the trees and causing lethal bark cankers. Serendipitously, a hyperparasitic Cryphonectria hypovirus 1 (CHV1), which attenuates C. parasitica virulence in combination with more tolerant European chestnut species, was able to ward off the worst effect of the disease. In North America, unfortunately, the native Castanea dentata is now functionally extinct since it occurs only as root sprouts in eastern deciduous forests where it was once dominant. In our work, we investigated changes in C. parasitica populations over time and the regional variability in chestnut populations’ tolerance toward the blight disease. While vegetative compatibility (vc) type diversity and prevalence of hypovirulence remained similar as in previous studies, in the Buje population, unlike in previous studies, we were unable to find any hypovirulent fungal strains. The most common vegetative compatibility types (vc types) were EU-1, EU-2 and EU-12. However, several rare EU-types were found, including one previously unreported: EU-46. By inoculating several C. parasitica strains on tree stems from several chestnut populations, we observed that the induced lesion size was affected by the type of inoculum (CHV1-free or CHV1-infected), genotype-related individual chestnut stem and chestnut stem population of origin-related variability. The largest lesions were induced by CHV1-free fungal isolate DOB-G: 20.13 cm2 (95% C.I. 18.10–22.15) and the smallest by CHV1-infected L14/EP713: 2.49 cm2 (95% C.I. 1.59–3.39). Surprisingly, the size of the lesions induced by other CHV1-infected strains fell somewhere in between these extremes. The size of induced lesions was dependent on the population of origin as well and ranged from 11.60 cm2 (95% C.I. 9.87–13.33) for stems from the Moslavačka gora population to 17.75 cm2 (95% C.I. 15.63–19.87) for stems from Ozalj.

The geography of wild American ginseng in North Carolina, USA: a comparative study of four capability analysis methods

Wild American ginseng is the root component of a family of plants called Panax, and it grows mainly in the understory of the eastern deciduous forests in North America. The growing market for wild American ginseng in Asia along with the scarcity of this plant in the wild due to rising illegal harvest have been simultaneously pushing up the price of American ginseng in the market, increasing incentives further for illegal harvest of this soon-to-be-extinct species. This paper studies the geography of wild American ginseng to identify the spatial distribution of the suitable habitat of this plant in the wild and provides advice on what conditions are required and what regions are suitable for cultivating it in farms, introducing an alternative to the wild American ginseng to decrease the harvesting pressure on its wild counterpart. By employing four popular geospatial methods, including the Binary Screening method, the Ordinal Ranking method (both Graduated Screening and Addition-of-Factors methods), and the Weighted Linear Combination method, this paper carries out a capability analysis and mapping for wild American ginseng in North Carolina (NC). After building the models, they are validated by using the data of the known locations of wild American ginseng plants in NC. Developing these models helps in gaining a more comprehensive understanding of where the plant naturally grows and sheds light on how government agencies can more effectively and more efficiently plan for law enforcement activities to better protect this plant from illegal harvest. The general pattern of our results suggests that western NC counties such as Jackson, Haywood, Transylvania, Henderson, Cherokee, and Ash are some of the most suitable geographical areas for wild American ginseng to grow. The results of our model validation analysis, along with the comparison of our models' predictions to the observed occurrences of wild American ginseng in nature, indicate that the Binary Screening method’s predictions align with almost 96% of the reported observations in nature. This suggests that the influential natural factors necessary for wild American ginseng are more of complementary factors to each other than being substitutes, meaning that they all must exist in the environment for it to grow, and it could not be that the lack of one natural factor can be compensated by the abundance of another natural factor.

Evidence of mesophication following selective cutting and shelterwood in Virginia’s eastern deciduous forest, USA

The replacement of oaks (Quercus) with mesic tree species in the eastern deciduous forests of North America involves a positive feedback loop being driven by fire suppression and climate change. In this study, we explored the impact of timber harvesting as a potential facilitator of mesophication. Young stands resulting from shelterwoods (on federal lands) and selective cutting (on private lands) were sampled to compare the composition and density of seedlings, saplings, and trees in western Virginia, USA. Oak overstory trees had lower importance values and densities at selective cutting sites compared to shelterwood sites. Among saplings, mesic species had higher importance values and densities than oaks at both selective cutting and shelterwood sites. Evidence of mesophication was found at both selective cutting and shelterwood sites; but a higher level of mesophication appeared to be occurring at the selective cutting sites than at shelterwood sites. At selective cutting sites scarlet oak (Quercus coccinea) was absent from all sampled plots and a dense midstory of subcanopy trees, especially eastern redbud (Cercis canadensis), appeared to be hindering successful oak regeneration. Our results indicate timber harvesting, without regard for the composition of the regeneration layer, may facilitate mesophication in the eastern deciduous forest, with selective cutting resulting in more successful establishment of mesic species compared to shelterwoods. These findings have implications for mesophication on private forest lands, where selective cutting is a very common method of timber harvesting.

The Effect of Fire on Multiple Tree Species in the Eastern Deciduous Forest

Fire is a disturbance that serves to maintain the diverse mosaic of vegetation in the Eastern Deciduous Forest. However, our ability to reconstruct fire occurrence from hardwood tree scars still lags far behind our expertise in reconstructing fire history from conifers in the western United States. This study examines the fidelity of fire scaring in multiple tree species in the Big Oaks National Wildlife Refuge in Indiana, which is located in the central hardwood region of the Eastern Deciduous Forest. All 15 species, except for red oak, showed evidence of past fires, and most samples recorded multiple fire events. No fire scars were recorded in the latewood of the samples. Most of the fires scars occurred in the earlywood (May) suggesting the dormant season fires are likely associated with fires in March to April before the growing season begins. No synchronous fires were recorded across all sites, but fires occurred in 1981, 1982, 1984, 1985, and 1988 across multiple sites. This suggests that these were larger spreading fires. Establishment pulses were documented in association with fire events in 1981, 1984, and 1995, suggesting that fire may benefit the establishment or root sprouting of some hardwood species. Fourteen of the fifteen species that we sampled preserved fire scars, suggesting that the diverse suite of species in the Eastern Deciduous Forest is a viable sampling pool for examining fire history across this forest type.

The invasive annual grass, Microstegium vimineum, is associated with reduced native species seed predation by small mammals in eastern deciduous forests

The invasive annual grass, Microstegium vimineum, is associated with reduced native species seed predation by small mammals in eastern deciduous forests

Factors Influencing Activity and Detection of Species in a Cross Timbers Snake Assemblage

The Cross Timbers of North America is an ecotone between the eastern deciduous forests and central grasslands and exhibits a diverse composite snake fauna. Over a 3-yr period, we performed repeated nocturnal road surveys of snakes across three transects in Wise County, Texas, and evaluated species composition, relative abundances, vehicular mortality, detection probability, and the influence of environmental variables on snake activity. Sixteen taxa and 406 observations were recorded over 250 surveys, and the three most frequently encountered species had detection probabilities of approximately 0.20: Pantherophis obsoletus, Agkistrodon laticinctus, and Nerodia rhombifer. Only the two species of Agkistrodon present at our study area showed significant differences in count frequencies across the three transects. Covariate effects on overall snake activity were subtle, with barometric pressure, ordinal date, and ambient temperature better explaining variation in combined snake counts than humidity, wind speed, or lunar phase. Furthermore, peak snake activity corresponded closely to the timing of peak warm-season precipitation in the study area, suggesting that snake activity coincides with rainfall periodicity in the Cross Timbers region. However, results of site-occupancy models indicated that covariate effects were different across species, and that several common species did not show clear responses to any of the survey covariates.

Seasonal trends in leaf-level photosynthetic capacity and water use efficiency in a North American Eastern deciduous forest and their impact on canopy-scale gas exchange.

Vegetative transpiration (E) and photosynthetic carbon assimilation (A) are known to be seasonally dynamic, with changes in their ratio determining the marginal water use efficiency (WUE). Despite an understanding that stomata play a mechanistic role in regulating WUE, it is still unclear how stomatal and nonstomatal processes influence change in WUE over the course of the growing season. As a result, limited understanding of the primary physiological drivers of seasonal dynamics of canopy WUE remains one of the largest uncertainties in earth system model projections of carbon and water exchange in temperate deciduous forest ecosystems. We investigated seasonal patterns in leaf-level physiological, hydraulic, and anatomical properties, including the seasonal progress of the stomatal slope parameter (g1 ; inversely proportional to WUE) and the maximum carboxylation rate (Vcmax ). Vcmax and g1 were seasonally variable; however, their patterns were not temporally synchronized. g1 generally showed an increasing trend until late in the season, while Vcmax peaked during the midsummer months. Seasonal progression of Vcmax was primarily driven by changes in leaf structural, and anatomical characteristics, while seasonal changes in g1 were most strongly related to changes in Vcmax and leaf hydraulics. Using a seasonally variable Vcmax and g1 to parameterize a canopy-scale gas exchange model increased seasonally aggregated A and E by 3% and 16%, respectively.

A checklist of the bees (Hymenoptera: Apoidea) of Minnesota.

Research studies and conservation actions aimed at improving conditions for bees require a basic understanding of which species are present in a given region. The US state of Minnesota occupies a unique geographic position at the confluence of eastern deciduous forests, northern boreal forests, and western tallgrass prairie, which has led to a diverse and unique bee fauna. In recent years there have been multiple ongoing bee-focused inventory and research projects in Minnesota. Combined with the historic specimens housed in the University of Minnesota Insect Collection and other regional collections, these furnished a wealth of specimens available to form the basis of a statewide checklist. Here, we present the first comprehensive checklist of Minnesota bee species, documenting a total of 508 species in 45 genera. County-level occurrence data is included for each species, and further information on distribution and rarity is included for species of regional or national interest. Some species have their taxonomy clarified, with Perdita citrinella Graenicher, 1910 syn. nov. recognized as a junior synonym of Perdita perpallida Cockerell, 1901, P. bequaerti syn. nov. recognized as a junior synonym of P. pallidipennis Graenicher, 1910 stat. nov., Anthidiellum boreale (Robertson, 1902) stat. nov. recognized as a full species, and Anthidiellium beijingense Portman & Ascher nom. nov. is proposed for A. boreale Wu to resolve the homonymy with A. boreale (Robertson). We further include a list of species that may occur in Minnesota and highlight 11 species occurring in the state that are considered non-native. Recent collecting efforts, as well as increased taxonomic attention paid to Minnesota bees, have resulted in 66 species that have only been documented in the last 10 years. As a first step in determining native bees of conservation concern, we document 38 species that have not been detected in the state during the last 50 years and discuss their conservation status, along with other species for which evidence of decline exists. The checklist of Minnesota bees will continue to grow and change with additional surveys and research studies. In particular, recent surveys have continued to detect new bee species, and many bee groups are in need of taxonomic revision, with the most recent revisions for many genera occurring decades ago. Overall, this checklist strengthens our understanding of the bees of Minnesota and the broader region, informs conservation assessments, and establishes a baseline for faunal change.

Islands in the shade: scattered ectomycorrhizal trees influence soil inoculum and heterospecific seedling response in a northeastern secondary forest.

The eastern deciduous forest is a mix of arbuscular (AM) and ectomycorrhizal (EM) trees, but land use legacies have increased the abundance of AM trees like Acer spp. (maple). Although these legacies have not changed the abundance of some EM trees like Betula spp. (birch), EM conifers like Tsuga canadensis (hemlock), and Pinus strobus (pine) have declined. We used a soil bioassay to investigate if the microbial community near EM birch (birch soil) contains a greater abundance and diversity of EM fungal propagules compatible with T. canadensis and P. strobus compared to the community associated with the surrounding AM-dominated secondary forest matrix (maple soil). We also tested the effectiveness of inoculation with soil from a nearby EM-dominated old-growth forest as a restoration tool to reintroduce EM fungi into secondary forest soils. Finally, we examined how seedling growth responded to EM fungi associated with each treatment. Seedlings grown with birch soil were colonized by EM fungi mostly absent from the surrounding maple forest. Hemlock seedlings grown with birch soil grew larger than hemlock seedlings grown with maple soil, but pine seedling growth did not differ with soil treatment. The addition of old-growth soil inoculum increased hemlock and pine growth in both soils. Our results found that EM trees are associated with beneficial EM fungi that are mostly absent from the surrounding AM-dominated secondary forest, but inoculation with old-growth soil is effective in promoting the growth of seedlings by reintroducing native EM fungi to the AM-dominated forests.

Historical forest disturbance results in variation in functional resilience of seed dispersal mutualisms.

Mutualistic interactions provide essential ecosystem functions that contribute to promoting and maintaining diversity in ecosystems. Understanding if functionally important mutualisms are "resilient" (i.e., able to resist or recover) to anthropogenic disturbance is essential for revealing the capacity for diversity to recover. Animal-mediated seed dispersal supports plant population growth and influences community structure, and disturbance affecting seed dispersal can contribute to low resiliency of plant diversity. Ant-seed dispersal mutualisms are sensitive to anthropogenic disturbance, as they rely on one to a few high-quality dispersal partners. In North American eastern deciduous forests, ants in the genus Aphaenogaster are "keystone dispersers" of understory forbs adapted to dispersal by ants (myrmecochores), which make up more than one-third of the understory herbaceous community. The majority of forests within this region have regenerated from previous disturbance in the form of clearing for agriculture. Previous studies have revealed that myrmecochore diversity is not resilient to previous clearing. Here, we ask if seed dispersal mutualisms are resilient to historical forest disturbance and if decreases in mutualistic interactions with partners, Aphaenogaster sp., or increases in antagonistic interactions cause degradation of function. In a large-scale natural experiment (20 sites), we measured seed removal, the abundance of mutualistic partners and other invertebrates interacting with seeds, myrmecochore cover, and diversity, along with ant habitat and forest structure. We found lower and more variable seed removal in secondary forests compared with remnant forests. A path analysis of all forests revealed that the abundance of mutualists was the primary determinant of the variation in seed removal, and that seed damage by antagonists (invasive slugs) negatively affected dispersal and was higher in secondary forests. In a path analysis of remnant forests, the link between mutualist abundance and seed removal was absent, but present in the secondary forest path, suggesting that seed dispersal is more variable and dependent on the mutualist abundance in secondary forests and is stable and high in remnant forests. Our results suggest that functional resilience to disturbance is variable, where seed dispersal is low in some secondary forests and not others. This work provides key insights into the effects of disturbance on mutualistic interactions and how the resilience of critical ecosystem functions impacts the capacity for diversity resiliency.

Effect of Deer and Forest Edge on Understory Plant Communities

White-tailed deer (Odocoileus virginianus) impact the ecological integrity of eastern deciduous forests by modifying plant community composition and structure. Previous studies have shown that overabundant deer can negatively impact the recruitment and persistence of both woody and herbaceous plants. However, the strength and nature of these interactions can depend on habitat context. Forest edges provide favorable habitat for deer along with many introduced plant species, and have the potential to modify the nature of deer impacts. Here, we explore whether forest edges shape the impacts of deer on plant communities within the forest landscape. Specifically, we excluded deer, or, alternatively, allowed deer access, in plots along the edge and within the interior of two northern hardwood forests. Background deer abundance in these forests was approximately 6–12 individuals per km2. After eight years of exclusion, we surveyed plant communities within plots to assess the impacts of deer on plant community composition across the forested landscape. We found that the impacts of deer were robust across habitat context within the forest, with relatively weak impacts on cover and richness of both native and introduced species. Edge habitat, on the other hand, had strong impacts on cover of both native and introduced species, as well as woody and herbaceous species, but the magnitude of these impacts was variable across the two forest sites. This work suggests that deer can have modest impacts when at relatively low densities, and that these effects can be consistent across forest habitat types, while forest fragmentation and subsequent generation of edge habitat can be an important driver of composition in the forest understory.

Drought reduces invasive grass performance by disrupting plant-microbe interactions that enhance plant nitrogen supply.

Non-native invasive plants can promote their dominance in novel ecosystems by accelerating soil nutrient cycling via interactions with decomposer microbes. Changes in abiotic conditions associated with frequent or prolonged drought may disrupt these interactions, but the effects of disruption on invasive plant performance and the underpinning mechanisms are poorly understood. Here, we used rainout shelters in an experimental field setting to test the hypothesis that drought reduces invasive plant performance by reducing microbial metabolic activity, resulting in decreased nitrogen flow to plants. We imposed growing season drought on populations of the exotic grass Microstegium vimineum, a widespread invasive plant in eastern deciduous forests, and quantified effects on aboveground and belowground biomass, and carbon (C) and nitrogen (N) cycling among plants, decomposers, and soil. Drought resulted in a 24% decrease in soil respiration, a 16% decrease in phenol oxidase enzyme activity, a 12% decrease in dissolved organic N concentration, and a decrease in the C:N ratio of particulate organic matter, suggesting reduced microbial metabolic activity and nutrient mining of soil organic matter. Drought also reduced aboveground Microstegium biomass 33% and increased Microstegium leaf C:N ratio, consistent with a decline in plant N uptake. We conclude that drought can reduce the performance of existing invasive species populations by suppressing plant-microbe interactions that increase nitrogen supply to plants, which may have consequences for the persistence of invasive plants under hydrologic change.

Evaluating the impact of prescribed surface fire on seedlings in the Central Hardwood Region, USA

Abstract Oak (Quercus) is being successionally replaced by maple (Acer) across much of the eastern deciduous forest. Past research on the close relationship between oak and fire has led forest managers to use prescribed surface fires to deter this replacement. However, there has not been a comprehensive evaluation of the effectiveness of prescribed fire by managers, particularly in the Central Hardwood Region. For example, it is not known how many repeat applications of prescribed fire are needed to accumulate enough oak reproduction to successfully re-establish oak-dominated stands. Tree reproduction and midstory composition were systematically surveyed across 63 mature, oak-dominated stands ranging in prescribed fire histories and aspects on the Hoosier and Wayne National Forests in southern Indiana and Ohio, respectively. These stands represent the vast majority of stands burned to promote oak regeneration since 1990 in these two National Forests. Across all sites, seedlings in the white oak group (section Quercus) and red oak group (section Lobatae) comprised 47.8 ± 3.3 per cent and 8.2 ± 1.6 per cent (mean ± SE), respectively, of all seedlings. In comparison, common competing species (maples and American beech) comprised 5.4 ± 1.4 per cent of all seedlings. Mid- and overstory basal area, percent slope, years since last burn, and total number of burns significantly affected oak seedling density. Greater increases in taller, competitive oak seedling density occurred after sites had been burned three times and with high frequency (≤4 years between burns). However, results also suggest that if an established midstory already exists or fire has not been used on the landscape for almost a decade, repeat applications of prescribed fire will not likely increase oak regeneration in the short term without concurrent treatment of midstory stems.

Mastication Fuels Did Not Alter Fire Severity or Stand Structure in an Upland Oak Woodland

Abstract In the eastern deciduous forest region, open oak woodlands once occupied significant areas that are now closed-canopy forests, negatively affecting wildlife habitat and biodiversity. We superimposed midstory mastication and prescribed fire treatments onto sites with ice storm damage, subsequently subjected to sanitation thinning for management restoration. Mastication reduced stem density and basal area, created a variable cover of masticated material, and increased cover of forbs, graminoids, and tree regeneration. Prescribed fire was implemented two years after mastication treatment. We examined fuel changes and whether masticated fuels altered fire severity. Masticated duff depth decreased significantly two years after treatment; no change occurred on nonmasticated treatments. Masticated 1-hour fuels decreased 80% compared to 35% in nonmasticated treatments and masticated 10 h fuels decreased 45% compared to 9.6% in treatments without mastication. Prescribed fire reduced 1, 10, and 100 h fuels on the burn only treatment, and 10 h fuels on the mastication/burn treatment. Burn severity, measured by composite burn index, did not differ between treatments, nor did we measure significant effects of mastication on fire temperature or char height. Fire had no significant effect on stand structure but should be reexamined in three to five years. Repeated burning at three to five y intervals may also be beneficial.

A Comparison of Early-European Settlement and Present-Day Species Mingling Patterns in the Eastern Deciduous Forest, USA

A Comparison of Early-European Settlement and Present-Day Species Mingling Patterns in the Eastern Deciduous Forest, USA

Myrmecochorous plants and their ant seed dispersers through successional stages in temperate cove forests

Anthropogenic disturbance can decrease woodland diversity in the species-rich herbaceous layer of eastern deciduous forests, and ant-dispersed (myrmecochorous) plants may be particularly affected due to their limited ability to re-colonise secondary forests. Consequently, we predicted that myrmecochorous plants and their keystone seed-dispersing ants would increase with time since the last disturbance, as reflected by young, middle or mature forest successional stage. Specifically, we hypothesized that myrmecochore abundance and richness would be relatively lowest in the youngest forests, moderate in middle-aged forests and highest in mature forests. We also hypothesized that experimentally introducing ant bait in a regular pattern, as might be expected from intact species-rich myrmecochore communities, would elicit greater ant foraging interest than intermittent baiting, as might be expected in recently disturbed depauperate myrmecochore communities. We found the highest myrmecochore plant abundance in mature forests, but we found the same for herbaceous plants overall. Moreover, regular and intermittent bait offerings elicited similar overall ant responses. The observational results suggested that myrmecochorous plants respond to forest successional stage as do other woodland plants, and our experimental results suggest that disrupted seed delivery by myrmecochores did not affect Aphaenogaster abundance or foraging behaviour. As such, the myrmecochore communities studied here appeared as resilient as other woodland herbs, and seed-dispersing ants did not appear dependent on myrmecochore plant communities. Indeed, given the relatively high myrmecochore richness and abundance across our study sites, forest type (e.g., rich cove forest) might better predict myrmecochore success than successional stage.

Beech Bark Disease in an Unmanaged Temperate Forest: Patterns, Predictors, and Impacts on Ecosystem Function

Beech Bark Disease (BBD) is a devastating threat to American beech (Fagus grandifolia), spreading through eastern mixed deciduous forests of North America at unprecedented rates. Understanding how and why some beech trees escape severe BBD effects is important; however, the biotic and abiotic factors that underpin the progression of BBD within unmanaged forests at local scales are not well explored. We surveyed 651 individual beech trees ≥ 10 cm diameter at breast height (DBH) for BBD, in a 13.5-ha unmanaged forest dynamics plot in Ontario, Canada, where >46,000 trees have been identified to species, mapped, and DBH measured at ∼5-year intervals. For each beech tree, BBD severity was ranked on a 5-point severity index, which was then evaluated as a function of tree characteristics including DBH and relative growth rate (RGR). Most beech trees were at either the insect or fungal stage of BBD, with only 22% of beech trees being free of symptoms. Ordinal logistic regression analysis indicated both DBH and RGR were significant predictors of BBD severity. These models, along with both randomization and Moran’s Eigenvector Maps (MEM) analyses, indicated that DBH and RGR and their spatial variation accounted for ∼44.6% of BBD severity in trees. Our MEMs also indicated ∼4.2% of variation in BBD severity was associated with unmeasured spatial variables, which may reflect either the spread of BBD through our study site, or the influence of abiotic variables on BBD severity. At our site, BBD is responsible for at least ∼6.0 Mg C ha–1, or ∼6.5% of the average 92.5 Mg of aboveground biomass C ha–1, transitioning from the live to dead biomass pool. Our study enhances the understanding of the factors predicting the severity of a major forest pathogen in North American temperate forests, assists the integration of BBD severity risk into forest C budget models, and provides insight into how large-scale forest inventories can inform screening for pest or pathogen resistance in trees.

Survival of white‐tailed deer fawns on Marine Corps Base Quantico

AbstractSome jurisdictions in the eastern United States have reduced harvest of white‐tailed deer (Odocoileus virginianus) because of perceived declines in recruitment and population size over the last decade. Although the restoration of American black bears (Ursus americanus) and the colonization of coyotes (Canis latrans) have increased fawn predation in some areas, limited information exists on how temporally dynamic resources and weather influence fawn survival. Therefore, we evaluated fawn survival probability, cause specific mortality, and if factors such as oak (Quercus spp.) mast abundance, winter severity, precipitation, and landscape composition influenced mortality risk on Marine Corps Base Quantico in northern Virginia, USA, from 2008 to 2019. We tracked 248 fawns outfitted with very high frequency radio‐collars and predation was the leading cause of mortality (n = 42; 45%). We estimated survival to 133 days and survival pooling all years (2008–2019) was 0.50 (95% CI = 0.42–0.60). Increased annual red oak (Quercus spp.) mast abundance from the previous fall reduced mortality hazard for fawns. The longevity of our study revealed a link between fawn survival and a specific maternal resource (red oak mast) only available during gestation. Our results highlight the importance of oak mast in eastern deciduous forests and, more broadly, overwinter maternal condition on white‐tailed deer recruitment.

Do invasive species provide a refuge from browsers? A test of associational resistance in a peri-urban habitat plagued by deer

White-tailed deer (Odocoileus virginianus) overbrowsing over the past several decades has caused substantial changes to plant communities in eastern deciduous forests. Deer-preferred species have declined or become locally extirpated in many areas while deer-tolerant species have greatly increased in abundance. Moreover, the abundance of nonnative invasive species has also increased over the last few decades, outcompeting many native species. Native shrubs such as Sambucus canadensis (American elderberry) are now much less common, particularly in urban forests and forests with high deer densities. Here, we performed a short-term study in which we introduced propagations of a native shrub into a replicated field experiment in which we factorially manipulated deer presence or absence and invasive species presence or absence by using exclosures and removing invasive species. We monitored metrics of S. canadensis fitness including leaf count and plant height over two growing seasons. Browsing substantially reduced survival whereas invasive species provided a modest degree of associational resistance. Browsing significantly decreased both leaf count and plant height. By the end of the study, individuals within exclosures had over twice the number of leaves, were five times taller, and had much lower mortality versus those exposed to browsing. Removing invasive species did not change plant height, however, S. canadensis individuals experienced marginally higher leaf counts inside exclosures where we had removed invasive species. This trend was opposite in individuals outside of fences such that those growing within patches where invasive species remained had slightly higher leaf counts, especially during the first growing season. Until the final census date, elderberry growing within patches of invasive species had slightly lower mortality versus those growing in patches where invasive species had been removed. The results from our short-term study indicate that browsing is more inimical to a native shrub than competition from invasive species and we did not find evidence of associational resistance to browsing from invasive cover.

The Importance of Preserving Birds and Their Habitats at Hanford Site and Oak Ridge Reservation: Information and Communication Tools for Governments, Local and Diverse Communities and Others

The Department of Energy (DOE) has one of the largest environmental remediation tasks in the world, cleaning up the radiologic and toxic contamination legacy of nuclear weapons production. DOE has committed itself to accomplish remediation “while protecting human health and the environment”. Many DOE sites are huge, encompassing habitats that are ecologically valuable because they have been protected from human disturbance for 70 years or more. Yet information on the importance of DOE lands for protecting specific ecological resources is often buried in volumes of data. In this paper, we examine the importance of DOE lands as habitats for birds using two sites as examples: the Hanford Site and Oak Ridge Reservation. Our overall goal was to provide a model for communication of key information useful for the public and decision-makers. Birds are conspicuous and familiar features of the landscape, and bird populations are important indicators of habitat quality. As future land use plans evolve, birds can convey important messages about habitat uniqueness and conservation importance and recreational values of designating DOE land for conservation, but only if they are in accessible formats. At the semi-arid Hanford site, shrub-steppe is an important habitat outside the Columbia River corridor. At the wet Oak Ridge Reservation eastern deciduous forest, interior forest is a particularly important habitat. There are different groups of bird species dependent on each habitat. We use two methods for each habitat: 1) a comparison of historical written records and 2) a comparison of land use/land cover data. Habitat loss through development, fragmentation, and degradation is one of the most important causes of avian decline. Importantly, we present the data in a manner suitable for discussion among diverse audiences regarding future use of sites now undergoing remediation. The Hanford Site has recorded 205 bird species, including shrub-steppe species of regional importance. The Oak Ridge Reservation has recorded 213 species of birds, including Neotropical migrants of international concern. In both cases, their respective habitat is key to protection of the unique avian assemblages, and there is a higher percentage of these habitats on the DOE lands than in the surrounding habitats. Our analysis also concludes that these habitats that are of high importance to the rare and declining avian assemblages are mostly increasing on the DOE sites as the once agrarian landscape has reverted to more natural habitat. Since acquisition, DOE has developed about 10% of the land for nuclear and industrial activities, leaving the rest of it as a security buffer for the nuclear production mission. The tables provided in this manuscript can serve as valuable tools in communicating the importance of these lands and protecting these lands for surrounding communities. We commend the DOE for its protection of ecological resources for the regions and the Nation, applaud their mechanisms for ecological protection, and recommend that more of each site’s respective unique and important habitats be designated as preserved in perpetuity as valued ecological resources. This designation entails communicating with Tribes, communities, government agencies and organizations, and the public about the ecological value of their protected lands.