Carya Glabra Research Articles

Interspecific, conspecific, and ontogenetic responses of tree rings to climate: A case study utilizing Carya glabra, Carya ovata, Carya tomentosa, and Quercus montana from an Oak-Hickory Forest in Southeastern Ohio

Climate change in eastern North America is likely to impact the abundance and distribution of the region’s tree species. However, determining the degree to which species will be impacted by altered climates is challenging. Dendrochronology research aimed at understanding relationships between climate and annual ring-width is one way of understanding how climate change may impact forest communities. Oak (Quercus spp.) and hickory (Carya spp.) are two foundational groups of trees likely to undergo changes in abundance and distribution due to climate change. The goal of this study was to compare the radial growth climate sensitivity of three common and co-occurring hickory species (Carya glabra, Carya ovata, and Carya tomentosa) to ecologically similar Quercus montana in southeast Ohio. Also, this study compared conspecific radial-growth climate responses between canopy and subcanopy trees to assess the impacts of climate and drought on subcanopy forest layers. All four species in the forest canopy demonstrated significant positive relationships to growing season precipitation, significant negative relationships with growing season temperature, and significant positive relationships with growing season site water balance. Subcanopy chronologies for all four species demonstrated weaker growth responses to climate, with only Carya glabra demonstrating significant growth relationships with May precipitation and site water balance. Additionally, the increased drought resistance of subcanopy trees provided some evidence of the forest overstory buffering the impacts of climate variability on understory trees. Overall, ontogenetic differences in tree sensitivity to climate variability and drought show that climate change likely has the potential to influence the forest understory, but the degree to which systems are impacted may be highly species-specific.

CentralBark Image Dataset and Tree Species Classification Using Deep Learning

The task of tree species classification through deep learning has been challenging for the forestry community, and the lack of standardized datasets has hindered further progress. Our work presents a solution in the form of a large bark image dataset called CentralBark, which enhances the deep learning-based tree species classification. Additionally, we have laid out an efficient and repeatable data collection protocol to assist future works in an organized manner. The dataset contains images of 25 central hardwood and Appalachian region tree species, with over 19,000 images of varying diameters, light, and moisture conditions. We tested 25 species: elm, oak, American basswood, American beech, American elm, American sycamore, bitternut hickory, black cherry, black locust, black oak, black walnut, eastern cottonwood, hackberry, honey locust, northern red oak, Ohio buckeye, Osage-orange, pignut hickory, sassafras, shagbark hickory silver maple, slippery elm, sugar maple, sweetgum, white ash, white oak, and yellow poplar. Our experiment involved testing three different models to assess the feasibility of species classification using unaltered and uncropped images during the species-classification training process. We achieved an overall accuracy of 83.21% using the EfficientNet-b3 model, which was the best of the three models (EfficientNet-b3, ResNet-50, and MobileNet-V3-small), and an average accuracy of 80.23%.

Dimensional stability and equilibrium moisture content of thermally modified hardwoods

The dimensional stability and equilibrium moisture content (EMC) of thermally modified hardwoods were studied. Lumber of yellow-poplar (Liriodendron tulipifera); red oak (Quercus borealis); white ash (Fraxinus americana), red maple (Acer rubrum); hickory (Carya glabra), and black cherry (Prunus serotina) were modified in industrial thermo-vacuum system. The water absorption rate, EMC, swelling, anti-swelling efficiency, shrinkage, anti-shrinkage efficiency, and anisotropy of the specimens were measured and compared to unmodified wood. The results show that thermal modification significantly decreased water absorption of wood which leads to improved dimensional stability. Specifically, thermally modified wood showed reduced EMC (22% in hickory to 59% in red maple), increased water absorption repellent (14.9% in black cherry to 29.6% in yellow-poplar), increased anti-swelling efficiency (14.2% in hickory to 71.4% in ash), increased anti-shrinkage efficiency (23.5% in red maple to 65.6% in ash), and reduced anisotropy coefficient (4.7% in red oak to 31.9% in black cherry).

Salinity exposure affects lower-canopy specific leaf area of upland trees in a coastal deciduous forest

Sea level rise and increasing storm surges are likely to affect the canopy physiology, ecology, and structure of coastal forests, even well in advance of tree mortality. Laboratory and greenhouse studies have documented that saltwater exposure can trigger changes in leaf-level physiology and morphology, but few in situ studies have examined how tree-specific leaf area (SLA), the ratio of leaf area to mass and a crucial trait and model parameter, is affected by saline soils. We conducted an observational study of SLA in a mid-Atlantic (USA) coastal deciduous forest, taking advantage of a natural gradient in salinity along a tidal creek. Measured SLA of the 239 trees and seven species sampled ranged from Carya glabra (N = 6 trees, mean SLA = 277.9 ± 36.3 cm2/g) to Fagus grandifolia (N = 60, 321.9 ± 62.9 cm2/g); as expected, trees species and canopy position (sun versus shade) significantly affected SLA. For trees (N = 100) directly exposed to the tidal creek, salinity was highly significant after accounting for species (P < 0.001), with trees in the lower reaches of the creek having lower SLA. Leaf area index (LAI), computed from SLA and litter traps, ranged from 4.8 to 15.8 and was inversely related to salinity exposure; the spatial variability in leaf litter production contributed much more to LAI uncertainty than did SLA variability. These in situ results are correlative but consistent with the hypothesis, based on previous greenhouse studies, that the stress of chronic salinity exposure changes species’ leaf morphology. Our findings are useful for understanding the growing effects of saltwater intrusion into upland forests, as well as parameterizing and testing ecosystem-scale models simulating forest stressors and disturbances at the terrestrial-aquatic interface.

Multivariate roles of litter traits on moisture and flammability of temperate northeastern North American tree species

BackgroundTree litter is the primary fuel affecting surface fire behavior in most fire-prone forest and woodland ecosystems in northeastern North America. Fire exclusion and land use changes have dramatically altered fire regimes in many of these ecosystems, shifting toward species that reinforce the continued diminution of fire. Comparative litter flammability studies provide a useful approach to identify the corresponding leaf and litter bed traits that drive the positive feedback termed “mesophication” in these ecosystems.ResultsIn this study, we measured laboratory flammability and moisture characteristics of leaf litter from 17 common tree species in temperate forests of northeastern North America. Principal components analysis of flammability and moisture data resulted in species separating along a pyrophyte-to-mesophyte gradient. Pyrophytic Quercus litter was the most flammable of all species, and Pinus litter dried the most rapidly and flamed for the longest duration. The remaining mesophytic species grouped into either a high moisture retention-poor burning cluster (Acer rubrum, Betula alleghaniensis, Nyssa sylvatica, Carya glabra, C. tomentosa) or an intermediate flammability cluster (Acer saccharum, C. ovata, Tilia americana). Several litter traits were associated with multivariate factors. Leaf length, density, curling, surface area-to-volume, and litter bed bulk density were associated with the factor comprising saturation moisture content, flaming time, and consumption. Specific leaf area was related to moisture time-lag and flame height. Litter bed packing ratio was most related to smoldering duration.ConclusionsInterspecific variability in leaf and litter bed traits explained substantial differences in moisture dynamics and flammability among the species examined. These findings extend our understanding of litter traits’ influence on the combustion environment and affirm the potential effects of pyrophytic and mesophytic tree species on contemporary fire regimes in northeastern North American forests.

Carya Species for Use in the Managed Landscape: Predicted Drought Tolerance

Impressive ornamental features including exfoliating bark and golden fall color are among the reasons why hickories [Carya (Nutt.)] are sought after by horticulturists. Their potential for application in the green industry continues to grow as producers and consumers in the United States become more interested in adopting native plants; however, an absence of knowledge that defines which species are tolerant of abiotic stresses in the landscape limits their use. If production of stress-tolerant hickories increases, they could be used to diversify urban forests and may bolster the resiliency of managed landscapes. We examined the predicted leaf water potential at the turgor loss point to estimate drought tolerance among several species of hickories and pecans adapted to growing in northern climates in the United States. Our hypotheses were that because some bottomland habitats experience seasonal drought in addition to flooding, taxa adapted to these sites may be more drought tolerant than previously assumed, and that the degree of drought tolerance would be variable within species and populations. Predicted mean leaf turgor loss measured in summer across species was −3.38 MPa. Kingnut hickory [Carya laciniosa (F. Michx.) Loud.] exhibited the lowest mean summer leaf turgor loss point −3.64 MPa), whereas pignut hickory [Carya glabra (Mill.) Sweet.] exhibited the highest (−3.20 MPa). Provenance of trees studied influenced estimated drought tolerance of C. laciniosa. Variability between individual trees within each species was observed, suggesting clonal selections of each taxon can be made for drought-prone landscapes. The results of this work imply that all the species studied are at least moderately drought tolerant and should be considered for planting in managed landscapes. Further, species often associated with riparian habitats may exhibit substantial tolerance to drought and should not be excluded from use on drought-prone sites.

Natural Forest Regeneration Changes in an Urban Natural Area Forest with White-Tailed Deer (Odocoileus virginianus) Exclusion and Felling by North American Beaver (Castor canadensis)

We examined natural regeneration changes in an urban natural area forest, the Good Woods, Cobbs Creek Park, Philadelphia, Pennsylvania, after placement of exclusion fencing to prevent white-tailed deer (Odocoileus virginianus) browsing and unplanned North American beaver (Castor canadensis) felling. Seedlings (stem dbh < 2.5 cm, stump at 15 cm < 3.0 cm), saplings (stem dbh > 2.5–10 cm, stump at 15 cm > 3.0–11 cm), and trees (stem dbh > 10 cm, stump at 15 cm > 11 cm) were surveyed in 65 permanent 10 m × 10 m plots: 6 y after fencing placement to exclude white-tailed deer and 5 mo after the start of beaver felling. Overall seedling abundance increased by 5% while sapling populations grew by 20% and the number of trees expanded by 34% after white-tailed deer exclusion. Red maple (Acer rubrum) seedlings, tulip poplar (Liriodendron tulipifera) seedlings, and red oak (Quercus rubra) saplings increased significantly while pignut hickory (Carya glabra) and white ash (Fraxinus americana) seedlings decreased significantly. Seedling and tree losses to North American beaver felling were small (<2% for all seedlings and <3% for all trees). However, beaver felling caused a greater than 60% loss of saplings for red maple, black cherry (Prunus serotina), white oak (Quercus alba), and red oak. Less than 30% of the saplings were lost for pignut hickory, white ash, and tulip poplar. Urban North American beaver preferences for native species saplings paralleled rural beaver in the eastern United States. Our results indicate white-tailed deer exclusion fencing is an effective management method for increasing natural regeneration of both seedlings and saplings in an urban natural area forest when the fencing also effectively excludes North American beaver.

Gibberellic Acid 4+7 Influences Shoot Growth of Seedling Pecan and Bitternut Hickory

Abstract Shoot development of seedling hickories is slow, limiting their success as viable crops using standard growing techniques. Because hickories are predominantly propagated by seed, we questioned whether gibberellic acid (GA) could be used on seedlings to overcome slow shoot development during juvenility. Treatments of one-year-old seedlings of bitternut hickory [Carya cordiformis (Wangenh.) K. Koch], pignut hickory [C. glabra (Mill.) Sweet], pecan [C. illinoinensis (Wangenh.) K. Koch], kingnut hickory [C. laciniosa (F. Michx.) Loud.], shagbark hickory [C. ovata (Mill.) K. Koch], and mockernut hickory [C. tomentosa (Lam.) Nutt.] began at bud break by applying a solution of 500 ppm GA4+7 dissolved in 95% ethanol directly to apical buds or stem tissue at three-day intervals for 27 days. After 160 days, neither treatment affected caliper of any taxon, although species differences were observed. Compared to nontreated control plants, treatment of buds resulted in a 234% and 144% increase in shoot height of bitternut hickory and pecan, respectively. In a second experiment, the same treatments were implemented on seedlings of bitternut hickory shortly after germination. Only shoot height and dry weight were affected (increased) by application of GA4+7. This study indicates plant growth regulators could be effective at increasing shoot extension of some hickories. Chemicals used in this study: Gibberellic acid 4+7 (GA4+7). Species used in this study: bitternut hickory [Carya cordiformis (Wangenh.) K. Koch]; pignut hickory [C. glabra (Mill.) Sweet]; pecan [C. illinoinensis (Wangenh.) K. Koch]; kingnut hickory [C. laciniosa (F. Michx.) Loudon]; shagbark hickory [C. ovata (Mill.) K. Koch]; and mockernut hickory [C. tomentosa (Lam.) Nutt.].

Phylogenetic Signal, Root Morphology, Mycorrhizal Type, and Macroinvertebrate Exclusion: Exploring Wood Decomposition in Soils Conditioned by 13 Temperate Tree Species.

Woodlands are pivotal to carbon stocks, but the process of cycling C is slow and may be most effective in the biodiverse root zone. How the root zone impacts plants has been widely examined over the past few decades, but the role of the root zone in decomposition is understudied. Here, we examined how mycorrhizal association and macroinvertebrate activity influences wood decomposition across diverse tree species. Within the root zone of six predominantly arbuscular mycorrhizal (AM) (Acer negundo, Acer saccharum, Prunus serotina, Juglans nigra, Sassafras albidum, and Liriodendron tulipfera) and seven predominantly ectomycorrhizal (EM) tree species (Carya glabra, Quercus alba, Quercus rubra, Betula alleghaniensis, Picea rubens, Pinus virginiana, and Pinus strobus), woody litter was buried for 13 months. Macroinvertebrate access to woody substrate was either prevented or not using 0.22 mm mesh in a common garden site in central Pennsylvania. Decomposition was assessed as proportionate mass loss, as explained by root diameter, phylogenetic signal, mycorrhizal type, canopy tree trait, or macroinvertebrate exclusion. Macroinvertebrate exclusion significantly increased wood decomposition by 5.9%, while mycorrhizal type did not affect wood decomposition, nor did canopy traits (i.e., broad leaves versus pine needles). Interestingly, there was a phylogenetic signal for wood decomposition. Local indicators for phylogenetic associations (LIPA) determined high values of sensitivity value in Pinus and Picea genera, while Carya, Juglans, Betula, and Prunus yielded low values of sensitivity. Phylogenetic signals went undetected for tree root morphology. Despite this, roots greater than 0.35 mm significantly increased woody litter decomposition by 8%. In conclusion, the findings of this study suggest trees with larger root diameters can accelerate C cycling, as can trees associated with certain phylogenetic clades. In addition, root zone macroinvertebrates can potentially limit woody C cycling, while mycorrhizal type does not play a significant role.

Using Floristic Analysis and Dendrochronology to Plan Ecological Restoration within a Forest–Prairie Ecotone

The limestone bluffs of the central Mississippi River Valley represent a significant portion of the remaining intermingled xeric hill prairie-savanna-woodland systems of the Midwest where different cover types may co-occur at very fine scales. Efforts to restore these landscapes would benefit from a data-driven tool to delineate existing vegetation cover characteristics and reconcile these with desired management outcomes on a spatially explicit basis. This study employed hierarchical cluster analysis and nonmetric multidimensional scaling in combination with indicator species analysis and dendrochronological methods to examine the structure, composition, and temporal community patterns of the forest–prairie gradient in the Mississippi River Bluffs of Jersey County, Illinois. Four distinct community types were identified on the gradient: (1) a woodland community dominated by Juniperus virginiana, Carya glabra, Quercus stellata, and Lonicera maackii; (2) open oak woodland with high exposed soil and overstory of Acer saccharum, Q. velutina, and Q. muehlenbergii; (3) a hill prairie community with grass coverage as the sole indicator; and (4) a transitioning community with 14 significant indicators and a trajectory advancing toward mesophytic forest composition. These data, within context with stem age, historical documents, and drought data, reveal the role of historical disturbances in temporal patterns of forest–prairie dynamics and provide a resolution in greater detail than previous studies of forest and nonnative invasive shrub encroachment. Pairing management activities to stand conditions, as informed by understanding drivers of ecosystem change, provides continuity with historical disturbance regimes and an objective basis for restoration activities and targets.

Predisposing factors\u2019 effects on mortality of oak (Quercus) and hickory (Carya) species in mature forests undergoing mesophication in Appalachian Ohio

BackgroundMature oak (Quercus spp.) and hickory (Carya spp.) trees are gradually being replaced by more shade-tolerant tree species across the eastern U.S., likely due to fire suppression and increased precipitation. Oaks and hickories are highly valuable to wildlife; therefore, studying their mortality patterns can provide information on the longevity of habitat quality for many animal species. Oak mortality has most often been studied following large oak decline events, but background mortality rates in forests with aging oak and hickory canopies warrant equal attention, especially in the context of widespread oak and hickory regeneration failure.MethodsWe studied background mortality rates of five oak and one hickory species over a 23–25 year time period (1993–1995 to 2018), using 82 1/20th hectare permanent plots on the Marietta Unit of the Wayne National Forest in southeastern Ohio. We calculated mortality rates based on remeasurement of individual trees for white oak (Quercus alba), chestnut oak (Quercus montana), northern red oak (Quercus rubra), black oak (Quercus velutina), scarlet oak (Quercus coccinea), and pignut hickory (Carya glabra). For each of these species other than scarlet oak, we also modeled the relationships of mortality probability with a priori topographic, soil, stand structural, and individual tree covariates, using a mixed-effects logistic regression framework.ResultsThe species with the highest mortality rate was scarlet oak (61.3%), followed by northern red oak (41.4%), black oak (26.7%), pignut hickory (23.9%), white oak (23.4%), and chestnut oak (19.1%). In our models, northern red oak mortality was associated with more mesic slope positions, shallower solums, more acidic soils, and older stand ages. Pignut hickory and chestnut oak mortality rates were associated with higher basal areas on the plot, while white oak mortality showed the opposite pattern.ConclusionsOur data suggest that red oak subgenus trees in mature forests of our area will become increasingly uncommon relative to white oak subgenus trees, as the result of higher mortality rates likely related to the shorter lifespans of these species. Particularly vulnerable areas may include more mesic topographic positions, shallower or more acidic soil, and older stands. Since maintaining oak subgenus diversity is beneficial to wildlife diversity in the eastern U.S., managers in areas with extensive mature mixed-oak forests could choose to favor the red oak subgenus when conducting silvicultural treatments.

Potential influences of forest mesophication on corticolous arthropods as a food base for insectivores in eastern deciduous forests

Decreased disturbance has allowed plant communities in some landscapes to transition from early- and mid-successional communities to later successional communities. In eastern deciduous forests, this process has been termed mesophication because of the transition from a xeric to a more mesic environment. Mesophytic trees tend to produce foliage that is less palatable than xerophytic trees, supporting fewer arthropods that provide an important food source for higher trophic organisms such as insectivorous birds and mammals. An additional characteristic that differs between xerophytic and mesophytic trees is bark texture. Xerophytic tree species tend to produce more deeply furrowed bark that protects trees from overheating. To better understand the potential impact of continued mesophication of eastern deciduous forest on forest dwelling insectivores, we tested the hypothesis xerophytic trees support a greater abundance, biomass, diversity, and richness of arthropods in the Shawnee National Forest of southern Illinois. More specifically, we tested the prediction we would catch a greater number and more diverse community of arthropods on the trunks of white oak (Quercus alba) and pignut hickory (Carya glabra) trees than on the trunks of sugar maple (Acer saccharum) and American beech (Fagus grandifolia) trees, with tulip poplar (Liriodendron tulipifera), a species with an intermediate level of bark roughness and found in both mesic and xeric conditions having an intermediate number of arthropods. Consistent with our prediction, we found the model that included tree species to be most parsimonious when describing variation in arthropod diversity, total arthropod length (as a surrogate for biomass), and arthropod abundance, but not arthropod richness. Differences in arthropod abundance and total length among tree species were driven by the greater total length and abundance of arthropods found on pignut hickory, while the difference in arthropod diversity among tree species was driven by lower Shannon diversity observed on pignut hickory. These results suggest that continued mesophication of eastern deciduous forests may be detrimental to branch and trunk gleaning insectivores, primarily due to the loss of pignut hickory in the forest community. Because both oak and hickory trees support more abundant and diverse foliage dwelling arthropod communities than more mesophytic species, because at least some species of hickory trees support greater total length and abundance of arthropods on their trunk bark, and because species of both genera are most frequently found in more xeric conditions, we recommend forest managers implement management activities that reset succession and maintain a more xerophytic tree community.

Nut crops collection of "Ustymivskyi" dentrological park

Aim. The aim of the work is to characterize the diversity of nut crops in terms of the efficiency of introduction in the conditions of the southern forest-steppe of Ukraine. Results and Discussion. In the collection of tree and shrub species of the State Dendrological Park "Ustymivskyi" numbering 472 species, nut crops are represented by more than 120 species. These include fruit species of temperate and subtropical zones from different botanical families. The climate in the area of the park is moderately continental with unstable humidity, frequent snowless winters with sharp fluctuations in air temperature. Dry winds are 2-3 times a year. The amount of precipitation is 254-777 mm per year. In the spring-summer period, there are periods without rain (up to two to three months). As a result of the study, the species and forms promising for introduction in such conditions have been identified. These are representatives of the genus Juglans: J. mandshurica Maxim. (Manchurian walnut), J. cinerea L. (gray walnut), J. nigra L. (black walnut) and J. regia L. (walnut). Corylus colurna (bear hazelnut) showed exceptionally good growth and abundant fruiting. However, in the last 10 years, the trees have become dry top and dry. Shrub species C. avellana (its forms 'Purpurea', 'Laciniata') and C. pontica C. Koch. turned out to be more adapted to climate change. The endemic steppe species Amygdalus nana L. (steppe almond) can be recommended in crosses when breeding for winter hardiness and an increased content of the alkaloid amygdalin (up to 4.5%). A. triloba Ricker. (almond three-bladed, regular and terry forms) is used as a decorative type. However, due to excessive disease damage (cercosporosis, orange spot, curly leaves, burns), plants lose their decorative effect. Repeated attempts to introduce into the collection such species as Carya alba (L.) C. Koch. (pignut hickory), Pterocarya pterocarpa (Michx.) Kunth ex Iljinsk. (caucasian wingnut), Fagus sylvatica L. (common beech) and Castanea sativa Mill. (sowing chestnut) were unsuccessful: the plants quickly died. Success has been achieved in the introduction and distribution of Xanthoceras sorbifolium and Ginkgo biloba in the forest-steppe and steppe zones. Conclusions. It is recommended to introduce walnut crops isolated as a result of the study into the range of plants used in landscaping, to create perennial plantations on lands unsuitable for agricultural production.

Fifty-Five Years of Change in a Northwest Georgia Old-Growth Forest

ABSTRACT Old-growth forests provide unique insight into historical compositions of forests in the eastern United States. Plots established within a mixed forest community within Marshall Forest in Rome, Georgia, in 1960 (and remeasured in 1989) were reassessed to determine changes in forest composition. The community has experienced approximately 10% increase in basal area since the previous measurement period. However, changes in species importance have occurred. Chestnut oak (Quercus montana), mockernut hickory (Carya tomentosa), white oak (Quercus alba), and flowering dogwood (Cornus florida) have all decreased in importance, while pignut hickory (Carya glabra), winged elm (Ulmus alata), yellow poplar (Liriodendron tulipifera), and red maple (Acer rubrum) have all increased in importance. Additionally, there are no Pinus spp. saplings in the study area, indicating seedlings are not being recruited into the midstory. These changes indicate continued succession to a composition increasingly dominated by ...

Differences in biotic interactions across range edges have only minor effects on plant performance

Summary It is widely expected that plant species will expand their ranges poleward in response to climate change. In the process, individuals establishing beyond existing range margins will be exposed to new biotic communities, including different assemblages of natural enemies. The resulting differences in biotic interactions could lead to scenarios of enemy release or biotic resistance, and if the interactions are strong, they could influence plant performance and therefore colonization success. In order to test whether natural enemies will affect range expansion dynamics, we transplanted seven species along a 450‐km latitudinal gradient that spanned the range edges of five of these species. The experiment was conducted over 5 years with ˜ 13 000 seedlings and included pesticide treatments to reduce invertebrate herbivory. We measured foliar damage caused by disease and invertebrate herbivores, seedling survival, light availability, soil moisture, soil nutrient concentrations and several other variables in nine forests located in four regions along the latitudinal gradient. We found that several species (Carya glabra, Liriodendron tulipifera, Quercus velutina and Robinia pseudoacacia) tended to have less foliar disease beyond their range, but there were few substantial differences in herbivory across range edges (with the exception of Liriodendron tulipifera). After accounting for other variables, including environmental conditions and vertebrate herbivory, we found that foliar disease decreased survival for four species (Acer rubrum, Quercus alba, Quercus rubra and Quercus velutina) and foliar herbivory reduced survival for three species (Acer rubrum, Liriodendron tulipifera and Quercus rubra). However, the effects of these biotic interactions on survival were very small (0–5% reductions in survival at observed levels of damage after four years), which is verified by the minor effects of the pesticide treatment on seedling survival. Synthesis. Our results suggest that foliar herbivores and pathogens are unlikely to play a major role in the range expansion dynamics of these temperate tree species.

Foliar damage beyond species distributions is partly explained by distance dependent interactions with natural enemies.

Plant distributions are expected to shift in response to climate change, and range expansion dynamics will be shaped by the performance of individuals at the colonizing front. These plants will encounter new biotic communities beyond their range edges, and the net outcome of these encounters could profoundly affect colonization success. However, little is known about how biotic interactions vary across range edges and this has hindered efforts to predict changes in species distributions in response to climate change. In contrast, a rich literature documents how biotic interactions within species ranges vary according to distance to and density of conspecific individuals. Here, we test whether this framework can be extended to explain how biotic interactions differ beyond range edges, where conspecific adults are basically absent. To do so, we planted seven species of trees along a 450-km latitudinal gradient that crossed the current distributional range of five of these species and monitored foliar disease and invertebrate herbivory over 5yr. Foliar disease and herbivory were analyzed as a function of distance to and density of conspecific and congeneric trees at several spatial scales. We found that within species ranges foliar disease was lower for seedlings that were farther from conspecific adults for Acer rubrum, Carya glabra, Quercus alba, and Robinia pseudoacacia. Beyond range edges, there was even less foliar disease for C.glabra, Q.alba, and R.pseudoacacia (A.rubrum was not planted outside its range). Liriodendron tulipifera did not experience reduced disease within or beyond its range. In contrast, Quercus velutina displayed significant but idiosyncratic patterns in disease at varying distances from conspecifics. Patterns of distance dependent herbivory across spatial scales was generally weak and in some cases negative (i.e., seedlings farther from conspecific adults had more herbivory). Overall, we conclude that differences in biotic interactions across range edges can be thought of as a spatial extension to the concept of distance dependent biotic interactions. This framework also provides the basis for general predictions of how distance dependent biotic interactions will change across range edges in other systems.

Old Field Communities and Restoration Potential at Mammoth Cave National Park, USA

Abstract Old fields (at least 67 years since abandonment) within Mammoth Cave National Park, USA are dominated by coniferous species (Juniperus virginiana L. and Pinus virginiana) instead of the desired deciduous species (Carya glabra, Quercus alba, Q. muehlenbergii, Q. prinus, and Q. velutina) that dominate much of the rest of the park. Species composition above ground and in the seedbank of old fields and adjacent desired future condition areas, (identified by the United States National Park Service (NPS) as oak and hickory-dominated) were evaluated and compared. Species composition and dominance have shifted from oak species toward conifer-dominated stands due to previous land conversion to agriculture and the exclusion of fire. Management practices that can be implemented by the NPS to alter the condition of the old fields to achieve the desired future condition include thinning treatments and reintroduction of the historic fire regime.

Restoration Results for a Maryland Shale Barren after Pignut Hickory Management and a Prescribed Burn

ABSTRACT Maryland shale barren (savanna) communities support rare, threatened, and endangered species, but biodiversity conservation sites are transitioning to pignut hickory woodland and forest as a result of fire exclusion. In Green Ridge State Forest, an exemplary community was studied for vegetation change after pignut hickory management and a prescribed burn. Portions of contiguous chestnut oak (Quercus montana) and streamside hardwood communities were also included. Prerestoration herbaceous layer characteristics were quantified in 2010 using transect plots before hickories were killed by herbicide. A prescribed burn was conducted in November 2011 followed by resampling in 2013. In the barren community, Carex pensylvanica remained the dominant herbaceous layer species, but codominant species changed. Ground cover increased from 63% to 76%, species richness from 48 to 52, and the Shannon-Wiener diversity index (H′) from 3.138 to 3.373. In the chestnut oak forest, the dominant herbaceous layer specie...

Climate, Deer and Hogs: Drivers of Rapid Change in a Hickory-Dominated Maritime Forest on St. Catherines Island

Maritime forests in the southeastern United States are very susceptible to climate change and have experienced dramatic reductions in extent following anthropogenic disturbances over the past two hundred years. St. Catherines Island, Georgia, an undeveloped barrier island, is home to an unusual pignut hickory (Carya glabra) maritime forest that is experiencing rapid rates of change, including a reduction in basal area from 23 m2·ha-1 in 1996 to 15 m2·ha-1 in 2014. Nine permanent forest plots and associated animal exclosures were installed across this 37 ha stand in 2012 to track forest change and seedling recruitment. From 2012 to 2014, declines in total basal area were caused by mortality of pignut hickory in the overstory and redbay (Persea borbonia) in the midstory. Pignut hickory continues to be ranked first in relative frequency, density and dominance, while Sabal palm (Sabal palmetto) is slightly increasing in relative density. In 2012, there were no woody species regenerating in any of the plots and following one year of animal exclosures, we found 478 pignut hickory seedlings ha-1; thus, deer browse and feral hog predation of nuts may be important drivers of change in this stand. The interplay among deer browse, exotic animal pressures, exotic insects and a drier climate has resulted in a very open forest with the regeneration of few woody plants. Without management of the feral hog and deer population, this unusual maritime forest, with trees as old as 250 years, may continue to decline.

Patterns and variability in seedling carbon assimilation: implications for tree recruitment under climate change.

Predicting future forests' structure and functioning is a critical goal for ecologists, thus information on seedling recruitment will be crucial in determining the composition and structure of future forest ecosystems. In particular, seedlings' photosynthetic response to a changing environment will be a key component determining whether particular species establish enough individuals to maintain populations, as growth is a major determinant of survival. We quantified photosynthetic responses of sugar maple (Acer saccharum Marsh.), pignut hickory (Carya glabra Mill.), northern red oak (Quercus rubra L.) and eastern black oak (Quercus velutina Lam.) seedlings to environmental conditions including light habitat, temperature, soil moisture and vapor pressure deficit (VPD) using extensive in situ gas exchange measurements spanning an entire growing season. We estimated the parameters in a hierarchical Bayesian version of the Farquhar model of photosynthesis, additionally informed by soil moisture and VPD, and found that maximum Rubisco carboxylation (V(cmax)) and electron transport (J(max)) rates showed significant seasonal variation, but not the peaked patterns observed in studies of adult trees. Vapor pressure deficit and soil moisture limited J(max) and V(cmax) for all four species. Predictions indicate large declines in summer carbon assimilation rates under a 3 °C increase in mean annual temperature projected by climate models, while spring and fall assimilation rates may increase. Our model predicts decreases in summer assimilation rates in gap habitats with at least 90% probability, and with 20-99.9% probability in understory habitats depending on species. Predictions also show 70% probability of increases in fall and 52% probability in spring in understory habitats. All species were impacted, but our findings suggest that oak species may be favored in northeastern North America under projected increases in temperature due to superior assimilation rates under these conditions, though as growing seasons become longer, the effects of climate change on seedling photosynthesis may be complex.