Central Hardwood Research Articles

Fungal Footprints: Soil Fungal Communities in Black Walnut and Red Oak Forests.

Soil fungal communities are critical for forest ecosystem functions in the Central Hardwood Region (CHR) of the USA. This evaluation, which took place in 2022-2023, investigates the influence of Juglans nigra (BW, black walnut) and Quercus rubra (NRO, Northern red oak) on soil properties and fungal community structures across three CHR sites. The objectives of this study are to investigate how the fungal communities identified beneath J. nigra and Q. rubra serve to influence biodiversity and soil health within hardwood plantations. Soils from two locations in Indiana and one in Michigan were examined and assessed for variations in fungal composition and diversity. Soil fungal communities were characterized using Illumina high-throughput sequencing while multivariate analysis was applied to analyze patterns in these fungal communities. These data provided insights into how environment, location, and tree species affect fungal community structure. Results indicate that J. nigra soils exhibited higher carbon (0.36%, 1.02%, 0.72%), nitrogen (25%, 29%, 56%), and pH (0.46, 1.08, 1.54) levels than Q. rubra soils across all three sites and foster greater fungal diversity. Specifically, J. nigra was associated with increased Ascomycota diversity, whereas Q. rubra supported a higher prevalence of Basidiomycota. Basidiomycota were negatively correlated with carbon and pH, while Ascomycota showed positive correlations with these variables. These findings highlight how crucial it is to understand how different tree species influence fungal communities and, consequently, how they influence forest soil health. Our findings serve to improve forest management practices by emphasizing the importance of fungal communities in maintaining the function and resilience of an ecosystem. Our study underscores that grasping these specific interactions is essential for effective forest management, especially when considering how to use fungal communities to boost plant growth. This work focuses on hardwood plantations rather than either agricultural ecosystems, monocultures, or native forests, thus filling a gap in the current literature where many studies are limited to specific fungal groups such as mycorrhizae. In future research, it is important to examine a wider range of tree species. This will deepen our understanding of fungal community dynamics and their impact on maintaining healthy forest ecosystems. Our hardwood plantation focus also notes the potential for adaptive forest management as environmental conditions change.

Spatial and temporal partitioning between eastern gray and fox squirrels in a Central Hardwood forest

Abstract Congeneric fox squirrels (Sciurus niger) and eastern gray squirrels (S. carolinensis) compete for resources within North American temperate forests. Both species exhibit regional variation in morphology and behavior—potentially due to differences in geography, community composition, or ecological pressures between forested regions. While many have studied these species in other forested regions of the United States, recent assessments of partitioning between these species in Central Hardwood forests remain scarce. We investigated spatial and temporal partitioning between squirrel species using photographic captures from camera traps at 2 scales (i.e., camera location and camera cluster) across a 16,058-km2 region of southern Illinois, United States, during January to April 2008 to 2010. We fitted single-season single-species and co-occurrence occupancy models to assess spatial partitioning at both scales and used kernel density analysis to assess temporal partitioning. We recorded 3,044 photographic captures of focal species (n = 918 fox squirrels and 2,126 eastern gray squirrels). Fox Squirrel occupancy was 0.26 ± 0.09 (SE) and 0.50 ± 0.17 at the camera location and camera cluster scales, respectively. Eastern Gray Squirrel occupancy was 0.47 ± 0.07 and 0.84 ± 0.23 at the camera location and camera cluster scales, respectively. Fox Squirrel occupancy increased with further distances to roads and had scale-dependent relationships to forest structure. Eastern Gray Squirrel occupancy increased with more hardwood basal area. Co-occurrence was influenced by distance to road at the camera location scale. We found a moderate level of activity overlap between species (Δ = 0.63, CI = 0.60 to 0.67); however, no evidence of temporal partitioning was observed. Habitat characteristics and spatial scale appear more influential in partitioning eastern gray and fox squirrels in Central Hardwood forests than peak activity.

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%.

Forest structural diversity is linked to soil microbial diversity

AbstractEfforts to catalog global biodiversity have often focused on aboveground taxonomic diversity, with limited consideration of belowground communities. However, diversity aboveground may influence the diversity of belowground communities and vice versa. In addition to taxonomic diversity, the structural diversity of plant communities may be related to the diversity of soil bacterial and fungal communities, which drive important ecosystem processes but are difficult to characterize across broad spatial scales. In forests, canopy structural diversity may influence soil microorganisms through its effects on ecosystem productivity and root architecture, and via associations between canopy structure, stand age, and species richness. Given that structural diversity is one of the few types of diversity that can be readily measured remotely (e.g., using light detection and ranging—LiDAR), establishing links between structural and microbial diversity could facilitate the detection of belowground biodiversity hotspots. We investigated the potential for using remotely sensed information about forest structural diversity as a predictor of soil microbial community richness and composition. We calculated LiDAR‐derived metrics of structural diversity as well as a suite of stand and soil properties from 38 forested plots across the central hardwoods region of Indiana, USA, to test whether forest canopy structure is linked with the community richness and diversity of four key soil microbial groups: bacteria, fungi, arbuscular mycorrhizal (AM) fungi, and ectomycorrhizal (EM) fungi. We found that the density of canopy vegetation is positively associated with the taxonomic richness (alpha diversity) of EM fungi, independent of changes in plant taxonomic richness. Further, structural diversity metrics were significantly correlated with the overall community composition of bacteria, EM, and total fungal communities. However, soil properties were the strongest predictors of variation in the taxonomic richness and community composition of microbial communities in comparison with structural diversity and tree species diversity. As remote sensing tools and algorithms are rapidly advancing, these results may have important implications for the use of remote sensing of vegetation structural diversity for management and restoration practices aimed at preserving belowground biodiversity.

Sustainability of White Oak (Quercus alba) Timber Supply in Kentucky

Abstract White oak is a major commercial tree species and an important timber resource in Kentucky. However, current forest inventory trends from the Central Hardwood Forest Region (CHFR) reveal a sustainability threat from declining white oak regeneration and recruitment leading to a disproportionate inventory structure. Using Forest Inventory and Analysis (FIA) data together with the Forest Vegetation Simulator (FVS), we performed a base run analysis of projected inventory levels of white oak sawlogs to better understand whether the inventory level is sustainable to support the current harvest level of white oak in the future. The projections were further examined by tree grades to provide a general outlook on the quality of white oak timber growing in Kentucky’s forests in posterity. By doing so, we generated results that indicate that projected inventory levels of white oak sawlogs cannot be considered sustainable to support current harvest levels from 2058 onwards. In addition, the long-term trends in inventory levels of high-quality white oak sawlogs would be continuously declining whereas that of low-quality sawlogs would be steadily increasing. On the brink of these significant inventory shifts, our study calls for proactive forest management approaches to stabilize the white oak timber resource supply in Kentucky and beyond.

Acorn production, climate, and tree-ring growth of five oak species in southern Appalachian forests

Oak (Quercus) are a dominant and important tree genus in the Central Hardwood Region (USA) due to their commercial timber value, and food value of their protein-rich seed – acorns – to wildlife. Acorn production is characteristic of masting, with highly variable crop sizes that are synchronized within populations, but with consideration variation among individual trees. Critical to acorn masting studies are longitudinal datasets, which are often difficult to maintain due to a host of constraints. One possible approach to extending mast datasets involves the use of dendrochronology, where tree-ring-width variability serves as a proxy for annual acorn production. In this study, we addressed the future utility of mast reconstructions by examining relationships between acorn production, climate, and tree-ring data from five common oak species in southern Appalachian hardwood forests (Bent Creek Experimental Forest). We found little evidence to suggest that acorn production influences seasonally resolved tree-ring data, even when we considered early and latewood growth separately, or when we analyzed trees with substantially higher overall investment in acorn production (i.e., super producers). Monthly climate (temperature, precipitation) correlated to acorn production was strongest when lagged, which could indicate weather conditions were more important for phases of flower production and fertilization than acorn maturation. However, relationships were relatively weak, indicating limited potential for the forecasting of acorn crops, or for reconstruction methods that combine observed weather data and tree-ring responses to masting. Overall, our findings provide some support for the role of resource dynamics in regulating masting in oaks, but relationships between radial growth and acorn production are not sufficiently strong, at least in this location, to permit tree-ring based reconstruction of masting in these oak species.

Predicting and indexing ungulate browse intensity from local to regional scales

The intensity of browsing by white-tailed deer (Odocoileus virginianus; hereafter deer) can be influenced directly by deer densities and food availability, and indirectly by landscape characteristics that influence these factors. However, the variables and spatial scales that influence browsing intensity likely differ in landscapes with varying composition and land use. Furthermore, because high browsing intensity can influence the structure and function of forests, determining the most effective and efficient indices of browsing intensity can aid forest management decisions. To evaluate differences in browsing intensity, we used Bayesian hierarchical models to estimate the probability of browsing for twigs from non-avoided species based upon woodlot and landscape-scale variables, which were calculated within 200, 500, 1000, and 1500 m buffers. We then evaluated the efficacy of the twig age, oak sentinel, and herbaceous indicator methods of indexing browsing intensity by correlating these to browsing intensity and deer density. We also evaluated the expense and required work time associated with each index method. Food availability seemed to drive browsing intensities in our study, however, deer density was also important in the region with the lowest cover of forest. When meaningful, landscape characteristics fit data best at the 500 m buffer size. The twig age method showed the strongest correlations to both browsing intensity and deer density and was among the most efficient methods, suggesting it is a reliable index of browsing intensity within Indiana and similar regions. Together, our results highlight that landscape characteristics can mediate the relationship between deer and forest plant communities, which emphasizes the need to tailor management actions to variable landscapes that may occur within a single state or region. Additionally, our results suggest that the twig age method is the most efficient and effective index to monitor browse intensity in agriculturally dominated landscapes, such as those of the Central Hardwood Forest Region.

Regeneration and Growth following Silvicultural Treatments in a Productive Central Hardwood Forest

The lack of desirable oak (Quercus spp.) regeneration on upland sites is a problem in the Central Hardwood Region. While the reintroduction of fire, thinning, and/or harvesting has been proposed as a solution to increase oak regeneration, these treatments may have limited impact on productive sites, and the effects on the growth of residual midstory oak stems is not clear. This study examined the regeneration response and growth of residual midstory white oak (Quercus alba) stems in a mature, oak-dominated, upland forest following four treatments: (1) burn, (2) thin and burn, (3) harvest and thin and burn, and (4) no treatment (control) at Trail of Tears State Forest located in southern Illinois. Results indicated there was no significant difference in oak density among treatments for any regeneration size class. In addition, none of the treatments resulted in a radial growth release in residual midstory white oak stems. These results suggested these treatments may need to be modified to increase oak regeneration on productive sites and indicated that there may not have been enough time since treatment application, or treatments may not have been intense enough, to release midstory residual stems.

The Impact of Tree Species on Microbial Community Structure and Soil Function on Forest Plantations in the Central Hardwoods Region (CHR)

Interactions between above- and below-ground monoculture forest plantation components are critical to tree growth and development. Within the Central Hardwoods Region (CHR), synergistic relationships between tree species and soil microbial community structure and function have received limited research attention. Soil microbes are integral to forest ecosystems as their activities intrinsically promote soil organic matter decomposition, nutrient cycling, and ecosystem functioning. Here, we examined soils from two perfectly aligned stands of black walnut (BW, Juglans nigra L.) and Northern red oak (RO, Quercus rubra L.) trees. Measurements of selected soil chemical properties, microbial community structure using ester-linked fatty acid methyl ester (EL-FAME), and soil enzyme activities (EAs) were used. Analysis of modifications within microbial communities showed a significant positive response to BW based upon soil EAs and microbial indicators, compared to RO. Seasonal comparisons predictably revealed higher microbial activities during summer. Fungi dominated the soil microbial community structure with a fungal/bacterial ratio of 2:1. Gram-positive rather than Gram-negative bacteria or actinomycetes dominated the bacterial community. The activity of the soil enzymes ß-glucosidase and arylsulfatase increased, but ß-glucosaminidase and acid phosphatase decreased. Additionally, acid phosphatase and arbuscular mycorrhizal fungi revealed strong correlations. The differences observed in biological properties, specifically microbial communities and EAs, highlight the varied responses to BW and RO soil biology and subsequent soil ecosystem functions. These results indicate that variations in microbial abundance and soil functions occur throughout the course of an entire year.

Selection rankings of woody species for white-tailed deer vary with browse intensity and landscape context within the Central Hardwood Forest Region

White-tailed deer (Odocoileus virginianus) selection of woody species can be influenced by deer densities, food availability, and local and regional landscape characteristics. Determining selection rankings across varying regional landscapes is important to the management of both deer and forests. However, these regional-scale rankings are currently lacking. Here, we develop selection rankings for 63 species within woodlots across the southern, central, and northern regions of Indiana by counting the number of available and browsed twigs by species along transects. We then classified species into five selection classes: highly selected, slightly selected, neutral, slightly avoided, and strongly avoided. Some species displayed consistent classification across regions, including selection for greenbrier (Smilax spp.), hackberry (Celtis occidentalis), white ash (Fraxinus americana), and white oak (Quercus alba) and avoidance of spicebush (Lindera benzoin) and pawpaw (Asimina triloba). For the 16 species that exhibited significant regional variation in selection, we modeled the probability of a twig being browsed using explanatory variables measured at the woodlot scale, and within 200, 500, 1000, and 1500 m buffers around woodlots. Browsing intensity within a focal woodlot was more often associated with increased selection of an individual species than other explanatory variables. Nonetheless, both woodlot and landscape-scale variables influenced selection of woody browse by deer. In general, factors that increased browsing opportunities (e.g., increased density of non-avoided twigs, increased forest edge density, and increased woodlot edge) increased the selection of an individual species, while those that decreased browsing opportunities (e.g., increased non-native stem density and increased avoided twig density) decreased selection. Our selection classifications for common species in the Central Hardwood Forest Region highlight species that may be at risk of being negatively affected by severe browsing, while simultaneously identifying species that decrease foraging habitat quality. Our results also provide evidence that local and regional conditions drive differences in selection; and thus, require evaluation prior to management. More broadly, we showcase that multiple variables and spatial scales can affect selection of individual browse species by deer and merit consideration by researchers when studying the effects of browsing on forest ecosystems.

Carbon dynamics in old-growth forests of the Central Hardwoods Region, USA

Managing old-growth forests and promoting old-growth complexity in aging forests for carbon emissions mitigation has become an important component of diversified land management strategies. In the midwestern US, the Central Hardwoods Region (CHR) is the largest continuous deciduous forested area and includes a diverse range of species compositions, forest structures, and topoedaphic environments. Understanding carbon storage potential in old-growth forests across the CHR is important for evaluating climate-adaptive management strategies to increase carbon sequestration in the region’s aging forests. We assessed forest carbon in two time periods (the early 1990s and the 2010s) in ten old-growth forests across a 770 km east-west productivity gradient from Indiana to Missouri. Further, we related anomalies in carbon pools between the two sampling periods to documented or observable disturbances. As expected, old-growth forests on more productive sites in the eastern portion of the study range stored more aboveground carbon (120–177 Mg C ha−1) than less productive sites to the west (93–117 Mg C ha−1). Over the twenty-year period, old-growth forests accumulated 9.2 ± 1.5 (mean ± SE) Mg C ha−1 or a 7 % increase in total aboveground carbon. Further, downed dead wood carbon increased 5 % (0.4 ± 0.7 Mg C ha−1), standing dead increased 7 % (0.3 ± 0.7 Mg C ha−1), live roots increased 4 % (1.0 ± 0.3), and dead roots increased by 68 % (0.3 ± 0.1 Mg C ha−1). However, stochastic disturbances can positively or negatively impact total carbon and carbon pools. Documenting carbon trends and disturbance effects in old-growth forests provides guidance to enhance the representation of structurally complex, late successional forests using active forest management. Old-growth forests are currently rare in the CHR landscape, but the abundance of aging forests in the region provides immense potential to store carbon, particularly when combined with strategies that optimize early- and late-successional habitats for carbon sequestration along with other ecological goods and services.

Critical Market Tipping Points for High-Grade White Oak Inventory Decline in the Central Hardwood Region of the United States

Abstract This study expands the spatial scope of the Subregional Timber Supply (SRTS) model to include states in the central hardwood region and examine critical market tipping points of high-grade (large diameter) white oak under a set of illustrative scheduled demand scenarios. In light of the growing concern for future white oak timber supply, we illustrate the sensitivity of future inventory tipping points to market structure and price responsiveness. Particularly, we examined the importance of market demand parameters, including growth rates for product demand and supply/demand elasticities, in influencing future inventory trajectories in different subregions over the projection horizon. Results of this study indicate that more elastic demand and more inelastic supply response concomitantly defers the time before inventory culminates. This modeling framework shows promise in examining key ecological, climatic, and economic interrelationships that will drive future resource changes.

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.

Selection Rankings of Woody Species for White-Tailed Deer Vary with Browse Intensity and Landscape Context within the Central Hardwood Forest Region

Selection Rankings of Woody Species for White-Tailed Deer Vary with Browse Intensity and Landscape Context within the Central Hardwood Forest Region

Prescribed Fire First-Order Effects on Oak and Maple Reproduction in Frequently Burned Upland Oak–Hickory Forests of the Arkansas Ozarks

Alteration of the fire regime in upland oak–hickory (Quercus L. spp.–Carya Nutt. spp.) forests of the Central Hardwood Region is a major factor for the current shifts in species’ composition and oak recruitment and regeneration failures. The reintroduction of fire into these ecosystems requires a better understanding of fire effects on oak and co-occurring competitors. First-order (i.e., during and immediately after) fire effects on oak and red maple (Acer rubrum L.) topkill and resprouting at neighborhood scales were evaluated in frequently burned upland oak–hickory forests. A groundline threshold of 5 cm provided oaks with high (60%) survival probability (p < 0.001). White (Quercus alba L.) and post (Quercus stellata Wangenh.) oak survival odds were 21 and 14 times higher than that of red maple (p = 0.01 and 0.03), respectively. Three and twelve months after burn, oaks had three to six times more sprouts per clump than red maple. Frequent fires may continue to topkill the maples, while maintaining oak dominance in the reproduction pool and, thus, providing higher recruitment potential into the overstory. Burns with fire behavior that is very low to low in these frequently burned systems may provide greater control in favoring oaks and selecting against red maple, especially if groundline diameter thresholds are considered.

First Report of Armillaria root disease of Celtis laevigata caused by A. gallica in South Carolina, USA.

Celtis laevigata (sugarberry, southern hackberry) is an important, shade-tolerant, deciduous hardwood tree species that occurs naturally in flood plains, along streams and rivers, and in urban landscapes of the southeastern USA (Kennedy 1990). In recent years, dieback and mortality of C. laevigata have been commonly observed in some areas of South Carolina (SC) and Georgia (GA) (Poole et al. 2021). In April/May of 2018, the crown conditions and root systems were examined for three C. laevigata trees in North Augusta, SC. The crown of each tree was visually assessed using the method of Poole et al. (2021). Root samples were obtained by excavating two main roots ca. 2 meters away from the stem of each tree. Tree SB474 (N33 29.472, W81 59.082, elev. 55.8 m) exhibited > 66% crown loss and decaying roots with white mycelial fans and dark rhizomorphs characteristic of Armillaria. Tree SB913 (N33 29.830, W81 59.349, elev. 58.8 m) exhibited ca. 34-66% crown loss, while tree SB914 (N33 29.837, W81 59.338, elev. 57 m) appeared healthy with no apparent crown loss. Roots of trees SB913 and SB914 appeared healthy, although rhizomorphs were attached to the root surfaces. Roots and/or attached rhizomorphs were surface disinfested and plated n a basidiomycete-selective medium (Hendrix and Kuhlman 1962). Three Armillaria isolates, one from each corresponding tree, were paired with each other, and two genets were identified (SB474 and SB913 = SB914). The two genets (SB474 and SB913) were used in somatic pairing tests against three known tester isolates for each of the following species: A. solidipes, A. mellea, A. gallica, A. mexicana, and Desarmillaria caespitosa (=A. tabescens). Pairing of isolates SB474 and SB913 showed the highest compatibility with A. gallica (isolates ST22, ST23, and M70) with 100% and 89%, respectively. These isolates were definitively confirmed as A. gallica by translation elongation factor 1α gene sequences (tef1; Klopfenstein et al. 2017) (GenBank accession nos. OM993577 and OM993578 for SB474 and SB913, respectively). GenBank nucleotide BLAST showed tef1 similarity for both SB474 and SB913 isolates was highest for A. gallica (≥98.7%; GenBank accession nos. MT761696, MT761697, and KF156772). This is the first report of A. gallica associated with Armillaria root disease of C. laevigata. Rhizomorphs on the surface of apparently healthy tree roots and root colonization in severely declining trees are a common sign of A. gallica (Baumgartner and Rizzo 2001). Pathogen colonization of root surfaces may provide an opportunity for infection of highly damaged trees, resulting in root disease (Gregory 1985). Primary agents of C. laevigata dieback and mortality in SC and GA remain undefined, but continued study is needed to confirm the role of A. gallica in C. laevigata dieback and mortality. Although pathogenicity tests are impractical for Armillaria, these A. gallica occurrences in SC further adds to our knowledge of this pathogen's distribution in the southeastern USA, where it has also been confirmed in Tennessee in hardwood forests (Bruhn et al. 1997), SC on Hemerocallis sp. (Schnabel et al. 2005), and GA on a Rhododendron/span> sp. and Quercus rubra (Hanna et al. 2020). The distribution and host range of A. gallica is likely more widespread in the southeastern USA than existing records indicate. Documenting Armillaria distribution, including A. gallica, is essential for predicting climate-change impacts on Armillaria root diseases (Kim et al. 2022). Baumgartner, K., and Rizzo, D. M. 2001. Plant Dis. 85:947-951. Bruhn, J. N., et al. 1997. In 11th Central Hardwood Forest Conference, USDA, FS, NC-GTR-188, 49-57. Gregory, S. C. 1985. Plant Path. 34:41-48. Hanna, J. W., et al. 2020. Plant Dis. 105: 1226. Hendrix Jr, F. F., and Kuhlman, E. G. 1962. PI. Dis. Rep. 46:674-676. Kennedy, Jr., H. E. 1990. Silvics of North America: 2. Hardwoods. USDA-FS. Agriculture Handbook 654. Kim, M.-S., et al. 2022. Front. For. Glob. Change 4:740994. Klopfenstein, N. B., et al. 2017. Mycologia 109:75-91. Poole, E. M., et al. 2021. J. For. 119:266-274. Schnabel, G., et al. 2005. Plant Dis. 89:683.

Fire history and vegetation data reveal ecological benefits of recent mixed-severity fires in the Cumberland Mountains, West Virginia, USA

BackgroundWithout periodic fire, fire-adapted plant communities across the Central Hardwood Forest Region (CHF) in the USA have undergone significant changes in forest structure and species composition, most notably a decrease in oak regeneration and herbaceous diversity and an increase in shade-tolerant, fire-sensitive tree species. In this study, we conducted a comparative analysis of two mixed pine-oak (Pinus-Quercus) forests with different land management histories in the Cumberland Mountains of southern West Virginia where fire ecology and fire effects are understudied. We reconstructed the fire history of both sites from fire-scarred shortleaf pine (Pinus echinata Mill.) and pitch pine (Pinus rigida Mill.) trees to describe variation in the fire regimes over time. We also made plant community measurements that spatially coincided with fire-scarred pines to assess present-day plant community structure in relation to recent fire history.ResultsBefore 1970, fires at Hite Fork and Wall Fork occurred frequently and almost exclusively in the dormant season, every 7–8 years on average. The fire regimes diverged in the Post-Industrial era (1970–2020), during which there was a single fire at Wall Fork, while six major fires, scarring more than 40% of sampled trees, occurred between 1985 and 2017 at Hite Fork. Four of these dormant-season fires correspond to late fall incendiary fires in the observational record. These differences in recent fire history had large effects on plant community structure. Recent mixed-severity fires at Hite Fork likely caused mortality of pole-sized trees and opened the canopy, creating conditions favorable for pine recruitment and resulted in significantly higher species richness in the herbaceous layer compared to Wall Fork, which exhibited the effects of mesophication.ConclusionsOur results suggest that frequent mixed-severity fire in pine-oak forests of the Cumberland Mountains can meet management objectives by reducing mesophytic tree abundance, increasing herbaceous diversity and pine recruitment, and generally promoting forest heterogeneity.

Feature-dependent group structures and hierarchical songbird-habitat relationships in a managed forest landscape

We examined the importance of local habitat features on forest songbird distributions using a feature-dependent group framework that organizes species in relation to variable importance of species-habitat relationships. Habitat features included vegetation structure, floristics, and environmental (i.e., topography) classes. We also examined evidence for hierarchical habitat selection by assessing feature positioning within the ensemble structural models, Random Forests. From the 44 species examined, we distinguished 14 groups, comprising two to eight species per group, and examined variation in habitat importance across the groups. Overall, floristic species turnover, shrub density, canopy height, and tree basal area were among the most important features. On average, however, no specific feature class was more important than the others across the entire collection of species. Instead, we interpreted group partitioning to occur primarily by species differentiating among specific forest types, such as bottomland riparian or oak-dominated (Quercus spp.) stands, and species responding to structural variation across successional gradients. The positioning of habitat features within individual tree models showed that for those species among specific forest types, floristics features were selected first in the models followed by environmental features. Whereas when vegetation structural features were most important, structural features were typically selected first followed by floristics. The large variability in responses likely reflects the large heterogeneity in vegetation structure and composition present in our Central Hardwood, USA, forest landscape. In such cases, avian community assembly processes incorporated the primary moisture (mesic-xeric tree species) and successional (open- to closed-canopy) vegetative gradients of these forestlands, which underscores the importance of maintaining vegetation heterogeneity under accelerating environmental change. By including diverse suites of habitat types, we demonstrate how these features vary in their importance across songbird assemblages in a diverse forestland and identify key habitat features in the conservation of these bird communities.

Long-term effects of succession, climate change and insect disturbance on oak-pine forest composition in the U.S. Central Hardwood Region

Long-term effects of succession, climate change and insect disturbance on oak-pine forest composition in the U.S. Central Hardwood Region

Characterization of stem volume and form tradeoffs in a northern red oak (Quercus rubra) breeding population in early stages of selection

Quercus rubra half sib progenies (N = 93) expressed high levels of variance for both growth and stem form traits in three locations in Indiana, USA at age 11 or 12. Height, diameter, and volume were measured and sweep, branch angle, forking, and branch retention were rated using a (+ / −) system. Families selected for volume showed no unfavorable increases in sweep or branch angle and only a slight increase in branch retention. Northern red oak (Quercus rubra L.) is the most planted hardwood in the central USA. Red oak seeds from sources with improved growth and form are unavailable in the Central Hardwood Region, in part because the absence of agreed methods for stem form evaluation diminishes the effectiveness of selection. To identify red oak families improved for growth and to determine if a simple + / − rating system could identify red oak families with improved form. We evaluated 93 open-pollinated families of 11 or 12-year-old red oak growing in three sites in central Indiana (USA) for height, diameter, volume, and four traits rated as + / − : sweep, branch angle, forking, and branch retention. Family × location effects were significant for all quantitative traits but not for any binary traits; differences among families were significant for all traits at all sites. Heritabilities for most traits were high. Selection of the top 20 families for volume at each site resulted in no change in population means for sweep or branch angle and only a small increase in the retention of large limbs. A + / − rating system to evaluate hardwood form can help breeders deliver improved red oak to landowners when more complex systems are impractical.