Upland Hardwood Forest Research Articles

Canopy reduction and fire seasonality effects on deer and turkey habitat in upland hardwoods

Understory conditions strongly influence the value of upland hardwood forests for white-tailed deer (Odocoileus virginianus) and wild turkey (Meleagris gallopavo). Canopy reduction can be paired with low-intensity prescribed fire to increase forage and cover. Most fire in these systems is applied during the dormant season, but there may be benefits to burning during different seasons to provide different resources throughout the year. We implemented a shelterwood harvest with reserves in four upland hardwood stands in east Tennessee in 2010, then applied fire during the early-growing season (EGS) and late-growing season (LGS) to different treatment units on approximately a 2.2-year return interval from 2012–2023. We recorded vegetation composition, measured vegetation structure, calculated deer forage availability, and tallied wildlife detections via camera traps in summer 2023 to evaluate our treatments relative to an unharvested and unburned control. We found canopy reduction and fire during either season resulted in greater understory coverage of plants, with tree and bramble coverage greatest following LGS fire, which was lower intensity on average than EGS fire. Vegetation structure following EGS fire was more open, which is typically selected by brooding turkeys. The taller structure following LGS fire provided conditions typically selected for bedding or fawning by deer and nesting for turkeys. Deer forage biomass in July was increased by both EGS and LGS relative to control, but forage of sufficient quality to support a lactating doe was increased only in EGS because of increased nutrition of recently resprouting vegetation. Deer and turkey detections were greater in EGS than control or LGS during May–June. Turkey detections remained greater in EGS during July–August, but deer use was similar between EGS and LGS during July–August. Our results indicate burning during different seasons following canopy reduction can promote different food and cover resources which are important for deer and turkeys during different times of the year.

Asiatic bittersweet presence and cover over 20 years in upland hardwood forests after hurricane disturbance

Asiatic bittersweet presence and cover over 20 years in upland hardwood forests after hurricane disturbance

Shelterwood harvests promote high breeding bird diversity and shrubland species for less than 10 years in hardwood forests

We compared forest structure and breeding bird communities between shelterwood harvests (SW; n = 15) and mature upland hardwood forests (M; n = 16) over 17 years (Y). Both were relatively static throughout the study period in M. In contrast, heavy canopy reduction and increased light after timber harvests in SW initiated rapid increases in small tree stem densities and shrub cover driven primarily by blackberry (Rubus spp.) - a clonal shrub that “pioneers” recently disturbed, high-light environments. This open-canopy forest structure with low, dense vegetation was short-lived; young trees reached canopy closure within 10 years, with concomitant reductions in blackberry cover and stem density. Total abundance, species richness, and diversity of breeding birds was greater in SW than M, especially the first several years post-harvest; in Y6 these metrics were more than twice as high in SW as in M. Higher abundance, richness, and diversity in SW was driven by an influx of shrubland associates (indigo buntings (Passerina cyanea), chestnut-sided warblers (Setophaga pensylvanica), Eastern towhees (Pipilo erythrophthalmus)) and positive or neutral responses by most other species; only ovenbirds (Seiurus aurocapilla) were more abundant in M. Abundances of shrubland bird species in particular tracked temporal changes in SW forest structure but each differed slightly in their patterns of increase, peak (with 15–26 times more in SW than M), and decline. By Y10 breeding bird communities in SW resembled those in M, although total abundance, species richness, and diversity remained slightly higher in SW throughout the study period. Total abundance, species richness, diversity, and abundance of shrubland bird species were positively- and ovenbird was negatively correlated with blackberry cover, indicating that it is a suitable stand-alone predictor of post-disturbance young forest and changes in breeding bird communities as forests mature. Our results show that young hardwood forests provide habitat for shrubland bird species and promote high breeding bird diversity for <10 years.

Reproduction drives changes in space use and habitat selection in a highly adaptable invasive mammal

Abstract For ungulates, it is not well understood how the interaction between habitat and reproduction affects movement behavior, space use, and habitat selection. We used known parturition (farrowing) data to validate First Passage Time (FPT) movement analysis to identify wild pig (Sus scrofa) parturition events from data collected with GPS collars. We examined home range and habitat selection during three physiologically distinct time periods in the reproductive cycle: late-gestation; farrowing; and neonate-care period. Sows exhibited a behavioral change 1-2 days prior to farrowing, suggesting FPT analysis can reliably identify parturition events for wide-ranging species that have a focused birthing area. Home range was smallest during the farrowing period, likely reflective of nest building, parturition, and protection of neonates. Home range size during the neonate-care period was intermediate between the late-gestation and farrowing periods, indicative of offspring care that may restrict maternal movement. Across all periods, sows avoided developed areas that have sparse canopy and ground cover and are associated with human activities. During late-gestation, sows avoided pine forests that have an open understory and less vegetative cover. During late-gestation and neonate-care, sows selected bottomland hardwood forests, habitat associated with ample food, cover, and water. During farrowing and neonate-care periods, sows selected upland hardwood forests, habitat with high quality food and cover for neonates. The physiological requirements of reproduction drive female habitat selection and spatial scale of movement patterns associated with parturition. Our study contributes to delineation of the appropriate scale at which to analyze movement data to provide insight about where individuals chose to place their home range, how much space to use, and how they use resources on the landscape to maximize reproductive success and fitness.

Are metapopulation species drivers of metacommunity structure in sandstone outcrop communities?

AbstractQuestionsThe extent to which metacommunities contain species exhibiting metapopulation dynamics is poorly understood. We investigate this issue within sandstone outcrop plant communities scattered across an upland hardwood forest. We investigate the life forms of metapopulation species and relationships between taxonomic, phylogenetic, and functional diversity, composition, and environmental factors.LocationTwenty‐three sandstone outcrop communities in southern Illinois, USA.MethodsFollowing vegetation surveys, species exhibiting metapopulation dynamics were identified and compared to all species based on origin, growth form, and lifecycle. Cohesion, turnover, and boundary clumping were utilized to determine metacommunity structure. Correlations evaluated associations between site‐based variables, and regressions evaluated associations between diversity indices. Multivariate analyses compared sites to determine which variables contributed to compositional differences.ResultsTwenty of 130 species exhibited metapopulation dynamics and were usually annual or biennial exotics. Metacommunity elements indicated a metacommunity structure where groups of species tended to replace one another across sites, in which species exhibiting metapopulation dynamics were subordinate as opposed to dominant or transient. The largest sites were the most regularly shaped, but not the most diverse. Species richness and species exhibiting metapopulation dynamics determined phylogenetic and functional diversity, but largely non‐standardized measures of diversity, indicating independence between types of diversity. Multivariate analyses showed that diversity metrics explained community composition differences, where more species‐rich sites with more metapopulation species were also more phylogenetically and functionally diverse.ConclusionsSandstone outcrop communities exhibited diverse plant communities, where phylogenetic and functional diversity were driven by both the number of all species and the subset of metapopulation species independently. SM dynamics were usually short‐lived and exotic species with their low number likely constrained via dispersal limitations. The communities exhibited a metacommunity structure indicating predictable community assemblages which tend to be replaced with others as opposed to just individual species being replaced individually, consistent with the concept of an integrated community. Functional traits indicated that these communities include species adapted to xeric, substrate‐poor conditions.

Replacing coal in Georgia's power plants with woody biomass to increase carbon benefit: A mixed integer linear programming model

To combat climate change, reducing carbon emissions from coal consumption in the power sector can be an effective strategy. We developed a price-exogenous mixed integer linear optimization model satisfying both traditional timber demand in Georgia and its neighboring states (Alabama, Florida, North Carolina, South Carolina, and Tennessee) and additional bioenergy demand to replace coal in the power plants of Georgia for 50 years, maximizing social welfare. We used Forest Inventory & Analysis unit level yield of five forest types (planted softwood, natural softwood, upland hardwood, bottomland hardwood, and mixed forest), timber demand, and price information, and developed three scenarios. In the Baseline scenario, traditional annual timber demand (152 million tons of wood) was satisfied with no coal replacement. In Scenario 1, 100% coal (7.34 million tons annually) was replaced using pulpwood only, along with traditional demand. In Scenario 2, also with traditional demand, 100% coal was replaced using pulpwood and logging residues. It would require approximately 336 and 98 thousand acres of additional annual timberland harvested in Scenario 1 and Scenario 2, respectively, compared to Baseline (1280 thousand acres). During 50 years, a total of 9.3, 10.2, and 9.6 billion tons of timber was produced in Baseline, Scenario 1, and Scenario 2, respectively. About one-third of all torrefaction plants would be located in the central region of Georgia. The net change in stand carbon was positive in all three scenarios—the highest in Baseline (1330 million tons C), followed by Scenario 2 (1261 million tons C), and the lowest in Scenario 1 (872 million tons C). About 240 million tons of carbon was avoided by using biomass instead of coal in Scenario 1 and Scenario 2. In Baseline, with continued emission from coal usage in the power plant for 50 years (285 million tons C), net carbon benefit was 1046 million tons C. Replacing 100% of coal with both pulpwood and logging residues provided a net benefit of 1501 million tons C, about 43% higher compared to baseline.

Comparison of Data Grouping Strategies on Prediction Accuracy of Tree-Stem Taper for Six Common Species in the Southeastern US

Clustering data into similar characteristic groups is a commonly-used strategy in model development. However, the impact of data grouping strategies on modeling stem taper has not been well quantified. The objective of this study was to compare the prediction accuracy of different data grouping strategies. Specifically, a population-level model was compared to the models fitted with grouped data based on taxonomic rank, tree form and size. A total of 3678 trees were used in the analyses, which included six common species in upland hardwood forests of the southeastern U.S. Results showed that overall predictions are more accurate when building stem taper models at the species, species group or division level rather than at the population level. The prediction accuracy was not considerably improved between species-specific functions and models fitted with species-related groups for the four hardwood species examined. Grouping data by taxonomic rank provided more reliable predictions than height-to-diameter ratio (H–D ratio) or diameter at breast height (DBH). The form/size-related grouping methods (i.e., data grouped by H–D ratio or DBH) generally did not improve the prediction precision compared to a population-level model. In this study, the effect of sample size in model fitting showed a minimal impact on prediction accuracy. The methodology presented in this study provides a modeling strategy for mixed-species data, which will be of practical importance when data grouping is needed for developing stem taper models.

Gobbling across landscapes: Eastern wild turkey distribution and occupancy-habitat associations.

Extensive restoration and translocation efforts beginning in the mid‐20th century helped to reestablish eastern wild turkeys (Meleagris gallopavo silvestris) throughout their ancestral range. The adaptability of wild turkeys resulted in further population expansion in regions that were considered unfavorable during initial reintroductions across the northern United States. Identification and understanding of species distributions and contemporary habitat associations are important for guiding effective conservation and management strategies across different ecological landscapes. To investigate differences in wild turkey distribution across two contrasting regions, heavily forested northern Wisconsin, USA, and predominately agricultural southeast Wisconsin, we conducted 3050 gobbling call‐count surveys from March to May of 2014–2018 and used multiseason correlated‐replicate occupancy models to evaluate occupancy–habitat associations and distributions of wild turkeys in each study region. Detection probabilities varied widely and were influenced by sampling period, time of day, and wind speed. Spatial autocorrelation between successive stations was prevalent along survey routes but was stronger in our northern study area. In heavily forested northern Wisconsin, turkeys were more likely to occupy areas characterized by moderate availability of open land cover. Conversely, large agricultural fields decreased the likelihood of turkey occupancy in southeast Wisconsin, but occupancy probability increased as upland hardwood forest cover became more aggregated on the landscape. Turkeys in northern Wisconsin were more likely to occupy landscapes with less snow cover and a higher percentage of row crops planted in corn. However, we were unable to find supporting evidence in either study area that the abandonment of turkeys from survey routes was associated with snow depth or with the percentage of agricultural cover. Spatially, model‐predicted estimates of patch‐specific occupancy indicated turkey distribution was nonuniform across northern and southeast Wisconsin. Our findings demonstrated that the environmental constraints of turkey occupancy varied across the latitudinal gradient of the state with open cover, snow, and row crops being influential in the north, and agricultural areas and hardwood forest cover important in the southeast. These forces contribute to nonstationarity in wild turkey–environment relationships. Key habitat–occupancy associations identified in our results can be used to prioritize and strategically target management efforts and resources in areas that are more likely to harbor sustainable turkey populations.

Effect of temperature on flocking propensity and species interactions in a subtropical mixed-species flocking system

Increased participation in mixed-species flocks is one hypothesized behavioral tactic used by forest birds to adjust to cold temperatures in winter. This phenomenon has been documented in temperate North America, but not at subtropical latitudes where temperatures are less extreme. To understand how temperature structures the size, richness, flocking propensity, and species interactions of subtropical mixed-species flocks, we performed paired mixed-species flock and point count surveys in upland hardwood forests in north-central Florida, USA. We described the composition of 92 mixed-species flocks across a ∼20 °C range of daytime temperatures, using linear mixed models and network analyses to test for effects of temperature. We found that both flock species richness and size were significantly smaller at higher temperatures while statistically controlling for effects of time of day, canopy height, and local site effects. Thirteen of 14 flocking species showed decreases in within-flock abundance with increasing temperature, although this effect was only significant for the nuclear Carolina Chickadee (Poecile carolinensis). Flock composition and species flocking propensities were less plastic than in temperate systems. By comparing metrics from 7 social networks corresponding to temperature ranges, we found that strength of flocking interactions was lower and that species were significantly less likely to co-occur with similarly foraging species at temperatures above 20 °C. Flocking propensities were lower for many species in the warmest temperature range. Thirteen of 14 species joined flocks in all 7 networks, and dissimilarity of social networks was consequently best explained by changes in species co-occurrence patterns rather than species turnover within flocks. In contrast to boreal flocking systems, changes to flocking behavior were prompted by unseasonably warm weather rather than cold spells, which suggests that warming winter temperatures could lead to breakdown of social behaviors in our system.

Improving Coastal Plain Hardwoods for Deer and Turkeys with Canopy Reduction and Fire

ABSTRACTPrescribed fire and canopy reduction are accepted forest management practices used to increase forage and cover for white‐tailed deer (Odocoileus virginianus) and wild turkeys (Meleagris gallopavo) in pine systems throughout the southeastern United States. However, use of prescribed fire to improve conditions for deer and turkeys has not been evaluated in upland hardwood forests of the Coastal Plain, and some land managers remain skeptical of the utility of fire in this ecoregion. We designed a manipulative experiment to measure deer and turkey habitat components following canopy reduction and prescribed fire in 4 upland hardwood stands in the Coastal Plain of Alabama, USA, during 2018 and 2019. Specifically, we used herbicide to kill trees with low value to deer and turkeys and retained oaks (Quercus spp.) and other species considered important as part of a forest stand improvement (FSI) operation to reduce canopy coverage. We then applied low‐intensity prescribed fire to half of each treatment unit. One unit in each replicate served as a control. We measured total understory plant coverage, biomass of deer forage, and turkey brooding cover for 2 years following canopy reduction and one year after fire. Coverage of herbaceous plants increased by 134% in FSI/Burn, and coverage of woody and semiwoody plants increased by 33% and 97%, respectively, following FSI only. Deer forage biomass was greater in both FSI and FSI/Burn compared to control, but there was no difference in deer forage biomass between FSI and FSI/Burn. FSI/Burn provided better turkey brooding cover than FSI or control. No overstory trees were killed by fire. We detected minor cambium damage to 13% of water oaks (Quercus nigra) in the FSI/Burn units; other species only showed light bark charring or no sign of burning. We recommend FSI and low‐intensity prescribed fire in Coastal Plain hardwoods to improve brooding cover for turkeys and understory forage for deer while retaining acorn production. © 2020 The Wildlife Society.

Predicting oak regeneration success at the stem exclusion stage of stand development in upland hardwood forests

Oaks (Quercus spp.) are becoming less abundant in most of the Central Hardwood Region of the eastern United States, and this is creating shifts in forest composition that will likely have important economic and ecological consequences. In large measure, these changes originate with deficiencies in the oak regeneration cohort preceding stand-replacement disturbances such as timber harvest. To sustain the oak resource, managers need better information on the connection between pre-harvest and early stand conditions and regeneration outcomes. In this study, we used direct observations of oak seedling dominance in the stem exclusion stage of stand development (mean age = 17.4 years) to model the probability of successful regeneration during stand initiation as a function of stand conditions before and after harvest (ages −1, 1, 4, and 7 years). For pre-harvest conditions, the most predictive model was based solely on the aggregate height of advance regeneration oak seedlings >15 cm in sample plots. As expected, post-harvest models were more predictive, and increasingly more predictive with the passage of time, and they were optimized by contrasting the height of the plot-dominant oak seedling with the heights of competing tree species. The predictive power of post-harvest models increased most between ages 1 and 4 years and only slightly between ages 4 and 7, indicating that age 4 is an optimal time to evaluate opportunities to favor oak regeneration with early silvicultural interventions. Of the two most common competitors, black birch (Betula lenta) had the more inhibitory effect on the success of oak regeneration when it was present. However, red maple (Acer rubrum) was the more important competitor because of its very high frequency of occurrence in plots occupied by oak seedlings.

Spatial and Temporal Variability of Throughfall among Oak and Co-Occurring Non-Oak Tree Species in an Upland Hardwood Forest

Canopy throughfall comprises the largest portion of net precipitation that is delivered to the forest floor. This water flux is highly variable across space and time and is influenced by species composition, canopy foliage, stand structure, and storm meteorological characteristics. In upland forests throughout the central hardwoods region of the Eastern United States, a compositional shift is occurring from oak-hickory to more mesic, shade-tolerant species such as red maple, sweetgum, and winged elm. To better understand the impacts of this shift on throughfall flux and the hydrologic budget, we monitored throughfall for one year in Northern Mississippi under the crowns of midstory and overstory oak (post oak and southern red oak) and non-oak species (hickory, red maple, and winged elm). In general, oak had more throughfall than co-occurring non-oak species in both canopy levels. In the overstory during the leaf-off canopy phase, white oak had relatively higher throughfall partitioning (standardized z-score = 0.54) compared to all other species (z-score = −0.02) (p = 0.004), while in the leaf-on canopy phase, red maple had relatively lower throughfall (z-score = −0.36) partitioning compared to all other species (z-score = 0.11). In the midstory, red maple was the only species to exhibit a difference in throughfall between canopy phases, with much lower throughfall in the leaf-off compared to the leaf-on canopy phase (z-score = −0.30 vs. 0.202, p = 0.039). Additionally, throughfall under oak crowns was less variable than under non-oak crowns. These results provide evidence that the spatial and temporal distribution of throughfall inputs under oak crowns are different than non-oak species, likely due to differences in crown architecture (i.e., depth and density). As oak dominance diminishes in these forests, it is possible that the portion of rainfall diverted to throughfall may decrease as well. The net impacts to watershed hydrology are still unknown, but these results provide one mechanism by which the distribution of water resources may be affected.

Influence of Forest Structure and Composition on Summer Habitat Use of Wildlife in an Upland Hardwood Forest

Oak-hickory (Quercus-Carya spp.) forest types are widespread across the midwestern United States, but changes in forest disturbance regimes are resulting in little to no oak recruitment and a compositional shift to shade-tolerant, mesophytic species, such as American beech (Fagus grandifolia) and sugar maple (Acer saccharum). We conducted camera trap surveys in a mature upland hardwood forest of southern Illinois, USA during May to August 2015–2016 to document mammal summer habitat use in relation to forest structure and composition to further understand how regional shifts in forests may affect mammal communities. With nearly 4000 camera days of effort, we modeled occupancy patterns for white-tailed deer (Odocoileus virginianus), raccoon (Procyon lotor), and eastern gray squirrel (Sciurus canadensis). Forest composition models outcompeted forest structure models for white-tailed deer, where we observed a statistically significant negative relationship between white-tailed deer habitat use and beech dominance. Further, we found a strong, positive association between deer and oak dominance. Model selection indicated little support for within-stand forest structure or composition characteristics influencing habitat use for raccoons. Eastern gray squirrel occurrence was best described by forest composition, revealing a positive relationship with beech–maple importance values. Our predictive models indicated that the impact of forest changes underway will have varying impacts on wildlife species. We can expect changes in habitat use patterns to be more pronounced with time barring revised forest management practices, and these changes are likely to be most influential at the landscape-scale. We conclude that a patchwork mosaic of forest conditions will likely best support a diverse and abundant mammal community across the region.

Breeding bird response to season of burn in an upland hardwood forest

Upland hardwood forest managers are increasingly burning during the growing-season in hopes of improving wildlife habitat and attaining or accelerating other restoration goals, highlighting the need for research addressing how season of burning affects wildlife, including breeding birds. We used 1-ha strip transects in nine units before (2011) and after (2013–2016) treatments to experimentally assess how breeding birds respond to early growing-season (26 April 2013; GSB) and dormant-season (5 March 2014; DSB) burns, and controls (C). Burn effects on forest structure were minor and transitory, regardless of burn season. Burns did not affect overstory or midstory tree basal area or density; shrub cover did not significantly differ among treatments, but within GSB and DSB it decreased for 1–2 years post-burn. A trend of reduced leaf litter depth immediately following both burn treatments was apparent, and recovery was rapid. Percent canopy cover decreased slightly in GSB within four years post-burn. Total bird species richness and density did not differ among treatments or years, and no treatment × year interaction effects were detected. A treatment effect was detected for one of the 10 species tested; Red-bellied woodpecker density was greater in GSB than C in 2013 and 2015. No treatment × year interaction effect was detected for any tested species. Density of birds within the tree-, cavity-, and shrub and midstory-nesting guilds were not detectably affected by either burn treatment, but ground-nester density was lower in GSB and DSB than C in 2014. Our results indicate that single, low-intensity burns, regardless of burn season, are not an effective tool in creating suitable forest structure for disturbance-dependent breeding bird species, or changing breeding bird community composition. In the short-term, substantial forest overstory reduction by timber harvests or high-severity burns will likely be required to improve forest conditions for disturbance-dependent species, and to increase species richness and abundance of breeding birds.

Vertically Stratified Arthropod Diversity in a Florida Upland Hardwood Forest

Species diversity is typically higher in tropical forest canopies than in ground layers, but this pattern is absent in temperate forests. However, hardwood forests of Florida are typified by the intermingling of temperate and tropical species. It is thus unclear how diversity in Florida forests might be vertically stratified. This project is one of the first investigations to compare arthropod communities at varying layers (strata) of a Florida hardwood forest, from ground to canopy habitats. We installed terrestrial and arboreal pitfall traps to survey the arthropod community along a vertical gradient from the forest ground to upper canopy. We collected 830 arthropods from the 34 traps, amounting to 103 morphospecies across 15 orders. Coleoptera was the most morphospecious order, followed by Diptera, Araneae, and Hymenoptera. Species alpha diversity, richness, and abundance all decreased with height from the ground and horizontal distance from the tree. We discuss the vertical stratification of orders in addition to diversity metrics. This study is the first to reveal canopy strata effects on arthropod diversity in a Florida forest, and shows how diversity and composition changes along within site gradients.

Season of burn effects on vegetation structure and composition in oak-dominated Appalachian hardwood forests

Previous research indicates that low-intensity single or multiple prescribed burns in oak-dominated upland hardwood forest do not substantially change stand structure or species composition of the arborescent regeneration layer, leading managers and ecologists to suggest that burns during the growing-season may better achieve restoration goals. We examined season of burn effects on dry-mesic oak-hickory forests in the southern Appalachian Mountains, North Carolina. Treatments included: (1) control (CON); (2) dormant-season burn (DSB), and (3) growing-season burn (GSB). Prior to burning and again after three growing seasons post-burn, we inventoried the forest overstory (stems ≥ 25 cm dbh), subcanopy (stems ≥ 5 and <25 cm dbh), sapling (stems ≥ 1.2 m and < 5 cm dbh), and seedling (stems < 1.2 m) strata. We found no effect of prescribed fire, regardless of burn season, on stem density or basal area of the overstory and subcanopy strata, leaving the light environment in the forest understory relatively unchanged. In general, treatment effects on the sapling and seedling layers were limited to the mesophytic species group, where seedling density post-burn was greater in GSB than both CON and DSB and sapling density post-burn was lower than pre-burn in DSB and GSB. Mortality of individually-tagged seedlings three growing seasons post-burn did not differ among treatments for the red oak, white oak, red maple, mesophytic, and pyrophilic species groups, and averaged 29.0, 28.5, 31.8, 29.3, and 25%, respectively. This study provides support for the notion that a single fire in a closed-canopy oak-hickory forest has little effect on forest structure or regeneration composition, regardless of the burn season. Prescribed fires should be repeated in subsequent years to assess whether the effects of burn season are amplified under a periodic burning regime.

Twenty-year survivorship of tree seedlings in wind-created gaps in an upland hardwood forest in the eastern US

Wind is a common canopy disturbance in the upland oak (Quercus)- and hickory (Carya)-dominated stands of the Central Hardwood Region of the eastern US. Canopy openings range from small gaps, resulting from windthrow of single dominant trees, to occasional large gaps of many hectares formed by straight-line winds associated with severe thunderstorms and rare subtropical hurricanes. Vegetation regeneration response in small gaps and larger artificially created (i.e., timber harvested) gaps has been extensively studied, but little has been reported on naturally formed large gaps (> 6 trees) where a partial canopy typically remains from residual overstory and midstory trees. We investigated advance regeneration survivorship on a landscape scale within and around 12 large wind-felled gaps created by Hurricane Opal (October 1995) in a Southern Appalachian watershed. We hypothesized that survivorship would (1) change along a linear distance gradient from the unaffected forest towards gap center (2) vary in relation to categorical gap locations-within-gaps versus in the adjacent unaffected forest and (3) be affected by vegetation and environmental variables. In early 1996 we tagged tree seedlings in quadrats located along linear axes that extended from gap center into the unaffected forest and measured a variety of vegetation and environmental variables. Overall mean survivorship declined from 1997 (0.96) to 2016 (0.56). We found that survivorship was related to linear distance gradients for species rated intermediate in shade tolerance, such as red oaks, but not for shade intolerant, tolerant, and semi-tolerant species (e.g. white oaks). We found that survivorship increased on a linear distance gradient from gap center into the unaffected forest over the first 9 years of our investigation. By year 20 this relationship had reversed: survivorship increased from the unaffected forest to gap centers. Survivorship was also modeled as a function of categorical location of tagged seedlings within-gaps versus in the unaffected forest. Again, we found that survivorship of only intermediate shade tolerant species was related to categorical locations. Survivorship decreased in relation to time and cohort competition and increased with initial seedling height. Our 20-year investigation revealed changes in dynamics of regeneration that would not have been apparent in a short-term study. These results will enable resource managers to assess regeneration development in large gaps following windstorms in oak-dominated hardwood stands.

Responses of early-successional songbirds to a two-stage shelterwood harvest for oak forest regeneration

BackgroundThe early stage of forest succession following disturbance is characterized by a shift in songbird composition as well as increased avian richness due to increased herbaceous growth in the forest understory. However, regeneration of woody species eventually outcompetes the herbaceous understory, subsequently shifting vegetation communities and decreasing availability of vital foraging and nesting cover for disturbance-dependent birds, ultimately resulting in their displacement. These early stages following forest disturbance, which are declining throughout the eastern United States, are ephemeral in nature and birds depend on such disturbances for nesting and other purposes throughout their lives.MethodsWe investigated the use of a two-stage shelterwood method to manage long-term persistence of seven early successional songbirds over a 13-year period in an upland hardwood forest within the southern end of the mid-Cumberland Plateau in the eastern United States.ResultsCanopy and midstory gaps created after initial harvest were quickly exploited by tree growth and canopy cover returned to these areas, accelerating the displacement of early-successional species. Woody stem densities increased substantially following stage two harvest as advanced tree regeneration combined with the re-opening of the overstory layer increased resource competition for early-successional plants in the understory. Carolina Wren (Thryothorus ludovicianus), Eastern Towhee (Pipilo erythrophthalmus), Indigo Bunting (Passerina cyanea), and Yellow-breasted Chat (Icteria virens) were characterized by immediate increases following initial harvest in 2001; while the American Goldfinch (Spinus tristis), Prairie Warbler (Setophaga discolor), and White-eyed Vireo (Vireo griseus) did not show an immediate response. Stage two harvest in 2011 rejuvenated vegetation which benefitted focal species, with six of seven species showing increases in densities between 2010 and 2012.ConclusionThe two-stage shelterwood method created conditions advantageous to early-successional birds by helping to re-establish understory vegetation through periodic disturbance to the canopy layer. This method provides evidence that early-successional species can be managed long-term (> 15 years) while using relatively small spatial disturbance through the two-stage shelterwood method.

Long-term avian response to fire severity, repeated burning, and mechanical fuel reduction in upland hardwood forest

Forest restoration, fuel reduction, and wildlife conservation management requires understanding if, and how repeated prescribed fire, fire severity, or mechanical methods can promote goals. We examined breeding bird response to repeated fuel reduction treatments by mechanical understory reduction (twice; Mechanical-only), prescribed burning (four times; Burn-only), or mechanical understory reduction plus burning (then three subsequent burns; Mechanical + Burn). Initial burns were hotter in Mechanical + Burn than Burn-only resulting in heavy tree mortality, canopy openness, thick shrub density, and abundant snags lasting several years. Relative density and species richness of birds increased in Mechanical + Burn within three breeding seasons of high-severity burns, and remained greater throughout subsequent burns. Increases were due to an influx of species associated with young forest conditions, with little change in most mature forest species. Repeated burning in Mechanical + Burn likely impeded forest maturation, allowing many scrub-shrub bird species to persist. Species richness in Burn-only did not differ from any treatment, but modest increases over time were apparent as structural heterogeneity increased with delayed tree mortality. Cavity-nester density was highest in Mechanical + Burn, but remained high even as snags fell to pretreatment levels. Ground-nester density was lower in Mechanical + Burn than Control and Mechanical-only, but ground-nesting species responded differently. Open woodlands were not created by any treatment due to persistent re-sprouting of top-killed trees and shrubs. We note that breeding birds appear to respond similarly to high-severity burns and silvicultural treatments with heavy canopy reduction, offering possible alternatives in managing upland hardwood forests for diverse breeding bird communities.

Reptile and amphibian response to season of burn in an upland hardwood forest

Abstract Growing-season burns are increasingly used in upland hardwood forest for multiple forest management goals. Many species of reptiles and amphibians are ground-dwelling, potentially increasing their vulnerability to prescribed fire, especially during the growing-season when they are most active. We used drift fences with pitfall traps to experimentally assess how herpetofaunal species and communities responded to early, growing-season burns, dormant-season burns, and unburned controls. We documented no adverse effects of either growing-season burns or dormant-season burns on any common herpetofaunal taxa, but capture rates of total, adult, and juvenile five-lined skinks (Plestiodon fasciatus) were greater following growing-season burns. Most measurements reflected little or transient change in forest structure. However, canopy cover decreased by an average of 16% in growing-season burns within four growing-seasons of burning, with some tree mortality in patches where fire temperature likely was hotter. Our study suggests that even modest reductions in canopy cover may positively affect relative abundance and reproductive success of P. fasciatus. We cautiously suggest that a higher mean ground-level fire temperature and the physiologically active condition of vegetation in growing-season burns interacted to damage a greater proportion of trees, resulting in more canopy thinning than in dormant-season burns. However, weather, fuel types and condition, vegetation structure, and topography interact to affect fire intensity and the level of mortality or damage to canopy trees within and among stands, regardless of season conducted. We suggest that herpetofaunal response, for the species we studied, is more closely linked to change in canopy cover than to season of burn per se.