Southern Red Oak Research Articles

Urban Forest Resilience: Assessment and Management Strategies for Stressed Trees in Diverse Environments

Variety of trees are found in both urban and wild areas; these trees are indispensable in maintaining ecosystem health and promoting human well-being. However, stressors affect the health of these trees; this makes them face management approaches. In this study, an assessment and management of five (5) different tree species at Southern University and A&M College in Baton Rouge-USA were carried out. The Southern Magnolia, Southern Red Oak, and Live Oak showed symptoms of stress, such as leaning and decay. The identified Loblolly Pine showed symptoms such as bark beetle infestations and resource competition. For each of these species, specific indicators of stress were identified and recommended management approaches. These include the installation of support systems, pruning of diseased branches, soil tillage, and pest control techniques. These practices allow the strengthening of urban forest, which ensures continued health and functioning of our ecosystems.

Wood dimensional stability enhancement by multivalent metal-cation-induced lignocellulosic microfibrils crosslinking

Wood is a hygroscopic material that responds to the moisture changes of the surrounding environment through swelling and shrinkage, making it dimensionally unstable. Here, we introduce a facile metal-ion-modification (MIM) approach to enhance the dimensional stability of wood. The MIM process involved swelling the wood samples with aqueous metal ion solutions and drying. The high valent metal cations, such as Fe3+, Al3+, and Zr4+, interacted with the hydrophilic groups (e.g., OH, COOH) present in the wood fibers, limiting their access to water and moisture, thereby enhancing the wood's hydrophobicity and dimensional stability. Evaluation of three wood species, southern yellow pine, poplar, and red oak, revealed water contact angles of 120–130° after MIM, indicative of enhanced surface hydrophobicity. Fe3+ treatment decreased southern yellow pine's swelling ratio from 6 % to 4 %. Fe3+-treated wood exhibited tangential anti-swelling efficiencies ranging from 39.83 % to 57.14 % and radial anti-swelling efficiencies from 34.74 % to 48.33 %, varying across wood species. The enhancement of wood dimensional stability can be attributed to the formation of irreversible coordination bonds between metal cations and lignocellulosic microfibrils in the wood cell wall. These bonds prevent the microfibrils from slipping in response to moisture absorption and desorption.

Quantifying Forest Litter Fuel Moisture Content with Terrestrial Laser Scanning

Electromagnetic radiation at 1550 nm is highly absorbed by water and offers a novel way to collect fuel moisture data, along with 3D structures of wildland fuels/vegetation, using lidar. Two terrestrial laser scanning (TLS) units (FARO s350 (phase shift, PS) and RIEGL vz-2000 (time of flight, TOF)) were assessed in a series of laboratory experiments to determine if lidar can be used to estimate the moisture content of dead forest litter. Samples consisted of two control materials, the angle and position of which could be manipulated (pine boards and cheesecloth), and four single-species forest litter types (Douglas-fir needles, ponderosa pine needles, longleaf pine needles, and southern red oak leaves). Sixteen sample trays of each material were soaked overnight, then allowed to air dry with scanning taking place at 1 h, 2 h, 4 h, 8 h, 12 h, and then in 12 h increments until the samples reached equilibrium moisture content with the ambient relative humidity. The samples were then oven-dried for a final scanning and weighing. The spectral reflectance values of each material were also recorded over the same drying intervals using a field spectrometer. There was a strong correlation between the intensity and standard deviation of intensity per sample tray and the moisture content of the dead leaf litter. A multiple linear regression model with a break at 100% gravimetric moisture content produced the best model with R2 values as high as 0.97. This strong relationship was observed with both the TOF and PS lidar units. At fuel moisture contents greater than 100% gravimetric water content, the correlation between the pulse intensity values recorded by both scanners and the fuel moisture content was the strongest. The relationship deteriorated with distance, with the TOF scanner maintaining a stronger relationship at distance than the PS scanner. Our results demonstrate that lidar can be used to detect and quantify fuel moisture across a range of forest litter types. Based on our findings, lidar may be used to quantify fuel moisture levels in near real-time and could be used to create spatial maps of wildland fuel moisture content.

East Texas forests show strong resilience to exceptional drought

Abstract Drought-induced tree mortality has increased in many parts of the world because of climate change, and in some regions, has altered forest structure, species composition and ecosystem functions. These developments have the potential to reduce forest resilience and push forests over a tipping point to an alternate state (i.e. a different forest type or a non-forest ecosystem). Texas experienced an exceptional drought in 2011, which killed an estimated 65.5 million trees in the heavily forested areas of the East Texas region. The objective of this study was to understand the effects of the 2011 drought on mortality, biomass and growth in this region and explore forest stability at species, forest and ecoregion levels. We categorized 19 years’ time-series data of 1455 Forest Inventory and Analysis plots into four periods, base (2001–2003), pre-drought (2004–2010), drought (2011–2016) and post-drought (2017–2019), and used repeated-measures analysis of variance to analyse annual mortality, biomass loss, growth rates and the Forest Stability Index to understand forest stability. Our results show that tree mortality and biomass loss increased significantly during the drought period and annual growth rates declined. During the post-drought period, mortality and biomass loss rates returned to the pre-drought level and growth partially recovered. During the drought period, FSI dropped at species, forest type and ecoregion levels but recovered during the post-drought period, except for the Oak Woods and Prairies ecoregion and for forests dominated by southern red oak. Our results indicate that East Texas forests are undergoing a reorganization and recovery stage (in terms of species composition and stand structure) but have yet to reach a tipping point. Given the increased frequency and severity of climate change-induced weather events, East Texas forests could approach a tipping point in the future if there is insufficient time between events for reorganization and recovery. Further analyses are needed to understand the fate of tree species and forests in East Texas under global climate change.

Effects of hurricane canopy gaps on longleaf pine and upland oak sapling growth

Longleaf pine forests and woodlands are an ecologically important ecosystem that once dominated much of the southeastern U.S. Frequent fire is well-known to be a driver of forest dynamics in these systems, but far less is known about how wind disturbance may reorganize plant communities. To gain a better understanding of how hurricane impacts may alter dynamics in a second-growth longleaf pine woodland, we investigated growth response of saplings from three competing upland species (Pinus palustris, Quercus falcata, Q. margaretta) following Hurricane Michael (2018) in southwest Georgia, United States. We used maximum likelihood to model height and radial growth of saplings as species-specific Michaelis-Menten functions of light availability and examined the effect of sapling size, soil water holding capacity, and annual precipitation using a model comparison approach. The best model for both height and radial growth included species-specific growth rates, a power function for sapling size, and an effect of 2-year lagged precipitation. Overall, we found that height growth rate increased with irradiance for all species, but asymptotic height growth rate for all species was approached at low irradiance. Rates of radial growth also increased with irradiance and were more strongly differentiated among species. Radial growth in longleaf pine and southern red oak responded most strongly to increasing irradiance. Our findings suggest that increases in light availability from hurricanes has direct effects on altering growth dynamics of saplings. Further, because stem radius is a strong predictor of survival from surface fires, hurricane damage may also have an indirect effect on sapling dynamics, by altering survival in future fires. Our results suggest that hurricanes can reinforce the dominance of longleaf pine and potentially play a role in stabilizing community structure. Understanding the effects of common disturbances like wind and fire—together and individually—can reveal important mechanisms that shape the structure and function of fire-prone ecosystems.

Effects of Leaf Litter Species on Cope's Gray Treefrog Oviposition Site Selection

Leaf litter is an important input to a variety of freshwater ecosystems. The species of leaf litter affects water chemistry, ecosystem processes, and the survival and growth of aquatic organisms. Given the potential fitness consequences, it is likely that aquatic organisms have preferences for aquatic habitats with particular species of leaf litter input. To investigate this, we placed shallow experimental pools at a field-forest edge in northern Louisiana, USA as potential sites for Cope's Gray Treefrog (Hyla chrysoscelis) oviposition with leaf litter from one of 14 different tree species in each pool. Tree species included 13 native trees and one invasive species, Bradford Pear (Pyrus calleryana). We measured the concentrations of tannins and 12 elements in leaf tissue, along with water quality and water depth in the pools. We used an information-theoretic approach and created different models to determine what variables best predict the number of treefrog eggs laid in each pool and thus may serve as a cue for female treefrogs during oviposition site selection. We found that tree species treatment was by far the best predictor of the number of eggs Cope's Gray Treefrogs laid in the pools. Treefrogs laid more eggs in pools with Post Oak and Sweetgum leaves and fewer eggs in pools with Southern Red Oak and Southern Magnolia leaves. It is unclear how female treefrogs are able to differentiate among these tree species or what cue they are using to make their choices. Our results highlight the importance of tree species to aquatic community assembly.

Fracture Behavior of Wood Under Mode I Loading in Tangential Direction

The aim of this study was to determine the fracture behavior of southern yellow pine (Pinus taeda L.) and red oak (Quercus falcata) wood under mode I loading in the tangential-radial and tangential-longitudinal crack propagation systems by a compact tension test method. The results of the study indicated that, in general, red oak had a significantly different fracture behavior than southern yellow pine for each of the two crack propagation systems. The fracture toughness was higher in the tangential-radial crack propagation system than that in the tangential-longitudinal crack system, but there was no significant difference between the two crack propagation systems for southern yellow pine. The specific fracture energy of the tangential-longitudinal crack propagation system for both wood species was significantly lower than that of the tangential-radial crack propagation system. It means that more energy per unit area for the tangential-radial crack propagation system was needed to separate a wood sample into two halves. The difference in the fracture behavior of wood by the crack propagation system can be explained by the structural features of the tested samples since the crack propagation of the tangentialradial system crosses the annual ring and wood fibers can bridge the crack surface.

Sulcatol and Fuscumol Increase Catches of Leptostylus asperatus and Styloleptus biustus (Coleoptera: Cerambycidae) in Ethanol-Baited Traps

Sulcatol and Fuscumol Increase Catches of <i>Leptostylus asperatus</i> and <i>Styloleptus biustus</i> (Coleoptera: Cerambycidae) in Ethanol-Baited Traps

Variation in Bark Allocation and Rugosity Across Seven Co-occurring Southeastern US Tree Species

Bark is a complex multifunctional structure of woody plants that varies widely among species. Thick bark is a primary trait that can protect trees from heat generated in surface fires. Outer bark on species that allocate resources to thick bark also tends to be rugose, with bark being thickest at the ridges and thinnest in the furrows. Tree diameter or wood diameter is often used as a predictor for bark thickness but little attention has been made on other factors that might affect bark development and allocation. Here we test multiple mixed effect models to evaluate additional factors (height growth rate, measure height) that correlate with bark allocation and present a method to quantify bark rugosity. We focused on seven co-occurring native tree species in the Tallahatchie Experimental Forest in north Mississippi. Approximately ten saplings of Carya tomentosa, Nyssa sylvatica, Prunus serotina, Pinus echinata, Pinus taeda, Quercus marilandica, and Quercus falcata were destructively sampled for stem analyses. Outer bark thickness (OBT) ranged from 0.01 to 0.77 cm with the thickest maximum outer bark occurring on P. taeda (0.77 cm) and the thinnest maximum outer bark occurring on P. serotina (0.17 cm). Our outer bark allocation models suggest that some individuals with rapid height growth allocate less to outer bark in C. tomentosa, N. sylvatica, P. taeda, and P. serotina, but not for P. echinata or either oak species. All species except for C. tomentosa and N. sylvatica showed evidence for outer bark taper, allocating more outer bark at the base of the bole. Inner bark also was tapered in Carya and the oaks. Bark rugosity varied among species from 0.00 (very smooth) to 0.17 (very rugose) with P. Serotina and C. tomentosa having the smoothest bark. OBT was the best fixed effect for all species. Aside from providing data for several important yet understudied species, our rugosity measures offer promise for incorporating into fluid dynamics fire behavior models.

Does allochthonous leaf litter structure terrestrial cave invertebrate assemblages?

ABSTRACT Allochthonous materials are the main sources of nutrients for most cave invertebrate communities. However, scant research exists about the differences in quality of various cave nutrient sources. We investigated whether different types of leaf litter would attract different terrestrial invertebrates within cave ecosystems. We placed six leaf types: (1) Maple (Acer saccharum) (2) Dogwood (Cornus florida) (3) Sweetgum (Liquidambar styraciflua) (4) Pine (Pinus taeda) (5) Swamp White Oak (Quercus bicolor) (6) Southern Red Oak (Quercus falcata) in three caves in north Alabama. Leaf sets were placed within the twilight and dark zones within each cave and gathered at 30, 60, and 100-day intervals. Leaves were dried, weighed, and C/N analyses of leaves were determined. Pine had significantly higher C/N ratios whereas dogwood and red oak had the lowest. However, abundances of the most commonly collected invertebrates (e.g. Collembola and Acari) were not affected by the leaf type despite some leaves (e.g. pine) being a lower quality food source. Additionally, no differences in overall invertebrate abundance or taxa richness were found neither among the leaf types nor between the twilight and dark zones. Our data suggests that terrestrial invertebrate abundance is not solely driven by food quality and could be driven by multiple factors.

Modeling and Monitoring of Wood Moisture Content Using Time-Domain Reflectometry

Time-domain reflectometry (TDR) can monitor the moisture content (MC) of water saturated logs stored in wet-decks where the MC exceeds the range that can be measured using traditional moisture meters (&gt;50%). For this application to become routine, it is required that TDR monitoring of wet-decks occurs after establishment, and tools are needed that automate data collection and analysis. We developed models that predict wood MC using three-rod epoxy encased TDR probes inserted into the transverse surface of bolts (prior wet-deck studies were installed on the tangential surface). Models were developed for southern pine, sweetgum, yellow poplar, hickory, red oak, and white oak using a Campbell Scientific TDR100. For each species, at least 37 bolts were soaked for a minimum of three months and then air dried with TDR waveforms, and MC was periodically recorded. Calibrations were developed between MC and the TDR signal using nonlinear mixed effects models. Fixed effects ranged from excellent (southern pine R2 = 0.93) to poor (red oak R2 = 0.36, hickory R2 = 0.38). Independent of wood species, random effects all had a R2 greater than 0.80, which indicates that TDR detects changes in MC at the individual sample level. Use of TDR combined with a datalogger was demonstrated in an operational wet-deck that monitored changes in MC over 12 months, and in a laboratory trial where bolts were exposed to successive wet-dry cycles over 400 days. Both applications demonstrated the utility of TDR to monitor changes in wood MC in high MC environments where periodic measurement is not feasible due to operational safety concerns. Because a saturated TDR reading indicates a saturated MC, and because of the relatively accurate random effects found here, developing individual species models is not necessary for monitoring purposes. Therefore, application of TDR monitoring can be broadly applied for wet-decks, regardless of the species stored.

Drivers of habitat partitioning among three Quercus species along a hydrologic gradient.

A critical process that allows multiple, similar species to coexist in an ecological community is their ability to partition local habitat gradients. The mechanisms that underlie this separation at local scales may include niche differences associated with their biogeographic history, differences in ecological function associated with the degree of shared ancestry and trait-based performance differences, which may be related to spatial or temporal variation in habitat. In this study we measured traits related to water-use, growth and stress tolerance in mature trees and seedlings of three oak species (Quercus alba L., Quercus falcata Michx. and Quercus palustris Münchh). which co-occur in temperate forests across the eastern USA but tend to be found in contrasting hydrologic environments. The three species showed significant differences in their local distributions along a hydrologic gradient. We tested three possible mechanisms that influence their contrasting local environmental distributions and promote their long-term co-existence: (i) differences in their climatic distributions across a broad geographic range, (ii) differences in functional traits related to water use, drought tolerance and growth and (iii) contrasting responses to temporal variation in water availability. We identified key differences between the species in both their range-wide climatic distributions (especially aridity index and mean annual temperature) and physiological traits in mature trees and seedlings, including daily water loss, hydraulic conductance, stress responses, growth rate and biomass allocation. Taken together, these differences explain the habitat partitioning that allows three closely related species to co-occur locally.

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.

Lagged mortality among tree species four years after an exceptional drought in east Texas

AbstractIn 2011, east Texas experienced the worst drought on record causing extensive tree mortality. Initial mortality estimates for 2012 varied among tree genera. A rapid damage assessment (RDA) estimated that 65.5 (± 7.3) million trees died as a result of the drought in this region one year post‐drought. However, this estimate was untested against established monitoring networks. Moreover, pests and physiological damage can elevate tree mortality multiple years beyond a drought event. Since the RDA was unable to quantify multi‐year trends, it remained unclear whether these drivers caused increased tree mortality in east Texas beyond one year post‐drought and how different species responded over time. To address these questions, we compared total 2012 standing dead tree (SDT) estimates (i.e., drought‐killed plus all other SDT excluding harvested or salvaged trees) derived from the RDA and U.S. Forest Service Forest Inventory and Analysis (FIA) data for east Texas. Total SDT estimates did not significantly differ between the RDA (120.5 ± 8.5 million) and FIA (108.4 ± 8.7 million). Furthermore, total SDT estimates for the four most common genera (Pinus, Quercus, Liquidambar, Ulmus), which comprised over 80% of all species, did not significantly differ between the RDA and FIA. Additionally, we used logistic regression and FIA data from east Texas for 2011 through four years post‐drought (2012–2015) to examine temporal trends in plot‐level drought‐ and pest‐driven tree mortality of seven key species (Pinus taeda, Pinus echinata, Quercus nigra, Quercus stellata, Quercus falcata, Liquidambar styraciflua, Ulmus alata) from the four most common genera. At the plot‐level, drought‐driven mortality was immediate for the three Quercus species (notably Q. falcata) and L. styraciflua which significantly increased in 2012 while P. taeda mortality was delayed, not increasing significantly until 2013. Pest‐driven mortality increased from 2013 to 2015 for all species, with the highest mortality observed in Q. falcata and lowest in P. taeda and U. alata. This study affirms the validity and value of independent sampling efforts to quantify mortality immediately following major disturbance and also demonstrates the need for longer‐term species‐level assessments beyond the initial year post‐drought to account for differential impacts from drought and pests.

Differential ecophysiological responses and resilience to heat wave events in four co-occurring temperate tree species

Extreme summer heat waves are known to induce foliar and stem mortality in temperate forest ecosystems, yet our mechanistic knowledge of physiological thresholds for damage is lacking. Current spatiotemporal simulations of forest growth responses to climate change fail to explain the variability between co-occurring tree species to climate extremes, indicating a need for new model frameworks that include mechanistic understanding of trait-specific responses. In this context, using manipulative heat wave (hw) experiments we investigated ecophysiological responses and physiological recovery in four co-occurring temperate tree species of the southeastern United States including three deciduous angiosperms: southern red oak (Quercus falcata Michx.), shumard oak (Q. shumardii Buckl.) and, tulip-poplar (Liriodendron tulipifera L.) and one evergreen conifer: eastern white pine (Pinus strobus L.). The objectives were to investigate inter-specific differences in ecophysiological responses to hw events to understand mechanistic differences in resilience that may be useful for future model development. Two-year-old, well-irrigated potted saplings were exposed to progressively increasing extreme hw diurnal cycles followed by a recovery cycle, with peak midday air temperature increasing from 37 °C to a maximum of 51 °C on the third day of the hw. Plants were assessed for various photosynthetic and water use responses, chlorophyll fluorescence and photosystem-II (PSII) activity, leaf temperature and foliar pigments. Intense heat caused progressive down-regulation in net photosynthesis, but the stomata remained operational, which helped cool leaves through loss of latent heat. Even though whole plant transpiration increased for all species, the rate plateaued at higher hw events that allowed leaf temperature to exceed 45 °C, well beyond the optimal range. A significant increase in non-photochemical quenching over the hw cycles was evident in all species though indications of both transient and chronic PSII damage were evident in the most heat sensitive species, pine and tulip poplar. The oaks, especially Q. falcata, showed greater thermotolerance than other species with a higher threshold for photodamage to PSII, rapid overnight recovery of photoinhibition and minimal heat-induced canopy necrosis. We conclude that these co-occurring tree species exhibit large variability in thermotolerance and in their capability to repair both transient and chronic photodamage. Our results indicate that extreme heat induced damage to PSII within the leaf chloroplasts may be a mechanistic trait that can be used to project how different species respond to extreme weather events.

Measurement of dimensional stability of heat treated southern red oak (Quercus falcata Michx.)

The objective of this study was to investigate the effect of heat treatment on physical and mechanical properties including oven-dry density, weight loss, swelling, shrinkage, and hardness of southern red oak (Quercus falcata Michx.). The samples were treated at a temperature level of 190°C for 3h and 8h. After heat treatment of the specimens, their dimensional stability in the form of swelling and shrinkage were determined by soaking them in water for 2 and 24h. Hardness of samples as function of heat treatment was also measured using Janka hardness (ASTM D 1037–12). Tangential, radial and longitudinal swelling values of the samples exposed to 8h heat treatment and soaked in water for 2h were 0.245%, 0.236%, 0.098%, respectively. Corresponding values for the control samples were 0.504%, 0.455%, 0.135%. Overall hardness of the specimens was adversely influenced due to heat treatment. Based on the findings in this study shrinkage and swelling of the samples improved as a result of heat exposure. It appears that heat treatment would be a viable method to enhance dimensional stability of red oak for more effective utilization where enhanced hygroscopicity of such species is desired.

Plant Remains from the Washington Square Mound site (41NA49), Nacogdoches, Texas

Botanical remains were identified from 27 lots from the Washington Square Mound site (41NA49). The primary occupation at the site is Middle Caddo period in age. The first pooled set of calibrated radiocarbon dates from the site fell into the period A.D. 1268-1302, while a recent set of five calibrated dates from samples of plant remains discussed in this article range from A.D. 1279 + 17; (2) A.D. 1358 + 57; and three dates on charred corn from Features 36, 81, and 86 range from as early as A.D. 1394 to as late as A.D. 1437. These dates as a group fall in the Middle Caddo period; there is limited evidence at the site for other, smaller occupations, including Late Caddo and Late Woodland/Early Caddo. At least three mounds were visible in the nineteenth century. Much of the site was never plowed, a situation that has resulted in intact shallow deposits and unusually large pottery sherds, although a high school has been built over parts of the non-mound site area. Labels of botanical lots that included excavation dates indicate a range from 1979 to 1983, associating the botanical remains with Stephen F. Austin State University Field School excavations that took place during this time. At least nine features are represented in the botanical lots. Four are described as charcoal-filled pits, one as a pit, and one as a post mold. Feature 36 was a corn cob concentration . Botanical lots for Features 62, 81, and 199 are also present. The Washington Square Mound site is situated in the city of Nacogdoches, Texas, on an interfluve between Banita Creek and La Nana Creek, which drain into La Nana Bayou and the Angelina River. The area lies squarely in the Pineywoods ecological zone, the westernmost extension of the great Southeastern Evergreen Forest that reaches across the southeastern United States to the Atlantic coast (Braun 2001:281). The dominant vegetation type in an upland area such as Washington Square during presettlement times would have been a shortleaf pine community, where shortleaf pines (Pinus echinata) share dominance with dry-site oaks such as southern red oak (Quercus falcata), post oak (Q. stellata), and blackjack oak (Q. marilandica), hickories (Carya spp.), and elms (Ulmus spp.) Springs and marshy areas nearby would have offered aquatic and wetland plants such as river cane (Arundinaria gigantea). A spring-fed pond is reported to have existed north of the site, and a marshy area to the southwest. Pollen studies indicate that use of the modern and recent vegetation is appropriate for understanding the plants and attendant animal resources available to occupants of the sites during prehistoric times. Some fluctuations in rainfall and temperature have taken place, however. In addition, more frequent fires would have made the understory in the uplands less prominent than today. Early explorers in East Texas and other parts of the Eastern Woodlands noted the open, park-like nature of many woodlands.

Importance of succession, harvest, and climate change in determining future composition in U.S. Central Hardwood Forests

Most temperate forests in U.S. are recovering from heavy exploitation and are in intermediate successional stages where partial tree harvest is the primary disturbance. Changes in regional forest composition in response to climate change are often predicted for plant functional types using biophysical process models. These models usually simplify the simulation of succession and harvest and may not consider important species‐specific demographic processes driving forests changes. We determined the relative importance of succession, harvest, and climate change to forest composition changes in a 125‐million ha area of the Central Hardwood Forest Region of U.S. We used a forest landscape modeling approach to project changes in density and basal area of 23 tree species due to succession, harvest, and four climate scenarios from 2000 to 2300. On average, succession, harvest, and climate change explained 78, 17, and 1% of the variation in species importance values (IV) at 2050, respectively, but their contribution changed to 46, 26, and 20% by 2300. Climate change led to substantial increases in the importance of red maple and southern species (e.g., yellow‐poplar) and decreases in northern species (e.g., sugar maple) and most of widely distributed species (e.g., white oak). Harvest interacted with climate change and accelerated changes in some species (e.g., increasing southern red oak and decreasing American beech) while ameliorated the changes for others (e.g., increasing red maple and decreasing white ash). Succession was the primary driver of forest composition change over the next 300 years. The effects of harvest on composition were more important than climate change in the short term but climate change became more important than harvest in the long term. Our results show that it is important to model species‐specific responses when predicting changes in forest composition and structure in response to succession, harvest, and climate change.

Changes in Tree Species Composition and Stand Structure in a Mature Upland Oak-Dominated Forest Reflect Differences in Recruitment, Survival, and Longevity

ABSTRACT: Poor regeneration of some species of oaks (Quercus spp.) within undisturbed closedcanopy forests is common throughout much of the eastern United States. Oak regeneration failure is often inferred from negatively skewed size-class distributions, but evidence of replacement by non-oaks requires investigation of changes in composition and size distributions. I examined how tree species composition and the log-transformed diameter distributions of oaks and non-oaks changed between 1999 and 2013 in an old-growth forest on the University of Mississippi campus. There was a general weak trend towards replacement of oaks by non-oaks. Oaks showed nonskewed or negatively skewed diameter distributions in 1999 and 2013. Diameter distributions of southern red oak (Quercus falcata) became significantly more negatively skewed, and the abundance of this species declined. However, there was no significant change in skewness of diameter distributions of the more fire-tolerant but longer-lived post oak (Q. stellata...

Factors affecting broadleaf woody vegetation in upland pine forests managed for longleaf pine restoration

Controlling broadleaf woody plant abundance is one of the greatest challenges in longleaf pine (Pinus palustris Mill.) ecosystem restoration. Numerous factors have been associated with broadleaf woody plant abundance in longleaf pine ecosystems, including site quality, stand structure, and fire frequency and intensity, yet the way in which these factors vary and interact across a landscape is poorly understood. The goal of this study was to quantify the importance of environmental and management factors and their interactions on the abundance of hardwood tree and shrub species in upland pine forests managed for longleaf pine restoration in Fort Benning, GA. We measured understory, midstory, and overstory vegetation in 189 fixed-area plots, and we assembled descriptive plot data about soil texture classes, slope and aspect, and fire management history. We used classification and regression trees to model broadleaf woody species abundance. Regression trees identified fire return interval, soil texture, and slope as the most important factors affecting understory woody plant cover, with high mean cover occurring in areas with longer fire return intervals (i.e. less frequent fire), on fine-textured soils (sandy clay loams and sandy loams), and on slopes less than 6%. An interaction between soil texture and fire return interval was present and suggested that frequent fire was especially important in controlling understory broadleaf woody plants on fine-textured soils. A significant interaction emerged between soil texture and pine basal area as well, suggesting that the potential to release woody competitors with canopy removal was higher on fine-textured soils than on coarse-textured soils. The presence of hardwood stems in the midstory was most dependent upon time since burn. Other factors, such as the number of burns conducted during the growing season and topographic aspect, did not contribute significantly to variation in woody plant cover or density. Of the woody species encountered, sweetgum (Liquidambar styraciflua L.) was the most abundant, especially on plots with fire return intervals ⩾2.6years, on fine-textured soils, and at low pine basal areas (<9.4m2/ha). Other species such as persimmon (Diospyros virginiana L.), winged sumac (Rhus copallinum L.), and southern red oak (Quercus falcata Michx.) were commonly encountered but at low densities. Our results demonstrate the general complexity of woody species control, but more importantly indicate site differences that could be used to prioritize prescribed fire application at the landscape scale.