Cherrybark Oak Research Articles

The role of oak species in long-term soil P loss in a humid river bottomland

There is a gap in our understanding of if and how bottomland forest type will affect long-term nutrient cycling and loss. This study aims to determine how different forests affect soil hydrologic variability and whole-soil P loss in a humid-subtropical setting. We used replicate-sampling and measured soil physical, chemical, and mineralogical properties at 12 sites in two forest ecosystems, post oak (Quercus stellata) and cherry bark oak (Quercus pagoda) in Clarks River National Wildlife Refuge in Western Kentucky. We hypothesize that wetting–drying events in redox soils of forested bottomlands can cause positive feedback in whole-soil P loss. Trees with greater P demand (e.g., post oak) take up more water creating more frequent and pronounced episodes in swelling and shrinking of expandable clays. Repeated swelling and shrinking of clays occlude the surface of Fe-Mn oxides from further adsorption of P in acidic soil. This can lead to greater loss or plant uptake of available P. Our results show (i) a significant difference in mean whole-soil P loss between the oak species with more loss in soils underlying the post oak forest, and (ii) a difference in the total P found in the sap- and heartwood of the two oak species. Soil analysis reveals that the clay mineralogy of the post and cherry bark oak sites are similar, and thus, may only play a minor role in governing the whole-soil P loss difference. However, the leaf data analysis suggests that the post oak site could be P and nitrogen-limited, while the cherry bark is only nitrogen limited. Our study shows that differences in the oak forest ecosystem may affect the long-term balance in water and nutrient uptake and may alter the redistribution of nutrients in the canopy and the underlying soils.

Forest composition and red oak (Quercus sp.) response to elevation gradients across greentree reservoirs

Elevation gradients within forested wetlands have long been recognized for their role in defining species composition through factors such as hydrology and soil characteristics. Greentree reservoirs (GTRs) are levee-impounded tracts of bottomland hardwood forest flooded throughout the winter months to provide habitat for overwintering waterfowl. Artificial flooding of GTRs alters the forest composition due to flood frequency, depth, and duration in combination with slight changes in topography. To evaluate the effect of elevation gradients, soil properties, and management techniques in the overstory species composition and red oak (Quercus spp.) species abundance, we inventoried 662 plots across 12 independent GTRs in eastern Arkansas. In the lower elevations ranging from 50.98 to 54.99 ​m above sea level, the importance value index (IVI) was highest for nuttall oak (Quercus texana) and overcup oak (Quercus lyrata), whereas IVI shifted to cherrybark oak (Quercus pagoda) in the higher elevations ranging from 54.99 to 58.00 ​m. Alpha diversity did not differ by elevation gradient, soil property, or management technique within GTRs. Beta diversity, using non-metric multi-dimensional scaling (NMDS) analysis, indicated site-specific variability significantly correlated with the environmental predictors, including elevation (R2 = ​0.57), easting (R2 = ​0.47), soil texture (R2 = ​0.21), and pH (R2 = ​0.12). Red oak species-specific mixed-effects modeling of abundance response using Poisson distribution suggested an inverse correlation of nuttall oak and a direct correlation of cherrybark oak abundance with elevation. However, willow oak (Quercus phellos) abundance was not significantly affected by elevation but was by silt loam soil texture and restoration management techniques. These findings will aid management efforts to reduce the dominance of less desirable species that are prominent under specific environmental conditions and promote the dominance of more desirable species. Ultimately GTR sustainability is increasingly important amid the unpredictable impacts of climate change on the preferred red oak species that are economically, ecologically, and environmentally valuable to the sustaining economy of the local community and managing habitats for wildlife.

Growth Response of Red Oaks to Climatic Conditions in the Lower Mississippi Alluvial Valley: Implications for Bottomland Hardwood Restoration with a Changing Climate

Bottomland hardwood forests (BHFs) offer a wide range of ecosystem services that are of high environmental and socioeconomic value. Yet, nearly 70% of BHFs in the southern United States have been lost during the past 100 years primarily due to land use change including agricultural expansion, calling for restoration efforts. We estimated the statistical relationship of the annual radial growth rate of three red oak species with climatic conditions and tree age using the tree ring data collected from a BHF plantation in the Arkansas Delta region. These species were Cherry bark oak (Quercus pagoda), Shumard oak (Quercus shumardii), and Nuttall oak (Quercus texana). The destructive sampling method was employed to obtain tree growth data and the cross-dating method was used for tree age determination. A log-linear regression model was estimated to uncover the statistical relationship between annual tree ring growth rate and climatic conditions. We identified the most critical time windows of climate variables that affect the growth of these trees. We found that the average temperature in October of the previous year and the minimum temperature between December of the previous year and January of the current year were positively associated with the radial growth rate in the current year although the maximum temperature from January to August and total precipitation from April to July of the current year were negatively correlated with the growth rate. Compared to Cherry bark and Shumard oaks, Nuttall oak was less sensitive to a rise in the minimum temperature between December and January. The projected climate change is likely to create slightly more favorable overall climatic conditions for these oak species in the region. Our findings suggest that these three red oak species are well suited for the study region for restoring BHFs, especially with a changing climate.

Competition intensity varies with hardwood species identity and constrains stand-level productivity in southeastern pine–hardwood mixtures compared to loblolly pine monocultures

We examined the performance of sweetgum ( Liquidambar styraciflua L.), cherrybark oak ( Quercus pagoda Raf.), and loblolly pine ( Pinus taeda L.) in two-species pine–hardwood mixtures (sweetgum : loblolly pine and cherrybark oak : loblolly pine) at various planting densities (1482–1976 trees per hectare (TPH)) over 23 years in northern Louisiana, USA. Species were planted in alternating rows with hardwood establishment occurring 1 year prior to loblolly pine. Mixtures were also compared to loblolly pine monocultures at a common density (1482 TPH) to assess whether mixing improved productivity. Sweetgum exerted more competitive pressure on loblolly pine than cherrybark oak. At final measurement, sweetgum survival statistically exceeded that of loblolly pine across mixture density. Moreover, sweetgum cumulative basal area and volume growth nearly tripled that of loblolly pine in balanced high-density mixtures (1976 TPH, 50 pine : 50 hardwood). In contrast, cherrybark oak basal area and volume growth did not significantly exceed loblolly pine at any density. At a common density (1482 TPH), loblolly pine monoculture cumulative basal area and volume significantly exceeded those of mixtures with sweetgum and cherrybark oak by 19% and 24%, respectively. Collectively, these results indicate that growing loblolly pine in mixture with these two species did not produce complementary interactions and negatively affected stand-level growth.

Evaluation of dendroremediation potential of ten Quercus spp. for heavy metals contaminated soil: A three-year field trial

Woody plants have gained considerable attention for remediating soils contaminated with heavy metals because of their cost-efficient and ecologically friendly nature. However, most studies on potential phytoremediation evaluation are limited to short-term experiments in greenhouse or field, meaning that differences may exist between laboratory results and application in natural environment. In this study, ten Quercus spp. were tested in a consecutive 3-year field trial (2018–2020) to assess their dendroremediation abilities for Cd and Zn contaminated soil. The results revealed that nine Quercus spp. demonstrated good survival ability without any stress, except for Quercus velutina Lam., in the 3-year growth period. In 2020, Quercus texana Buckley and Quercus fabri Hance plants produced the greatest biomass (2100 and 1880 g plant−1) among the nine Quercus spp. Quercus texana had the highest total Cd accumulation (39.3 mg plant−1) in 2020, which was 8.5 times higher than that in 2018, followed by Quercus pagoda Raf. (8.85 mg plant−1) and Q. fabri (8.07 mg plant−1) plants, respectively, whereas Cd accumulation increased by 7.4 times for Q. pagoda and 22 times for Q. fabri compared to 2018. The results from 2020 indicated that Q. fabri had the highest Zn accumulation (205 mg plant−1), followed by Quercus nigra L. (149 mg plant−1) and Q. texana (140 mg plant−1), respectively, and these values increased 14, 6.4, and 6.2 times in comparison to 2018. The comprehensive bioaccumulation index (CBAI) was proposed to evaluate the dendroremediation potential of Quercus spp., suggesting that Q. texana and Q. fabri had the most outstanding potential for remediation of Cd and Zn polluted soil, with the values of 0.82 and 0.60, respectively. In summary, Q. texana and Q. fabri are ideal for remediating Cd/Zn-contaminated soil, and long-term field trials and the CBAI method are helpful for comprehensively evaluating the remediation capacity of trees.

Stem profile of red oaks in a bottomland hardwood restoration plantation forest in the Arkansas Delta (USA)

Bottomland hardwoods are among the most diverse and productive forest ecosystems in the southeastern United States and are critically important for the provision of timber and non-timber ecosystem services. Red oaks, the dominant species in this group of forests, are of high ecological and economic value. Stem profile models are essential for accurately estimating the merchantable volume of oak trees, which is also closely indicative of total tree biomass and other ecosystem services given their allometric relationships. This study aims to develop and compare stem profiles among three red oak species in an 18-year old plantation forest using destructive sampling. Sixty trees randomly selected from an oak restoration plantation in the Arkansas Delta were felled for measuring the diameter-outside-bark (DOB) and diameter-inside-bark (DIB) at different stem heights. These sample composed of twenty trees from each of three species: cherry bark oak (CBO - Quercus pagoda Raf), Nuttall oak (NUT - Quercus texana Buckley), and Shumard oak (SHU - Quercus shumardii Buckl). Multiple models, including the segmented-profile model, form-class profile model, and second-and third-order polynomial models were fitted and compared. Results demonstrate that the form-class profile model was the best fitted for CBO and NUT, whereas the third-order polynomial model was the best for SHU. CBO tends to grow taller and has a higher wood density than NUT and SHU. These findings will inform restoration and management decisions of bottomland hardwood forests, especially red oaks in the region.

Tree-level Growth of Four Oak Species in a Bottomland Hardwood Plantation: Implications for Silvicultural Treatments

Abstract A 41-year-old bottomland hardwood plantation experiment located in southeastern Arkansas was revisited in 2017 to evaluate basal area increment (BAI) of four oak species [cherrybark oak (Quercus pagoda Raf.), swamp chestnut oak (Q. michauxii Nutt.), Nuttall oak (Q. texana Buckl.), and water oak (Q. nigra L.)] planted in monoculture in relation with species, spacing, thinning, and neighborhood competition. Species had a significant effect on BAI (P = 0.04), with cherrybark oak and Nuttall oak demonstrating the greatest (21.5 ± 2.5 cm2 year−1) and lowest (12.7 ± 2.9 cm2 year−1) growth rates, respectively, whereas BAI declined significantly with increasing competition (P = 0.03). However, rates of growth decline with competition did not differ between species (P > 0.05 for competition × species term), and thinning and spacing treatments had no effect on BAI (P > 0.05). We recommend that repetitive thinning, rather than a single thinning, would be appropriate to maintain a positive impact on oak growth. Managing stand density would not only provide opportunities for improving timber production, but also would enhance ecological benefits (e.g., wildlife habitat) through diversification of structure within monoculture plantations.

Effects of drought on water use of seven tree species from four genera growing in a bottomland hardwood forest

For floodplain forests such as bottomland hardwood forests, large fluctuations in moisture availability can lead to stress from both flooded as well as drought conditions. Likewise, these forests can be diverse in species composition and the water use and drought strategies of co-occurring species will impact surrounding hydrology, nutrient dynamics and productivity. Therefore, the objectives of this study were to compare water use, canopy stomatal conductance and its response to environmental drivers in co-occurring bottomland hardwood species from four genera (Carya, Fraxinus, Quercus, Ulmus) during a drought and average rainfall year. Water use was similar across years in cherrybark oak and winged elm. For swamp chestnut oak, willow oak and shagbark hickory water use was about two thirds in the drought year compared with the average rainfall year and in American elm and green ash it was about one half. Species also varied in their responses of water use to VPD, reference canopy stomatal conductance values, and the timing of leaf senescence during the drought and average rainfall year which will impact ecosystem processes based on drought conditions and species composition. Shagbark hickory, winged elm and swamp chestnut oak exhibited the most declines in water use due to soil saturation. In general, species exhibited a tradeoff between flood tolerance and drought tolerance as well as between maximal water use potential and drought tolerance. In total, differences in water use and its response to environmental drivers during drought and non-drought years for bottomland hardwood forests will depend on species composition and these findings can benefit modeling efforts in temperate floodplain forests.

Co-planting of Quercus nuttallii, Quercus pagoda with Solanum nigrum enhanced their phytoremediation potential to multi-metal contaminated soil

To screen the efficient tree-herb co-planting patterns to remediate the heavy metal polluted soil, a greenhouse experiment was conducted for 150 days to examine the plant growth and metals accumulation across three co-planting patterns, including Solanum nigrum (S) co-planted with Quercus nuttallii (NS) or Quecrus pagoda (PS), and those three species are co-planted together (NPS). Results showed that the NPS pattern slightly decreased the tree biomass, while NS and PS treatments improved the plant growth (1.51–10.68%). It is worth noting that the NS treatment significantly (p < 0.05) increased photosynthetic pigment content (82.61–113.93%), net CO2 assimilation (21.44%), and the uptake of Cd (44.58%) in Q. nuttallii; the PS treatment significantly (p < 0.05) increased the net CO2 assimilation (8.61%) and the uptake of Cd (42.23%), Zn (31.18%) in Q. pagoda; and the uptake of Cd and Zn in the NPS co-planting treatment were only slightly increased. For S. nigrum, the photosynthetic pigment content was elevated and the metal accumulation in itself also maintained the relative stable in all the co-planting treatments. Thus, co-planting of Quercus with S. nigrum was a promising way to remediate heavily polluted soil by heavy metals. Novelty statement: Co-planting with multiple plant species, as a novel strategy, has great value for the remediation of heavy metal contaminated soil. The paper aimed to explore the suitable co-planting pattern of Quercus, arbor trees which showed phytoremediation potential, co-planted with Cd hyperaccumulator, Solanum nigrum. The result suggested the co-planting with S. nigrum enhanced the plant growth, photosynthesis, and metals extraction of Q. nuttallii and Q. pagoda. Co-planting also improved ecological adaptation of S. nigrum via elevating pigment content. Thus, co-planting of Quercus with S. nigrum was a promising way to remediate polluted soil.

Effects of Stand Density on Loblolly Pine, Cherrybark Oak, and Sweetgum Productivity in Monocultures and Pine-Hardwood Mixtures Over 23 Years in Northwestern Louisiana, USA

Effects of Stand Density on Loblolly Pine, Cherrybark Oak, and Sweetgum Productivity in Monocultures and Pine-Hardwood Mixtures Over 23 Years in Northwestern Louisiana, USA

Diversity or Redundancy in Leaf Physiological and Anatomical Parameters in a Species Diverse, Bottomland Hardwood Forest?

Research Highlights: Bottomland hardwood forests exhibit seasonal flooding, are species diverse, and provide numerous ecosystem services including floodwater storage, wildlife habitat and nutrient mitigation. However, data are needed to adequately predict the potential of individual species to achieve these services. Background and Objectives: In bottomland hardwood forests, increasing tree species richness may increase functional diversity unless species exhibit an overlap in physiological functioning. Therefore, the objectives of this study were to (1) compare physiological and anatomical leaf parameters across species, (2) determine if leaf anatomical and nutrient properties were correlated with physiological functioning, (3) determine intra-species variability in leaf stomatal properties and determine how whole crown metrics compare with leaves measured for gas exchange and (4) measure soil nitrogen for evidence of denitrification during inundation periods. Materials and Methods: We measured gas exchange, leaf nutrients and anatomical properties in eight bottomland hardwood species including Carya ovata, Fraxinus pennsylvanica, Quercus michauxii, Quercus nigra, Quercus pagoda, Quercus phellos, Ulmus alata and Ulmus americana. Additionally, we quantified soil ammonium and nitrate content during winter inundated conditions to compare with non-inundation periods. Results: We found that leaf-level water use parameters displayed greater variability and diversity across species than photosynthesis and leaf nitrogen parameters, but green ash and shagbark hickory exhibited generally high leaf N concentrations and similar physiological functioning. Elms and oaks displayed larger variability in leaf physiological functioning. Stomatal density was significantly correlated with photosynthetic capacity and tree-level water use and exhibited high intra-species variability. Conclusions: This bottomland hardwood forest contains more diversity in terms of water use strategies compared with nitrogen uptake, suggesting that differences in species composition will affect the hydrology of the system. Green ash and shagbark hickory exhibit higher leaf nitrogen concentrations and potential for nutrient mitigation. Finally, leaf anatomical parameters show some promise in terms of correlating with leaf physiological parameters across species.

Tree species effects on understory forage productivity and microclimate in a silvopasture of the Southeastern USA

Ecosystem services provided by silvopastoral systems are mediated by specific management practices, environmental conditions, and overall design of the system. We hypothesized that selection of tree species affects understory forage nutritive value and productivity, light/shade environment, and microclimate. The silvopastoral system was located at the Center for Environmental Farming Systems in Goldsboro, North Carolina, USA. Three overstory tree-species were Pinus palustris (PP; longleaf pine), Pinus taeda (PT; lobloblly pine), and Quercus pagoda (QP; cherrybark oak). The understory forage component consisted of a four-way mixture of native warm-season grasses [big bluestem (Andropogon gerardii, ‘Eastern’, KY origin), eastern gamagrass (Tripsacum dactyloides, MO origin), indiangrass (Sorghastrum nutans, ‘NC ecotype’), and switchgrass (Panicum virgatum, ‘Alamo’)]. The experimental design was an RCBD with 3 replicates. There was no effect of seedbed preparation (till versus no-till) on forage establishment. Understory dry matter yield, crude protein and total digestible nutrient concentrations of the harvested forage were not affected by tree species, with the exception at the 3.5 south sampling point. Overstory effects on microclimate variables were not different among tree-species, but were more noticeable during the daytime of the summer months, and were at the most 1-degree point for temperature and temperature-humidity index and 3 points for relative humidity. The silvopasture design in our study provided year-round shade by the tree-component, with varying levels of shade (ranging from 90 to 6% of incident photosynthetic active radiation) due to geographic location, tree species, and season. Our results describe and highlight the potential of trees in a silvopasture design in the southeastern USA to mitigate changes in temperature, humidity, the temperature-humidity index, and forage productivity and as a function of tree species and at different distance from the trees.

Seasonal physiology and growth of planted oaks with implications for bottomland hardwood restoration

Afforestation and reforestation of once dominant bottomland hardwood forests in the southeastern United States can provide ecosystem services and wildlife habitat. However, challenges of prior site conditions, seasonal flooding, soil texture and lack of nearby seed sources can necessitate planting of seedlings to achieve desirable results, particularly for large-seeded species like oaks. Therefore, the objectives of this study were to compare growth and survival of two species of oaks common to southeastern and bottomland hardwood forests, cherrybark oak (Quercus pagoda Raf.) and willow oak (Quercus phellos L.) from 1-0 bareroot, conventional container (0.24 L) and large container (3.8 L) planting stocks across two growing seasons. Additionally, we sought to compare physiology across seedling types to determine the underlying differences in functioning that led to the growth responses. Despite above average rainfall, growth was modest particularly at the site that was previously pasture land and for willow oak which also exhibited net dieback. Two-year survival was adequate (> 75%) for bareroot and large container seedlings but was suboptimal (~ 50%) for conventional container seedlings. Large container seedlings had about 40% higher photosynthetic rates and 70% higher water use efficiencies compared to bareroot and conventional container seedlings. Cherrybark oak exhibited greater stomatal regulation across the growing season than willow oak, however all seedling types displayed increased stomatal conductance and decreased water use efficiency throughout the growing season. Overall, these findings highlight the importance of matching species to site conditions and providing competition control particularly on grassland sites and during above average rainfall conditions.

The Influence of Dormancy Break Requirements on Germination and Viability Responses to Winter Submergence in Acorns of Three Bottomland Red Oak (Sect. Lobatae) Species

Abstract The objective of this study was to examine the relation of dormancy break requirements to winter submergence effects on germination and viability in cherrybark, willow, and Nuttall oak acorns. Acorns were submerged in a greentree reservoir and received 0, 21, 42, 63, or 84 days of winter submergence, followed by 8 weeks of incubation in four temperature regimes (15/6°, 20/10°, 25/15°, and 30/20° C). Winter submergence substituted for cold stratification requirements of cherrybark oak acorns, and dormancy break was achieved with 63 days of submergence. Although winter submergence exerted a positive effect on germination in Nuttall and willow oak acorns, dormancy break was not achieved in acorns of either species. Germination percentages were highest in the 30/20° C incubation temperature—cherrybark oak acorns (75–83 percent), followed by Nuttall oak (33–55 percent) and willow oak (14–52 percent). Among treatment combinations, all willow oak nongerminants were viable. Viability loss in cherrybark and Nuttall oak acorns was greatest in the 63- and 84-day treatments. The dynamics of acorn germination in response to winter hydrologic regime is influenced by submergence duration that may, or may not, satisfy dormancy break requirements in acorns of these red oak species.

Regulating acorn germination and seedling emergence in Quercus pagoda (Raf.) as it relates to natural and artificial regeneration

Dormancy break and germination requirements for Quercus pagoda (Raf.) acorns were determined, as well as the effects of acorn pretreatment and post-germination temperatures on epicotyl emergence, seedling development, and seedling biomass accumulation. There was an inverse linear relationship between length of cold stratification (5/1 °C for 0–12 weeks) and cumulative germination percentages in all incubation temperatures (15/6, 20/10, 25/15, 30/20 °C). Acorns required 12 weeks of cold stratification to break dormancy. Gibberellic acid substituted for cold stratification; although, it was not as effective as 12 weeks cold stratification. At 16 weeks of cold stratification, 20% of acorns had germinated, and the remaining 80% of ungerminated acorns reached ≥ 97 ± 1% cumulative germination within 4 days in all incubation temperatures. Post-germination time to epicotyl emergence and to leaf flush was a function of temperature, and time decreased with increased temperatures. With light held constant (50 μmol m−2 s−1), seedlings accumulated greater biomass in temperatures > 20/10 °C. Q. pagoda acorns possess Type 2 nondeep physiological dormancy, and this allows for artificial manipulation of timing and duration of germination. Extending cold stratification 4 weeks beyond dormancy break (i.e., 16 weeks) yields more uniform germination across a range of temperatures. Epicotyl emergence, seedling development, and biomass accumulation may be regulated by manipulating growing temperature. In this study, the most uniform seedling cohort with the greatest total biomass was produced when acorns received 16 weeks of cold stratification, followed by transfer of germinants to 30/20 °C.

Site Index Prediction for Willow and Cherrybark Oaks in East Texas Bottomland Forests

Estimating site quality for a specific tree species is an important tool in forest management. While intensively managed pine species are often the focus of site quality studies using site index, hardwood species found in bottomland hardwood sites are often lacking in quality growth prediction equations. Two valuable hardwood species, willow oak (Quercus phellos) and cherrybark oak (Q. pagoda), are of interest for forest managers of east Texas bottomland sites. The objective of this study was to develop site index prediction equations and curves for these two species. Using height and age data from 267 cherrybark oaks and 460 willow oaks collected from sites across east Texas, remarkably similar equations were developed, with coefficient of determination (R2) of 0.63 for cherrybark oak and 0.52 for willow oak.

Greenhouse gas emissions in an agroforestry system of the southeastern USA

Agroforestry systems may provide diverse ecosystem services and economic benefits that conventional agriculture cannot, e.g. potentially mitigating greenhouse gas emissions by enhancing nutrient cycling, since tree roots can capture nutrients not taken up by crops. However, greenhouse gas emission data from agroforestry systems are not available in the southeastern USA, thus limiting our ability to optimize agroforestry management strategies for the region. We hypothesized that tree-crop interactions could prevent excess N from being released to the atmosphere as nitrous oxide (N2O). We determined N2O and carbon dioxide (CO2) emissions, soil temperature, water content, and surface-soil inorganic N in an 8-year-old agroforestry site at the Center for Environmental Farming Systems in Goldsboro, North Carolina, USA. The experimental design was a factorial arrangement of soil texture (loamy sand, sandy loam, and clay loam) and canopy cover (cropped alley, margin between crops and trees, and under Pinus palustris, Pinus taeda, and Quercus pagoda) with three replications. Sampling occurred 42 times within a year using static, vented chambers exposed to the soil for 1-h periods. Soil N2O emission was lower under tree canopies than in cropped alleys, and margin areas were intermediate. Soil texture, water content, and inorganic N were key determinants of the magnitude of N2O emission. Soil CO2 emission was controlled by temperature and water content as expected, but surprisingly not by their interaction. Soil temperature was 1.8 ± 1.3 °C lower and soil water content was 0.043 ± 0.15 m3 m−3 lower under tree canopy than in cropped alleys, which helped to reduce CO2 emission under trees relative to that in cropped alleys. Our results provide a foundation for reducing greenhouse gas emissions in complex agricultural landscapes with varying soil texture by introducing timber production without abandoning agricultural operations.

Leaf Anatomical Changes Induced by Paclobutrazol Tree Growth Regulator in Cherrybark Oak

Leaf Anatomical Changes Induced by Paclobutrazol Tree Growth Regulator in Cherrybark Oak

Differences in impacts of Hurricane Sandy on freshwater swamps on the Delmarva Peninsula, Mid-Atlantic Coast, USA

Hurricane wind and saltwater surge may have different influences on the subsequent composition of forests. During Hurricane Sandy, while damaging winds were highest near landfall in New Jersey, inundation occurred along the entire eastern seaboard from Georgia to Maine. In this study, a comparison of damage from salinity intrusion vs. wind/surge was recorded in swamps of the Delmarva Peninsula along the Pocomoke (MD) and Nanticoke (DE) Rivers, south of the most intense wind damage. Hickory Point Cypress Swamp (Hickory) was closest to the Chesapeake Bay and may have been subjected to a salinity surge as evidenced by elevated salinity levels at a gage upstream of this swamp (storm salinity=13.1ppt at Nassawango Creek, Snow Hill, Maryland). After Hurricane Sandy, 8% of the standing trees died at Hickory including Acer rubrum, Amelanchier laevis, Ilex spp., and Taxodium distichum. In certain plots of Hickory, up to 25% of the standing trees were dead, corresponding with high soil salinity. The most important variables related to structural tree damage were soil salinity and proximity to the Atlantic coast as based on Stepwise Regression and NMDS procedures. Wind damage was mostly restricted to broken branches although tipped-up trees were found at Hickory, Whiton and Porter (species: Liquidamabar styraciflua, Pinus taeda, Populus deltoides, Quercus pagoda and Ilex spp.). These trees fell mostly in an east or east-southeast direction (88–107°) in keeping with the wind direction of Hurricane Sandy on the Delmarva Peninsula. Coastal restoration and management can be informed by the specific differences in hurricane damage to vegetation by salt vs. wind.

Comparing individual-tree approaches for predicting height growth of underplanted seedlings

Individual-tree seeding height growth models developed using tree inventory data were comparable to those requiring the unique observation of point-based canopy structure data at each seedling. Quantitative approaches describing the relationship between canopy structure and seedling growth can inform silvicultural decision making regarding the development of tree reproduction beneath a dominant forest canopy. Individual-tree seedling growth models with canopy structure predictors derived from tree inventory data have not been well-explored. This study compared a model framework fit using point-based measures of canopy structure observed at the seedling level to one fit using area-wide canopy structure variables derived from standard inventory plot data. Species-specific models predicting 5-year height growth were fit for cherrybark oak (Quercus pagoda Raf.), water oak (Quercus nigra L.), and yellow-poplar (Liriodendron tulipifera L.) underplanted within a canopy structure gradient created by silvicultural manipulation of a closed-canopy forest in Georgia, USA. Though the species varied in shade tolerance and growth rates, the general relationship between the predictor variables and height growth was similar among species and model type. Models highlight the importance of including predictor variables that describe seedling size along with openness and vertical structure of the forest canopy. While the two model frameworks had comparable fit statistics, the one with predictors derived from tree inventory data may have enhanced utility as it can be directly integrated into existing individual-tree forest growth simulators.