James S. Rentch

Oak establishment and canopy accession strategies in five old-growth stands in the central hardwood forest region

Using a radial growth averaging technique, decadal-scale changes in growth rates of overstory oaks were used to identify canopy accession events at five old-growth sites. A review of tree-ring chronologies yielded three growth strategies: (1) one-half of the oaks originated in a large opening and achieved overstory status before canopy closure; (2) 38% originated in a smaller opening and required a second gap event to attain overstory status; and (3) 13% achieved overstory status after an extended period of very low growth in understory shade and one or two subsequent gap releases. For trees that required a major canopy release, understory residence times averaged 89, 54, 50 and 38 years for white oak, northern red oak, black oak, and chestnut oak, respectively. Average diameters (inside bark) at canopy accession were 13.3, 11.7, 10.0, and 6.2 cm for the four oak species, respectively. Although there is some historical precedence for these values, few contemporary second-growth forests contain understory oaks of this age, particularly red oak. These long understory residence times suggest that the level of understory shade, and by inference, the abundance of shade tolerant understory species, was considerably less before 1900.

A COMPARISON OF PLANT COMMUNITIES IN MITIGATION AND REFERENCE WETLANDS IN THE MID-APPALACHIANS

Wetland destruction has plagued the U.S. for decades, but the need to compensate for these losses has only been embraced within the last 20 years. Because so many compensatory mitigation wetlands have been created, there is a need to assess the function of these valuable ecosystems relative to natural wetlands. The goal of this study was to evaluate the functional equivalency of mitigation wetlands in West Virginia in supporting hydrophytic plant communities. A series of nested quadrats was used to compare plant community structure among eleven mitigation and four naturally occurring reference wetlands. For all species combined, mean total percent cover across all sampling quadrats per wetland was similar between mitigation and reference wetlands. Species richness, evenness, and diversity were greater in mitigation than in reference wetlands. Mean weighted averages of plant communities calculated using cover values and wetland indicator status were similar between mitigation and reference wetlands. There were, however, major differences in species composition. Mitigation sites tended to have more pioneer species, non-native dominants, and species with relatively lower conservation quality. Ordination analyses suggested that compositional differences become smaller as mitigation sites age. Both mitigation and natural wetlands met criteria for hydrophytic vegetation according to the 1987 U.S. Army Corps of Engineers Wetland Delineation Manual. These data suggest that the mitigation wetlands investigated in this study adequately support hydrophytic vegetation and appear to be developing vegetation similar to reference standards.

Aspect Induced Differences in Vegetation, Soil, and Microclimatic Characteristics of an Appalachian Watershed

Abstract This study evaluates and quantifies the variation in vegetation, plant nutrients, and microclimate across four topographic aspects in an Appalachian watershed (39°39′43′′N, 79°45′28′′W). The study found that the north and east aspects were 27–50% more productive than the west and southwest aspects. Species groups that showed strong aspect preference included yellow poplar (Liriodendron tulipifera), black cherry (Prunus serotina), chestnut oak (Quercus prinus), and white oak (Quercus alba); the former two being dominant on the north and east aspects while the latter two dominate the west and southwest aspects. Red oak (Quercus rubra) and red maple (Acer rubrum) showed mild aspect preference indicating their broad ecological amplitude. Although the north and east aspects had greater biomass, the west and southwest aspects had about 23% more stems per hectare. There were large differences in microclimate among the four aspects. Air temperature during midday period averaged 25.2°C, 24.9°C, 30.5°C, and 29.4°C for the north, east, west and southwest aspects respectively. The maximum temperature difference between the mesic (north and east aspects) and xeric (west and southwest aspects) sites was 5.55°C and was observed at noon. The relative humidity at the xeric site was about 25% lower than that at the mesic site during midday periods. Plant water stress as measured by vapor pressure difference was about 37% higher on west and southwest aspects than on north and east aspects. Plant nutrients only showed minor differences with concentrations being higher on the north and east aspects except for phosphorus, which was higher on the west and southwest aspects.

Aquatic plant community composition and distribution along an inundation gradient at two ecologically-distinct sites in the Pantanal region of Brazil

In spite of its size and biological significance, we know little about the ecology of the Pantanal, a 140,000 km2 floodplain in west-central Brazil. Increasing human pressures make this lack of understanding particularly critical. Using transects and 1 m2 circular plots, we documented floristic composition and interacting-environmental conditions associated with littoral herbaceous vegetation along inundation gradients at two ecologically-distinct sites in the Pantanal. We recorded water depth and percent cover for each species in Baía Piuval, a bay in the Bento Gomes River (Mato Grosso), and in a bay in the Acurizal Reserve (Mato Grosso do Sul). Baía Piuval and Acurizal plots contained a total of 22 and 18 macrophyte species, respectively. At both sites Eichhornia azurea and Salvinia auriculata occurred most frequently as dominant or co-dominant species. Chi2 analysis, used to quantify zonations along depth gradients, generated four different groups of species ( p < 0.05) for Baía Piuval. For Acurizal, two significantly different groups ( p < 0.05) occurred with an intermediate assemblage of species that could be assigned to either group. Canonical correspondence analysis, used to analyze species distributions, showed a pattern consistent with the Chi2 results for Baía Piuval but not for Acurizal. Higher species richness and diversity occurred where dry season and low water levels coincided and richness was generally highest in proximal plots where water depths were lowest. Our results are consistent with the few other plant ecological studies reported for the Pantanal. This study can be considered additive to needed baseline data on biota and ecology of this region of South America.

Properties of boundary-line release criteria in North American tree species.

Abstract• Boundary line release criteria are increasingly applied to evaluate forest disturbance histories from tree-ring data. However, a number of important properties central to the technique have not been evaluated, including: (i) the ability of boundary line release criteria to standardize releases across various sites, species, and tree life stages (ii) the minimum sample sizes necessary for developing boundary lines, and (iii) the degree to which the criteria can resolve the degree of crown exposure following a disturbance event.• In an analysis of eleven North American tree species, boundary line release criteria do not fully compensate for declines in release response a tree experiences with increasing age and size, with the exception Tsuga canadensis.• A bootstrapping analysis indicates that approximately 50 000 ring width measurements are necessary to develop boundary line release criteria for a given species.• In a Quercus prinus stand, boundary line release criteria better predict the degree of crown exposure following a disturbance than an earlier running mean technique.• Despite certain limitations, boundary line release criteria have the potential to standardize release calculation across most life stages of a tree, and possibly among sites and species.Résumé• Les lignes limites de dégagement sont des critères de plus en plus appliqués pour évaluer l’historique des perturbation des forêts à partir des données des cernes des arbres. Toutefois, un certain nombre de propriétés importantes au cœur de la technique n’ont pas été évaluées, y compris : (i) la capacité du critère de la ligne limite de dégagement pour standardiser les dégagements à travers différents sites, espèces et stades de la vie des arbres, (ii) la taille minimale des échantillons nécessaires pour le développement de lignes limites, et (iii) le degré avec lequel les critères peuvent résoudre le degré d’exposition de la couronne suite à un événement perturbant.• Dans une analyse de onze espèces d’arbres d’Amérique du Nord, les critères de ligne limite ne compensent pas entièrement la baisse de réponse au dégagement d’un arbre en relation avec l’âge et la dimension, à l’exception Tsuga canadensis.• Une analyse bootstrap indique que près de 50 000 mesures de largeur sont nécessaires pour développer des critères de ligne limite de dégagement pour une espèce donnée.• Dans un peuplement de Quercus prinus, les critères de ligne limite de dégagement permettent de mieux prédire le degré d’exposition de la couronne à la suite d’une perturbation que la technique de la moyenne courante.• En dépit de certaines limitations, les critères de ligne de limite de dégagement ont le potentiel de standardiser les calculs de dégagement dans la plupart des étapes de la vie d’un arbre et, éventuellement, entre les sites et les espèces.

Using maximum entropy modeling to identify and prioritize red spruce forest habitat in West Virginia

Red spruce forests in West Virginia are found in island-like distributions at high elevations and provide essential habitat for the endangered Cheat Mountain salamander and the recently delisted Virginia northern flying squirrel. Therefore, it is important to identify restoration priorities of red spruce forests. Maximum entropy modeling was used to identify areas of suitable red spruce habitat, with a total of 32 variables analyzed. Maximum temperature of the warmest month and minimum temperature of the coldest month were identified as variables explaining the most information about red spruce forest habitat. In addition, habitat maps identifying areas of high, medium, and low suitability were created and quantified at the county level. These results will benefit current and future conservation and restoration management activities as they identify core areas that possess the necessary environmental conditions for supporting future complex red spruce communities. Restoration efforts focused in areas possessing high suitability ensure peak potential of success and will ultimately give red spruce forests in West Virginia the greatest resilience to future climatic conditions by establishing connectivity between red spruce forests and increasing genetic diversity.

Release of Suppressed Red Spruce Using Canopy Gap Creation—Ecological Restoration in the Central Appalachians

ABSTRACT: Red spruce (Picea rubens) and red spruce-northern hardwood mixed stands once covered as much as 300,000 ha in the Central Appalachians, but now comprise no more than 21,000 ha. Recently, interest in restoration of this forest type has increased because red spruce forests provide habitat for a number of rare animal species. Our study reports the results of an understory red spruce release experiment in hardwood-dominated stands that have a small component of understory red spruce. In 2005, 188 target spruce were identified in sample plots at six locations in central West Virginia. We projected a vertical cylinder above the crown of all target spruces, and in 2007, we performed a release treatment whereby overtopping hardwoods were treated with herbicide using a stem injection technique. Release treatments removed 0–10% (Control), 11–50% (Low), 51–89% (Medium), and ≤90% (High) of the basal area of overtopping trees. We also took canopy photographs at the time of each remeasurement in 2007, 2010, and 2013, and compared basal removal treatments and resulting 2010 canopy openness and understory light values. The high treatment level provided significantly greater six-year dbh and height growth than the other treatment levels. Based on these results, we propose that a tree-centered release approach utilizing small canopy gaps that emulate the historical, gap-phase disturbance regime provides a good strategy for red spruce restoration in hardwood forests where overstory spruce are virtually absent, and where red spruce is largely relegated to the understory.

Rare Plant Communities in Canaan Valley, West Virginia

Abstract Canaan Valley (hereafter, the Valley) is a 34,600-ac (14,000-ha), high-elevation valley in the Central Appalachian Mountains of West Virginia. Its diverse wetland and upland habitats support a wide variety of plant communities, many of which are extremely rare. The prominence of rare communities is associated with the diversity of topographic settings, soils, geology, and hydrology, as well as the effects of human settlement and resource exploitation. Most of the rare plant communities are found in the wetlands of the Valleys floor. Virtually all of the communities associated with the Valleys extensive cold peatlands are rare, including (1) mixed conifer swamp-forests of Picea rubens (Red Spruce), Abies balsamea (Balsam Fir), and Tsuga canadensis (Eastern Hemlock), (2) mixed conifer-Fraxinus nigra (Black Ash) bog-forests in limestone-influenced wetlands in the central and southern parts of the Valley, and (3) extensive Sphagnum and Polytrichum bogs in the central and northern parts of Canaan Valley. Shrub communities such as Alnus incana ssp. rugosa (Speckled Alder), Viburnum recognitum (Smooth Arrowwood), and Salix discolor (Glaucous Willow) growing on mineral soils along waterways are also rare. Populus tremuloides (Trembling Aspen) groves, although abundant in the Valley, are extremely limited in the Appalachian region. Lastly, the grassand forb-dominated grass-bald communities on the surrounding mountain rims show an extremely limited distribution throughout the Central Appalachians.

Using Known Occurrences to Model Suitable Habitat for a Rare Forest Type in West Virginia Under Select Climate Change Scenarios

Many studies now identify the impacts of global climate change as a conservation threat to terrestrial ecosystems. In West Virginia, red spruce (Picea rubens) forests are a rare forest community of great ecological value, occurring in ‘island-like’ distributions among higher elevations. In this study, 168 red spruce presence localities and 24 environmental and sitespecific variables were used to model red spruce habitat using select climate change scenarios. Maximum entropy models were created for aggressive and conservative climate change scenarios, with each scenario model performed for three time periods (i.e., 2020, 2050, and 2080). Results for both model analyses identified three variables which contributed significantly to model performance: mean temperature of the coldest quarter of the year, elevation, and minimum temperature of the coldest month of the year. Changes in suitable habitat area were also assessed for both model scenarios at each time period examined. Approximately 6.2% of the land area in West Virginia was modeled under current habitat conditions as suitable red spruce habitat. However, by the time period 2020, a loss of 78% and 52% was identified for the aggressive and conservative climate change models, respectively. By the time period 2080, no suitable red spruce habitat was modeled using the aggressive climate change scenario with an 85% reduction in current modeled habitat identified using the conservative model. These findings indicate the potential impacts of climate change on red spruce forest habitat in West Virginia and provide valuable guidance for future restoration efforts by identifying areas most likely to succeed under altered climatic conditions.

Using two classification schemes to develop vegetation indices of biological integrity for wetlands in West Virginia, USA

Bioassessment methods for wetlands, and other bodies of water, have been developed worldwide to measure and quantify changes in “biological integrity.” These assessments are based on a classification system, meant to ensure appropriate comparisons between wetland types. Using a local site-specific disturbance gradient, we built vegetation indices of biological integrity (Veg-IBIs) based on two commonly used wetland classification systems in the USA: One based on vegetative structure and the other based on a wetland’s position in a landscape and sources of water. The resulting class-specific Veg-IBIs were comprised of 1–5 metrics that varied in their sensitivity to the disturbance gradient (R2 = 0.14 − 0.65). Moreover, the sensitivity to the disturbance gradient increased as metrics from each of the two classification schemes were combined (added). Using this information to monitor natural and created wetlands will help natural resource managers track changes in biological integrity of wetlands in response to anthropogenic disturbance and allows the use of vegetative communities to set ecological performance standards for mitigation banks.