Wetland seed dispersal by white-tailed deer in a large freshwater wetland complex

Mechanisms of long-distance dispersal are important in establishing and maintaining plant populations in isolated wetland habitats. White-tailed deer (Odocoileus virginianus) have been cited as long-distance dispersers of both native and exotic plant species in North America; however, knowledge regarding their influence in wetlands is limited. Given traditional classification methods for seed dispersal, white-tailed deer are not likely viewed as important dispersal mechanism for wetland plants. We collected naturally deposited white-tailed deer faecal pellet piles from wetlands in Canaan Valley, West Virginia, USA. Pellet piles were cold-stratified and germinated seedlings over a layer of sterile potting mix. The percentage of germinated seedlings with a facultative wetland (FACW) or obligate wetland (OBL) plant indicator status were compared to the frequency of occurrence to those of germinated plants with facultative upland (FACU) or upland (UPL) indicator status. We identified 38 species. Of these, 1 % were UPL, 38 % were FACU, 18 % were FACW and 21 % were OBL. Graminoid species accounted for 42 %; forbs and woody species accounted for 29 % each. Our research has suggested that endozoochory by herbivores contributes to long-distance dispersal of wetland plants

Large-Scale Forest Inventories Of The United States And China Reveal Positive Effects Of Biodiversity On Productivity

Background With the loss of species worldwide due to anthropogenic factors, especially in forested ecosystems, it has become more urgent than ever to understand the biodiversity-ecosystem functioning relationship (BEFR). BEFR research in forested ecosystems is very limited and thus studies that incorporate greater geographic coverage and structural complexity are needed. Methods We compiled ground-measured data from approx. one half million forest inventory sample plots across the contiguous United States, Alaska, and northeastern China to map tree species richness, forest stocking, and productivity at a continental scale. Based on these data, we investigated the relationship between forest productivity and tree species diversity, using a multiple regression analysis and a non-parametric approach to account for spatial autocorrelation. Results In general, forests in the eastern United States consisted of more tree species than any other regions in the country. The highest forest stocking values over the entire study area were concentrated in the western United States and Central Appalachia. Overall, 96.4 % of sample plots (477,281) showed a significant positive effect of species richness on site productivity, and only 3.6 % (17,349) had an insignificant or negative effect. Conclusions The large number of ground-measured plots, as well as the magnitude of geographic scale, rendered overwhelming evidence in support of a positive BEFR. This empirical evidence provides insights to forest management and biological conservation across different types of forested ecosystems. Forest timber productivity may be impaired by the loss of species in forests, and biological conservation, due to its potential benefits on maintaining species richness and productivity, can have profound impacts on the functioning and services of forested ecosystems

Tree Fall Gap Characteristics within an Appalachian Hardwood Forest in West Virginia

We examined the attributes of canopy gaps on the 3,100 ha West Virginia University Research Forest (WVURF) near Morgantown, WV. The WVURF is a 70-80 year-old, second-growth, Appalachian hardwood forest. The objectives of this study were: 1) to describe specific gap characteristics (size, age, and fraction) of the forest as a whole, and 2) to assess whether gap characteristics varied by slope position (cove, mid, ridge), aspect (NE, NW, SE, SW), and forest cover type (cove hardwood, mesic oak, xeric oak). Transect lines were digitized using GIS in ArcMap and systematically placed throughout the forest to include a range of aspects and slope positions. Sixty transects were established, with a total length of 22,508 m. Line intersect sampling was used to select gaps. Eighty gaps were identified. The average gap size was 98.59 (+134.17) m². The average expanded gap size was 287.64 (+ 238.49) m². Gap age ranged from 2-29 years old with a mean age of 16.42 (+6.3) years. Overall, 2.73 (+2.48) % of the forest was composed of gaps. These figures are small compared to old growth forests in the region. WVURF is a young forest, therefore the gaps created are relatively small and scattered. We speculate the WVURF remains in the late stem exclusion to early understory re-initiation stage. There were no differences in gap size by aspect or slope position. Cove hardwoods had larger gap sizes than mesic and xeric oak. There were no differences in gap age based on slope position, aspect, or forest type. Gap fraction did not differ by slope position, but gap fraction was greatest on northwest slopes and in cove hardwoods. Gap fraction showed a significant interaction between aspect and position

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

• 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.Propriétés des critères des lignes limites de dégagement chez les arbres Nord Américains. • 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