SummaryHemlock woolly adelgid (HWA) is an exotic insect pest causing severe decimation of native hemlock trees. Extensive research has been conducted on the ecological impacts of HWA, but the exact physiological mechanisms that cause mortality are not known.Water relations, anatomy and gas exchange measurements were assessed on healthy and infested eastern (Tsuga canadensis) and Carolina (Tsuga caroliniana) hemlock trees. These data were then used in a mechanistic model to test whether the physiological responses to HWA infestation were sufficiently significant to induce changes in whole-plant water use and carbon uptake.The results indicated coordinated responses of functional traits governing water relations in infested relative to healthy trees. In response to HWA, leaf water potential, carbon isotope ratios, plant hydraulic properties and stomatal conductance were affected, inducing a reduction in tree water use by > 40% and gross primary productivity by 25%. Anatomical changes also appeared, including the activation of traumatic cells.HWA infestation had a direct effect on plant water relations. Despite some leaf compensatory mechanisms, such as an increase in leaf hydraulic conductance and nitrogen content, tree water use and carbon assimilation were diminished significantly in infested trees, which could contribute to tree mortality.
A study of the diversity and density of ectomycorrhizal (EM) fungi in two Fraser fir stands near Clingmans Dome, Great Smoky Mountains National Park was conducted over a period of three years. Plots were established in three naturally occurring age class treatments including mature tree, sapling, and low regeneration (no trees) sites. Lesser vegetation data were determined for nine plant species within all plots including two ferns and two grasses that impeded survival of Fraser fir seedlings. Diversity and densities of vegetation were significantly greater in low regeneration plots as compared to other treatments. For each plot bryophyte mat forest floor percent occurrence/cover was obtained and percent root colonization/sclerotia of the EM fungus taxa were collected from the three management treatments including 11 decomposers and 33 ectomycorrhizal species. Clavulina cristata occurred in 22.5% of all plots and had a frequency of 1.7% in low regeneration treatments. Four species of Laccaria occurred in Fungi 9(1): 1-21 17.3% of all plots, and Laccaria laccata and L. laccata var. pallidifolia were the most common of these species, the former having the highest frequency of occurrence (1.9%) in low regeneration treatments. Four species of Cortinarius occurred in 10.3% of the plots, and Cortinarius anomalus s.l., the most common Cortinarius, occurred in 4.4% of all plots. Seven of the 44 species had significantly greater percent frequency among the three treatments, and six of those were the most frequent in sapling plot treatments at the two locations. Species found at the two locations were similar, although in 2009 their frequency values were greater than in 2010 and 2011 due to greater total precipitation. Mature and sapling plot frequency values were significantly greater than those for low regeneration sites due to the low establishment of Fraser fir. Significant results for species richness, diversity and evenness between years, locations and treatments are present below. Based on percent frequency values, Laccaria could be used in reforestation of Fraser firs in all plots. A project is underway to evaluate seedling establishment and survival following inoculation with Laccaria spp. on a low regeneration site at Mount Buckley.2 Baird et al. Diversity and density of EM Fungi in high elevation Fraser fir. North American
Optimal deployment of improved loblolly pine (Pinus taeda L.) planting stock in the southeastern United States requires knowing how diverse seed sources and families perform over time across the wide range of sites used for plantations. This study tests if the relative growth performance of provenances and families is the same at the individual-tree and stand levels for family block plantings and determines what type of adjustment may be required to account for genetic differences when modeling growth and yield. Ten open-pollinated families from two very different provenances, Atlantic Coastal Plain and "Lost Pines" Texas, were grown in single-family block plots to test for growth differences between provenances and among families under severely deficient and optimal nutrition regimes on a nutrient-deficient, dry site. The three-parameter Chapman-Richards function was fit to plot means over time by provenance, family, and nutrition treatments. Models with provenance-or family-specific parameters of the Chapman-Richards function were tested for significant improvement over global parameters. At age 14 years, family, provenance, and nutrition treatments all significantly affected individual-tree growth traits of height, diameter, and volume. Significant nutrition by provenance interactions were found for stand-level traits of basal area per hectare and volume per hectare. Family differences were also significant for these traits. Provenance-or family-specific asymptotic parameters accounted for differences in growth over time. Several traits required the use of local asymptotic and rate parameters in the fertilized treatment only. For modeling growth, a multiplier would be sufficient to account for genetic effects on the majority of traits.Résumé : Le déploiement optimal des plants améliorés de pin à encens (Pinus taeda L.) dans le sud-est des États-Unis demande des connaissances sur le rendement des plantations dans le temps en fonction de l'origine des graines et des familles pour toute la gamme de stations utilisées. Cette étude vérifie la similitude de croissance relative entre les provenances et les familles aux échelles de l'arbre et du peuplement pour des familles plantées en bloc. On veut aussi vérifier quel type d'ajustement peut être nécessaire pour tenir compte des différences génétiques lors de la modélisation de la croissance et du rendement. Dix familles à pollinisation libre de deux provenances très différentes, la plaine côtière de l'Atlantique et « Lost Pines » au Texas, ont été plantées dans des parcelles composées de blocs à famille unique pour vérifier les différences de croissance entre les provenances et les familles sous des régimes nutritifs optimal et fortement carencé sur une station sèche et pauvre en nutriments. La fonction de Chapman-Richards à trois paramètres a été ajustée aux moyennes des parcelles en fonction du temps, de la provenance, de la famille et du traitement nutritionnel. Nous avons testé si les modèles avec des paramètres de Chapman-Richards spécifiques à la provenance ou ...
Size-density trajectories and self-thinning boundary lines were modeled for two diverse provenances of Pinus taeda L. and five open-pollinated families within each provenance. The data used come from a single site with replicated 64-tree block plots measured through age 25 years. The effects of provenance and family were tested using linear and nonlinear mixed-effects self-thinning models. The drought-hardy Lost Pines of Texas provenance displayed a greater predicted carrying capacity (almost 200 more trees per hectare at reference diameter 25.4 cm) and had a more abrupt approach to the self-thinning line than the widely planted Atlantic Coastal Plain provenance. However, the growth rate of the Lost Pines of Texas provenance was considerably slower and stem form was unacceptable for timber production. Families from the Atlantic Coastal Plain differed in their maximum stand density index predictions (from 1,118 to 1,282 trees per hectare at the reference diameter), suggesting there is an opportunity for artificial selection to change maximum stand density index in this breeding population of loblolly pine. A novel method for predicting the self-thinning boundary line using random effects inherent to the experimental design is presented and recommended for repeated measures data. Experimental design considerations for evaluating genetic differences in self-thinning are discussed. Study Implications Genetic improvement of growth rate in forest trees has resulted in large gains in plantation productivity, but the effect on carrying capacity has not been addressed. This study indicated that artificial selection on tolerance to competition in the widely planted Atlantic Coastal Plain provenance of loblolly pine can potentially increase harvest yield without sacrificing growth rate. The drought-hardy Lost Pines of Texas provenance displayed greater carrying capacity but had poor stem form and slow growth. The Lost Pines provenance may be attractive for aboveground carbon sequestration, since it sustained substantially more biomass because of greater maximum stand density and denser wood.
The present paper describes a methodology for evaluating impacts of Superfund remedial alternatives on the regional economy in the context of a broader sustainability evaluation. Although economic impact methodology is well established, some applications to Superfund remedial evaluation have created confusion because of seemingly contradictory results. This confusion arises from failure to be explicit about 2 opposing impacts of remediation expenditures: 1) positive regional impacts of spending additional money in the region and 2) negative regional impacts of the need to pay for the expenditures (and thus forgo other expenditures in the region). The present paper provides a template for economic impact assessment that takes both positive and negative impacts into account, thus providing comprehensive estimates of net impacts. The paper also provides a strategy for identifying and estimating major uncertainties in the net impacts. The recommended methodology was applied at the Portland Harbor Superfund Site, located along the Lower Willamette River in Portland, Oregon, USA. The US Environmental Protection Agency (USEPA) developed remedial alternatives that it estimated would cost up to several billion dollars, with construction durations possibly lasting decades. The economic study estimated regional economic impacts-measured in terms of gross regional product (GRP), personal income, population, and employment-for 5 of the USEPA alternatives relative to the "no further action" alternative. Integr Environ Assess Manag 2018;14:32-42. © 2017 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC).
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