Treesearch

Rates of nitrogen (N) deposition are increasing in industrialized and rapidly developing nations. Simulated N deposition suppresses plant litter decay rates, in particular for low quality (high lignin) litter. Litter quality is a primary driver of litter decomposition; however, it is not clear how changes in litter quality caused by long-term ecosystem exposure to chronic N additions interact with altered soil N-availability to influence litter decay dynamics. To document the effects of simulated N deposition on litter quality, we conducted a meta-analysis of available litter nutrient data...

Iran is reported to be a center of diversity for Juglans regia and wild walnut trees are found in virtually every corner of the country. Thus Iran is considered a rich natural pool of walnut germplasm for developing improved genotypes. Kerman province is the most important Iranian province for walnut culture and has the largest walnut plantations in Iran. Genetic structure and gene flow were analyzed in six walnut populations of this province using 17 microsatellite loci. The number of alleles per locus ranged from 4 to 11, with a total of 147 alleles and 5.16 effective alleles per locus....

Atmospheric deposition of sulfur (S) and nitrogen (N) has decreased steadily in the northeastern U.S. since the federal 1970 Clean Air Act was passed, yet deposition remains elevated above natural background levels throughout the region. Epiphytic macrolichens are highly sensitive to air pollution and their status is a good indicator of ecological health. We used deposition modeling for 2000–2013 and multiple metrics of lichen status (i.e., species composition, species richness, thallus condition, lichen sensitivity indices, lichen elemental analysis) to assess air pollution effects at 24...

Field studies were conducted to determine levels of gill aluminium as an index of acidification effects on migrating Atlantic salmon Salmo salar smolts in the north-eastern U.S.A. along mainstem river migration corridors in several major river basins. Smolts emigrating from the Connecticut River, where most (but not all) tributaries were well buffered, had low or undetectable levels of gill aluminium and high gill Na+/K+-ATPase (NKA) activity. In contrast, smolts emigrating from the upper Merrimack River basin where most tributaries are characterized by low pH and high inorganic aluminium...

Climate change is predicted to change the distribution and abundance of species, yet underlying physiological mechanisms are complex and methods for detecting populations at risk from rising temperature are poorly developed. There is increasing interest in using physiological mediators of the stress response as indicators of individual and population-level response to environmental stressors. Here, we use laboratory experiments to show that the temperature thresholds in brook trout (Salvelinus fontinalis) for increased gill heat shock protein-70 (20.7°C) and plasma glucose (21.2°C) are...

Although recent U.S. Supreme Court rulings indicate surface hydrologic connectivity (SHC) between geographically isolated wetlands and nearby streams may be used, in part, to determine wetland jurisdictional status, and ecologic implications are considerable regardless of policies, wetland–stream SHC has rarely been quantified. Furthermore, the impact of cultivation and restoration on wetland–stream SHC is largely unknown. To help fill these knowledge gaps, we recorded SHC patterns during water year 2010 in nonperennial streams connecting Delmarva bay wetlands, which are commonly considered...

Los moluscos terrestres son un grupo altamente diverso cuyo trabajo investigativo en Nicaragua ha sido mayoritariamente en la vertiente del Pacífico de Nicaragua. Evaluar el potencial de estas especies como indicadores de la perdida de la masa boscosa así como de su recuperación ayudará el impacto de las actividades humanas en esta biota de escasa movilidad. La colectas de conchas y especímenes fué realizada en bosques húmedos, nubosos y secos en los departamentos de Rivas y Jinotega en hábitats específicos dentro de la matrix del paisaje. Las identificaciones a posteriori fueron hechas...

The present study describes natural regeneration on five permanent research plots (PRP) in juvenile growth and development phases (regrowth and advanced growth) in autochthonous beech forests in Broumovské stěny National Nature Reserve located in the Protected Landscape area in the northeast part of Czech Republic. The stands of herb-rich beech forests were studied in the optimum to break-up stage. Natural regeneration was not evenly spaced but rather was clustered. Mean regeneration density ranged from 1,472 to 44,888 recruits per ha. European beech (Fagus sylvatica L.) made up 78.5–98.0%...

Crested wheatgrass (Agropyron cristatum [L] Gaertm) has been seeded on more than 5 million hectares in western North America because it establishes more readily than native bunchgrasses. Currently, there is substantial interest in reestablishing native species in sagebrush steppe, but efforts to reintroduce native grasses into crested wheatgrass stands have been largely unsuccessful, and little is known about the long-term dynamics of crested wheatgrass/native species mixes. We examined the abundance of crested wheatgrass and seven native sagebrush steppe bunchgrasses planted concurrently...

The loss of big sagebrush (Artemisia tridentata Nutt.) on sites disturbed by fire has motivated restoration seeding and planting efforts. However, the resulting sagebrush establishment is often lower than desired, especially in dry areas. Sagebrush establishment may be increased by addressing factors such as seed source and condition or management of the plant community. We assessed initial establishment of seeded sagebrush and four populations of small outplants (from different geographies, climates, and cytotypes) and small sagebrush outplants in an early seral communitywhere mowing,...