Treesearch

Ecosystem-based forest management requires long planning horizons to incorporate forest dynamics - changes resulting from vegetation growth and succession and the periodic resetting of these by natural and anthropogenic disturbances such as fire, wind, insects, and timber harvests. Given these dynamics, ecosystem-based forest management plans should specify desired conditions such as tree species composition, age class, tree density and structure, size and density of snags and course woody debris, and the size, shape, and juxtaposition of trees, groups of trees, and stands in order to...

Studies on the relationship between rhododendron and Phytophthora ramorum include the influence of wounds on leaf infection and on the development of leaf necrosis (De Dobbelaere et al. 2010; Denman et al. 2005), the influence of the inoculum type (Widmer 2009), and tissue colonization by P. ramorum (Brown and Brasier 2007; Parke and Lewis 2007; Pogoda and Werres 2004). There are only a few studies on the development of the pathogen on the leaf surface (Moralejo and Descals 2011; Moralejo et al. 2006) and there is no information on the infection process on leaves. Therefore the aim of the...

Recent population declines have prompted the International Union for the Conservation of Nature to list Cerulean Warbler (Setophaga cerulea: Parulidae) as a Vulnerable species. It is believed that this decline may be related to habitat loss through its entire range, mainly due to deforestation and degradation of its habitats. In response, members of El Grupo Cerúleo, a subcommittee of the Cerulean Warbler Technical Group that addresses wintering ground issues faced by the species, developed a predictive model of wintering habitat for Cerulean Warblers throughout the northern and central...

The breeding range of the Cerulean Warbler has expanded into second-growth forest and converted agricultural land in the northeastern United States where, according to the North American Breeding Bird Survey, the population is increasing. Despite this expansion in one part of its range, the population as a whole is still in rapid decline implying that habitat quality supersedes habitat expansion in importance. The Delaware Water Gap National Recreation Area (DEWA) in New Jersey and Pennsylvania, USA, is representative of recently occupied northeastern habitat. We found Cerulean Warblers...

This paper explores opportunities for administrative discretion in decision-making for natural resource management. We carried out an exploratory study in the USDA Forest Service to understand factors affecting administrative actions related to recreation use in riparian areas. We conducted semi-structured interviews with 27 resource professionals from a national forest in the northwest region of the United States. Questions focused on professional judgments about recreation in riparian areas, administrative actions related to management of these activities, and the potential for personal...

Physiological adjustments to enhance tolerance or avoidance of summer drought and winter freezing were studied in shallow- to deep-rooted Patagonian cold desert shrubs. We measured leaf water potential, osmotic potential, tissue elasticity, stem hydraulic characteristics, and stomatal conductance across species throughout the year, and assessed tissue damage by subzero temperatures during winter.

The amber-marked birch leafminer has caused severe infestations of birch species in Anchorage, AK, since 2002. Its spatial distribution has been monitored since 2006 and summarized using interpolated surfaces based on simple kriging. In this study, we developed methods of assessing and describing spatial distribution of the leafminer as they vary from year to year, and speculate on potential causes of these trends in landscape patterns.

Juniper (Juniperus spp.) encroachment into sagebrush (Artemisia spp.) and bunchgrass communities has reduced understory plant cover and allowed juniper trees to dominate millions of hectares of semiarid rangelands. Trees are mechanically masticated or shredded to decrease wildfire potential and increase desirable understory plant cover. When trees are masticated after a major increase in tree population density and associated decrease in perennial understory cover, there is a risk that invasive annual grasses will dominate because they are highly responsive to the increased resource...

Ethyl acetate extracts of Armillaria tabescens (strain JNB-OZ344) showed significant fungistatic and bacteristatic activities against several major human pathogens including Candida albicans, Cryptococcus neoformans, Escherichia coli and Mycobacterium intracellulare. Chemical analysis of these extracts led to the isolation and identification of four new compounds, emestrin-F (1), emestrin-G (2), 6-O-(4-O-methyl--D-glucopyranosyl)-8-hydroxy-2,7-dimethyl-4H-benzopyran- 4-one (3) and cephalosporolide-J (4), along with five other previously known compounds, emestrin (5), cephalosporolide-E...

There is increasing interest in actively managing forests to increase their resilience to climate-related changes. Although forest managers rely heavily on the use of silvicultural treatments that manipulate stand structure and stand dynamics to modify responses to climate change, few studies have directly assessed the effects of stand structure or canopy position on climate-growth relationships, or examined how this relationship may vary among species or across environmental gradients. In this study, we analyzed variability in tree-ring series from 15 low-elevation stands in northeastern...