John D. Shaw

Tree mortality from drought, insects, and their interactions in a changing climate

Climate change is expected to drive increased tree mortality through drought, heat stress, and insect attacks, with manifold impacts on forest ecosystems. Yet, climate-induced tree mortality and biotic disturbance agents are largely absent from process-based ecosystem models. Using data sets from the western USA and associated studies, we present a framework for determining the relative contribution of drought stress, insect attack, and their interactions, which is critical for modeling mortality in future climates. We outline a simple approach that identifies the mechanisms associated with two guilds of insects - bark beetles and defoliators - which are responsible for substantial tree mortality. We then discuss cross-biome patterns of insect-driven tree mortality and draw upon available evidence contrasting the prevalence of insect outbreaks in temperate and tropical regions. We conclude with an overview of tools and promising avenues to address major challenges. Ultimately, a multitrophic approach that captures tree physiology, insect populations, and tree-insect interactions will better inform projections of forest ecosystem responses to climate change.

Global patterns of drought recovery.

Drought, a recurring phenomenon with major impacts on both human and natural systems, is the most widespread climatic extreme that negatively affects the land carbon sink. Although twentieth-century trends in drought regimes are ambiguous, across many regions more frequent and severe droughts are expected in the twenty-first century. Recovery time—how long an ecosystem requires to revert to its pre-drought functional state—is a critical metric of drought impact. Yet the factors influencing drought recovery and its spatiotemporal patterns at the global scale are largely unknown. Here we analyse three independent datasets of gross primary productivity and show that, across diverse ecosystems, drought recovery times are strongly associated with climate and carbon cycle dynamics, with biodiversity and CO2 fertilization as secondary factors. Our analysis also provides two key insights into the spatiotemporal patterns of drought recovery time: first, that recovery is longest in the tropics and high northern latitudes (both vulnerable areas of Earth’s climate system) and second, that drought impacts (assessed using the area of ecosystems actively recovering and time to recovery) have increased over the twentieth century. If droughts become more frequent, as expected, the time between droughts may become shorter than drought recovery time, leading to permanently damaged ecosystems and widespread degradation of the land carbon sink.

Widespread Triploidy in Western North American Aspen (Populus tremuloides)

We document high rates of triploidy in aspen (Populus tremuloides) across the western USA (up to 69% of genets), and ask whether the incidence of triploidy across the species range corresponds with latitude, glacial history (as has been documented in other species), climate, or regional variance in clone size. Using a combination of microsatellite genotyping, flow cytometry, and cytology, we demonstrate that triploidy is highest in unglaciated, drought-prone regions of North America, where the largest clone sizes have been reported for this species. While we cannot completely rule out a low incidence of undetected aneuploidy, tetraploidy or duplicated loci, our evidence suggests that these phenomena are unlikely to be significant contributors to our observed patterns. We suggest that the distribution of triploid aspen is due to a positive synergy between triploidy and ecological factors driving clonality. Although triploids are expected to have low fertility, they are hypothesized to be an evolutionary link to sexual tetraploidy. Thus, interactions between clonality and polyploidy may be a broadly important component of geographic speciation patterns in perennial plants. Further, cytotypes are expected to show physiological and structural differences which may influence susceptibility to ecological factors such as drought, and we suggest that cytotype may be a significant and previously overlooked factor in recent patterns of high aspen mortality in the southwestern portion of the species range. Finally, triploidy should be carefully considered as a source of variance in genomic and ecological studies of aspen, particularly in western U.S. landscapes.

Feasibility of High-Density Climate Reconstruction Based on Forest Inventory and Analysis (FIA) Collected Tree-Ring Data

AbstractThis study introduces a novel tree-ring dataset, with unparalleled spatial density, for use as a climate proxy. Ancillary Douglas fir and pinon pine tree-ring data collected by the U.S. Forest Service Forest Inventory and Analysis Program (FIA data) were subjected to a series of tests to determine their feasibility as climate proxies. First, temporal coherence between the FIA data and previously published tree-ring chronologies was found to be significant. Second, spatial and temporal coherence between the FIA data and water year precipitation was strong. Third, the FIA data captured the El Nino–Southern Oscillation dipole and revealed considerable latitudinal fluctuation over the past three centuries. Finally, the FIA data confirmed the quadrature-phase coupling between wet/dry cycles and Pacific decadal variability known to exist for the Intermountain West. The results highlight the possibility of further developing high-spatial-resolution climate proxy datasets for the western United States. (T...

Examining dog owners’ beliefs regarding rabies vaccination during government-funded vaccine clinics in Grenada to improve vaccine coverage rates

Vaccination of domestic pets is an important component of rabies control and prevention in countries where the disease is maintained in a wildlife reservoir. In Grenada, vaccine coverage rates were low, despite extensive public education and advertising of government-sponsored vaccine clinics where rabies vaccine is administered to animals at no cost to animal owners. Information was needed on reasons for decreased dog owner participation in government-funded rabies vaccination clinics. A total of 120 dog owners from 6 different parishes were asked to complete a questionnaire assessing their currently held beliefs about rabies vaccination and perception of the risk posed by rabies. Over 70% of respondents believed that problems in the organization and management of clinic sites could allow for fighting between dogs or disease spread among dogs, while 35% of owners did not believe that they had the ability or adequate help to bring their dogs to the clinic sites. Recommendations for improving vaccine coverage rates included: improved scheduling of clinic sites and dates; increased biosecurity at clinic locations; focused advertising on the availability of home visits, particularly for aggressive dogs or dogs with visible skin-related diseases such as mange; and the recruitment of community volunteers to assist with bringing dogs to the clinic sites.

Forest Ecology and Biogeography of the Uinta Mountains, U.S.A

ABSTRACT The Uinta Mountains form a crossroads of forests and woodlands in the central Rocky Mountains. Although no tree species is endemic to the area, all species characteristic of the central Rocky Mountains are found there, and the ranges of several other species terminate in the Uinta Mountains and the surrounding area. The peninsula-like shape, east-west orientation, and complex terrain of the range create a wide variety of potential forest sites that contrast with other ranges in the central Rockies. As a result, the Uinta Mountains are home to sites of unexpectedly high tree species diversity. Throughout most of the range, vegetation is organized in predictable zones that are characteristic of the Intermountain West; the range exhibits excellent vegetation zonation. However, across much of the northern slope several important species are absent, resulting in unexpectedly low diversity and “missing” vegetation zones. In this paper we provide an overview of the forest ecology and biogeography of the Uinta Mountains and update the local model for vegetation zonation. We also consider some possible explanations for the unexpected vegetation patterns and identify opportunities for future research.

A density management diagram for Norway spruce in the temperate European montane region

Norway spruce is one of the most important conifer tree species in Europe, paramount for timber provision, habitat, recreation, and protection of mountain roads and settlements from natural hazards. Although natural Norway spruce forests exhibit diverse structures, even-aged stands can arise after disturbance or as the result of common silvicultural practice, including off-site afforestation. Many even-aged Norway spruce forests face issues such as senescence, insufficient regeneration, mechanical stability, sensitivity to biotic disturbances, and restoration. We propose the use of Density Management Diagrams (DMD), stand-scale graphical models designed to project growth and yield of even-aged forests, as a heuristic tool for assessing the structure and development of even-aged Norway spruce stands. DMDs are predicated on basic tree allometry and the assumption that self-thinning occurs predictably in forest stands. We designed a DMD for Norway spruce in temperate Europe based on wide-ranging forest inventory data. Quantitative relationships between tree- and stand-level variables that describe resistance to selected natural disturbances were superimposed on the DMD. These susceptibility zones were used to demonstrate assessment and possible management actions related to, for example, windfirmness and effectiveness of the protective function against rockfall or avalanches. The Norway spruce DMD provides forest managers and silviculturists a simple, easy-to-use, tool for evaluating stand dynamics and scheduling needed density management actions.

Prevalence of and examination of exposure factors for Salmonella on commercial egg-laying farms in Barbados

During January-March 2009, an outbreak of Salmonella was diagnosed in four commercial egg-laying farms in Barbados. During the outbreak, 511 layers died while 3257 layers were voluntarily culled from one affected farm. Salmonella ser Enteritidis was identified in avian tissues (ovaries, liver, and uterus), and egg samples submitted to the Ministry of Agriculture, Food, Fisheries, and Water Resource Management (MAFFW) Veterinary Services (VS) Laboratory by managers of the affected farms. As a result of this outbreak, MAFFW VS conducted a survey to investigate the prevalence of Salmonella on commercial egg-laying farms in Barbados. In addition, the relationships between farm-level exposure factors and diagnosis of Salmonella were examined. This paper describes the results of this survey. Nineteen of 26 farms (73%; 95% CI=56-90%) were classified as positive for Salmonella. The odds of testing positive for Salmonella were 10 times higher in large farms, compared to small farms (OR=10.80; 95% CI=1.01, 115.10; p=0.04). More small farms (8/11) cleaned and disinfected poultry facilities quarterly or more often than large farms did (1/10) (p<0.01). Prevalence of Salmonella in commercial egg-laying farms in Barbados is high. Salmonella ser Enteritidis was the most common serotype identified in study farms, and this is a public health issue of concern. This is the first prevalence survey of Salmonella in egg-laying farms in Barbados. Study results can be used as a baseline for future control programmes aimed at reducing the prevalence of Salmonella in egg-laying farms in the country.

Interaction between research and diagnosis and surveillance of avian influenza within the Caribbean animal health network (CaribVET).

The Caribbean region is considered to be at risk for avian influenza (AI) because of predominance of the backyard poultry system, important commercial poultry production, migratory birds and disparities in the surveillance systems. The Caribbean animal health network (CaribVET) has developed tools to implement AI surveillance in the region: (i) a regionally harmonized surveillance protocol, (ii) specific web pages for AI surveillance on http://www.caribvet.net, and (iii) a diagnostic network for the Caribbean including AI virus molecular diagnostic capability in Guadeloupe and technology transfer. Altogether 303 samples from four Caribbean countries were tested between June 2006 and March 2009 by real time PCR either for importation purposes or following clinical suspicion. Following AI H5N2 outbreaks in the Dominican Republic in 2007, a questionnaire was developed to collect data for risk analysis of AI spread in the region through fighting cocks. The infection pathway of Martinique commercial poultry sector by AI through introduction of infected cocks was designed and recommendations were provided to the Caribbean veterinary services to improve fighting cock movement controls and biosecurity measures. Altogether, these CaribVET activities contribute to strengthen surveillance of AI in the Caribbean region and may allow the development of research studies on AI risk analysis.

New Mexico's forest resources, 2008-2012

This report presents a summary of the most recent inventory of New Mexico’s forests based on field data collected between 2008 and 2012. The report includes descriptive highlights and tables of area, numbers of trees, biomass, volume, growth, mortality, and removals. Most sections and tables are organized by forest type or forest type group, species group, diameter class, or owner group. The report also describes the inventory’s design, inventory terminology, and data reliability. Results show that New Mexico’s forest land covers 24.8 million acres. Forty-four percent (10.8 million acres) of this forest land is privately owned, and another 31 percent (7.8 million acres) is administered by the USDA Forest Service. The State’s most abundant forest type is pinyon/juniper woodland, which covers more than 10 million acres. Pinyon/juniper woodlands, combined with pure juniper woodland, cover a total of 13.6 million acres, or more than half of New Mexico’s forest land area. Gambel oak is the most abundant tree species by number of trees, and ponderosa pine is the most abundant by volume or biomass. New Mexico’s forests contain 17.5 billion cubic feet of net volume in trees 5.0 inches diameter and larger. Gross growth of all live trees 5.0 inches diameter and larger averaged 211.5 million cubic feet per year. Average annual mortality totaled 165.1 million cubic feet per year, and net growth was 46.4 million cubic feet per year, or 0.26 percent of the State’s total wood volume.