Research Database
Displaying 1 - 20 of 27
Climatic, Landform, Microtopographic, and Overstory Canopy Controls of Tree Invasion in a Subalpine Meadow Landscape, Oregon Cascades, USA
Year: 2012
Tree invasions have been documented throughout Northern Hemisphere high elevation meadows, as well as globally in many grass and forb-dominated ecosystems. Tree invasions are often associated with large-scale changes in climate or disturbance regimes, but are fundamentally driven by regeneration processes influenced by interactions between climatic, topographic, and biotic factors at multiple spatial scales. The purpose of this research was to quantify spatiotemporal patterns of meadow invasion; and how climate, larger landforms, topography, and overstory trees have interactively influenced…
Publication Type: Journal Article
Spatio-temporal prediction of site index based on forest inventories and climate change scenarios
Year: 2012
A methodological framework is provided for the quantification of climate change effects on site index. Spatio-temporal predictions of site index are derived for six major tree species in the German state of Baden-Württemberg using simplified universal kriging (UK) based on large data sets from forest inventories and a climate sensitive site-index model. It is shown by a simulation study that, with the underlying large sample size, residual kriging using ordinary least squares (OLS) estimates of the mean function leads to an approximately unbiased spatial predictor. Moreover, the simulated…
Publication Type: Journal Article
Delayed Phenology and Reduced Fitness Associated with Climate Change in a Wild Hibernator
Year: 2012
The most commonly reported ecological effects of climate change are shifts in phenologies, in particular of warmer spring temperatures leading to earlier timing of key events. Among animals, however, these reports have been heavily biased towards avian phenologies, whereas we still know comparatively little about other seasonal adaptations, such as mammalian hibernation. Here we show a significant delay (0.47 days per year, over a 20-year period) in the hibernation emergence date of adult females in a wild population of Columbian ground squirrels in Alberta, Canada. This finding was related…
Publication Type: Journal Article
Afternoon Rain More Likely Over Drier Soils
Year: 2012
Land surface properties, such as vegetation cover and soil moisture, influence the partitioning of radiative energy between latent and sensible heat fluxes in daytime hours. During dry periods, soil-water deficit can limit evapotranspiration, leading to warmer and drier conditions in the lower atmosphere. Soil moisture can influence the development of convective storms through such modifications of low-level atmospheric temperature and humidity, which in turn feeds back on soil moisture. Yet there is considerable uncertainty in how soil moisture affects convective storms across the world,…
Publication Type: Journal Article
Harmful filamentous cyanobacteria favoured by reduced water turnover with lake warming
Year: 2012
Anthropogenic-induced changes in nutrient ratios have increased the susceptibility of large temperate lakes to several effects of rising air temperatures and the resulting heating of water bodies. First, warming leads to stronger thermal stratification, thus impeding natural complete water turnover (holomixis), which compensates for oxygen deficits in the deep zones. Second, increased water temperatures and nutrient concentrations can directly favour the growth of harmful algae. Thus, lake-restoration programmes have focused on reducing nutrients to limit toxic algal blooms. Here we present…
Publication Type: Journal Article
Eco-Evolutionary Responses of Biodiversity to Climate Change
Year: 2012
Climate change is predicted to alter global species diversity, the distribution of human pathogens and ecosystem services. Forecasting these changes and designing adequate management of future ecosystem services will require predictive models encompassing the most fundamental biotic responses. However, most present models omit important processes such as evolution and competition. Here we develop a spatially explicit eco-evolutionary model of multi-species responses to climate change. We demonstrate that both dispersal and evolution differentially mediate extinction risks and biodiversity…
Publication Type: Journal Article
Changes to Dryland Rainfall Result in Rapid Moss Mortality and Altered Soil Fertility
Year: 2012
Arid and semi-arid ecosystems cover ~40% of Earth's terrestrial surface, but we know little about how climate change will affect these widespread landscapes. Like many drylands, the Colorado Plateau in southwestern United States is predicted to experience elevated temperatures and alterations to the timing and amount of annual precipitation. We used a factorial warming and supplemental rainfall experiment on the Colorado Plateau to show that altered precipitation resulted in pronounced mortality of the widespread moss Syntrichia caninervis. Increased frequency of 1.2mm summer rainfall events…
Publication Type: Journal Article
The push and pull of climate change causes heterogeneous shifts in avian elevational ranges
Year: 2012
Projected effects of climate change on animal distributions primarily focus on consequences of temperature and largely ignore impacts of altered precipitation. While much evidence supports temperature-driven range shifts, there is substantial heterogeneity in species' responses that remains poorly understood. We resampled breeding ranges of birds across three elevational transects in the Sierra Nevada Mountains, USA, that were extensively surveyed in the early 20th century. Presence absence comparisons were made at 77 sites and occupancy models were used to separate significant range shifts…
Publication Type: Journal Article
Evidence of Enhanced Freezing Damage in Treeline Plants During Six Years of CO 2 Enrichment and Soil Warming
Year: 2012
Climate change and elevated atmospheric CO 2 levels could increase the vulnerability of plants to freezing. We analyzed tissue damage resulting from naturally occurring freezing events in plants from a longterm in situ CO 2 enrichment (+ 200 ppm, 2001-2009) and soil warming (+ 4°C since 2007) experiment at treeline in the Swiss Alps (Stillberg, Davos). Summer freezing events caused damage in several abundant subalpine and alpine plant species in four out of six years between 2005 and 2010. Most freezing damage occurred when temperatures dropped below -1.5°C two to three weeks after snow melt…
Publication Type: Journal Article
Using niche models with climate projections to inform conservation management decisions
Year: 2012
Conservation science strives to inform management decisions. Applying niche models in concert with future climate projections to project species vulnerability to extinction, range size loss, or distribution shifts has emerged as a potentially useful tool for informing resource management decisions. Making climate change niche modeling useful to conservation decisions requires centering studies on the types of decisions that are made regarding the focal taxa of a niche model study. Recent recommendations for climate adaptation strategies suggest four types of decision makers: policy, habitat…
Publication Type: Journal Article
Pattern and process of prescribed fires influence effectiveness at reducing wildfire severity in dry coniferous forests
Year: 2012
We examined the effects of three early season (spring) prescribed fires on burn severity patterns of summer wildfires that occurred 1–3 years post- treatment in a mixed conifer forest in central Idaho. Wildfire and prescribed fire burn severities were estimated as the difference in normalized burn ratio (dNBR) using Landsat imagery. We used GIS derived vegetation, topography, and treatment variables to generate models predicting the wildfire burn severity of 1286–5500 30- m pixels within and around treated areas. We found that wildfire severity was significantly lower in treated areas than in…
Publication Type: Journal Article
Comparative Hazard Assessment for Protected Species in a Fire-Prone Landscape
Year: 2012
We conducted a comparative hazard assessment for 325,000 ha in a fire-prone area of southwest Oregon, USA. The landscape contains a variety of land ownerships, fire regimes, and management strategies. Our comparative hazard assessment evaluated the effects of two management strategies on crown fire potential and northern spotted owl (Strix occidentalis caurina) conservation: (1) no action, and (2) active manipulation of hazardous fuels. Model simulations indicated that active management of sites with high fire hazard was more favorable to spotted owl conservation over the long term (75 years…
Publication Type: Journal Article
Projecting future distributions of ecosystem climate niches: Uncertainties and management applications
Year: 2012
Projecting future distributions of ecosystems or species climate niches has widely been used to assess the potential impacts of climate change. However, variability in such projections for the future periods, particularly the variability arising from uncertain future climates, remains a critical challenge for incorporating these projections into climate change adaptation strategies. We combined the use of a robust statistical modeling technique with a simple consensus approach consolidating projected outcomes for multiple climate change scenarios, and exemplify how the results could guide…
Publication Type: Journal Article
Commonalities of Carbon Dioxide Exchange in Semiarid Regions with Monsoon and Mediterranean Climates
Year: 2012
Comparing biosphereatmosphere carbon exchange across monsoon (warm-season rainfall) and Mediterranean (cool-season rainfall) regimes can yield information about the interaction between energy and water limitation. Using data collected from eddy covariance towers over grass and shrub ecosystems in Arizona, USA and Almeria, Spain, we used net ecosystem carbon dioxide exchange (NEE), gross ecosystem production (GEP), and other meteorological variables to examine the effects of the different precipitation seasonality. Considerable crossover behavior occurred between the two rainfall regimes. As…
Publication Type: Journal Article
Simulating effects of climate change and ecological restoration on fire behaviour in a south-western USA ponderosa pine forest
Year: 2012
Global climate change has the potential to affect future wildfire activity, particularly in south-western USA ponderosa pine forests that have been substantially altered by land-use practices and aggressive fire suppression. Using two regional general circulation models for the A1B greenhouse gas emission scenario, Australia's CSIRO:MK3 and Germany's MPIM:ECHAMS, we predicted fire behaviour under the 80th, 90th and 97th percentiles of future fire-weather conditions at a study site on the Kaibab National Forest, Arizona. We then altered the fuel structure by simulating alternative ecological…
Publication Type: Journal Article
Atmospheric Interactions with Wildland Fire Behaviour I. Basic Surface Interactions, Vertical Profiles and Synoptic Structures
Year: 2012
This paper is the first of two reviewing scientific literature from 100 years of research addressing interactions between the atmosphere and fire behaviour. These papers consider research on the interactions between the fuels burning at any instant and the atmosphere, and the interactions between the atmosphere and those fuels that will eventually burn in a given fire. This first paper reviews the progression from the surface atmospheric properties of temperature, humidity and wind to horizontal and vertical synoptic structures and ends with vertical atmospheric profiles. (The companion paper…
Publication Type: Journal Article
Atmospheric Interactions with Wildland Fire Behaviour II. Plume and Vortex Dynamics
Year: 2012
This paper is the second of two reviewing scientific literature from 100 years of research addressing interactions between the atmosphere and fire behaviour. These papers consider research on the interactions between the fuels burning at any instant and the atmosphere, and the interactions between the atmosphere and those fuels that will eventually burn in a given fire. The first paper reviews the progression from the surface atmospheric properties of temperature, humidity and wind to horizontal and vertical synoptic structures and ends with vertical atmospheric profiles. This second paper…
Publication Type: Journal Article
Climate Change and Disruptions to Global Fire Activity
Year: 2012
Future disruptions to fire activity will threaten ecosystems and human well-being throughout the world, yet there are few fire projections at global scales and almost none from a broad range of global climate models (GCMs). Here we integrate global fire datasets and environmental covariates to build spatial statistical models of fire probability at a 0.58 resolution and examine environmental controls on fire activity. Fire models are driven by climate norms from 16 GCMs (A2 emissions scenario) to assess the magnitude and direction of change over two time periods, 2010–2039 and 2070–2099. From…
Publication Type: Journal Article
Projected range shifting by montane mammals under climate change: implications for Cascadia's National Parks
Year: 2012
We examined potential impacts of climate change over the next century on eight mammal species of conservation concern in western Washington State, under four warming scenarios. Using two species distribution models, including a logistic regression-based model and the "maximum entropy" (MaxEnt) model, we predicted the location and extent of the potential current and future range of each species based on a suite of environmental and geographical variables. Both models projected significant losses in range size within the focal area over the next century across all warming scenarios. Projections…
Publication Type: Journal Article
The Age of Western Wildfires
Year: 2012
The 2012 wildfire season isn’t over yet, but already this year is shaping up to be the one of the worst on record in the American West. According to the National Interagency Fire Center, with nearly two months still to go in the fire season, the total area already burned this year is 30 percent more than in an average year, and fires have consumed more than 8.6 million acres, an area larger than the state of Maryland. Yet, what defines a “typical” wildfire year in the West is changing. In the past 40 years, rising spring and summer temperatures, along with shrinking winter snowpack, have…
Publication Type: Report