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Your Yukon is a weekly column about environmental issues and research, from Canada's Yukon. This column discusses how climate change, especially drought stress, may be affecting the boreal forest.--Includes text from publisher's website.
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Native grasslands have been altered to a greater extent than any other biome in North America. The habitats and resources needed to support breeding performance of grassland birds endemic to prairie ecosystems are currently threatened by land management practices and impending climate change. Climate models for the Great Plains prairie region predict a future of hotter and drier summers with strong multiyear droughts and more frequent and severe precipitation events. We examined how fluctuations in weather conditions in eastern Colorado influenced nest survival of an avian species that has experienced recent population declines, the Mountain Plover (Charadrius montanus). Nest survival averaged 27.2% over a 7-yr...
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Unprecedented rates of climate warming over the past century have resulted in increased forest stress and mortality worldwide. Decreased tree growth in association with increasing temperatures is generally accepted as a signal of temperature-induced drought stress. However, variations in tree growth alone do not reveal the physiological mechanisms behind recent changes in tree growth. Examining stable carbon isotope composition of tree rings in addition to tree growth can provide a secondary line of evidence for physiological drought stress. In this study, we examined patterns of black spruce growth and carbon isotopic composition in tree rings in response to climate warming and drying in the boreal forest of interior...
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Owing to large climatic and orographic variation, British Columbia covers a variety of ecosystems extending from temperate rainforests on the Pacific coast to boreal forests in the north-east. The aim of this study is to investigate the spatial variation of trends in wildfire activity and their relationship to summer drought for the entire province of British Columbia. Time series of annual wildfire extent and occurrence, summer self-calibrating Palmer Drought Severity Index and summer Aridity Index were derived from spatially explicit data. Sixteen landscape regions according to the provincial Biogeoclimatic Ecosystem Classification system served as spatial reference. The regional series for 1920-2000 were subjected...
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Increment cores from the boreal forest have long been used to reconstruct past climates. However, in recent years, numerous studies have revealed a deterioration of the correlation between temperature and tree growth that is commonly referred to as "divergence". In the Brooks Range of northern Alaska, studies of white spruce (Picea glauca) revealed that trees in the west generally showed positive growth trends, while trees in the central and eastern Brooks Range showed mixed and negative trends during late 20th century warming. The growing season climate of the eastern Brooks Range is thought to be drier than the west. On this basis, divergent tree growth in the eastern Brooks Range has been attributed to drought...
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High latitude trees are increasingly showing mixed growth responses to climate warming. Recent studies of white spruce (Picea glauca ) in the Brooks Range of Alaska have revealed that trees in the west have generally shown positive growth responses, while trees in the central and eastern Brooks Range have shown mixed and negative growth responses, respectively. An earlier study suggested that the growing season climate of the eastern Brooks Range is warmer and drier than in the west. On this basis, growth declines in the eastern Brooks Range were attributed to drought stress, caused by rising temperature and increasing evaporative demand. I investigated the hypothesis that drought stress can explain white spruce...
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Climate has warmed substantially in interior Alaska and several remote sensing studies have documented a decadal-scale decline in the normalized difference vegetation index (NDVI) termed a ‘browning trend’. Reduced summer soil moisture due to changing climatic factors such as earlier springs, less snowpack, and summer drought may reduce boreal productivity and NDVI. However, the relative importance of these climatic factors is poorly understood in boreal interior Alaska. In this study, I used the remotely sensed peak summer NDVI as an index of boreal productivity at 250 m pixel size from 2000 to 2014. Maximum summer NDVI was related to last day of spring snow, early spring snow water equivalent (SWE), and a...
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Trends of summer precipitation and summer temperature and their influence on trends in summer drought and area burned in British Columbia (BC) were investigated for the period 1920–2000. The complexity imposed by topography was taken into account by incorporating high spatial resolution climate and fire data. Considerable regional variation in trends and in climate–fire relationships was observed. A weak but significant increase in summer temperature was detected in northeastern and coastal BC, whereas summer precipitation increased significantly in all regions—by up to 45.9 %. A significant decrease in province-wide area burned and at the level of sub-units was strongly related to increasing precipitation, more...
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The northern treeline is generally limited by available warmth. However, in recent years, more and more studies have identified drought stress as an additional limiting factor for tree growth in northern boreal forests and at treelines. Three growth responses to warming have been identified: increase in growth, decrease in growth, and nonsignificant correlation of tree growth with climate. Here we investigate the effect of drought stress on radial growth of white spruce at northern treelines along a longitudinal gradient spanning the entire Brooks Range in Alaska. We systematically sampled 687 white spruce at seven treeline sites. Where possible, we sampled three site types at a given site: high-density forest,...
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The potential ecological and economic effects of climate change for tropical islands were studied using output from 12 statistically downscaled general circulation models (GCMs) taking Puerto Rico as a test case. Two model selection/model averaging strategies were used: the average of all available GCMs and the average of the models that are able to reproduce the observed large-scale dynamics that control precipitation over the Caribbean. Five island-wide and multidecadal averages of daily precipitation and temperature wereestimated by way of a climatology-informed interpolation of the site-specific downscaled climate model output. Annual cooling degree-days (CDD) were calculated as a proxy index for air-conditioning...
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Executive summary: Tamarisk control and removal has become a priority of riparian ecosystem management, due in part to its potential negative impacts on stream flow and groundwater recharge. Among the most controversial, and potentially most effective tamarisk control approaches is the introduction of the tamarisk leaf beetle, Diorhabda carinulata. The beetle has spread throughout virtually the entire upper Colorado River Basin, established major populations at Lake Mead in 2012, and is now poised to expand into the lower Colorado River Basin concordant with documented evolutionary change in beetle developmental response that may enable survival in southern regions. Superimposed on this direct plant/herbivore relationship...
Categories: Data, Publication; Types: Citation, Map Service, OGC WFS Layer, OGC WMS Layer, OGC WMS Service; Tags: 2012, AZ-01, AZ-02, AZ-03, AZ-04, All tags...
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Algae are important to many of the processes that characterize wetland ecosystems. Despite their importance, we know relatively little about the factors that regulate algal communities in wetlands. This is particularly true for northern boreal regions where wetlands are abundant and are considered to be extremely vulnerable to disturbances associated with climate change. My dissertation research investigates how nutrients, grazing, light, and hydrology regulate algal primary production and taxonomic structure in high latitude wetlands. I documented spatial and temporal variability in algal structure and function in six northern boreal wetlands in interior Alaska to determine the contribution of algal primary production...
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Global vegetation models predict that boreal forests are particularly sensitive to a biome shift during the 21st century. This shift would manifest itself first at the biome?s margins, with evergreen forest expanding into current tundra while being replaced by grasslands or temperate forest at the biome?s southern edge. We evaluated changes in forest productivity since 1982 across boreal Alaska by linking satellite estimates of primary productivity and a large tree-ring data set. Trends in both records show consistent growth increases at the boreal?tundra ecotones that contrast with drought-induced productivity declines throughout interior Alaska. These patterns support the hypothesized effects of an initiating...
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Wildfires are a common experience in Alaska where, on average, 3,775 km^sup 2^ burn annually. More than 90% of the area consumed occurs in Interior Alaska, where the summers are relatively warm and dry, and the vegetation consists predominantly of spruce, birch, and cottonwood. Summers with above normal temperatures generate an increased amount of convection, resulting in more thunderstorm development and an amplified number of lightning strikes. The resulting dry conditions facilitate the spread of wildfires started by the lightning. Working with a 55-year dataset of wildfires for Alaska, an increase in the annual area burned was observed. Due to climate change, the last three decades have shown to be warmer than...
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Vegetation and land-cover changes are not always directional but follow complex trajectories over space and time, driven by changing anthropogenic and abiotic conditions. We present a multi-observational approach to land-change analysis that addresses the complex geographic and temporal variability of vegetation changes related to climate and land use. Using land-ownership data as a proxy for land-use practices, multitemporal land-cover maps, and repeat photography dating to the late 19th century, we examine changing spatial and temporal distributions of two vegetation types with high conservation value in the southwestern United States: grasslands and riparian vegetation. In contrast to many reported vegetation...
map background search result map search result map Drought and Cooler Temperatures Are Associated with Higher Nest Survival in Mountain Plovers Historical and Contemporary Geographic Data Reveal Complex Spatial and Temporal Responses of Vegetation to Climate and Land Stewardship Precipitation-driven decrease in wildfires in British Columbia Stable carbon isotope analysis reveals widespread drought stress in boreal black spruce forests Impacts of drought on forest growth and regeneration following fire in southwestern Yukon, Canada Drought-induced stomatal closure probably cannot explain divergent white spruce growth in the Brooks Range, Alaska Carbon isotope discrimination in tree ring alpha-cellulose indicates that drought stress cannot explain white spruce growth declines in the eastern Brooks Range, Alaska Relationship between fire, climate oscillations, and drought in British Columbia, Canada, 1920–2000 Remote sensing of interannual boreal forest NDVI in relation to climatic conditions in interior Alaska Response of plant community structure and primary productivity to experimental drought and flooding in an Alaskan fen Longitudinal variation of radial growth at Alaska's northern treeline; recent changes and possible scenarios for the 21st century Regulation of benthic algal structure and function in northern boreal wetlands Spatial variation of trends in wildfire and summer drought in British Columbia, Canada, 1920-2000 The sensitivity of carbon fluxes to spring warming and summer drought depends on plant functional type in boreal forest ecosystems [electronic resource] Reduced growth of Alaskan white spruce in the twentieth century from temperature-induced drought stress Drought stress changing the Takhini landscape Final Report and Publication: From Genotype to River Basin: The combined impacts of climate change on bio-control on a dominant riparian invasive tree/shrub Climate Change Implications for Tropical Islands: Interpolating and Interpreting Statistically Downscaled GCM Projections for Management and Planning Regulation of benthic algal structure and function in northern boreal wetlands Drought stress changing the Takhini landscape Response of plant community structure and primary productivity to experimental drought and flooding in an Alaskan fen Historical and Contemporary Geographic Data Reveal Complex Spatial and Temporal Responses of Vegetation to Climate and Land Stewardship Climate Change Implications for Tropical Islands: Interpolating and Interpreting Statistically Downscaled GCM Projections for Management and Planning Impacts of drought on forest growth and regeneration following fire in southwestern Yukon, Canada Reduced growth of Alaskan white spruce in the twentieth century from temperature-induced drought stress Final Report and Publication: From Genotype to River Basin: The combined impacts of climate change on bio-control on a dominant riparian invasive tree/shrub Stable carbon isotope analysis reveals widespread drought stress in boreal black spruce forests Drought-induced stomatal closure probably cannot explain divergent white spruce growth in the Brooks Range, Alaska Carbon isotope discrimination in tree ring alpha-cellulose indicates that drought stress cannot explain white spruce growth declines in the eastern Brooks Range, Alaska Longitudinal variation of radial growth at Alaska's northern treeline; recent changes and possible scenarios for the 21st century Drought and Cooler Temperatures Are Associated with Higher Nest Survival in Mountain Plovers Remote sensing of interannual boreal forest NDVI in relation to climatic conditions in interior Alaska The sensitivity of carbon fluxes to spring warming and summer drought depends on plant functional type in boreal forest ecosystems [electronic resource] Precipitation-driven decrease in wildfires in British Columbia Relationship between fire, climate oscillations, and drought in British Columbia, Canada, 1920–2000 Spatial variation of trends in wildfire and summer drought in British Columbia, Canada, 1920-2000