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Climate change is an increasing concern for Yukon and its communities. Many observable changes have occurred across the Territory over the past fifty years, especially an increase in the annual temperature and precipitation of the Western Arctic. The potential outcomes of changing climate have raised subsequent concerns for Yukon residents including a shifting distribution of country foods, the thaw of permafrost, changing landscape conditions, drought, and a host of other regional vulnerabilities. In response to this growing concern about climate change, the Northern Climate ExChange submitted a proposal to the Northern Strategy Trust in 2007 to develop and implement adaptation plans in three Yukon communities:...
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To determine the influence of fire and thermokarst in a boreal landscape, we investigated peat cores within and adjacent to a permafrost collapse feature on the Tanana River Floodplain of Interior Alaska. Radioisotope dating, diatom assemblages, plant macrofossils, charcoal fragments, and carbon and nitrogen content of the peat profile indicate approximately 600 years of vegetation succession with a transition from a terrestrial forest to a sedge-dominated wetland over 100 years ago, and to a Sphagnum-dominated peatland in approximately 1970. The shift from sedge to Sphagnum, and a decrease in the detrended tree-ring width index of black spruce trees adjacent to the collapse coincided with an increase in the growing...
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Boreal forests play critical roles in global carbon, water and energy cycles. Recent studies suggest drought is causing a decline in boreal spruce growth, leading to predictions of widespread mortality and a shift in dominant vegetation type in interior Alaska. We took advantage of a large set of tree cores collected from random locations across a vast area of interior Alaska to examine long-term trends in carbon isotope discrimination and growth of black and white spruce. Our results confirm that growth of both species is sensitive to moisture availability, yet show limited evidence of declining growth in recent decades. These findings contrast with many earlier tree-ring studies, but agree with dynamic global...
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A growing body of evidence suggests that climate change will have complex effects on the boreal forests of western Canada. Studies that examine historical species responses over large geographic and climatic distances may provide insights into the temporal and spatial complexities underlying forest vulnerabilities to climate change. We analyzed annual tree-ring data collected from 56 white spruce (Picea glauca (Moench) Voss) populations across the species’ distribution in Yukon, Canada. Regional growth patterns were identified and correlation and response functions were computed to determine primary climatic influences on growth within each region. The temporal stability of climate–growth relationships was also...
Many dendroclimatic studies have been conducted in Alaska to understand recent climate changes, identify past and current warming trends, and determine how climate change may influence ecosystems. Four new white spruce (Picea glauca [Moench] Voss) ring-width chronologies from four sites along a 30 kilometer north-south transect in the Lake Clark National Park and Preserve on the Alaskan Peninsula span a common interval from AD 1769 to 2003. Two sites show an internally consistent positive growth response to increasing April-July temperatures after 1950. The two other sites each contain two subpopulations showing varying growth responses. One subpopulation diverges from historical temperature data after 1950 and...
Mast-seeding conifers such as Picea glauca exhibit synchronous production of large seed crops over wide areas, suggesting climate factors as possible triggers for episodic high seed production. Rapidly changing climatic conditions may thus alter the tempo and spatial pattern of masting of dominant species with potentially far-reaching ecological consequences. Understanding the future reproductive dynamics of ecosystems including boreal forests, which may be dominated by mast-seeding species, requires identifying the specific cues that drive variation in reproductive output across landscape gradients and among years. Here we used annual data collected at three sites spanning an elevation gradient in interior Alaska,...
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To determine the influence of fire and thermokarst in a boreal landscape, we investigated peat cores within and adjacent to a permafrost collapse feature on the Tanana River Floodplain of Interior Alaska. Radioisotope dating, diatom assemblages, plant macrofossils, charcoal fragments, and carbon and nitrogen content of the peat profile indicate ~600 years of vegetation succession with a transition from a terrestrial forest to a sedge-dominated wetland over 100 years ago, and to a Sphagnum-dominated peatland in approximately 1970. The shift from sedge to Sphagnum, and a decrease in the detrended tree-ring width index of black spruce trees adjacent to the collapse coincided with an increase in the growing season temperature...
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Landsat 8, a NASA and USGS collaboration, acquires global moderate-resolution measurements of the Earth's terrestrial and polar regions in the visible, near-infrared, short wave, and thermal infrared. Landsat 8 extends the remarkable 40 year Landsat record and has enhanced capabilities including new spectral bands in the blue and cirrus cloud-detection portion of the spectrum, two thermal bands, improved sensor signal-to-noise performance and associated improvements in radiometric resolution, and an improved duty cycle that allows collection of a significantly greater number of images per day. This paper introduces the current (2012–2017) Landsat Science Team's efforts to establish an initial understanding of Landsat...
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Abstract. To determine the influence of fire and thermokarst in a boreal landscape, we investigated peat cores within and adjacent to a permafrost collapse feature on the Tanana River Floodplain of Interior Alaska. Radioisotope dating, diatom assemblages, plant macrofossils, charcoal fragments, and carbon and nitrogen content of the peat profile indicate ~600 years of vegetation succession with a transition from a terrestrial forest to a sedge-dominated wetland over 100 years ago, and to a Sphagnum-dominated peatland in approximately 1970. The shift from sedge to Sphagnum, and a decrease in the detrended tree-ring width index of black spruce trees adjacent to the collapse coincided with an increase in the growing...
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Stream fragmentation alters the structure of aquatic communities on a global scale, generally through loss of native species. Among riverscapes in the Great Plains of North America, stream fragmentation and hydrologic alteration (flow regulation and dewatering) are implicated in the decline of native fish diversity. This study documents the spatio–temporal distribution of fish reproductive guilds in the fragmented Arkansas and Ninnescah rivers of south-central Kansas using retrospective analyses involving 63 years of fish community data. Pelagic-spawning fishes declined throughout the study area during 1950–2013, including Arkansas River shiner (Notropis girardi) last reported in 1983, plains minnow (Hybognathus...
Categories: Data, Publication; Types: Citation, Map Service, OGC WFS Layer, OGC WMS Layer, OGC WMS Service; Tags: CATFISHES/MINNOWS, Colorado, Colorado, FISH, Federal resource managers, All tags...
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The Prairie Pothole Region (PPR) of the north-central U.S. and south-central Canada contains millions of small prairie wetlands that provide critical habitat to many migrating and breeding waterbirds. Due to their small size and the relatively dry climate of the region, these wetlands are considered at high risk for negative climate change effects as temperatures increase. To estimate the potential impacts of climate change on breeding waterbirds, we predicted current and future distributions of species common in the PPR using species distribution models (SDMs). We created regional-scale SDMs for the U.S. PPR using Breeding Bird Survey occurrence records for 1971–2011 and wetland, upland, and climate variables....
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Watersheds draining the Arctic Coastal Plain (ACP) of Alaska are dominated by permafrostand snowmelt runoff that create abundant surface storage in the form of lakes, wetlands, and beaded streams. These surface water elements compose complex drainage networks that affect aquatic ecosystem connectivity and hydrologic behavior. The 4676 km2 Fishand Creek drainage basin is composed of three watersheds that represent a gradient of theACP landscape with varying extents of eolian, lacustrine, and fluvial landforms. In each watershed, we analyzed 2.5-m-resolution aerial photography, a 5-m digital elevationmodel, and river gauging and climate records to better understand ACP watershed structureand processes. We show that...
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Canadian Fire Weather Index (FWI) System components and head fire intensities were calculated for fires greater than 2 km2 in size for the boreal and taiga ecozones of Canada from 1959 to 1999. The highest noon-hour values were analysed that occurred during the first 21 days of each of 9333 fires. Depending on ecozone, the means of the FWI System parameters ranged from: fine fuel moisture code (FFMC), 90 to 92 (82 to 96 for individual fires); duff moisture code (DMC), 38 to 78 (10 to 140 for individual fires); drought code (DC), 210 to 372 (50 to 600 for individual fires); and fire weather index, 20 to 33 (5 to 60 for individual fires). Fine fuel moisture code decreased, DMC had a mid-season peak, and DC increased...
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This paper calibrates climate controls over radial growth of floodplain white spruce (Picea glauca (Moench) Voss) and examines whether growth in these populations responds similarly to climate as upland trees in Interior Alaska. Floodplain white spruce trees hold previously unrecognized potential for long-term climate reconstruction because they are the source of driftwood that becomes frozen in coastal deposits, where archeological timbers and beach logs represent well-preserved datable material. We compared ring width chronologies for 135 trees in six stands on the Yukon Flats and Tanana River with temperature and precipitation at Fairbanks from 1912–2001. Our sample contains a stable common signal representing...
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The eddy covariance method was applied to measure net ecosystem CO2 exchange (NEE) at a subarctic black spruce forest in interior Alaska during 2003 and 2004. To clarify the budget of CO2, we divided photosynthesis and respiration by applying the Carbon Budget Analysis Tool, in which the potential photosynthetic rate, the light use efficiency, and the suppression factors on photosynthesis were evaluated. The potential photosynthetic rate and the light use efficiency were related with the understory leaf area index. The determined optimal temperature of photosynthesis was higher than 15 degrees C, which was higher than that of other boreal forests. Drought in midsummer of 2004 suppressed both photosynthesis and respiration,...
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Northern peatlands provide important global and regional ecosystem services (carbon storage, water storage, and biodiversity). However, these ecosystems face increases in the severity, areal extent, and frequency of climate-mediated (e.g., wildfire, drought) and land-use change (e.g., drainage, flooding, and mining) disturbances that are placing the future security of these critical ecosystem services in doubt. Here we provide the first detailed synthesis of autogenic hydrological feedbacks that operate within northern peatlands to regulate their response to changes in seasonal water deficit and varying disturbances. We review, synthesize, and critique the current process-based understanding and qualitatively assess...
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Compared to lakes and streams, we know relatively little about algal ecology in freshwater wetlands. This discrepancy is particularly acute in boreal regions, where wetlands are abundant and processes related to climate change are expected to alter the hydrology, pH and nutrient concentrations of aquatic ecosystems. To evaluate how accelerated nutrient inputs might affect algal structure and function in boreal wetlands, I enriched mesocosms in an Alaskan marsh with all possible combinations of nitrogen (N), phosphorus (P) and silica (Si). Algal growth was not stimulated following enrichment with any nutrient alone or with P and Si together, but increased significantly with the addition of N in any combination with...
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Water samples were collected biweekly from the Chena River, Alaska, during 2005-2006 for analysis of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), total dissolved carbohydrate (TCHO), including monosaccharide (MCHO) and polysaccharide (PCHO), particulate organic carbon (POC) and its isotopic compositions, and Si(OH) sub(4). Carbon species exhibit strong temporal variations with elevated DOC, POC, and TCHO but depleted DIC and Si(OH) sub(4) during the spring freshet and decreased DOC, POC, and TCHO but elevated DIC and Si(OH) sub(4) concentrations under winter ice. Organic matter is mostly derived from surface soil leaching, whereas DIC and Si(OH) sub(4) are associated with groundwater and mineral...
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Climate change vulnerability assessments are commonly used to identify species or populations at risk from global climate change, but few translate impact assessments to climate change adaptation actions. Furthermore, most climate change adaptation efforts emphasize where to implement management actions, whereas timing remains largely overlooked. The rate of modern climate change introduces urgency in evaluating whether delaying conservation actions compromises their efficacy for reaching important conservation targets. We evaluated the importance of multiple climate change adaptation strategies including timing of actions on preventing extinctions for a threatened climate-sensitive species, the Eastern Massasauga...
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Carbon dioxide accumulating in our atmosphere is one of the most important environmental threats of our time. Humans and changing climate, separately or in concert, have affected global vegetation, biogeochemical cycles, biophysical processes, and primary production. Recent studies have found temporary carbon stores in North American vegetation due to land-cover land-use change, but have yet to characterize regional mechanisms across the continent. This research implemented multi-resolution remote sensing data, coupled with ecosystem simulations, to determine the importance of fine-scale disturbance in our understanding of dynamics that drove and/or perturbed carbon sequestration in North America from 1982 through...
map background search result map search result map Controlling factors on the interannual CO2 budget at a subarctic black spruce forest in interior Alaska Future Histories of Whitehorse: Scenarios of Change Climate sensitivity of reproduction in a mast-seeding boreal conifer across its distributional range from lowland to treeline forests Environmental controls on algal community structure and function in boreal wetlands Divergent tree growth response to recent climatic warming, Lake Clark National Park and Preserve, Alaska Temporal variations of organic carbon species and fluxes from the Chena River, Alaska Wetland succession in a permafrost collapse: interactions between fire and thermokarst Wetland succession in a permafrost collapse: interactions between fire and thermokarst Wetland succession in a permafrost collapse; interactions between fire and thermokarst Consistent negative temperature sensitivity and positive influence of precipitation on growth of floodplain Picea glauca in Interior Alaska Landsat-8: Science and product vision for terrestrial global change research Hydrological feedbacks in northern peatlands Identifying and understanding North American carbon cycle perturbations from natural and anthropogenic disturbances Geographic and temporal patterns in white spruce climate–growth relationships in Yukon, Canada Vulnerability of Breeding Waterbirds to Climate Change in the Prairie Pothole Region Publication: Fragmentation and drying ratchet down Great Plains stream fish diversity Limited evidence of declining growth among moisture-limited black and white spruce in interior Alaska Drainage Network Structure and Hydrologic Behavior of Three Lake-Rich Watersheds on the Arctic Coastal Plain, Alaska Publication: Delaying conservation actions matters for species vulnerable to climate change Wetland succession in a permafrost collapse: interactions between fire and thermokarst Wetland succession in a permafrost collapse: interactions between fire and thermokarst Wetland succession in a permafrost collapse; interactions between fire and thermokarst Future Histories of Whitehorse: Scenarios of Change Controlling factors on the interannual CO2 budget at a subarctic black spruce forest in interior Alaska Temporal variations of organic carbon species and fluxes from the Chena River, Alaska Drainage Network Structure and Hydrologic Behavior of Three Lake-Rich Watersheds on the Arctic Coastal Plain, Alaska Divergent tree growth response to recent climatic warming, Lake Clark National Park and Preserve, Alaska Climate sensitivity of reproduction in a mast-seeding boreal conifer across its distributional range from lowland to treeline forests Limited evidence of declining growth among moisture-limited black and white spruce in interior Alaska Consistent negative temperature sensitivity and positive influence of precipitation on growth of floodplain Picea glauca in Interior Alaska Environmental controls on algal community structure and function in boreal wetlands Publication: Fragmentation and drying ratchet down Great Plains stream fish diversity Geographic and temporal patterns in white spruce climate–growth relationships in Yukon, Canada Vulnerability of Breeding Waterbirds to Climate Change in the Prairie Pothole Region Publication: Delaying conservation actions matters for species vulnerable to climate change Identifying and understanding North American carbon cycle perturbations from natural and anthropogenic disturbances Landsat-8: Science and product vision for terrestrial global change research Hydrological feedbacks in northern peatlands