A5036479378- Climate change and permafrost
- Cryospheric studies and observations
- Tree-ring climate responses
- Geology and Paleoclimatology Research
- Plant Water Relations and Carbon Dynamics
- Peatlands and Wetlands Ecology
- Fire effects on ecosystems
- Geological Studies and Exploration
- Atmospheric and Environmental Gas Dynamics
- Methane Hydrates and Related Phenomena
- Polar Research and Ecology
- Forest ecology and management
- Ecology and Vegetation Dynamics Studies
- Smart Materials for Construction
- Arctic and Antarctic ice dynamics
- Indigenous Studies and Ecology
- Hydrocarbon exploration and reservoir analysis
- Species Distribution and Climate Change
- Climate variability and models
- Forest Ecology and Biodiversity Studies
- Winter Sports Injuries and Performance
- Soil and Unsaturated Flow
- Landslides and related hazards
- Rangeland and Wildlife Management
- Plant responses to elevated CO2
University of Alaska Anchorage
2015-2024
Providence College
2017-2022
University of Alaska System
2010
Colorado State University
2004
University of Notre Dame
1982
Snow is an important driver of ecosystem processes in cold biomes. accumulation determines ground temperature, light conditions, and moisture availability during winter. It also affects the growing season’s start end, plant access to nutrients. Here, we review current knowledge snow cover’s role for vegetation, plant-animal interactions, permafrost microbial processes, biogeochemical cycling. We compare studies natural gradients with experimental manipulation assess time scale difference...
Unprecedented modern rates of warming are expected to advance boreal forest into Arctic tundra1, thereby reducing albedo2-4, altering carbon cycling4 and further changing climate1-4, yet the patterns processes this biome shift remain unclear5. Climate warming, required for previous advances6-17, is not sufficient by itself range expansion conifers forming forest-tundra ecotones5,12-15,17-20. No high-latitude population conifers, dominant North American treeline taxon, has previously been...
Boreal forests play critical roles in global carbon, water and energy cycles. Recent studies suggest drought is causing a decline boreal spruce growth, leading to predictions of widespread mortality shift dominant vegetation type interior Alaska. We took advantage large set tree cores collected from random locations across vast area Alaska examine long-term trends carbon isotope discrimination growth black white spruce. Our results confirm that both species sensitive moisture availability,...
The structure and function of Alaska's forests have changed significantly in response to a changing climate, including alterations species composition climate feedbacks (e.g., carbon, radiation budgets) that important regional societal consequences human forest ecosystems. In this paper we present the first comprehensive synthesis climate-change impacts on all forested ecosystems Alaska, highlighting changes most critical biophysical factors each region. We developed conceptual framework...
Abstract Arctic and Boreal terrestrial ecosystems are important components of the climate system because they contain vast amounts soil carbon (C). Evidence suggests that deciduous shrubs increasing in abundance, but implications for ecosystem C budgets remain uncertain. Using midsummer CO 2 flux data from 21 sites spanning 16° latitude biomes, we show air temperature explains c . one‐half variation respiration ( ER ) drives pattern net exchange across ecosystems. Woody were slightly...
Abstract Climate change in the Arctic is altering watershed hydrologic processes and biogeochemistry. Here, we present an emergent threat to watersheds based on observations from 75 streams Alaska’s Brooks Range that recently turned orange, reflecting increased loading of iron toxic metals. Using remote sensing, constrain timing stream discoloration last 10 years, a period rapid warming snowfall, suggesting impairment likely due permafrost thaw. Thawing can foster chemical weathering...
Climate-induced northward advance of boreal forest is expected to lessen albedo, alter carbon stocks, and replace tundra, but where when this will occur remains largely unknown. Using data from 19 sites across 22 degrees longitude along the tree line northern Alaska, we show a stronger temporal correlation ring growth with open water uncovered by retreating Arctic sea ice than air temperature. Spatially, our results suggest that growth, recruitment, range expansion are causally linked...
The temperature response of soil respiration in deserts is not well quantified. We evaluated the to temperatures spanning 67°C from seven across North America and Greenland. Deserts have similar rates dry at 20°C, as expected, are greater under wet conditions, rivaling observed for more mesic systems. However, differ their 20°C strength effect current antecedent moisture on sensitivity magnitude respiration. Respiration increases with below 30°C but declines exceeding 35°C. Hot lower than...
Abstract Changes in the terrestrial carbon cycle may ameliorate or exacerbate future climatic warming. Research on this topic has focused almost exclusively abiotic drivers, whereas biotic factors, including trophic interactions, have received comparatively little attention. We quantified singular and interactive effects of herbivore exclusion simulated warming ecosystem CO 2 exchange over two consecutive growing seasons W est G reenland. Exclusion caribou muskoxen past 8 years led to...
The position of the Arctic treeline, which is a key regulator surface energy exchange and carbon cycling, widely thought to be controlled by temperature. Here, we present evidence that soil nutrient availability, rather than temperature, may proximate control on growth treeline trees at our study site in northwest Alaska. We examined constraints allocation white spruce three contrasting habitats. habitats had similar aboveground climates, but temperature declined from riverside terrace...
Abstract Observational and experimental studies have generally shown that warming is associated with greater growth abundance of deciduous shrubs in arctic ecosystems. It uncertain, however, if this trend will persist the future. Our study examined responses to climate change over late 20th early 21st centuries near Kangerlussuaq western Greenland. We combined shrub dendrochronology, stable isotope analysis weekly measurements leaf gas exchange examine drivers secondary two widespread...
Abstract Tall shrubs and trees are advancing into many tundra wetland ecosystems but at a rate that often falls short of predicted due to climate change. For forest, tall shrub, in two pristine mountain ranges Alaska, we apply Bayesian, error‐propagated calculation expected elevational rise (climate velocity), observed (biotic their difference inertia). We show sensitive dependence velocity on lapse derive biotic as rigid shift. Ecosystem presence identified from recent historic orthophotos...
Climate change over the past ∼50 years has resulted in earlier occurrence of plant life-cycle events for many species. Across temperate, boreal and polar latitudes, seasonal warming is considered key mechanism leading to leaf expansion growth. Yet, seasonally snow-covered ecosystems, timing spring growth may also be cued by snowmelt, which occur a warmer climate. Multiple environmental cues protect plants from growing too early, but understand how climate will alter magnitude growth,...
Significance Two defining features of climate change in the Arctic are rapid decline sea ice and “shrubification” tundra. While previous studies have inferred warming-related linkages between two, these been limited to a few locations. Our Pan-Arctic analysis shrub growth chronologies reveals two important insights. Tundra dynamics associated with throughout Arctic; however, while shrubs from most locations increased their growth, more than one-third showed evidence declining response...
Articulating the consequences of global climate change on terrestrial ecosystem biogeochemistry is a critical component Arctic system studies. Leaf mineral nutrition responses tundra plants an important measure changes in organismic and attributes because leaf nitrogen carbon contents effect photosynthesis, primary production, budgets, litter, soil organic matter decomposition as well herbivore forage quality. In this study, we used longterm experiment where snow depth summer temperatures...
The Arctic has experienced rapid warming and, although there are uncertainties, increases in precipitation projected to accompany future warming. Climate changes expected affect magnitudes of gross ecosystem photosynthesis (GEP), respiration (ER) and the net exchange CO2 (NEE). Furthermore, responses climate change likely be characterized by nonlinearities, thresholds interactions among system components driving variables. These complex increase difficulty predicting necessitate use...
Boreal forests are critical sinks in the global carbon cycle. However, recent studies have revealed increasing frequency and extent of wildfires, decreasing landscape greenness, tree mortality declining growth black white spruce boreal North America. We measured ring widths from a large set increment cores collected across vast area interior Alaska examined implications data processing decisions for apparent trends growth. found that choice detrending method had important long-term strength...
Tree-ring time series provide long-term, annually resolved information on the growth of trees. When sampled in a systematic context, tree-ring data can be scaled to estimate forest carbon capture and storage landscapes, biomes, and-ultimately-the globe. A effort sample tree rings national inventories would yield unprecedented temporal spatial resolution dynamics help resolve key scientific uncertainties, which we highlight terms evidence for greening (enhanced growth) versus browning...