A5071464620- Climate change and permafrost
- Peatlands and Wetlands Ecology
- Fire effects on ecosystems
- Cryospheric studies and observations
- Geology and Paleoclimatology Research
- Coastal wetland ecosystem dynamics
- Atmospheric and Environmental Gas Dynamics
- Methane Hydrates and Related Phenomena
- Botany and Plant Ecology Studies
- Rangeland and Wildlife Management
- Arctic and Antarctic ice dynamics
- Indigenous Studies and Ecology
- Soil Carbon and Nitrogen Dynamics
- Geological Studies and Exploration
- Forest Ecology and Biodiversity Studies
- Bryophyte Studies and Records
- Lichen and fungal ecology
- Ecology and Vegetation Dynamics Studies
- Hydrocarbon exploration and reservoir analysis
- Forest ecology and management
- Plant Water Relations and Carbon Dynamics
- Climate variability and models
- Landslides and related hazards
- Marine and coastal ecosystems
- Atmospheric chemistry and aerosols
University of Colorado Boulder
2020-2025
University of Colorado System
2021-2025
Institute of Arctic and Alpine Research
2020-2024
International Institute for Applied Systems Analysis
2024
APEC Climate Center
2024
University of Guelph
2014-2023
Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung
2023
University of Colorado Denver
2021
University of California, Santa Barbara
2021
University of Alaska Fairbanks
2010-2019
We used historic records from 1959–99 to explore fire regime characteristics at ecozone scales across the entire North American boreal region (NABR). Shifts in NABR between 1960s/70s and 1980s/90s were characterized by a doubling of annual burned area more than frequency larger years because large events (>1,000 km 2 ). The proportion total human‐ignited fires decreased over this same time period, while burning during early late‐ growing‐seasons increased. Trends increased consistent...
Abstract Forest fires are a significant and natural element of the circumboreal forest. Fire activity is strongly linked to weather, increased fire due climate change anticipated or arguably has already occurred. Recent studies suggest doubling area burned along with 50% increase in occurrence parts by end this century. management agencies' ability cope these increases limited, as organizations operate narrow margin between success failure; disproportionate number may escape initial attack...
Significance Over many millennia, northern peatlands have accumulated large amounts of carbon and nitrogen, thus cooling the global climate. shorter timescales, peatland disturbances can trigger losses peat release greenhouses gases. Despite their importance to climate, remain poorly mapped, vulnerability permafrost warming is uncertain. This study compiles over 7,000 field observations present a data-driven map nitrogen stocks. We use these maps model impact thaw on find that will likely...
management. How does our behavior (including urban development and land-use, water consumption, pollution) influence the movement of energy, water, elements at local, regional, national or global scales? Will perturbations to chemical energy cycles alter existing controls on ecosystem processes, can we learn enough about them for effective regulation? Plants are critical in regulating biogeochemical cycles. Their growth exchange gases that support life current biosphere, affects soil...
Here, we present results from the most comprehensive compilation of Holocene peat soil properties with associated carbon and nitrogen accumulation rates for northern peatlands. Our database consists 268 cores 215 sites located north 45°N. It encompasses regions within which data have only recently become available, such as West Siberia Lowlands, Hudson Bay Kamchatka in Far East Russia, Tibetan Plateau. For all peatlands, content organic matter was estimated at 42 ± 3% (standard deviation)...
Abstract Wetlands are the largest natural source of atmospheric methane. Here, we assess controls on methane flux using a database approximately 19 000 instantaneous measurements from 71 wetland sites located across subtropical, temperate, and northern high latitude regions. Our analyses confirm general emissions soil temperature, water table, vegetation, but also show that these relationships modified depending type (bog, fen, or swamp), region (subarctic to temperate), disturbance. Fen was...
Abstract Thermokarst is the process whereby thawing of ice-rich permafrost ground causes land subsidence, resulting in development distinctive landforms. Accelerated thermokarst due to climate change will damage infrastructure, but also impact hydrology, ecology and biogeochemistry. Here, we present a circumpolar assessment distribution landscapes, defined as landscapes comprised current landforms areas susceptible future development. At 3.6 × 10 6 km 2 , are estimated cover ∼20% northern...
Abstract [1] This synthesis addresses the vulnerability of North American high-latitude soil organic carbon (SOC) pool to climate change. Disturbances caused by warming in arctic, subarctic, and boreal environments can result significant redistribution C among major reservoirs with potential global impacts. We divide current northern SOC pools into (1) near-surface soils where is affected seasonal freeze-thaw processes changes moisture status, (2) deeper permafrost peatland strata down...
Nitrification and denitrification processes are crucial to plant nutrient availability, eutrophication greenhouse gas production both locally globally. Unravelling the major environmental predictors for nitrification is thus pivotal in order understand model nitrogen (N) cycling. Here, we sampled five community types characteristic of interior Alaska, including black spruce, bog birch, tussock grass two fens. We assessed abundance functional genes affiliated with (bacterial archaeal amoA)...
Methane (CH4 ) emissions from the northern high-latitude region represent potentially significant biogeochemical feedbacks to climate system. We compiled a database of growing-season CH4 terrestrial ecosystems located across permafrost zones, including 303 sites described in 65 studies. Data on environmental and physical variables, conditions, were used assess controls emissions. Water table position, soil temperature, vegetation composition strongly influenced had interacting effects. Sites...
A synthesis was carried out to examine Alaska’s boreal forest fire regime. During the 2000s, an average of 767 000 ha·year –1 burned, 50% higher than in any previous decade since 1940s. Over past 60 years, there a decrease number lightning-ignited fires, increase extreme events, human-ignited and events. The fraction area burned from fires fell 26% for 1950s 1960s 5% 1990s result change policy that gave highest suppression priorities events occurred near human settlements. amount during...
In the boreal forests of interior Alaska, feedbacks that link forest soils, fire characteristics, and plant traits have supported stable cycles succession for past 6000 years. This high resilience stands to disturbance is by two interrelated feedback cycles: (i) interactions among regime plant–soil–microbial regulate soil organic layer thickness cycling energy materials, (ii) conditions, regeneration traits, effects on environment maintain community composition. Unusual events can disrupt...
Approximately 1700 Pg of soil carbon (C) are stored in the northern circumpolar permafrost zone, more than twice as much C atmosphere. The overall amount, rate, and form released to atmosphere a warmer world will influence strength feedback climate change. We used survey quantify variability perception vulnerability Experts were asked provide quantitative estimates change response four scenarios warming. For highest warming scenario (RCP 8.5), experts hypothesized that release from zone...
High-latitude ecosystems store approximately 1700 Pg of soil carbon (C), which is twice as much C currently contained in the atmosphere. Permafrost thaw and subsequent microbial decomposition permafrost organic matter could add large amounts to atmosphere, thereby influencing global cycle. The rates at being released from zone different depths across physiographic regions are poorly understood but crucial understanding future changes storage with climate change. We assessed inherent...