A5081271417- Peatlands and Wetlands Ecology
- Climate change and permafrost
- Plant Water Relations and Carbon Dynamics
- Cryospheric studies and observations
- Coastal wetland ecosystem dynamics
- Geology and Paleoclimatology Research
- Atmospheric and Environmental Gas Dynamics
- Climate variability and models
- Botany and Plant Ecology Studies
- Fire effects on ecosystems
- Hydrology and Watershed Management Studies
- Soil and Unsaturated Flow
- Science and Climate Studies
- Tree-ring climate responses
- Remote Sensing in Agriculture
- Remote Sensing and LiDAR Applications
- Forest ecology and management
- Arctic and Antarctic ice dynamics
- Methane Hydrates and Related Phenomena
- Meteorological Phenomena and Simulations
- Ecology and Vegetation Dynamics Studies
- Ecology and biodiversity studies
- Geological Studies and Exploration
- Urban Heat Island Mitigation
- Integrated Water Resources Management
Trent University
2016-2025
Universität Hamburg
2014
Wisconsin Disability Association
2002
Institut National de Recherche Forestière
2001
McMaster University
1986-1988
Thawing permafrost and the resulting microbial decomposition of previously frozen organic carbon (C) is one most significant potential feedbacks from terrestrial ecosystems to atmosphere in a changing climate. In this article we present an overview global C pool processes that might transfer into atmosphere, as well associated ecosystem changes occur with thawing. We show accounting for stored deep more than doubles previous high-latitude inventory estimates, new estimate equivalent twice...
Abstract Northern peatlands contain up to 25% of the world's soil carbon (C) and have an estimated annual exchange CO 2 ‐C with atmosphere 0.1–0.5 Pg yr −1 CH 4 10–25 Tg . Despite this overall importance global C cycle, there been few, if any, complete multiyear balances for these ecosystems. We report a 6‐year balance computed from continuous net ecosystem (NEE), regular instantaneous measurements methane (CH ) emissions, export dissolved organic (DOC) northern ombrotrophic bog. From...
Eddy covariance measurements of net ecosystem carbon dioxide (CO 2 ) exchange (NEE) were taken at an ombrotrophic bog near Ottawa, Canada from 1 June 1998 to 31 May 2002. Temperatures during this period above normal except for 2000 and precipitation was in 1999, 2000, well below 2001. Growing maximum daytime uptake (−0.45 mg CO m −2 s −1 similar all years nighttime respiration typically 0.20 , however, larger values recorded very dry conditions the fourth year study. Winter flux considerably...
Summary Above‐ground biomass was measured at bog hummock, hollow and poor‐fen sites in Mer Bleue, a large, raised ombrotrophic near Ottawa, Ont., Canada. The average above‐ground 587 g m −2 the bog, composed mainly of shrubs Sphagnum capitula. In poor fen, 317 , comprising sedges herbs Vascular plant greater where water table lower, with similar but weaker relationship for capitula vascular leaf biomass. Below‐ground averaged 2400 hummock site, which 300 fine roots (< 2 mm diameter),...
Abstract. Although Arctic tundra has been estimated to cover only 8% of the global land surface, large and potentially labile carbon pools currently stored in soils have potential for emissions (C) under a warming climate. These as radiatively active greenhouse gases form both CO2 CH4 could amplify warming. Given sensitivity these ecosystems climate change expectation that will experience appreciable over next century, it is important assess whether responses C exchange regions are likely...
Our current understanding of terrestrial carbon processes is represented in various models used to integrate and scale measurements CO 2 exchange from remote sensing other spatiotemporal data. Yet assessments are rarely conducted determine how well simulate across vegetation types environmental conditions. Using standardized data the North American Carbon Program we compare observed simulated monthly 44 eddy covariance flux towers America 22 biosphere models. The analysis period spans ∼220...
Abstract Many wetland ecosystems such as peatlands and wet tundra hold large amounts of organic carbon (C) in their soils, are thus important the terrestrial C cycle. We have synthesized data on dioxide (CO 2 ) exchange obtained from eddy covariance measurements 12 sites, covering 1–7 years at each site, across Europe North America, ranging ombrotrophic minerotrophic to ecosystems, spanning temperate arctic climate zones. The average summertime net ecosystem CO (NEE) was highly variable...
Abstract The regional variability in tundra and boreal carbon dioxide (CO 2 ) fluxes can be high, complicating efforts to quantify sink‐source patterns across the entire region. Statistical models are increasingly used predict (i.e., upscale) CO large spatial domains, but reliability of different modeling techniques, each with specifications assumptions, has not been assessed detail. Here, we compile eddy covariance chamber measurements annual growing season gross primary productivity (GPP),...
Methane flux from northern peatlands is believed to be an important contribution the global methane budget. High latitude regions are predicted experience significant changes in surface temperature and precipitation associated with 2 × CO2 climate scenarios, but effects of these on emission poorly understood. A peatland hydrologic model June - August decreases water storage between 82 144 mm, using as inputs increases temperatures 3 °C rainfall 1 mm d-1. These translate into a table drop,...
Abstract Evapotranspiration (ET) was measured via the eddy covariance technique at a shrub bog peatland in southeastern Ontario for 5 years. For most of study period temperature above normal. Precipitation variable, but, 2 years, late summer dry periods resulted an extended deep drawdown water table (WT). Growing‐season (May–September) daily ET varied considerably; maximum rates were 4 to mm day −1 . Winter order magnitude smaller than summer, yet total winter loss important, accounting 23...
We analyzed the relationship between net ecosystem exchange of carbon dioxide (NEE) and irradiance (as photosynthetic photon flux density or PPFD), using published unpublished data that have been collected during midgrowing season for balance studies at seven peatlands in North America Europe. NEE measurements included both eddy‐correlation tower clear, static chamber methods, which gave very similar results. Data were by site, as aggregated sets peatland type (bog, poor fen, rich all fens)...
Eddy covariance measurements of the carbon dioxide flux from an ombrotrophic bog near Ottawa, Canada, were made between June 1, 1998, and May 31, 1999. Net ecosystem exchange CO 2 (NEE) showed a distinct annual cycle, with net daily uptake increasing rapidly after snowmelt, peaking in midsummer declining toward fall. Summer (June to September) mean NEE was −2.8±0.23 (standard error) g m −2 d −1 , but values ranged considerably loss 4.8 maximum −8.3 . Daytime fluxes closely related...
Northern peatlands contain enormous quantities of organic carbon within a few meters the atmosphere and play significant role in planetary balance. We have developed new, process‐oriented model contemporary balance northern peatlands, Peatland Carbon Simulator (PCARS). Components PCARS are (1) vascular nonvascular plant photosynthesis respiration, net aboveground belowground production, litterfall; (2) aerobic anaerobic decomposition peat; (3) oxidation, emission methane; (4) dissolved loss...
Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric dioxide because potential accelerating effects positive climate–carbon cycle feedbacks. However, directly observed CO2 with atmosphere across biomes continents are lacking. Here we present data describing net ecosystem (NEE) factors as measured using eddy covariance method at 125 unique sites in various over six a total 559 site-years. We find that...
Methane flux from northern peatlands is believed to be an important contribution the global methane budget.High latitude regions are predicted experience significant changes in surface temperature and precipitation associated with 2 x C0 climate scenarios, but effects of these on emission poorly understood.A peatland hydrologic model June-August decreases water storage between 82 144 mm, using as inputs increases temperatures 3 °C rainfall 1 mm d -1 • These translate into a table drop,...
In this study we examined ecosystem respiration (RECO) data from 104 sites belonging to FLUXNET, the global network of eddy covariance flux measurements. The goal was identify main factors involved in variability RECO: temporally and between as affected by climate, vegetation structure plant functional type (PFT) (evergreen needleleaf, grasslands, etc.). We demonstrated that a model using only climate drivers predictors RECO failed describe part temporal dependency on gross primary...
Abstract Tundra‐atmosphere exchanges of carbon dioxide (CO 2 ) and water vapour were measured near Daring Lake, Northwest Territories in the Canadian Low Arctic for 3 years, 2004–2006. The measurement period spanned late‐winter until end growing period. Mean temperatures during varied from about °C less than historical average 2004 2005 to greater 2006. Much added warmth 2006 occurred at beginning study, when snow melt weeks earlier other years. Total precipitation (163 mm) was more double...
• It is well established that individual organisms can acclimate and adapt to temperature optimize their functioning. However, thermal optimization of ecosystems, as an assemblage organisms, has not been examined at broad spatial temporal scales. Here, we compiled data from 169 globally distributed sites eddy covariance quantified the response functions net ecosystem exchange (NEE), ecosystem-level property, determine whether NEE shows optimality explore underlying mechanisms. We found...
Abstract Soils are warming as air temperatures rise across the Arctic and Boreal region concurrent with expansion of tall-statured shrubs trees in tundra. Changes vegetation structure function expected to alter soil thermal regimes, thereby modifying climate feedbacks related permafrost thaw carbon cycling. However, current understanding impacts on temperature is limited local or regional scales lacks generality necessary predict stability a pan-Arctic scale. Here we synthesize shallow...
Micrometeorological measurements were made over a northern boreal fen near Thompson, Manitoba, Canada, as part of the Boreal Ecosystem‐Atmosphere Study. The measurement period extended from start snowmelt until early fall, at which time senescence was widespread throughout fen. Data analysis concentrated on identifying seasonal trends in energy, water, and carbon dioxide fluxes linking them to observed surface cover changes. Albedos (solar photosynthetically active radiation (PAR)) showed...
Northern peatlands are a diverse group of ecosystems varying along continuum hydrological, chemical, and vegetation gradients. These contain about one third the global soil carbon pool, but it is uncertain how water cycling processes response to climate change differ among peatland types. This study examines midsummer CO 2 H O fluxes measured using eddy covariance technique above seven northern including low‐shrub bog, two open poor fens, wooded moderately rich extreme‐rich fens. Gross...