期刊
GLOBAL CHANGE BIOLOGY
卷 20, 期 11, 页码 3439-3456出版社
WILEY
DOI: 10.1111/gcb.12640
关键词
eddy-covariance; evapotranspiration; latent heat; phenology; stomatal resistance
资金
- Nordic Center of Excellence CRAICC (Cryosphere-atmosphere interactions in a changing Arctic climate)
- Center of Excellence [1118615, ICOS 271878, ICOS-Finland 281255, ICOS-ERIC 281250]
- EU through project GHG-Europe
- EU through project InGOS
- Fluxnet-Canada
- AmeriFlux
- US National Science Foundation
- Canadian Foundation for Climate and Atmospheric Sciences (CFCAS)
- Natural Sciences and Engineering Research Council (NSERC) of Canada
- BIOCAP Canada
- Natural Resources Canada
- CFCAS
- Ministry of Environment (Ontario)
- Forestry Research Parnership (Canada)
- Forestry Canada
- NASA [NAG5-11154, NASA NNG05GA76G]
- Helmholtz Association (Helmholtz Young Investigators Group) [VH-NG-821]
- Environment Canada
- Direct For Biological Sciences
- Emerging Frontiers [1065587] Funding Source: National Science Foundation
- Grants-in-Aid for Scientific Research [26242026] Funding Source: KAKEN
In this study latent heat flux (E) measurements made at 65 boreal and arctic eddy-covariance (EC) sites were analyses by using the Penman-Monteith equation. Sites were stratified into nine different ecosystem types: harvested and burnt forest areas, pine forests, spruce or fir forests, Douglas-fir forests, broadleaf deciduous forests, larch forests, wetlands, tundra and natural grasslands. The Penman-Monteith equation was calibrated with variable surface resistances against half-hourly eddy-covariance data and clear differences between ecosystem types were observed. Based on the modeled behavior of surface and aerodynamic resistances, surface resistance tightly control E in most mature forests, while it had less importance in ecosystems having shorter vegetation like young or recently harvested forests, grasslands, wetlands and tundra. The parameters of the Penman-Monteith equation were clearly different for winter and summer conditions, indicating that phenological effects on surface resistance are important. We also compared the simulated E of different ecosystem types under meteorological conditions at one site. Values of E varied between 15% and 38% of the net radiation in the simulations with mean ecosystem parameters. In general, the simulations suggest that E is higher from forested ecosystems than from grasslands, wetlands or tundra-type ecosystems. Forests showed usually a tighter stomatal control of E as indicated by a pronounced sensitivity of surface resistance to atmospheric vapor pressure deficit. Nevertheless, the surface resistance of forests was lower than for open vegetation types including wetlands. Tundra and wetlands had higher surface resistances, which were less sensitive to vapor pressure deficits. The results indicate that the variation in surface resistance within and between different vegetation types might play a significant role in energy exchange between terrestrial ecosystems and atmosphere. These results suggest the need to take into account vegetation type and phenology in energy exchange modeling.
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