Latent heat exchange in the boreal and arctic biomes

Research output: Contribution to journalReview article

Abstract

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.

Details

Authors
  • Ville Kasurinen
  • Knut Alfredsen
  • Pasi Kolari
  • Ivan Mammarella
  • Pavel Alekseychik
  • Janne Rinne
  • Timo Vesala
  • Pierre Bernier
  • Julia Boike
  • Moritz Langer
  • Luca Belelli Marchesini
  • Ko Van Huissteden
  • Han Dolman
  • Torsten Sachs
  • Takeshi Ohta
  • Andrej Varlagin
  • Adrian Rocha
  • Altaf Arain
  • Walter Oechel
  • Magnus Lund
  • Achim Grelle
  • Andy Black
  • Mika Aurela
  • Tuomas Laurila
  • Annalea Lohila
  • Frank Berninger
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Physical Geography

Keywords

  • eddy-covariance, evapotranspiration, latent heat, phenology, stomatal, resistance
Original languageEnglish
Pages (from-to)3439-3456
JournalGlobal Change Biology
Volume20
Issue number11
Publication statusPublished - 2014
Publication categoryResearch
Peer-reviewedYes