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Energy exchange and water budget partitioning in a boreal minerogenic mire
Author(s) -
Peichl Matthias,
Sagerfors Jörgen,
Lindroth Anders,
Buffam Ishi,
Grelle Achim,
Klemedtsson Leif,
Laudon Hjalmar,
Nilsson Mats B.
Publication year - 2013
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1029/2012jg002073
Subject(s) - evapotranspiration , mire , environmental science , boreal , sensible heat , eddy covariance , atmospheric sciences , precipitation , energy budget , hydrology (agriculture) , vapour pressure deficit , soil water , growing season , latent heat , surface water , zoology , transpiration , ecology , ecosystem , peat , geography , photosynthesis , soil science , meteorology , botany , biology , geotechnical engineering , environmental engineering , engineering , geology
This study investigated patterns and controls of the seasonal and inter‐annual variations in energy fluxes (i.e., sensible heat, H , and latent heat, λE ) and partitioning of the water budget (i.e., precipitation, P ; evapotranspiration, ET ; discharge, Q ; and soil water storage, ∆S ) over five years (2001–2005) in a boreal oligotrophic fen in northern Sweden based on continuous eddy covariance, water table level ( WTL ), and weir measurements. For the growing season (May 1 to September 31), the 5 year averages (± standard deviation) of the midday (10:00 to 14:00 h) Bowen ratio ( β , i.e., H / λE ) was 0.86 ± 0.08. Seasonal and inter‐annual variability of β was mainly driven by λE which itself was strongly controlled by both weather (i.e., vapor pressure deficit, D , and net radiation, R n ) and physiological parameters (i.e., surface resistance). During the growing season, surface resistance largely exceeded aerodynamic resistance, which together with low mean values of the actual ET to potential ET ratio (0.55 ± 0.05) and Priestley‐Taylor α (0.89) suggests significant physiological constrains on ET in this well‐watered fen. Among the water budget components, the inter‐annual variability of ET was lower (199 to 298 mm) compared to Q (225 to 752 mm), with each accounting on average for 34 and 65% of the ecosystem water loss, respectively. The fraction of P expended into ET was negatively correlated to P and positively to R n . Although a decrease in WTL caused a reduction of the surface conductance, the overall effect of WTL on ET was limited. Non‐growing season (October 1 to April 30) fluxes of H , λE , and Q were significant representing on average −67%, 13%, and 61%, respectively, of their growing season sums (negative sign indicates opposite flux direction between the two seasons). Overall, our findings suggest that plant functional type composition, P and R n dynamics (i.e., amount and timing) were the major controls on the partitioning of the mire energy and water budgets. This has important implications for the regional climate as well as for ecosystem development, nutrient, and carbon dynamics.