The importance of wetlands in the energy balance of an agricultural landscape

• DOI: 10.1007/s11273-013-9334-2
• Publication Date: 2013-12-23T16:36:07Z
• Authors: Hanna Huryna; Jakub Brom; Jan Pokorny
• Keywords: Bowen ratio; Energy budget; Arable land; Water balance; Available energy

Energy fluxes, including net radiation, latent heat flux and sensible heat flux were determined on clear days during the vegetative period in four types of land cover: wet meadow, pasture, arable field, and an artificial concrete surface. The average net radiation ranged between 123 W m−2 at the concrete surface and 164 W m−2 at the wet meadow. The mean maximum daytime latent heat ranged between 500 and 600 W m−2, which corresponds to an evapotranspiration rate of about 0.2 g m−2 s−1 under the prevailing conditions of the wet meadow. The results demonstrated that the wet meadow dissipated about 30 % more energy through evapotranspiration than the field or the pasture, and up to 70 % more energy than the concrete surface. The evaporative fraction indicated that more than 100 % of the energy released by the wet meadow was dissipated through evapotranspiration; this was attributed to local heat advection. Wetland evapotranspiration thus contributes significantly to the cooling of agricultural landscapes; the energy released can reach several 100 MW km−2. Wetland evapotranspiration has a double ‘air conditioning’ effect through which it equalises temperature differences: (1) surplus solar energy is bound into water vapour as latent heat; (2) The vapour moves towards cooler portions of the atmosphere where the energy is released. The air-conditioning effect of wetlands plays an important role in mitigating local climate extremes; this ecosystem service tends to be disregarded in relation to other better-known wetland functions such as nutrient retention and provision of high biodiversity.