Energy, water vapor and carbon fluxes in Andean agroecosystems: conceptualization and methodological standardization

This paper presents the conceptualization, methodological adjustment and experimental application of the micrometeorological technique eddy covariance - EC, to measure energy, water vapor and CO2 fluxes in two coffee agroecosystems: the first under full sunlight, and the second under shade, both with equatorial Andean hillslope conditions. With a footprint and fetch calculation, the required distance from the edge of the field in the prevailing wind direction to the EC tower is three times higher under shade than full sun. The shaded agroecosystem reached maximum average carbon fixation rates of 21.26 ± 2.469 μmolCO2.m-2s-1 ( = 0.05) (61% higher than under 100% sunlight) which gives a high carbon sink capacity to the association of coffee plants with shading Pigeon peas (Cajanus cajan L). The average evapotranspiration rate was 2.33 ± 0.0102 mm.d-1 ( = 0.05) and 2.08 ± 0.00732 mm.d-1 under shade and 100% sunlight, respectively. The proportion of net radiation that reached the soil was 2% under shade and 4% under 100% sunlight. Likewise, the soil energy loss during the night was lower under shade, indicating less day-night temperature range in the latter agroecosystem. The methodological adjustment and the results of this first work using EC in Colombian coffee plantations, contribute to the development of reliable research regarding gas and energy exchanges between the atmosphere and ecosystems in conditions of the equatorial Andean hillslope.