Analysis of energetic exchange processes within the two different forest ecosystems

The utilisation of energy within the floodplain forest ecosystem near Lednice - south Moravia, and spruce monoculture ecosystem near R jec Jestýeb¡ - central Moravia during the years 1988 and 1989 was measured. Net radiation balance, global solar radiation, wet bulb and dry bulb temperatures and soil heat flux directly by instruments and sensors; latent, sensible heat flux and heat flux to the vegetation was calculated. It is possible to say, considering hitherto results, that well watered (groundwater) floodplain forest ecosystem shows greater evapotranspiration and therefore latent heat flux than spruce monoculture. Greater flux of energy was recorded in a daily course of sensible heat flux (65% proportion to net radiation), in contrast with the spruce monoculture. The floodplain forest latent heat flux proportion to net radiation was found to be variable within the growing season; in the middle of the vegetation period (from June to August) it reached the value of about 70%, at the end (in October) of about 20%. The estimation of the floodplain forest actual evapotranspiration was possible almost all over the season, the actual evapotranspiration reached its maximum of about 0.72 mm/square m per h one hour after the maximum of radiation balance. The time lag of about 4 hours was observed when compared the diurnal course of air humidity gradient to the air temperature gradient above the forest canopy. This phenomenon caused the left side asymmetry of the diurnal course of the Bowen ratio. It was not possible to measure the spruce monoculture latent heat flux all over the season, probably due to smaller gradient of the air humidity although it was measured across at greater distance than in the floodplain forest (12 m in comparison with 9 m). The values of the second half of May and the first half of June ones were at our disposal only. The spruce monoculture latent heat flux proportion to radiation balance was found about 25%, the actual evapotranspiration reached maximum of about 0.28 mm/square m per h, nearly 3 times less than in case of floodplain forest. Daily curve of humidity gradient above spruce monoculture canopy displayed rather symmetric but not sinusoidal course. These values were comparable with the measuring accuracy. That is what considerably determines availability of chosen method within insufficient water conditions environment