There are many ways of micrometeorological description of the environment. One of them is the analysis of heat balance of an active surface which characterizes very well areas with different plant cover. In literature, the heat balance of an active surface is described as: Rn+LE+S+G=0. In the paper there are analyses of results of the measurements of the heat balance structure carried out in the vegetation season of 2000, during 43 days of July and August, over three agricultural ecosystems: maize, alfalfa and spring wheat. The daily dynamics of the heat balance structure as well as the influence of factors such as: radiation, precipitation and wind speed on the heat balance structure of the ecosystems and the landscape are examined in the paper.