Studies of the comparative micrometeorology of two plant communmes, a field of wheat and a forest of Pmu~ radiata, are described. They were made over a period of four weeks m the spring, in the region of Canberra, where both communities grow under natural rainfall in similar aerial environments.
Components of the energy balance are compared. For a given short-wave solar radmtion intensity, quite large differences existed between the communities in net radmtlon, evaporation, photosynthesis and so~l heat flux The first three of these were greater for the forest, and the last was smaller
The data suggested that not only was net radiation generally h~gher for the forest, but also more of the available energy was partmoned into latent heat. Approximate calculatmns of mean fohage temperatures were made from the radlanon balance of both communmes, fhese indicated that, in general, fohage temperatures of the forest were close to, or even less than, air temperatures, while those of the wheat field were several degrees higher. The calculations provided independent ewdence for greater propomonal evaporation from the forest than the wheat field. In view of these differences, some comments are offered on the concept of potentml evapotransp~ratmn.
Because of differences m surface roughness, eddy dlffUSlWnes were generally almost an order of magnitude greater over the forest than over wheat, Since gradients of the various entitles were correspondingly smaller over the forest and therefore harder to detect, it was sometimes d~fficult to arrive at satisfactory flux estimates for that community.
In terms of product~wty, photosynthesis per umt of evaporation was greater for the forest, despite its greater water use.