Abstract: Based on the materials of plant geographical distribution and records of 342 meteorological stations, Penman's potential evapotranspimtion (PE) and aridity (A) of dominants and main companions of the subtropical evergreen broadleaved forest in China have been calculated. The groups of Penman' s water-temperature have been classified into five types. They are G1 (microthermai humid type), G2(micmthermal semihumid type), G3(mesothennai humid type), G4(mesothermal semihumid type), and G5 ( megathermal humid type). The ecoclimatic characteristics of these groups have been analyzed from which the results indicated a rather good setup of the distribution of tree species along with the water and thermal gradients. The calculation of Penman' s indices is relatively more complicated, but has been very widely used because of its reasonable and substantial physical basis. Penman' s indices are validated for studies of the relationship between tree species and climate of evergreen broadleaved forest in China.

Key words: Evergreen broadleaved forest, Dominants and companions, Penman's potential evapotranspiration, Aridity, Water-temperature groups