Abstract: The species, quantity and population fluctuation of pests and their natural enemies are investigated in 1988 in larch-Scot pine and larch-Amorpha mixed forests at Panshi county of Jilin province. Shannon's index H', Simpon's index Dand Piolon's index J' are used to compare the popultion diversities of pests and their natural enemies in the two types of forest. Detailed results are presented in the paper.

Key words: wheat, drought stress, drought tolerance, photosynthesis, root system