Abstract: Chinese Journal of Ecology,1993,12(1) ：62-66。The dynamic system of cotton seedling aphids,its natural enemies and climate is studied. A definitemodel of cusp mutation is set up and mutation regions are determined. The control and state variables ofthe system vary with time,and the boundary values determined by control variables can be used as thedynamic controlling targets of cotton seedling aphids, The model provides scientific basis for determiningcontrolling time and targets of cotton seedling aphids.

Key words: soil aggregate, soil organic carbon, primary forest, Karst cluster-peak depression.