Abstract: The study on the soil physical properties,nutrient contents,microbial amounts and enzyme activities of clear cutting and controlled burning Chinese fir stands showed that in comparing with the control,soil non?capillary porosity of clear cutting stand increased by 23%,whereas soil natural water capacity and capillary moisture capacity decreased by 25%.In controlled burning stand,soil bulk density increased by 10%,while soil non-capillary porosity, natural water capacity and capillary moisture capacity decreased by 61%,48% and 26%,respectively.The contents of soil organic matter,total N,total P and total K in clear cutting stand decreased by 14%,14%,35% and 22%,and in controlled burning stand,they decreased by 37%,37%,47% and 7%,respectively.Soil alkalized N and available K in clear cutting stand increased by 24% and 31%,respectively,but soil available P decreased by 15%.The contents of soil alkalized N,available P and available K in controlled burning stand decreased by 25%,43% and 40%,respectively.In clear cutting stand,the amounts of soil bacteria,fungi and actinomyces increased by 1.4,11.3 and 0.8 times,respectively,but in controlled burning stand,the amounts of soil bacteria decreased by 24%,while those of soil fungi and actinomyces increased by 5.0 and 0.5 times,respectively.The activities of soil urease,catalase and cellulase in clear cutting stand increased by 1.9,1.6 and 2.1 times,and in controlled burning land,they were 35%,90% and 106% of the control,respectively.Damp soil had higher contents of organic matter,total N and total P,whereas porous soil was favorable for the accumulation of alkalized N,available P and available K and for the increase of soil urease activity.The amount of soil fungi decreased with increasing soil capillary porosity.Aerated soil was favorable for the increase of soil catalase activity.

Key words: Latent root regression, Natural enemy brown planthopper complex population, Predation quantity