Abstract: This paper studied the change trends of soil microbial biomass carbon and enzyme activities in the process of vegetation change from natural evergreen broadleaved forest to Chinese fir (Cunninghamia lanceolata) plantation and then to Chinese fir and Michelia macclurei mixed plantation in Huitong, Hunan Province. During the vegetation change, the soil microbial biomass carbon decreased significantly. The soil microbial biomass carbon in Chinese fir plantation and in Chinese fir and M. macclurei mixed plantation was deceased by 76.8% and 71.5%, respectively, compared with that in natural evergreen broadleaved forest. After the vegetation change from natural evergreen broadleaved forest to Chinese fir plantation, the activities of soil invertase, urease, and phosphatase decreased by 35.8%, 22.1%, and 45.1%, respectively, while the activity of soil polyphenoloxidase increased by 40.0%. On the contrary, after the vegetation change from Chinese fir plantation to Chinese fir and M. macclurei mixed plantation, the activities of soil invertase, urease, and phosphatase increased by 20.3%, 12.6%, and 67.8%, respectively, while the activity of soil polyphenoloxidase decreased by 41.0%. The results showed that forest vegetation change greatly affected soil microbial biomass carbon and enzyme activities, and the effects varied obviously with tree species.

Key words: Grazing resistance, Resistant and tolerant thresholds, Grazing resistant strategies