Abstract: This paper studied the changes of urease, alkaline phosphatase and catalase activities and nitrate nitrogen, ammonium nitrogen, and available phosphorus contents in the rhizosphere soils of transgenic Bt+CpTI cotton and its parental isoline in different growth periods (30, 60, 90, and 120 d after sowing) under field condition. There was a similar change trend in the rhizosphere soil nitrate nitrogen, ammonium nitrogen, and available phosphorus contents between transgenic Bt+CpTI cotton and its parental isoline, but the change range varied with growth period. The rhizosphere soil alkaline phosphatase activity had less difference between transgenic Bt+CpTI cotton and its parental isoline 30, 60, and 120 d after sowing. Though the urease and catalase activities in the rhizosphere soils had different change trend with the growth of transgeniccotton and its parental isoline, no significant difference was observed in the two enzyme activities at the same growth periods between the two cotton cultivars. Our results indicated that the enzyme activities and available nutrient contents of rhizosphere soil were less affected by transgenic cotton, but mainly affected by the growth period.

Key words: arbuscular mycorrhizal fungi, species diversity, elevational gradient, Tibetan Plateau