Effect of transgenic Bt cotton on soil invertebrate community structure

Soil invertebrates were collected by Tullgren and Baermann funnels and analyzed using community ecology method. Then soil invertebrate community structures in the 0~15 cm soil layer in transgenic Bt cotton (cvs. “GK12” and “NuCOTN 33B”) fields were compared with those in non-Bt cotton (cv. “SM3”) fields. Nematodes and acarids are dominant soil invertebrate groups with frequencies above 54% and over 18% respectively in each cotton cultivar field. Compared with parental non-Bt cv. “SM3”field, “GK12” field has more enchytraelidae and less homopetera, psocoptera and diptera. Cumulative numbers of most soil invertebrate groups do not significantly differ in “GK12” and “NuCOTN33B” fields, except that there are less homoptera and more araneae in “GK12” field. Soil invertebrate group richness, Shannon diversity and Pielou evenness are significantly lower in “GK12” field than in “SM3” field. Those in “NuCOTN 33B” field are also higher than in “GK12” field. Scalable one-parametric Rényi-diversity profiles also indicate significantly lower diversity in “GK12” than in “SM3” field, and generally lower diversity in “GK12” than in “NuCOTN 33B” field, except for dominant and common invertebrate groups in the 10~15 cm soil layer. The dynamics of soil invertebrate abundance, diversity and evenness have a similar fluctuation trend for the three cotton cultivar fields. Abundance of soil invertebrate reaches its peak in October during the period from July to November. At the peak, soil invertebrates are concentrated in the 0~5 cm and 10~15 cm soil layers in “SM3” field, but in the 10~15 cm soil layer in “GK12” and “NuCOTN 33B” fields. While invertebrate diversity and evenness decrease in November in “SM3” field, they increase in “GK12” field. The above findings imply that planting “GK12” changes the abundance, and decreases the richness, diversity and evenness of soil invertebrate groups. Soil invertebrate community structures also differ between the two Bt cotton cultivars, with higher diversity in “NuCOTN 33B” than in “GK12” field.