Effect of elevated O3 associated with Bt cotton on the abundance, diversity and community structure of soil Collembola

Abstract

A strain of cotton that was modified to express a gene derived from the bacterium Bacillus thuringiensis (Bt) to combat cotton bollworm was extensively planted in China. Meanwhile, tropospheric ozone (O3) concentrations have increased alongside rapid industrialization and urbanization. Four treatments including two cotton varieties (Bt vs. non-Bt) and two concentrations of O3 (current vs. doubled) were designed to investigate the abundance and community structure of soil Collembola in open-top chambers (OTCs) in 2009.The above- and below-ground plant biomass and abundance of Collembola strongly decreased under elevated O3 compared with ambient atmospheric O3 in the OTCs. The abundance of Collembola from the genus Onychiurus and the diversity of Collembola were significantly lower in the Bt cotton OTCs compared with the non-Bt cotton OTCs. Under the elevated O3 level, the abundance and diversity of Collembola were significantly reduced in the non-Bt cotton fields but not in the Bt cotton fields at some cotton stages. In addition, the Bt cotton cultivation strongly decreased the diversity of Collembola under atmospheric conditions but not with elevated O3 levels.Our results suggest that Bt cotton can buffer the effect of elevated O3 on soil collembolans through the root-derived ways. In addition, elevated O3 had an extensive adverse effect on soil Collembola, but the effect of the Bt crop on Collembola was species-specific.