Response of soil enzymes and microbial communities to root extracts of the alien Alternanthera philoxeroides

Alternanthera philoxeroides is an alien invasive species, which can cause substantial damage to the local ecosystem by secreting allelochemicals. The objective of the present study was to appraise the effects of root extracts of the invasive plant Alternanthera philoxeroides on soil enzyme and native microbial community. Urease activity was measured using the phenol sodium hypochlorite colorimetric method, sucrase activity was determined by 3, 5-dinitrosalicylic acid colorimetric method, catalase activity was determined using the KMnO4 titration method and alkaline phosphatase activity was determined by the disodium phenyl phosphate colorimetric method. The soil microbial community was investigated by pyrosequencing of the 16S rRNA gene. Results showed that the alkaline phosphatase, sucrase and urease activities were all significantly lower than that of the control treatment. The structure of the soil microbial community in the treatments with root extracts addition clearly differed from that of the control treatment. The result showed that the relative abundance of microorganism decreased including Burkhholderia, Gp6, Gp1 and Gp4 in the applied treatments at genus level as compared to control treatment. Hence, we inferred that A. philoxeroides could inhibit the growth of native plant species through toxic effects on soil enzyme activities and the microbial community.