Responses of wetland soil bacterial community and edaphic factors to two-year experimental warming and Spartina alterniflora invasion in Chongming Island

Abstract

Climate warming and plant invasions are among the most serious threads to biodiversity and stability in terrestrial ecosystems. A particular challenge is to predict how soil microbial communities and edaphic factors will change under future conditions. Despite evidence that soil microbial community structure can be shifted by experimental warming and plant invasion, few studies were conducted to quantify the interactive effect of both factors. Here, we compared soil microbial diversity, bacterial community, and soil physiochemical properties in both surface (0–5 cm) and subsurface (5–20 cm) soils of two-year open-top chambers (OTCs) warming and Spartina alterniflora (S. alterniflora) invasion treatments with no warming and Phragmites australis (P. australis) treatments. Results showed that surface soil water content, total organic carbon, total nitrogen (TN), and the ratio of TN to total phosphorous (N:P) were significantly decreased by experimental warming, while pH was significantly enhanced. Soil TN was significantly enhanced in the mixed community of P. australis and S. alterniflora compared with single species community. Soil TP was gradually decreased with the proportion of S. alterniflora increasing by experimental warming. Soil bacterial α diversity was not changed by either experimental warming or S. alterniflora invasion. Experimental warming significantly shifted soil bacterial community, whereas S. alterniflora invasion and their interaction showed no impact. Redundancy analysis showed soil bacterial community structure was highly correlated with soil edaphic factors (i.e. pH, TN, and NH4+-N). Prediction of microbial function profiles revealed that several bacterial functions, especially carbon and nitrogen metabolism pathways, were adjusted to tolerate warming. Overall, our results demonstrated that experimental warming significantly altered soil bacterial community and physiochemical properties of S. alterniflora and P. australis communities, and should be considered in ecologically sustainable development of Chongming Island and wetland ecosystem.