Freezing saline water irrigation and plastic mulching change microbial diversity and assembly in coastal saline soil.

Amelioration of coastal saline soil is an important issue for coastal areas to cope with the shortage of arable land and the threat of climate changes. And the effects of amelioration practices on soil physicochemical properties have been widely studied. However, there is little information about the influence of amelioration on soil microbial ecology. In this study, microbial communities in a coastal saline soil under the amelioration practice of freezing saline water irrigation (WI), plastic mulching (M) and the combination of WI and M (WIM) were detected through high-throughput sequencing. Results showed that the coastal saline soil contained high relative abundance of taxa mostly found in sea water or marine sediment, but they were diluted in the ameliorated treatments. Amelioration decreased soil archaeal richness, increased bacterial richness and little impacted fungal richness. Species replacements had greatest contribution of the changes of bacterial community, then followed by archaeal community, and the changes of fungal community mostly resulted from changes in species abundance. The changes of soil microbial communities structure were mostly correlated with soil salt concentration, but the prokaryotic community had higher correlation with salt concentration than fungal community. Deterministic processes structured microbial communities across all the treatments, but it became less important in the ameliorated soil. Functional prediction revealed the opposite changes of archaea and bacteria with the same function, and the taxa with the function of degrading complex organic matter was enriched in M or WIM treatments, where supported plant growth. Taken together, these results demonstrated the different response of archaeal, bacterial and fungal communities to the amelioration in coastal saline soil, and these differences may be an important mechanism for soil community coping with environmental changes. The freezing saline water irrigation and plastic mulching, especially the combined of the both methods, alleviated the strong niche filter from high salt concentration in coastal saline soil, and stimulated microbial succession to form a community which may be benefit for agricultural production.