Short communicationEffects of snow cover plus straw mulching on microorganisms in paddy soil during winter

- Variations of microbial communities in paddy systems are revealed during winter.
- The impacts of snow cover plus straw mulching on microorganisms are assessed.
- Snow cover plus straw mulching exert vital impacts on variations of microorganisms.
- Soil without snow and straw may loss massive organic carbon when soil thaws.

Soil microorganisms play key roles in the biogeochemical cycling of soil carbon and are sensitive to changes in the soil microclimate. A field experiment was conducted to investigate the effects of snow cover and straw mulching on microbial communities in paddy soils during winter, and four treatments were established: (i) snow removal with no straw mulching (Sn-SM-), (ii) snow cover with no straw mulching (SC), (iii) snow removal with straw mulching (SM), and (iv) snow cover with straw mulching (SC+SM+). The SC, SM, and, especially, SC+SM+ groups had more bacterial, gram-positive (G＋) bacterial, gram-negative (G－) bacterial, fungal, and total phospholipid fatty acids (PLFAs) than the Sn-SM- group from the freezing stage to the hard frost stage. The ratio of fungal/bacterial PLFAs first decreased, with the highest value in the SC+SM+ treatment, from the freezing to the hard frost stages and increased during the thawing stage, while the ratio of G＋/G－ PLFAs showed the opposite trend. The Sn-SM- treatment resulted in a rapid increase in microorganisms during the thawing stage. Our results demonstrated that the SC, SM, and, especially, SC+SM+ treatments reduced the losses of microbial biomass from the unfrozen stage to the hard frost stage and prevented an increase in microbial activity during the thawing stage in a paddy system.