Abstract

not-yet-known not-yet-known not-yet-known unknown Salinization severely impacts soil health. The seasonal freeze-thaw period is a crucial time for the restoration of soil fertility, and soil microorganisms play an important role in the cycling of soil ecosystems. Therefore, it is essential to determine the changes in microbial abundance under the influence of soil salinity gradients during the seasonal freeze-thaw period and to understand their relationships with soil environmental factors.This study designed 19 different gradients of chloride and sulfate salts. Soil samples were collected after the seasonal freeze-thaw period to examine the abundance of soil microorganisms and soil environmental factors, followed by correlation analysis. We found that with increasing salinity, the abundance of soil bacteria and fungi significantly decreased, but chloride and sulfate concentrations at 3 g/kg promoted fungal proliferation.We also observed that during the seasonal freeze-thaw period under the chloride gradient: in the 0-5 cm soil layer, soil bacteria and fungi exhibited a symbiotic relationship, with the abundance of soil bacteria primarily influenced by soil pH, Na +, Ca 2+, Cl -, organic matter, and nitrate nitrogen; the abundance of soil fungi was mainly affected by soil pH. In the 5-20 cm soil layer, the abundance of soil bacteria was mainly influenced by soil salinity, soil pH, Ca 2+, Cl -, and nitrate nitrogen, while the abundance of soil fungi was affected by soil salinity, soil pH, Na +, Ca 2+, Cl -, and nitrate nitrogen.We also found that under the sulfate gradient during the seasonal freeze-thaw period: in the 0-5 cm soil layer, the abundance of soil bacteria was not significantly correlated with various soil indicators, and the abundance of soil fungi was mainly influenced by Na +, Ca 2+, Cl -, and SO 4 2-; in the 5-20 cm soil layer, the abundance of soil bacteria was influenced by soil pH, Na +, Ca 2+, Cl -, and SO 4 2-, while the abundance of soil fungi was affected by nitrate nitrogen. The thresholds for chloride and sulfate concentrations were 5.5 g/kg and 6.5 g/kg, respectively.