Abstract: To clarify the effects of subsoiling on the dynamics of soil hydrothermal conditions, soil enzyme activity and bacterial community diversity in black soil, seven treatments were set up from 2016 to 2017, including rotary tillage (CK), one year of surface tillage (QS1), two years of surface tillage (QS2), one year of deep subsoiling (SS1), two years of deep subsoiling (SS2), one year of extradeep subsoiling (CS1), and two years of extradeep subsoiling (CS2). The variations of soil water content, temperature, catalase activity, saccharase activity, urease activity and bacterial community structure among different treatments were assessed. The results showed that subsoiling significantly reduced soil water content of 0-20 cm layer, with SS1 and SS2 showing the lowest reduction, and improved soil water content of 20-40 cm layer, with the highest enhancement in QS2. Soil water content in subsoiling for two years was higher than that in subsoiling for one year. The soil temperature of subsoiling treatments was significantly lower than that of CK at the flowering stage, while soil temperature at jointing stage, tasseling stage, mature stage was significantly higher compared to CK. Soil temperature declined significantly with the increases of subsoiling depth. Subsoiling could maintain longterm soil enzyme activity in 0-20 cm soil layer, and increase soil enzyme activity in 20-40 cm soil layer. Subsoiling improved the richness and diversity of bacterial communities in the rhizosphere soil of 0-20 cm layers. The richness of bacterial communities in subsoiling for two years was higher than that for one year, with SS2 being the best. Subsoiling increased the relative abundance of Acidobacteria, Gemmatimonadetes, Planctomycetes and Thaumarchaeota, but reduced that of Actinobacteria and Firmicutes. Our results indicated that subsoiling can optimize soil hydrothermal environment, maintain high and stable soil enzyme activity, coordinate the structure of bacterial community, and promote the sustainable use of black soil.

Key words: landscape ecological pattern, optimization strategy, urban forest, gradient analysis