降水变化和氮沉降对荒漠草原土壤细菌群落结构及酶活性的影响

为明确降水变化和氮沉降对土壤细菌及酶活性的互作效应，本研究以短花针茅荒漠草原为研究对象，试验设计采用裂区设计，主区为自然降雨(CK)、增雨30%(W)和减雨30%(R)3个水分梯度，副区为0、30、50、100 kg·hm^-2·a^-14个氮素梯度(分别记为N0、N30、N50、N100)，共12个处理。结果表明：降水变化和氮沉降改变了土壤细菌群落组成，但未显著改变土壤细菌Alpha多样性；降水变化和氮沉降对土壤酶活性有显著影响。土壤过氧化氢酶活性在R-N100中最低(1.63 mg·g^-1·d^-1)，与CK-N0相比显著降低了7.4%；土壤蔗糖酶活性在W-N0中最高(2.20 mg·g^-1·d^-1)，与CK-N0相比显著增加了14.6%，在R-N100中最低(1.52 mg·g^-1·d^-1)，与CK-N0相比显著降低了20.8%；土壤脲酶活性在W-N0中最高(17.66 mg·g^-1·d

Effects of precipitation variation and nitrogen deposition on soil bacterial community structure and enzyme activity in desert steppe

A twelve-treatment experiment was designed in the Stipa breviflora desert steppe, with a main plot[three water treatments:30% increase(W), 30% reduction(R), and natural rainfall(CK)], and a split-plot with four nitrogen gradients[0(N0), 30 kg·hm^-2·a^-1(N30), 50 kg·hm^-2·a^-1(N50), and 100 kg·hm^-2·a^-1(N100)] to investigate the interaction effect of nitrogen deposition and rainfall fluctuations on soil bacterial community structure and enzyme activity. The results revealed that precipitation changes and nitrogen deposition altered the composition of the soil bacterial community, but not the alpha diversity of soil bacteria, and that precipitation changes and different nitrogen treatments had significant effects on soil enzyme activities. Soil catalase activity was the lowest in R-N100(1.63 mg·g^-1·d^-1) and significantly decreased by 7.4% compared with CK-N0. Soil sucrase activity was the highest in W-N0(2.20 mg·g^-1·d^-1) and significantly increased by 14.6% compared with CK-N0, and the lowest in R-N100(1.52 mg·g^-1·d^-1) and significantly decreased by 20.8% compared with CK-N0. Soil urease activity was the highest in W-N0(17.66 mg·g^-1·d^-1) and significantly increased by 16.7% compared with CKN0, and the lowest in CK-N100(9.27 mg · g^-1 · d^-1) and significantly decreased by 38.7% compared with CK-N0. Soil catalase was positively correlated with the bacterial richness index, whereas sucrase was positively correlated with both the bacterial diversity index and the bacterial richness index. The structural equation model showed that soil enzyme activity was primarily regulated by the diversity and pH of soil bacterial communities, with soil nitrate nitrogen content being the main environmental factor driving the change in soil bacterial community diversity. Comprehensive analysis revealed that water and nitrogen management influenced soil bacterial community structure and enzyme activity by changing the physical and chemical properties of the soil. The key parameters affecting soil enzyme activity were bacterial community diversity and soil pH, and it could be inhibited by a decrease in soil pH. The increased diversity of the bacterial community was beneficial to the enhancement of soil enzyme activity.