覆膜玉米不同生育期土壤酶活性对大气CO_2浓度升高的响应

Effects of elevated CO_2 on soil enzyme activities at different growth stages of maize grown with plastic film mulching

为探讨旱区覆膜玉米农田土壤酶活性对未来气候变化的响应,在田间条件下通过改进的开顶式气室(OTC)系统自动控制大气CO_2浓度,设置自然大气CO_2浓度(CK)、OTC对照(OTC)、OTC系统自动控制CO_2浓度(700μmol·mol^(-1),OTC+CO_2)3个处理,研究了旱区覆膜高产栽培春玉米播前、六叶期(V6)、十二叶期(V12)、吐丝期(R1)、乳熟期(R3)及完熟期(R6)土壤脲酶、碱性磷酸酶、蔗糖酶及过氧化氢酶活性对大气CO_2浓度升高的响应特征。研究发现:OTC处理条件下,土壤碱性磷酸酶活性相比CK在V12期降低8.80%(P<0.05),而在R6期提高8.95%(P<0.05);蔗糖酶活性在播前、V6、R1期降低12.65%～21.43%(P<0.05),R3期升高17.50%(P<0.05);过氧化氢酶活性在V12、R1、R6期均显著降低。大气CO_2浓度升高对玉米各生育期土壤脲酶活性均无显著影响;使R1、R6期碱性磷酸酶活性降低8.74%和6.39%(P<0.05);使V6、R3期蔗糖酶活性升高30.18%和18.37%(P<0.05);此外,增加了V12期过氧化氢酶活性,而降低了R3期过氧化氢酶活性。结果表明:当前旱作覆膜高产栽培模式下,大气CO_2浓度升高对春玉米农田土壤酶活性的影响因作物生育期和酶种类不同而异;土壤酶活性对OTC及大气CO_2浓度升高的响应程度不一,在当前试验条件下,OTC对土壤酶活性的影响较大气CO_2浓度升高更为显著。

A field experiment was conducted in a semiarid area to investigate the response of soil enzyme activities to climate change in a farmland of spring maize where plastic film mulching was used. Open-top chamber(OTC)system was used to control elevated CO2 concentrations(700 μmol·mol^-1, marked as OTC+CO2)during the growing period of maize. At the same time, OTC systems with the current atmospheric CO2 concentration(marked as OTC)and natural atmospheric CO2 concentration(control, marked as CK)were also set up. Activities of soil urease, alkaline phosphatase, sucrase, and catalase, at the different growth stages of spring maize(i.e., pre-sowing, sixth leaf(V6)stage, twelfth leaf(V12)stage, silking(R1)stage, milk(R3), and physiological maturity(R6)stage), were measured. The results showed that, compared with CK, OTC treatment decreased the activity of soil alkaline phosphatase by 8.80% at the V12 stage(P<0.05),and increased it by 8.95%(P<0.05)at the R6 stage, decreased the soil invertase activity by 12.65%~21.43%(P<0.05)at the pre-sowing,V6, and R1 stages, but increased it by 17.50%(P<0.05)at the R3 stage, and significantly decreased the activity of catalase at the V12, R1,and R6 stages under OTC. Compared with OTC, OTC+CO2 treatment had no significant effect on soil urease activity, increased the activity of soil sucrase by 30.18% and 18.37% at the V6 and R3 stages(P<0.05), respectively, and decreased the activity of alkaline phosphatase at the R1 and R6 stages by 8.74% and 6.39%(P<0.05), respectively. In addition, elevated CO2 increased activity of catalase at the V12 stage, but reduced it at the R3 stage. In conclusion, the effect of elevated CO2 on soil enzyme activities in spring maize farmland varied with the growth period and the enzyme. Further, under the current experimental conditions, the effect of OTC on soil enzyme activities was more significant than that of elevated CO2.