[Effects of elevated CO2 concentration, warming, and winter wheat planting on soil enzyme activities.]

Understanding the responses of soil enzyme activities to elevated CO2 concentration and warming can provide a scientific basis for nutrient management of croplands under global climate change. We conducted a pot expe-riment with climate chamber to examine the effects of elevated CO2 concentration and warming and winter wheat growth on soil enzyme activities. There were four climate scenarios: control (CK, 400 μmol·mol-1 CO2 concentration+normal ambient temperature), and CO2 concentration elevation (ECO2, 800 μmol·mol-1 CO2 concentration+normal ambient temperature), elevated temperature (ET, 400 μmol·mol-1 + temperature increased 4 ℃), and elevated CO2 concentration and temperature (ECO2+T, 800 μmol·mol-1 CO2 concentration + temperature increased 4 ℃). We measured the activities of soil β-glucosidase (βG), β-N-acetyl glucosidase (NAG), alkaline phosphate (ALP) and polyphenol oxidase (PPO) at four growth stages (JS, jointing stage; AS, anthesis stage; FS, filling stage and MS, maturity stage), with and without winter wheat planting. Without winter wheat planting, there was no significant difference in four kinds of soil enzyme activities between ECO2 and CK, while ET and ECO2+T treatments had significant negative effect on soil enzyme activities. With winter wheat planting, compared with CK, ECO2 and ECO2+T treatments did not affect the activities of those four soil enzyme; but the ET treatment had great impact on soil ALP and PPO activities. The activities of four kinds of soil enzyme were significantly diffe-rent between the ET and ECO2+T treatments. Compared with ET treatment, ECO2+T treatment increased soil βG activity at the JS, decreased NAG activity at the JS, increased ALP activity at both AS and FS, decreased PPO activity in the JS and increased in the AS. The interaction of elevated CO2 concentration and warming had significant effect on soil NAG and ALP activities with and without winter wheat planting. The interaction of warming and expe-rimental stage had significant effect on four kinds of soil enzyme activities without winter wheat planting, but the interaction of warming and crop growth stage had significant effect on ALP and PPO activities with winter wheat planting. The interaction of elevated CO2 concentration, warming and experimental period had significant effect on soil βG, ALP and PPO activities without winter wheat growth, while with winter wheat growth, it had significant impact on NAG, ALP and PPO activities. The winter wheat growth had significantly inhibitory effect on βG, NAG and ALP activities in the two early growth periods (JS+AS), significant promoting effect in the later growth periods (FS+MS), and significantly inhibitory effect on PPO activity during whole growth period. Overall, elevated CO2 concentration did not affect soil enzyme activities, while the elevation of CO2 concentration and temperature on soil enzyme activities differed among the soil enzymes at different growth stages. In addition, the responses of four soil enzyme activities to the interaction of elevated CO2 concentration and warming varied with and without winter wheat planting.研究农田土壤酶活性对CO2浓度升高和增温的响应,可为气候变化背景下农田生态系统养分管理提供科学依据。本研究在人工模拟气候室进行盆栽控制试验,设置了4种气候情景,分别为对照(CK,CO2浓度400 μmol·mol-1+正常环境温度)、CO2浓度升高(ECO2,CO2浓度800 μmol·mol-1+正常环境温度)、增温(ET,CO2浓度400 μmol·mol-1+增温4 ℃)及CO2浓度和温度均升高(ECO2+T,CO2浓度800 μmol·mol-1+增温4 ℃),研究有、无冬小麦生长下β--葡萄糖苷酶(βG)、β-N-乙酰葡糖苷酶(NAG)、碱性磷酸单脂酶(ALP)和多酚氧化酶(PPO)4种土壤酶活性在冬小麦拔节期(JS)、开花期(AS)、灌浆期(FS)和成熟期(MS)对CO2浓度升高和增温的响应。结果表明:无冬小麦生长下,ECO2与CK间4种土壤酶活性差异不显著,而ET和ECO2+T处理对4种土壤酶活性有显著抑制作用。有冬小麦生长条件下,与CK相比,ECO2和ECO2+T处理对4种土壤酶活性均无显著影响;ET处理对土壤ALP和PPO活性有显著影响;ECO2+T与ET间4种土壤酶活性有显著差异,与ET相比,ECO2+T处理的土壤βG活性在JS期显著增加,NAG活性在JS期显著降低,ALP活性在AS和FS期显著增加,PPO活性在JS期显著降低,而在AS期显著增加。CO2浓度升高与增温的交互作用在有、无冬小麦生长下均对土壤NAG和ALP活性有显著影响;无冬小麦生长下,增温和试验时段的交互作用对4种土壤酶活性有显著影响,而在有冬小麦生长下,增温和生育期的交互作用仅对ALP和PPO活性有显著影响;CO2浓度升高、增温与试验时段的交互作用在无冬小麦生长下对土壤βG、ALP和PPO活性有显著影响,而在有冬小麦生长下CO2浓度升高、增温与生育期对土壤NAG、ALP和PPO活性有显著影响。冬小麦生长对土壤βG、NAG和ALP活性在前两个生育期(JS+AS期)表现为显著抑制作用,在后两个生育期(FS+MS期)表现为显著促进作用,对土壤PPO活性在全生育期均表现为显著抑制作用。总体上,CO2浓度升高对冬小麦土壤酶活性的影响不显著,而CO2浓度与温度均升高对冬小麦土壤酶活性的影响在不同生育期因土壤酶种类不同而不同;此外,有、无冬小麦条件下4种土壤酶活性对CO2浓度升高与增温的交互作用响应程度不一。.