增温增CO2对间作玉米光合特性的影响

【目的】明确增温增CO2对玉米||花生体系中玉米光合特性的影响,以期为未来气候变化条件下玉米||花生绿色高产高效栽培提供理论依据。【方法】以玉米||花生2﹕4模式为研究对象,2018年设常温常CO2(TC)和增温增CO2(+T+C)处理,2019年增设增温增CO2(+TC)处理,在P0(0)和P180(180 kg P2O5·hm^-2)2个磷水平下,研究了增温增CO2对间作玉米叶绿素含量、SPAD值、光合-光强、光合-CO2响应曲线及其相关参数的影响。【结果】(1)与TC处理相比,+TC处理提高了间作玉米苗后34 d叶绿素b和叶绿素a+b含量,降低了叶绿素a/b值,苗后55 d施磷条件下,SPAD值、AQY、CE、Amax、Vc,max、Jmax和TPU分别提高了7.80%、18.18%、18.86%、13.34%、13.33%和20.14%,产量提高了19.2%—28.1%;与+TC处理相比,+T+C处理提高了苗后55 d和65 d间作玉米AQY,降低了LCP,苗后55 d间作玉米CE、Amax、Vc,max、Jmax和TPU分别提高13.58%—32.96%、21.31%—11.61%、9.35%—14.55%、9.52%—15.13%和8.82%—26.16%,产量提高5.25%—18.70%,均达到显著差异水平(P<0.05)。(2)与TC处理相比,+T+C处理间作玉米大喇叭口期和灌浆期SPAD值分别提高4.68%—12.91%和7.88%—18.37%,蜡熟期却降低8.63%—12.72%;间作玉米苗后35 d叶绿素a、b和a+b分别提高17.58%—19.54%、52.55%—59.55%和26.08%—28.47%,叶绿素a/b降低了23.04%—25.18%;间作玉米苗后55 d的AQY和LSPn分别提高了30.30%—75.76%和16.87%—19.44%;CE、Amax、Vc,max、Jmax和TPU分别提高了15.72%—36.78%、24.91%—32.66%、20.77%—29.83%、20.93%—30.48%和27.16%—30.74%,产量提高了7.24%—52.0%,均达到显著差异水平(P<0.05)。(3)与不施磷相比,施磷提高了TC、+TC和+T+C处理苗后85 d时叶绿素b含量,增幅分别为24.15%、18.64%和22.04%;苗后34 d的LSPn分别提高了13.30%、17.0%和9.86%,产量分别提高了24.2%—67.2%、55.6%和27.8%—38.0%,均达到显著差异水平(P<0.05)。【结论】增温和增CO2均能提高间作玉米生育前期叶绿素含量和净光合速率,两者表现出正向协同作用,而在其生育中后期增CO2能缓解增温带来的负效应;增温增CO2能提高间作玉米的产量,关键在于其生育前中期叶绿素含量、羧化效率、最大电子传递速率和磷酸丙糖利用率的提高。施磷具有明显的正效应。

A Meta-analysis of the Effects of Warming and Elevated CO_2 on Soil Microbes

Soil microbes play important roles in terrestrial ecosystem carbon and nitrogen cycling. Climatic warming and elevated CO2 are two aspects of climatic change. In this study, we used a meta-analysis approach to synthesise observations related to the effects of warming and elevated CO2 on soil microbial biomass and community structure. Ecosystem types were mainly grouped into forests and grasslands. Warming methods included open top chambers and infrared radiators. Experimental settings included all-day warming, daytime warming and nighttime warming. Warming increased soil actinomycetes and saprotrophic fungi, while elevated CO2 decreased soil gram-positive bacteria(G+). Mean annual temperature and mean annual precipitation were negatively correlated with warming effects on gram-negative bacteria(G–) and total phospholipid fatty acid(PLFA), respectively. Elevation was positively correlated with the warming effect on total PLFA, bacteria, G+ and G–. Grassland exhibited a positive response of total PLFA and actinomycetes to warming, while forest exhibited a positive response in the ratio of soil fungi to bacteria(F/B ratio) to warming. The open top chamber method increased G–, while the infrared radiator method decreased the F/B ratio. Daytime warming rather than all-day warming increased G–. Our findings indicated that the effects of warming on soil microbes differed with ecosystem types, warming methods, warming times, elevation and local climate conditions.