Global Change Biology：二氧化碳升高环境对温室气体排放和作物产量的影响

中国科学院大气物理研究所姚志生研究员团利用多点位长期原位FACE系统研究了二氧化碳升高环境对温室气体排放和作物产量的影响。相关成果发表于Global Change Biology（IF=8.555）。

 

Abstract

 

Increasing levels of atmospheric CO2 are expected to enhance crop yields and alter soil greenhouse gas fluxes from rice paddies. While elevated CO2 (ECO) effects on CH4 emissions from rice paddies have been studied in some detail, little is known how ECO might affect N2O fluxes or yieldscaled emissions. Here, we report on a multisite, multiyear insitu FACE (freeair CO2 enrichment) study, aiming to determine N2O fluxes and crop yields from Chinese subtropical rice systems as affected by ECO In this study, we tested various N fertilization and residue addition treatments, with rice being grown under either ECO (+200 μmol mol1) or ambient control. Across the six siteyears, rice straw and grain yields under ECO were increased by 940% for treatments fertilized with ≥ 150 kg N ha1, while seasonal N2O emissions were decreased by 2373%. Consequently, yieldscaled N2O emissions were significantly lower under ECO. For treatments receiving insufficient fertilization (≤ 125 kg N ha1), however, no significant ECO effects on N2O emissions were observed. The mitigating effect of ECO upon N2O emissions is closely associated with plant N uptake and a reduction of soil N availability. Nevertheless, increases in yieldscaled N2O emissions with increasing N surplus suggests that N surplus is a useful indicator for assessing N2O emissions from rice paddies. Our findings indicate that with rising atmospheric CO2 soil N2O emissions from rice paddies will decrease, given that the farmers’ N fertilization is usually sufficient for crop growth. The expected decrease in N2O emissions was calculated to compensate 24% of the simultaneously observed increase in CH4 emissions under ECO. This shows that for an agronomic and environmental assessment of ECO effects on rice systems, not only CH4 emissions, but also N2O fluxes and yieldscaled emissions need to be considered for identifying most climatefriendly and economicallyviable options for future rice production.

 

大气中CO2水平的增加可能会提高作物产量，并改变稻田的土壤温室气体通量。虽然目前已有一些CO2升高（ECO）对稻田CH4排放的影响研究，但ECO如何影响N2O通量或单位产量相对应的排放的研究还较少。本文进行了一个多点位长期原位FACE （开放式CO2控制系统）的研究，在ECO（+200 μmol·mol1）或普通环境下，进行了不同施氮及添加处理下的水稻种植试验，旨在确定中国亚热带水稻系统中ECO对N2O通量和作物产量的影响。在6年试验期间，≥150 kg N·a1处理下，秸秆和粮食产量在ECO条件下增加了9%~40%，而季节性的N2O排放下降了23%~73%。因此，在ECO条件下，单位产量相对应的N2O排放显著降低。施肥量较低处理（≤125 kg N·ha1）下，ECO对N2O排放没有明显影响。ECO对N2O排放的降低作用与植物氮素吸收和土壤氮素利用率的下降密切相关。然而，随着氮素过剩量的增加，与产量相对应的N2O排放增加，这表明，氮素过剩是评估稻田N2O排放的一个有用指标。研究结果表明，由于农民的氮肥施用量通常足以促进作物生长，因此随着大气中CO2的增加，稻田中的N2O排放量将减少。预计减少的N2O排放量可以补偿ECO条件下同时观测到的CH4排放量增加的24％。这表明，要对ECO对水稻系统的影响进行农业和环境评估，不仅要考虑CH4排放，而且还应考虑N2O通量和单位产量相对应的排放量，以确定未来水稻生产中气候友好和经济可行的对应措施。