Global Change Biology：中国主要农田温室气体排放强度时空变化评估

美国奥本大学Hanqin Tian团队与中国科学院生态环境研究中心合作对1949年至2012年中国小麦、玉米和水稻的温室气体排放强度的时空变化率进行了国家尺度的最新评估。相关成果发表于Global Change Biology（IF=8.555）。

Abstract

Balancing crop production and greenhouse gases (GHGs) emissions from agriculture soil requires a better understanding and quantification of crop GHGs emission intensity, a measure of GHG emissions per unit crop production. Here, we conduct a state‐of‐the‐art estimate of the spatial‐temporal variability of GHG emission intensities for wheat, maize, and rice in China from 1949‐2012 using an improved agricultural ecosystem model (DLEM‐AG2.0) and meta‐analysis covering 172 field‐GHG emission experiments. The results show that the GHG emission intensities of these croplands from 1949‐2012, on average, were 0.10‐1.31 kg CO₂‐eq kg^‐1, with a significant increase rate of 1.84‐3.58×10^‐3 kg CO₂‐eq kg^‐1 yr^‐1. Nitrogen fertilizer was the dominant factor contributing to the increase in GHG emission intensity in northern China and increased its impact in southern China in the 2000s. Increasing GHG emission intensity implies that excessive fertilizer failed to markedly stimulate crop yield increase in China but still exacerbated soil GHG emissions. This study found that overfertilization of more than 60% was mainly located in the winter wheat‐summer maize rotation systems in the North China Plain, the winter wheat‐rice rotation systems in the middle and lower reaches of the Yangtze River and southwest China, and most of the double rice systems in the South. Our simulations suggest that roughly a one‐third reduction in the current N fertilizer application level over these “overfertilization” regions would not significantly influence crop yield but decrease soil GHG emissions by 29.60%‐32.50% and GHG emission intensity by 0.13‐0.25 kg CO₂‐eq kg^‐1. This reduction is about 29% and 5% of total agricultural soil GHG emissions in China and the world, respectively. This study suggests that improving nitrogen use efficiency would be an effective strategy to mitigate greenhouse gas emissions and sustain China's food security.

想要平衡作物生产和农业土壤的温室气体排放，需要更好地了解和量化作物温室气体排放强度。本文使用改进的农业生态系统模型（DLEM-AG2.0）及包含172个野外温室气体排放试验的meta分析，对1949年至2012年中国小麦、玉米和水稻的温室气体排放强度的时空变化率进行了国家尺度的最新评估。结果表明，1949—2012年，农田的温室气体排放强度平均为0.10~1.31 kg CO₂‐eq kg^‐1，增长率为1.84~3.58×10^‐3 kg CO₂‐eq kg^‐1 yr^‐1。2000年以来，氮肥是导致中国北方温室气体排放强度增加的主要因素，对南方的影响也有所增加。温室气体排放强度的增加意味着过度施肥不仅没有显著促进作物增产，反而加剧了土壤温室气体排放。本研究发现，超过60%的过度施肥主要位于华北平原的冬小麦-夏玉米轮作区，长江中下游和西南地区的冬小麦-水稻轮作区，以及南方大部分的双稻轮作区。模拟结果表明，“过度施肥”地区当前的氮肥施用水平减少约1/3，不会显著影响作物产量，但会使土壤温室气体排放减少29.60%~32.50%，温室气体排放强度减少0.13~0.25 kg CO₂‐eq kg^‐1。这分别相当于中国和世界农业土壤温室气体排放总量的29%和5%。研究表明，提高氮肥利用效率将是减少温室气体排放、保障中国粮食安全的有效策略。