农田生态系统碳足迹法:误区、改进与应用——兼析中国集约农作碳效率(续)

THE MISSTEPS,IMPROVEMENT AND APPLICATION OF CARBON FOOTPRINT METHODOLOGY IN FARMLAND ECOSYSTEMS WITH THE CASE STUDY OF ANALYZING THE CARBON EFFICIENCY OF CHINA'S INTENSIVE FARMING

近10多年来，国内外农田生态系统碳足迹研究蓬勃开展并取得了某些成果。同时也存在着问题与误区，主要是碳流路径的短路和指标逻辑起点不一，导致研究结果的失真与扭曲。该文论述了全环式与半环式碳流路径的利弊，提出了改进3原则，对当前世界流行的5种指标体系进行比较、综合、筛选、补充与改进，初步形成了适合中国实际情况的包括碳流路径、指标体系及相应参数的碳足迹方法论，并通过1950年以来的全国性农田系统碳流分析和现代高效农田的案例加以验证和剖析，与当前流行的一些主流观点相悖，运用改进的碳足迹法进行的案例研究发现：（1）与多年生林木相似，农田上连年种植的一年生作物同样具有净固碳作用；（2）1952～2012年期间，随着农业集约化程度的不断提高，全国农田生态系统碳效率仍保持在正平衡状态；（3）尽管农田化合物大量投入，但在农田生态系统内增加的固碳量仍超过耗碳量，化学合成物在农田生态系统的合理应用也有减少温室气体的可能性。

In recent ten years, research on the carbon footprint of farmland ecological system has made vigorous progress at home and abroad, but there are some problems and missteps, e. g. , the distortion and distorted results which were resulted from unreasonable short circuit path of carbon flux and the different logical starting point of the index. In this paper, the full ring and half ring carbon flow path were discussed ; three principle items for improve- ment were put forward; five popular index systems were compared, synthesized, selected, complemented and re- vised, and thus a preliminary improved carbon footprint methodology suitable for China＇s conditions, including car- bon flow paths, index system and corresponding parameters, was formed and verified using the national farmland system carbon flux history case. Contradicts with the current mainstream view, three conclusions were obtained from the ease study： （1） Similar to perennial trees, annual crops planted on farmland year by year also possessed the function of net carbon sequestration. （2） During the 1952 -2012 years, along with the increasing agricultural in- tensification, the national farmland ecosystem carbon efficiency had remained a positive equilibrium. （3） Although a large of chemicals were input into farmland during last 60 years, the increase of carbon in the farmland ecosystem was still higher than the carbon consume, indicating that farmland chemicals had possible characteristics of reduc- ing greenhouse gases.