张掖市农田生态系统碳源/汇时空分布特征

目的]探究农田生态系统的碳源/汇状况,为绿洲农田生态系统农作物类型及其种植模式研究提供参考。方法]利用2001—2010年张掖市主要农作物产量、耕地面积、农作物播种面积及农业投入等数据,根据农田碳吸收、碳排放模型估算各县区农田生态系统的碳吸收、碳排放及碳汇,并分析其时空分布特征。结果]张掖市各县区碳吸收、碳排放、碳汇强度存在明显的时空差异;同一农作物的碳吸收强度仅与单产量有关,且成正比;经济作物中棉花的单位面积变化量对碳吸收的贡献率最大,粮食作物中大豆的贡献率最大。碳排放量是化肥施用量、农作物种植面积、农业机械总动力及灌溉面积的一次函数,化肥施用量的单位变化量对碳排放的贡献率最大,碳排放量呈逐年增加的趋势;灌溉面积次之,且逐年有降低的趋势;农业机械碳排放所占比例较小,低于碳排放总量的5%。结论]近10a来张掖市农田生态系统碳吸收总量整体上呈显著增加趋势,碳排放总量呈减小趋势,表明张掖市农田生态系统具有较强的碳汇能力。

Spatiotemporal Variation Characteristics of Carbon Source and Sink of Farmland Ecosystem in Zhangye City

Objective] The carbon source and sink of farmland ecosystem were illustrated to provide a reference for the crop types and cropping patterns of oasis farmland. Methods] Based on the collected data of main crop production, arable land, crop cultivated area and agricultural inputs data in Zhangye City during 2001-2010, the carbon absorption, carbon emissions and carbon sinks of farmland ecosystem of each county were estimated using models of agricultural carbon sequestration, and carbon emission, and the temporal and spatial distribution of these indices were analyzed. Results] There were obvious temporal and spatial differences in carbon absorption, carbon emission and carbon sink. The carbon absorption intensity was found only positively relevant to crop yield per unit area. The per unit change of cotton among the economic crops, and the soybean among grain crops had the maximum contributions to carbon absorption. The total carbon emission was a function of the chemical fertilizers, crop cultivated area, the total power of agricultural machinery and irrigation area. The unit volume change of chemical fertilizers had the maximum contribution rate to carbon emissions, and the carbon emissions showed an increasing trend. The contribution of irrigated area followed and it had a decreasing trend year by year. Agricultural machinery had the minimal proportional contribution, with a less than 5% of total carbon emissions. Conclusion] In recent 10 years, the total carbon absorption showed a significant increasing trend, while the carbon emissions showed a decreasing trend, all of which indicated that the farmland ecosystem of Zhangye City had a strong capacity of carbon sink.