草地农业生态系统的碳平衡分析方法

Carbon balance analysis methods of grassland agro-ecosystems

根据草地农业生态系统的结构,它的碳平衡为4个生产层的碳平衡之和,也是3个界面的碳平衡之和,而某一生产层或者某一界面的碳平衡则是其固定、输入、排放和输出的碳之和。草地农业生态系统4个生产层的碳平衡分析方法定量重要生产环节的碳汇与碳源过程,便于草业生产改进碳汇管理;草地农业生态系统3个界面的碳平衡分析方法显示碳源和碳汇的发生机理,及其空间和数量关系,便于调控草业生产组分以增汇减排;但是,这两个方法不易区分碳的来源和去向,难以明确其利用效率。草地农业生态系统碳平衡分析的输入/输出法定量地指示碳的来源和去向,以及碳效率,计算简单,但是较为概括,不利于牧场尺度的草业碳汇管理。以中国祁连山甘肃马鹿牧场和澳大利亚塔斯玛尼亚奶牛牧场为例,用3种方法分析了两个牧场的碳平衡,结果表明,放牧管理的草业系统的主要碳源是休闲旅游、产品加工流通环节产生的温室气体,主要碳汇是草地和土壤中贮存的碳,好的草地管理可以增汇减排。

According to the structures of grassland agro-ecosystems, their carbon balance represent the sum of the carbon balances of the four production levels, or the sum from its three interfaces. The carbon balance per production level or interface is the sum of the carbon that is taken up and lost through the different processes in that level or interface. The carbon balance analysis method based on four production levels can quantify which of the processes in the production are either a carbon sink or source. For example, carbon and nitrogen accumulation such as Carbon and Nitrogen sink, soil and water conservation are carbon sink process in Pre-plant production level. The grassland tourism hunting and so on, are the process of carbon source in Pre-plant production level. Photosynthesis and carbon and nitrogen assimilation of biological nitrogen fixation are the process of carbon sink in Plant production level. Greenhouse gases emission is the process of carbon source in Plant production level. The process of carbon sink and source in Animal production level are mostly Carbon fixation in animal product and greenhouse gases emission of ruminant. Carbon fixation in forage and animal products are the process of carbon sink in Post-biological production level. Processing and transport activities are the process of carbon source in Post-biological production level. This can subsequently facilitate improvements in the management of carbon sequestration in grassland production. Furthermore, the carbon balance analysis method based on three interfaces can determine the production mechanisms of carbon sinks and sources, as well as their spatial and quantitative relationships. This can contribute to regulating and controlling the carbon emissions from grassland agro-ecosystems. However, both methods cannot accurately quantify a grassland system＇s paths of carbon uptake and output, or its utilization efficiency. The carbon balance analysis by the balance between carbon input and output can quantify the pathway of carbon movement. This method is simple and more succinct ; however, it is not applicable to farmland scale management of carbon sequestration. Considering a ranch in the Qilian Mountains, China, and a dairy farm in Tasmania, Australia, as examples, three methods were used for analyzing their carbon balances. The results showed that carbon emissions from tourism, product Processing, and marketing accounted for the major portions of the total emissions from the grazing management system. Their main carbon sinks were carbon stored in the forage and the soil. Overall, optimal grassland management would benefit from adding carbon sinks and reducing carbon emissions.