Study on Interaction between Global Warming and Permafrost Thawing

在西伯利亚针叶林中部，对扰动样地和对照样地的碳收支、传热和传质进行了长期野外测量。在调查方面，设置了两座瞭望塔。干扰前，完整的针叶林吸收二氧化碳的量为86mg/m^2。白天，但扰动后二氧化碳从地面排放140毫克/平方米。白天由于植被的损失和土壤呼吸的增加。地表植被的消失导致地表热通量增加了20%，并引起了上层多年冻土的大规模融化。利用敞顶拱法进行的长期田间土壤呼吸测量表明，土壤呼吸程度与土壤温度和土壤湿度成正比。得到了这两个因素的新的经验方程。高达2000ppm的高浓度甲烷被储存在永久冻土中。在扰动之后，上层永久冻土层的额外解冻导致储存的甲烷向大气中排放。全球变暖下冻土扰动的影响可能是西伯利亚永久冻土区二氧化碳和甲烷的来源。由火灾干扰产生的温室气体有三种来源。1)燃烧过程中二氧化碳的直接排放2)土壤温度的升高迫使燃烧地土壤呼吸增加3)多年冻土融化过程中储存的甲烷排放到大气中。它可能导致未来全球变暖的正反馈。

In the Mid of Siberian Taiga, long term field measurements at disturbed and control sites on Carbon budget, heat and mass transfers were conducted. As to investigation, two observation towers were installed. Before disturbance intact Taiga forest absorbed carbon dioxide by 86mg/m^2.day, but after disturbance carbon dioxide was emitted from the ground by 140 mg/m2.day due to the loss of vegetation and increase of soil respiration. Loss of surface vegetation resulted in the increase of flux heat to the ground by 20% and it caused the large scale thawing of upper permafrost. The long term filed measurements of soil respiration by the method of open top camber indicated that the degree of soil respiration is proportional to soil temperature as well as soil moisture. The new empirical equations of these two factors were obtained. The highly concentrated methane as much as 2000 ppm was stored in the permafrost. After disturbance an additional thawing of upper permafrost resulted in the emission of stored methane to the atmosphere. Impact of permafrost disturbance under the global warming may the source of carbon dioxide and methane in Siberian permafrost area. There are three sources of green house gases induced by fire disturbance. 1) direct emission of carbon dioxide during combustion 2) at the burned site soil respiration was forced to increase by the increased soil temperature 3) in the process of permafrost thawing, stored methane was emitted to atmosphere. It may cause to the positive feedback of future global warming.