西藏高原农田土壤CO_2排放研究初报

A TENTATIVE STUDY OF CO2 EMISSION FROM FARMLANDSOIL IN TIBETAN PLATEAU

根据１９９５～１９９６年作物生长季在中国科学院拉萨农业生态站进行的试验研究，西藏高原农牧地不同植被覆盖下的土壤ＣＯ２排放通量为１７～１０５ｋｇＣＯ２ｈｍ－２ｈ－１。各类植被覆盖下土壤ＣＯ２排放通量均表现为白天高于夜间，午后高于午前。在作物生长季，由于土壤排放的ＣＯ２补充了高原大气ＣＯ２含量的不足，作为光合作用原料的重要组成部分被植物同化，因而不会增加大气中的ＣＯ２浓度。影响土壤ＣＯ２排放速率的因子主要有植被发育期、植被类型及环境因子。在环境因子中，土壤ＣＯ２排放速率与地温（地面０ｃｍ、地中５ｃｍ、１０ｃｍ）及气温均呈明显正相关，与大气压及空气中ＣＯ２浓度呈明显负相关。

Experimental studies at the Lhasa agroecological station of the Chinese Academy of Sciences during growth seasons of 1995～1996 indicated that the CO2 emission flux of soil in the farmland and pasture land in Tibetan Plateau was 1 7～10 5kgCO2ha-2h-1(1 6～6 6μmol CO2m-2s-1). CO2 emission flux of soil under several vegetation covers during daytime is higher than that at night, and afternoon higher than the morning. During the growth period of crops and herbage, the CO2 emission amount in the farmland is about of that absorbed by plant photosynthesis. As raw materials for photosynthesis, the soil emitted CO2 forms organic matter for the plants, acting as carbon fixation. CO2 emission amount can not lead to CO2 concentration increase in the atmosphere. Factors affecting CO2 emission flux of soil are mainly the factors of growth period, vegetation type and environment. In terms of environmental factor, the CO2 emission flux of soil in the farmland is positively correlated with air and soil temperature (soil surface temperature at 0cm,land underground temperature at the depth of 5cm and 10cm), and is negatively correlated with air pressure and atmospheric CO2 concentration.