祁连山疏勒河上游多年冻土区高寒草甸土壤CO_2通量特征

Soil CO_2 flux characteristics in alpine meadow of permafrost regions in the upper reaches of the Shule River,Qilianshan Mountains

研究青藏高原多年冻土区高寒草甸土壤CO2通量有助于准确估算该区域的土壤CO2排放,对认识高原土壤碳循环及其对全球气候变化的响应具有重要意义.利用静态箱-气相色谱法和LI-8100土壤CO2通量自动测量系统对疏勒河上游多年冻土区高寒草甸土壤CO2通量进行了定期观测,结合气象和土壤环境因子进行了分析.结果表明：整个观测期高寒草甸土壤表现为CO2的源,土壤CO2通量的日变化范围为2.52~532.81 mg·m-2·h-1.土壤CO2年排放总量为1 429.88 g·m-2,年均通量为163.23 mg·m-2·h-1;其中,CO2通量与空气温度和相对湿度、活动层表层2 cm、10 cm、20 cm、30 cm土壤温度、含水量和盐分均显著相关.2 cm土壤温度、空气温度和总辐射、空气温度、2 cm土壤盐分分别是影响活动层表层2 cm土壤完全融化期、冻结过程期、完全冻结期、融化过程期土壤CO2通量的最重要因子.在完全融化期、冻结过程期和整个观测期,拟合最佳的温度因子变化分别能够解释土壤CO2通量变化的72.0%、82.0%和38.0%,对应的Q10值分别为1.93、6.62和2.09.冻融期（含融化过程期和冻结过程期）和完全冻结期的土壤CO2排放量分别占年排放总量的15.35%和11.04%,在年排放总量估算中不容忽视.

Researches on soil CO2 fluxes in alpine meadow of permafrost regions could facilitate accurate estima- tion of annual total fluxes of the soil CO2 in the Tibetan Plateau. It is also of great significance to reveal soil carbon cycles and its response to global climate change in the plateau. An alpine meadow site in the permafrost region of the upper reaches of the Shule River in the northeast margin of the Tibetan Plateau was selected as a study area, and soil CO2 fluxes were regularly measured using static chamber/gas chromatogram method and LI-8100 automatic soil CO2 flux system. Combined with environmental factors （included soil temperature, soil moisture, soil salinity, air temperature, relative humidity and solar radiation）, the emission characteristics of soil CO2 and the main influence factors were investigated. The results show that the alpine meadow soils were atmospheric CO2 sources during the whole observation periods, with the soil CO2 diurnal flux rate ranging from 2.52 to 532.81 mg m^-2 . h^-1. The annual total emission of soil COz was 1 429.88 g m^-2, with annual mean fluxes of 163.23 mg m^-2 h^-1. The soil CO2 flux had significant correlation with air temperature and relative humidity, soil temperature, water content and salt content at the depth of 2 cm, 10 cm, 20 cm and 30 cm. The soil temperature at the depth of 2 cm, air temperature, solar radiation and soil salt content at the depth of 2 cm were the most important influence factors for soil CO2 flux during the completely thawed period, freezing process, completely frozen period and thawing processes, respectively. The 72. 0%, 82. 0% and 38. 0% changes of soil CO2 flux variation can be explained with the best fitting temperature factor variation in the completely thawed period, freezing process and whole observation period, corresponding to 1.93, 6.62 and 2.09 of Q10 value, respectively. The results also show that the cumulative soil CO2 flux during freezing-thawing periods （including thawing and freezing periods） and completely frozen period accounts for 15. 35% and 11.04% of the annual total emission, which should not be neglected in estimation of the soil CO2 flux in the alpine meadow of permafrost regions in the Tibetan Plateau.