疏勒河上游多年冻土区植物生长季主要温室气体排放观测

选取青藏高原东北部疏勒河上游多年冻土区的高寒草甸样地为研究对象, 对2011年植物生长季(6-10月)主要温室气体(CO₂、 CH₄CH₄和CO₂)的排放进行了观测. 结果显示: 疏勒河上游多年冻土区高寒草甸地表CO₂、 CH₄和N₂O排放速率范围分别为7.58~418.60 mg·m^-2·h^-1, -0.20~0.14 mg·m^-2·h^-1和-27.22~39.98 μg·m^-2·h^-1. 0~10 cm土壤温度、 含水量和盐分与CO₂和CH₄排放速率显著相关, 但与N₂O排放速率无显著相关. 日均排放速率显示, CO₂和N₂O在整个观测期均表现为排放; CH₄在植物返青期和生长旺盛期表现为排放, 在枯黄期伴随表层土壤发生日冻融循环时为吸收. 从9月30日12:00-10月6日14:40, 表层0~10 cm土壤经历了3次日冻融循环, CO₂和N₂O日均排放速率分别由冻融前的60.73 mg·m^-2·h^-1和9.91 μg·m^-2·h^-1提高到122.33 mg·m^-2·h^-1和11.70 μg·m^-2·h^-1. 土壤温度、 含水量和盐分是影响CO₂和CH₄排放的重要因子, 表层土壤冻融交替作用可提高地表CO₂和N₂O的排放速率.

Main Greenhouse Gases Emissions during Plant Growing Season in Permafrost Region of the Upper Reaches of Shule River,Qilianshan

Research on emissions of greenhouse gases from permafrost region has been of importance and concerns recently in the study of global climatic and environmental change. Alpine meadow plot of permafrost zone in the upper reaches of Shule River in the northeast margin of Qinghai-Tibetan Plateau was selected as study area, and emissions of CH₄, N₂O and CO₂ were measured using method of static chamber-gas chromatograph techniques during plant growing season (from June to October of 2011). Combined with environmental factors (included soil temperature, soil moisture, soil salinity, air temperature and relative humidity), the emission characteristics of three greenhouse gases and their main influence factors were investigated. The results showed that diurnal flux rates ranged from 7.58 to 418.60 mg5m^-2·h^-1 for CO₂, from -0.20 to 0.14 mg·m^-2·h^-1 for CH₄, from -27.22 to 39.98 μg·m^-2·h^-1 for N₂O. Soil temperature, soil moisture and soil salinity was positively correlated with CO₂ and CH₄ emission rates on a diurnal scale, respectively, whereas there were not significant correlations between these environmental factors and N₂O emission rates. Based on mean diurnal flux rates, CO₂ and N₂O emissions occurred in surface soil during the whole observation periods, whereas CH₄ emission in plant returning green stage and vigorously growing stage and absorption in plant scorching stage with diurnal soil freeze-thawing were observed. There were three diurnal freezing-thawing cycles in surface soil (0~10 cm) from 12:00 30th September to 14:40 6th October in 2011. The effect of diurnal freeze-thawing cycle on the CO₂ and N₂O emissions were obvious, and their emissions rate increased from 60.73 mg·m^-2·h^-1 and 9.91 μg·m^-2·h^-1 before freeze-thawing to 122.33 mg·m^-2·h^-1 and 11.70 μg·m^-2·h^-1 in the initial stage of freeze-thawing, respectively. Results indicate that with growing seasons, the daily variation patterns of emission/uptake of greenhouse gases differ greatly. Soil temperature, soil moisture, soil salinity are important influence factors for CO₂ and CH₄ emissions. Freeze-thawing cycle, directly influenced soil moisture and contents of active substances, facilitated emission rates of CO₂ and N₂O in initial period of diurnal freeze-thawing on October.