矮嵩草草甸植被-土壤系统CO_2的释放特征

A Primary Study on CO_2 Emission from Soil-Plant Systems of Kobresia Humilis Meadow

采用静态箱气相色谱法,对高寒矮嵩草草甸植被土壤系统CO2释放特征研究结果表明:3个处理(FC、FJ、FL)CO2释放速率具有明显的日变化规律,日最大释放速率出现在13:00左右,最小释放速率在4:00前后,且白天的释放速率均大于夜间;CO2释放速率也具有明显的季节变化特征,植物生长期释放速率明显高于枯黄期,且均表现为正排放;在整个观测期间(6月30日～1月28日)CO2平均释放速率依次为FC>FJ>FL,矮嵩草草甸植物土壤系统CO2释放速率为438 34±264 12mg (m2·h)(FC),土壤呼吸速率为313 20±189 74mg (m2·h)(FJ),土壤微生物呼吸速率为230 34±145 46mg (m2·h)(FL),植物根系呼吸占土壤呼吸的26 5%。植物、植物根系以及土壤微生物CO2释放速率与土壤5cm温度呈极显著正相关关系,相关系数分别为0 858、0 628和0 672(P<0 01)。整个系统呼吸、土壤呼吸与土壤5cm温度可拟和为一指数方程,方程为y=168 03e0 1086x(R2=0 8783)和y=149 69e0 0745x(R2=0 8189)。

Elevated atmospheric greenhouse gases concentrations are major causes of global warming. Due to its high elevation and special geographical location, the Tibetan Plateau is very sensitive to the climate change. As one of the most important ecosystems in the Plateau, alpine meadow has been playing an important role in carbon balance. There are many reports about CO_2 emission from such ecosystem, however, simultaneous study on ecosystem respiration and soil respiration seldom occurred. In addition, for the chamber method, accurate estimation of NEP (net ecosystem productivity) needs a separation of root respiration and soil microbial respiration from total soil respiration. In this study, three treatments FC, FJ, FL, (FC represents plant-soil system treatment, FJ is aboveground plant exclusion treatment, and FL is whole plant removal treatment) were set to study CO_2 emissions from alpine Kobresia humilis meadow at Haibei research station, CAS from 30 June of 2003 to 28 January of 2004, using static chamber-GC method. Results indicate that CO_2 emission rates from different treatments showed clear diurnal variation and seasonal dynamics, with maximum rate appeared around 13:00, and the minimum rate around 4:00; rate of CO_2 emission in the daytime was greater than that in the night, and higher in the growing period than that in the plant-drying period. During the experiment period, CO_2 emission rates varied with different treatments showing an order of FC>FJ>FL. The total respiration rate of soil-plant system (FC) was 438.34±264.12 mg CO_2m^(-2)h^(-1), soil respiration rate (FJ) was 313.20±189.74 mg CO_2 m^(-2)h^(-1), soil microbial respiration rate (FL) approximated 230.34±145.46 mg CO_2 m^(-2)h^(-1). By comparison, root respiration rate approximated 82.86 mg CO_2 m^(-2)h^(-1), accounting for 26.5 percent of soil respiration. In addition, there was a significant correlation between soil temperature at 5 cm depth and respiration rates of the total plant, plant roots and soil microbe. The correlative coefficient is 0.858、0.628 and 0.672 (P<0.01) respectively. The separation of root respiration from total soil respiration, as practiced in this study, will contribute significant to the chamber method NEP estimation of alpine meadow.