青藏高原多年冻土区不同草地类型生态系统呼吸季节差异性

研究多年冻土区不同草地类型及季节生态系统呼吸，对理解青藏高原碳源汇关系及其对气候变化响应具有重要意义。在青藏高原风火山选取高寒草甸和沼泽草甸对生长季和非生长季生态系统呼吸进行观测。结果表明：生态系统呼吸呈明显的日变化和季节变化，高寒草甸日变异系数（0.30~0.92）高于沼泽草甸（0.12~0.29），高寒草甸非生长季生态系统呼吸白天/晚上比高于生长季，而沼泽草甸季节变化较小；季节变化与5 cm地温变化一致。高寒草甸和沼泽草甸非生长季生态系统呼吸平均速率分别为0.31和0.36 μmol·m^-2·s^-1，生长季分别为1.99和2.85 μmol·m^-2·s^-1。沼泽草甸生态系统呼吸年排放总量为1 419.01 gCO₂·m^-2，显著高于高寒草甸（1 042.99 gCO₂·m^-2），其中非生长季高27%，生长季高39%。高寒草甸和沼泽草甸非生长季生态系统呼吸总量分别为268.13和340.40 gCO₂·m^-2，分别占全年的25.71%和23.99%。两种草地类型生态系统呼吸与气温、5 cm和20 cm地温均显著相关，可解释37%~73%的季节变异，除生长季沼泽草甸外，生态系统呼吸与5 cm地温相关性最高。非生长季5 cm地温对应Q₁₀为4.34~5.02，高于生长季（2.35~2.75），且沼泽草甸高于高寒草甸。生长季生态系统呼吸与土壤水分无显著关系，而非生长季生态系统呼吸受土壤水分显著影响（R²：0.21~0.40），随土壤水分增加而增加。

The seasonal variation of ecosystem respiration in different vegetation types in the permafrost regions of Qinghai-Tibet Plateau

The ecosystem respiration (ER) of various vegetation and in various seasons is very important for accurate estimation of CO₂ emissions in the Qinghai-Tibet Plateau. The ER had been measured of alpine meadow and swamp meadow in different seasons in 2013 on Fenghuoshan Mountain in the permafrost regions of the Qinghai-Tibet Plateau. ER diurnally and seasonally varied significantly in the two meadows; the diurnal variable coefficient of alpine meadow (0.30~0.92) was higher than that of swamp meadow (0.12~0.29); the seasonal variations of ER changed dynamically with soil temperature (for example, at 5 cm depth). The mean ER was 0.31 and 0.36 mol·m^-2·s^-1 in non-growing season and 1.99 and 2.85 mol·m^-2·s^-1 in growing season in alpine meadow and swamp meadow, respectively. The annual emission of ER was higher in swamp meadow (1 419.01 gCO₂·m^-2) than that in alpine meadow (1 042.99 gCO₂·m^-2), the former was 27% higher than the latter in non-growing season and 39% higher than the latter in non-growing season, respectively. ER in non-growing season was 268.13 and 340.40 gCO₂·m^-2 in alpine meadow and swamp meadow, respectively, contributed to 25.71% and 23.99% of annual ER. Of both meadows, the ER was correlated significantly to air temperature, as well as soil temperature, for example, at 5 cm and 20 cm depths, account for 37%~73% of seasonal variations. It was found that a highest correlation between ER and soil temperature at 5 cm depth, expect for the swamp meadow in growing season. There was no significant relationship between ER and soil moisture in the growing season, but there was a positive relationship (R²:0.21~0.40) in non-growing season. The Q₁₀ corresponding to the ground temperature of 5 cm in the non-growing season was 4.34~5.02, higher than that in the growing season (2.35~2.75), and that in swamp meadow higher than that in alpine meadow. There was no significant relationship between ER and soil moisture in the growing season, but ER in the non-growing season was significantly affected by soil moisture (R²:0.21~0.40), increasing with soil moisture.