羊草草原和贝加尔针茅草原生态系统呼吸的差异分析

应用静态暗箱-气相色谱法对羊草草原和贝加尔针茅草原的生态系统呼吸CO2通量进行了测算,分析了生态系统呼吸的影响因素,比较了2种草原生态系统呼吸的差异并分析了产生差异的原因.观测期间羊草草原生态系统呼吸CO2通量平均为(12.03±2.10)mg·(m2·min)-1,显著低于贝加尔针茅草原(20.09±4.41)mg·(m2·min)-1];而羊草草原生物量显著大于贝加尔针茅草原(p0.001).羊草草原和贝加尔针茅草原生态系统呼吸都与温度(箱内气温、5cm和15cm地温)具有显著的指数函数关系.通过偏相关分析发现,在地温作为控制变量时,生态系统呼吸与土壤Eh、pH间不再具有显著的相关性,Eh、pH对CO2通量的影响可能是由地温变化间接引起的,而CO2通量与活体生物量呈现出了一定的相关性,与凋落物生物量无显著相关性.2种草原的CO2通量都可以用温度指数模型进行很好地模拟,基于地温的模拟效果(R2为0.568～0.639)显著好于基于箱内气温的(R2为0.323～0.426).地温是2种草原生态系统呼吸最重要的影响因素,它掩盖了地上部植物体对生态系统呼吸的影响.在该区域,土壤呼吸占生态系统呼吸比例较高,贝加尔针茅草原较高的有机质含量导致了其生态系统呼吸CO2通量较高.

Analysis of Difference Between Ecosystem Respirations of Leymus chinensis Steppe and Stipa baicalensis Steppe

Static opaque chamber-chromatographic technique was applied to measure the ecosystem respirations of Leymus chinensis steppe and Stipa baicalensis steppe. The affecting factors of ecosystem respiration were analyzed. The difference between ecosystem respirations of the two grasslands was compared and the reasons resulting in the difference were analyzed. Ecosystem respiration of Leymus chinensis steppe averaged (12.03 +/- 2.10) mg x (m2 x min)(-1)] was significantly smaller than that of Stipa baicalensis steppe averaged (20.09 +/- 4.41) mg x (m2 x min)(-1)], while aboveground biomass of Leymus chinensis steppe was significantly larger than that of Stipa baicalensis steppe (p < 0.001). CO2 fluxes of Leymus chinensis steppe and Stipa baicalensis steppe were significantly correlated with air temperature in chamber, soil temperature at 5 cm and 15 cm depth. The results of partial correlation analysis showed that there were no significantly correlation between CO2 flux and Eh, pH, biomass of litter when soil temperature was unchanged, while it shows some correlation with biomass of living plant. The apparent liner relationship between CO2 flux and Eh, pH may be caused by the change of soil temperature. The CO2 fluxes of the two grasslands can be well explained by exponential models based on temperatures. Soil temperature can explain more variations of ecosystem respirations (R2 0.568-0.639) than air temperature in chamber (R2 0.323-0.426). Soil temperature was the most important affecting factor of ecosystem respiration and it may had concealed the effect of aboveground biomass on CO2 flux. The contribution of soil respiration to ecosystem respiration was large in this region and its higher soil organic matter content led to higher CO2 flux of Stipa baicalensis steppe.