典型草原CO2通量变化特征对环境因子的响应

为准确估算评价草原生态系统碳源/汇和合理利用草地资源提供科学依据。采用涡度相关法对锡林浩特典型草原生态系统CO₂通量的日变化、牧草不同生育期CO₂通量变化规律以及与环境因子的关系进行分析。结果表明，草原生态系统CO₂通量具有明显的日变化特征，白天以吸收CO₂为主，夜间表现为呼吸排放CO₂，夜间较白天变化相对稳定；CO₂通量晴天与阴天日变化趋势一致，但阴天变幅大于晴天；在牧草不同生育期和不同天气背景下，CO₂通量的日变化特征不同。CO₂通量波动晴天大于阴天，但无论晴天还是阴天，返青期、黄枯期为大气CO₂的源；开花期为大气CO₂的汇，且开花期CO₂净吸收通量明显高于生长初期和黄枯期，而黄枯期CO₂呼吸排放通量明显高于生长初期和开花期。牧草在不同生育期的CO₂通量与光合有效辐射强度、平均气温、地表平均温度、5 cm平均地温和平均风速等环境因子密切相关。

Typical Grassland CO2 Fluxes in Response to Environmental Factors

In order to accurately estimate and evaluate grassland ecosystem carbon/sink and provide a scientific basis for rational utilization of grassland resources, the author used the eddy covariance method to analyze the day Xilinhaote steppe ecosystem CO₂ flux changes, changes of CO₂ fluxes at different growth stages and the relationship between pasture and environmental factors. The results showed that the grassland ecosystem CO₂ flux had obvious diurnal variation, absorbed CO₂ during the day and had mainly nocturnal emission performance of respiratory CO₂, changes was relatively stable in the night than during the day. CO₂ flux had the consistent trend in cloudy and sunny days, but greater change in cloudy days than in sunny days. At different forage growth stages and under different weather backgrounds, diurnal variations of CO₂ fluxes are different. CO₂ flux was greater in sunny days than in cloudy days, but no matter sunny or cloudy, stage of turning green, yellow and withered were the source of atmospheric CO₂, and flowering period was atmospheric CO₂ sinks. Net absorption of CO₂ fluxes of flowering period was significantly higher than that of the early flowering period and wilting period, and CO₂ respiration fluxes of wilting was significantly higher than that of the initial growing period and flowering period. Therefore, CO₂ flux of different growth stages is closely related to PAR intensity, the average temperature , average surface temperature, 5 cm equally modest average wind speed and other environmental factors .