青藏高原高寒草甸生态系统CO_2交换量的“转折气温”(英文)

"Turning point air temperature" for alpine meadow ecosystem CO_2 exchange on the Qinghai-Tibetan Plateau

为了理解青藏高原高寒草地生态系统的碳动态变化和环境因子对其的调控关系,分析2年(2002和2003年)的涡度相关数据。结果表明,高寒草地生态系统是"碳汇",2年分别从大气吸收了286.74和284.94 g CO2。相关分析表明,高寒草甸生态系统CO2交换量与日平均气温有十分明显的相关性,而与光量子通量密度和土壤含水量没有明显的相关性。"转折气温",是生态系统光合通化增长速率开始大于生态系统的呼吸增长速率时的气温。通过线性指数模型,发现高寒草甸生态系统的"转折气温"是2.47℃。在降雨和光量子通量密度基本不变,生态系统比较稳定的条件下,如果增温效应发生在气温大于2.47℃,高寒草甸生态系统的"碳汇"功能将得以加强,反之,发生在气温小于2.47℃,"碳汇"功能将被削弱乃至转变为"碳源"。

To understand the carbon dynamics and correlation between net ecosystem CO2 exchange and environmental conditions of alpine meadow ecosystem in the Qinghai-Tibetan Plateau, we analyzed two years （from 2002 to 2003） data measured by eddy covariance method. The results showed that in those two years the ecosystem behaved as the carbon sink and absorbed carbon dioxide 286.74 g/（m^2· a） and 284.94 g/（m^2· a）,respectively. It suggested that there were not distinct correlations between the daily CO2 flux （net ecosystem exchange, NEE） and photosynthetic photon flux density （PPFD） and soil water content （SWC） while daily NEE was evidently corresponded to air temperature. The ＂turning point air temperature＂, was meant at that air temperature, when the increase rate of ecosystem photosynthesis （gross primary production, GPP） began to be above the increase rate of ecosystem respiration （Remax）, and was 2.47 ℃ by an exponential-linear model established in the alpine meadow. Then, if the precipitation and PPFD doesn＇t change greatly, moreover, the alpine meadow keeps balance （not lots of variations among years, especially in plant species, plant growth）, the capacity of alpine meadow ecosystem carbon sink will be enhanced when the increase of air temperature at above 2.47 ℃, and decreased when that of air temperature at below 2.47 ℃.