若尔盖泥炭地地下水位和土壤温度对二氧化碳排放的影响

Effect on CO_2 Emissions of Water Tables and Soil Temperatures in Zoigê Peatlands

利用中型实验生态系,对若尔盖典型泥炭地二氧化碳排放通量开展地下水位控制实验。通过比较不同地下水位条件下泥炭地生长季(5~10月)二氧化碳排放通量的日变化和月变化,探讨若尔盖泥炭地地下水位和土壤温度对二氧化碳排放的影响。结果显示,5~7月中水位(控制水位为地表以下10 cm)下的二氧化碳排放通量最高,其次是低水位(控制水位为地表以下20 cm)下的排放通量,高水位(控制水位为地表0 cm)下的排放通量最低;8月各水位下二氧化碳排放通量差异不明显;9~10月的二氧化碳排放通量随水位降低而增加;整个生长季,水位由低到高的二氧化碳排放通量平均值分别为404.65 mg/(m2·h)、438.76 mg/(m2·h)和359.18 mg/(m2·h);二氧化碳排放通量随土壤温度变化而变化,其中,中水位条件下二氧化碳排放通量对温度变化最为敏感,其次是低水位下,高水位下相对最不敏感。暖干化的气候变化趋势将导致若尔盖典型泥炭地释放更多的二氧化碳到大气中。

A large portion of the global carbon pool is stored in peatlands, which are sensitive to a changing environment conditions. We quantified the relationship between water table positions and CO2 emissions by manipulating water table from mesocosms during the plant growth period(from May to October, 2012) in Zoigêpeatland. Daily and monthly CO2 emissions were measured and three water tables were considered 0 cm depth, 10 cm depth and 20 cm depth(presented below as W0, W10 and W20, respectively). Results showed that,from May to July, mean CO2 emissions were lowest at the highest water tables(W0), followed by those under W20 and W10. No significant difference was observed in August. While in September and October, mean CO2 emissions were highest at the lowest water tables(W20), followed by those under W10 and W0. During the growth period, mean CO2 emission fluxes under W20, W10 and W0were 404.65 mg/(m2·h), 438.76 mg/(m2·h) and359.18 mg/(m2·h), respectively. There was a positive correlation between CO2 emissions and soil temperature,which was most significant under W10 while under W0 was of the least significance. The results suggested that the warming and drying of the climate would result in additional CO2 emissions from Zoigê peatland.