积雪对藏北高寒草甸CO2和水汽通量的影响

于2002和2003年冬季运用涡度相关法测定藏北草甸在有积雪和无雪条件下的CO2和水汽通量.结果表明:在同一层次CO2浓度,在有雪时CO2浓度低于无雪时,其中只有20 cm和160 cm层次间差异极显著(P＜0.01);在同一层次,前者的水汽浓度极显著地高于后者(P＜0.01);积雪时,CO2通量与5 cm土温相关不显著;高寒草甸CO2交换量,随着积雪时间的延长呈线性降低,而高寒灌丛和沼泽则相反;沼泽和草甸在有雪时,CO2通量值极显著高于无雪时(P＜0.01),而灌丛在这两个条件下CO2通量值之间差异不显著.

Effects of Snow Cover on CO2 Flux of Northern Alpine Meadow on Qinghai-Tibetan Plateau

The alpine meadow ecosystem on Qinghai-Tibetan plateau plays a significant role in the regional carbon cycle. To assess the CO_2 flux and its relationship to environmental controls in the ecosystems, eddy covariance of CO_2 was measured from both snow-covered areas and on snow areas with open-path system in an alpine meadow of the plateau, during the winters of 2002 and 2003. The results indicated: At the same height, average CO_2 concentration in snow-covered conditions was less intense than in nosnow conditions, but significant differences occurred between 20 cm height and 160 cm level (P<0.01). The average H_2O con-centration in snow covered conditions was significantly more intense than in no snow conditions, respectively (P<0.01). In snow covered conditions, there was no significant relationship between CO_2 flux (and 5 cm) (soil temperature). There was a significant, linearity relationship between CO_2 flux and the number of (snow-covered) days in the alpine meadow; however, no such relationship existed in both the shrub meadow and the swamp meadow. Net ecosystem CO_2 exchange in snow-covered condition was significantly more frequent (than in no) snow conditions(P<0.01). The CO_2 flux of the shrub meadow in snow covered condition ((0.86 g/m~2 d)), however was not significantly different from no snow condition (0.60 g/m~2 d). The seasonal snow influences the C cycling in winter of the Qinghai-Tibetan plateau.