盐生荒漠CO_2通量对两个极端降水年份响应

Responses of CO_2 flux in a saline desert of Northwest China to two contrasting extreme precipitation years

以中国科学院新疆阜康荒漠生态站为试验平台,涡度相关技术为主要技术手段,对盐生荒漠生态系统进行长期水汽、CO_2通量观测,探讨年总降水量变化对盐生荒漠生态系统CO_2通量的影响。选取2个极端降水年份2006年(129 mm)和2007年(231 mm)比较CO_2通量的年内变化特征。2006年的碳吸收强度明显低于2007年,其最大碳吸收值分别为-0.4和-1.6 g C·m^(-2)·d^(-1),2006年的生长季长度为120 d,2007年为160 d。2006年表现为弱的碳吸收,其吸收值为-5 g C·m-2·a-1,群落总生产力与总呼吸分别为114.9和110.1 g C·m-2·a-1,2007年表现为较强的碳吸收,吸收值为-40 g C·m^(-2)·a^(-1),群落总生产力与总呼吸分别为257.7和218.2 g C·m^(-2)·a^(-1)。在干旱年份(2006年),群落总生产力与生态系统蒸散量的线性关系明显弱于湿润年份(2007年),二者的决定系数分别为0.40和0.71。对群落结构进行调查结果表明,在湿润年份,一年生草本植物的比例增加,可以充分利用降水,提高生态系统生产力。

Eddy covariance technique was used to measure carbon flux in a desert halophyte community in Fukang of Xinjiang during two hydrological years （2006 and 2007） with contrasting precipitation. The first hydrological year was dry （2006）, with the total annual precipitation of 129 mm and the second was wet （2007）, with the total annual precipitation of 231 mm. The main objective of this study was to characterize the seasonal and annual carbon flux of a desert halophyte community using the eddy covariance technique to determine the sensitivity of the system to the varying amounts of precipitation. The results showed that the daily carbon absorption rate of the ecosystem was obviously lower in 2006 than in 2007, with the maximum value being -0.4 g C·m-2·d-1 and -1.6 g C·m-2·d-1, respectively. The duration of the growth season was 120 days in 2006, and 160 days in 2007. The carbon absorption, gross ecosystem production （GEP）, and ecosystem respiration （Reco） were -5 g C·m-2·a-1, 114.9 g C·m-2·a-1 and 110.1 g C·m-2·a-1 in 2006, and -40 g C·m-2·a-1, 257.7 g C·m-2·a-1 and 218.2 g C·m-2·a-1 in 2007, respectively. The linear relationship between the GEP and ecosystem evapotranspiration was obviously weaker in 2006 than in 2007, with the coefficient of determination being 0.40 and 0.71, respectively. The vegetation community survey revealed that the proportion of annual herbaceous plants in 2007 increased, which could fully utilize precipitation to improve the ecosystem productivity.