As an important component of ecosystem carbon（C） budgets, soil carbon dioxide（CO2） flux is determined by a combination of a series of biotic and abiotic processes. Although there is evidence showing that the abiotic component can be important in total soil CO2 flux（R（total））, its relative importance has never been systematically assessed. In this study, after comparative measurements of CO2 fluxes on sterilized and natural soils, the R（total） was partitioned into biotic flux（R（biotic）） and abiotic flux（R（abiotic）） across a broad range of land-cover types（including eight sampling sites： cotton field, hops field, halophyte garden, alkaline land, reservoir edge, native saline desert, dune crest and interdune lowland） in Gurbantunggut Desert, Xinjiang, China. The relative contribution of R（abiotic） to R（total）, as well as the temperature dependency and predominant factors for R（total）, R（biotic） and R（abiotic）, were analyzed. Results showed that R（abiotic） always contributed to R（total） for all of the eight sampling sites, but the degree or magnitude of contribution varied greatly. Specifically, the ratio of R（abiotic） to R（total） was very low in cotton field and hops field and very high in alkaline land and dune crest. Statistically, the ratio of R（abiotic） to R（total） logarithmically increased with decreasing R（biotic）, suggesting that R（abiotic） strongly affected R（total） when R（biotic） was low. This pattern confirms that soil CO2 flux is predominated by biotic processes in most soils, but abiotic processes can also be dominant when biotic processes are weak. On a diurnal basis, R（abiotic） cannot result in net gain or net loss of CO2, but its effect on transient CO2 flux was significant. Temperature dependency of R（total） varied among the eight sampling sites and was determined by the predominant processes（abiotic or biotic） of CO2 flux. Specifically, R（biotic） was driven by soil temperature while
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。
