张掖湿地甲烷通量动态特征及其影响因子
张 强1,2,3,蒋国庆1,2,3,孙 睿1,2,3,*,徐自为1,2,刘绍民1,2
【摘 要】摘要:于2012年7月—2014年6月对地处干旱区的张掖湿地甲烷(CH4)通量进行观测,分析其CH4通量的变化特征及其影响因子。结果表明：CH4通量的日变化趋势总体表现为白天大于夜间；不同季节CH4通量排放特征差异明显,夏季最大,春秋次之,冬季最小；CH4通量日总量与空气温度、土壤温度之间指数相关关系显著,其中4 cm处土壤温度与之相关性最强；1—6月摩擦风速(U*)与CH4通量显著正相关；结合CO2通量观测数据,研究时段张掖湿地净碳吸收量为495.92 g C m-2 a-1,为明显碳汇。 【期刊名称】生态学报 【年(卷),期】2017(037)017 【总页数】10
【关键词】湿地；涡动相关；CH4通量；温度；摩擦风速
Abstract： Analyzing the characteristics and variations of CH4 flux in wetland would be very helpful in order to understand the importance of the carbon cycle in the terrestrial ecosystem. In the arid area, the Zhangye wetland features complex meteorological conditions, which have introduced obvious uncertainties into the carbon fluxes. However, there are few research studies on the carbon flux of wetland in the arid areas. It is helpful to strengthen the study of wetland ecological system in the arid areas. In order to study the dynamics of carbon flux in a wetland ecosystem, CO2 flux and CH4 flux were measured using an
eddy covariance technique over a phragmites-dominated wetland in Zhangye, Gansu Province (from June in 2012 to August in 2014). In the present study, the CH4 flux variations and its main driving factors were analyzed based on the eddy covariance observations. The raw 10 Hz data were processed into 30 min mean values based on data quality control (spike detection, coordinate rotation, frequency response correction, etc.) and gap-filling (linear interpolation and Look-up Table method). The result showed the CH4 flux reaching its maximum in summer (0.34 g CH4 m-2 d-1), then spring and autumn, while getting the minimum values in winter (0.02 g CH4 m-2 d-1). Diurnal variation of CH4 flux indicated that the daytime values were higher than that of nighttime. There was an exponential relationship between CH4 flux and air temperature and soil temperature, and it was mostly correlated with the soil temperature in 4-cm depth, where the relationship was y=0.07614e0.03402x and R2 is 0.3560. CH4 fluxes also exhibited a strong relationship with friction velocity (R2=0.91 and 0.94, respectively, from January to March and from April to June). The enhanced turbulence could increase the ventilation and exchange of CH4 flux. CH4 flux significantly influenced the total carbon budget. By considering the absorption and emission of CO2 and CH4 fluxes, the net carbon uptake was 495.92 g C m-2 a-1. The carbon sink in Zhangye wetland was apparent during the study period.
Key Words: wetland; eddy covariance; CH4 flux; temperature; friction velocity
甲烷(CH4)的排放源主要包括天然湿地、稻田、天然气溢出、垃圾填埋场以及生物物质的燃烧,其中湿地占所有天然CH4排放的70%,占全球CH4通量的20%左右[1]。湿地生态系统水分过饱和造成的厌氧特性,为CH4的产生提供了有利的条件[2]。CH4排放是由CH4产生、氧化和传输过程共同决定的,这些过程受到多种因素的影响,如温度、水位、植被状况等,都是湿地生态系统中影响CH4通量的主要因子[1,3]。CH4作为引起全球变暖的另一种重要气体,虽然在大气中的浓度相较CO2偏低,但作为一种红外辐射活性气体,有很强的红外吸收带,在百年尺度上,单位质量CH4在大气中的增温效果是CO2的25倍[4]。一方面大气中CH4浓度的升高会导致全球变暖,另一方面全球气温升高将加速北方冻土融化,土壤中富含的有机碳分解释放到大气中,进一步加剧了全球变暖的趋势。因此,研究湿地CH4的变化规律及其对环境因素的响应特性,不仅可以增加对湿地生态系统的了解,更对加强湿地生态系统保护以及了解全球变暖的影响有重要意义。 目前,国内外学者已从多个方面对湿地CH4变化特性和影响因素进行过研究。不同环境和植被类型,湿地CH4通量有明显差异。黄国宏等[5]用封闭式箱法测定的辽河三角洲芦苇湿地CH4观测结果表明,其排放有明显的季节变化规律,淹水前土壤为CH4汇,淹水期间有大量的CH4排放,排水后CH4排放明显减少。Kang等[6]对英国北威尔士酸性泥炭沼泽和森林沼泽CH4的测定,发现不同类型湿地CH4排放存在差异：酸性泥炭沼泽CH4排放高峰在春季和秋季,而在森林沼泽,其释放峰值出现在10月和11月。Rinne[7]等利用涡动相关技术观测北方沼泽湿地CH4排放,发现无明显的日变化规律,非雪期CH4排放量占全年的
张掖湿地甲烷通量动态特征及其影响因子
