【作者】 周丽艳；

【导师】 贺康宁；

【作者基本信息】 北京林业大学 ， 水土保持与荒漠化防治， 2011， 博士

【摘要】 北方针叶林生态系统是地球上第二大陆地生物群区,位于北半球中高纬度地区,增温剧烈,对气候变化敏感,在全球碳平衡和气候系统中起着至关重要的作用。本研究以中国北方针叶林生态系统为研究对象,以涡动相关法为主要技术手段,利用北方针叶林生态系统定位观测站2007年和2008年生长季（6月～10月）碳通量和气象观测数据,采用EdiRe （Eddy Reprocessing）软件将10HZ原始通量数据转化为30 min数据并进行质量控制,分析了北方针叶林总生态系统生产力（GEP）、生态系统呼吸（Re）和净生态系统C02交换（NEE）的日、季节动态变化特征及其影响因子,研究结果表明：（1）总生态系统生产力的日、季动态均呈单峰型曲线,日高峰值出现在上午9：00-10：00左右,6月-10月生态系统碳吸收持续时间随着白天日照长度的减少呈逐渐缩短趋势,变动于11个小时（10月）～16个小时（6月）之间；整个生长季节,7月气温最高,降雨量最多,总生态系统生产力最大,2007年和2008年整个生长季节总生态系统生产力日均值分别为19.45g CO2·m-2·d-1和17.67g CO2·m-2·d-1。北方针叶林总生态系统生产力与温度和光合有效辐射具有很好的线性关系,其中与5cm土壤温度的相关系数达到0.55左右。这表明,温度是北方针叶林生长的主要限制因子,而太阳辐射是植物进行光合作用的前提条件。北方针叶林生态系统雨水充沛,水分并不是一个主要的限制因子,土壤含水量和水汽压差与总生态系统生产力相关性均不明显。（2）北方针叶林生态系统呼吸日动态变化呈单峰型曲线,高峰值均出现在下午15：30～16：30,白天生态系统呼吸量及变动幅度均明显大于夜间。整个生长季节,7月和8月生长旺盛期生态系统呼吸达到最大,2007年和2008年生长季节生态系统呼吸日均值分别为15.15 g CO2·m-2·d-1和14.11 g CO2·m-2·d-1。温度是北方针叶林生态系统呼吸的主要影响因子,夜间生态系统呼吸与土壤温度的相关性（R2平均值为0.492）高于气温（R2平均值为0.369）,温度可以解释北方针叶林夜间生态系统呼吸34%～57%的动态变化。（3）北方针叶林净生态系统CO2日交换呈单峰型曲线,最大值出现在上午9：00～10：00。6月～10月北方针叶林生态系统生长季每天的固碳时间从14小时（5：00-19：00）逐渐缩短为9小时（7：30-16：30）。北方针叶林生态系统的NEE在生长季前期（6月～8月）呈净碳吸收,生长季末期（9月～10月）呈碳排放。2007年和2008年整个生长季节净生态系统碳交换日均值分别为-1.45 g CO2·m-2·d-1和-1.37 g CO2·m-2·d-1。北方针叶林白天净生态系统CO2日交换与各环境因子的相关性从大到小依次为：光合有效辐射、1.5 m气温、5 cm土壤温度、水汽压差。2007年和2008年北方针叶林的NEE与光合有效辐射相关性最大,两者呈明显的正相关性,相关系数分别为0.558和0.494。（4）2007年碳通量各组分均大于2008年,可能与2007年生长季平均气温（12.46℃）高于2008年（11.04℃）以及2007年生长季平均光合有效辐射(697.17μmol·m^-2·S^-1高于2008年(638.55μmol·m^-2·S^-1)有关。更多还原

【Abstract】 Boreal forest is the second largest biome on the earth, which lies in middle-high latitude of the northern hemisphere and where temperature increases strongly. Thus, boreal forest is an important research object in global climate change and carbon cycle. Larix gmelinii forest in Daxing’an Mountains of Northeast China is an important component of boreal forest. Long-term measurement of the CO2 fluxes between the vegetation and the atmosphere has facilitated the research on carbon cycle and its controlling mechanisms in boreal forest ecosystem and its response to global climatic change in the future. Based on two-year continuous CO2 exchange observation during growing seasons from 2007 to 2008 over Chinese boreal forest by eddy covariance method in northeast China, we analyzed diurnal and seasonal dynamics of gross ecosystem productivity(GEP), ecosystem respiration(Re) and net ecosystem CO2 exchange(NEE) and their controls. Major conclusions are summarized as follows:(1) The diurnal pattern of GEP could be expressed as one-humped curves with the maximum appeared at 9:00-10:00. The daily length of carbon sequestration from the atmosphere was reduced from 16 hours in June to 1.1 hours in October. GEP was the largest in July with the highest air temperature and precipitation during the whole growing seasons. Mean daily GEP in 2007 and 2008 were 19.45 g CO2·m-2·d-1 and 17.67g CO2·m-2·d-1, respectively. GEP had close linear relationship with both temperature and photosynthetically active radiation (PAR), and especially, the correlative coefficient for soil temperature at 5 cm depth was around 0.55. It indicated that temperature was a major limited factor in boreal forest ecosystem, and PAR was the basis of photosynthesis. Precipitation was enough in boreal forest ecosystem, which was not a limited factor.(2) The diurnal pattern of Re could be expressed as one-humped curves with the maximum appeared at 15:30-16:30. Re and its range in daytime were both larger than those in nighttime. Re was the largest in July and August during the whole growing seasons. Mean daily Re in 2007 and 2008 were 15.15 g CO2·m-2·d-1 and 14.11 g CO2·m-2·d-1. Re was mainly influenced by temperature, and the correlative coefficients with soil temperature (average R=0.492) were higher than those with air temperature (average R2=0.369). Temperature could explain about 34%-51% of seasonal dynamics of Re in Chinese boreal forest ecosystem.(3) The diurnal patterns of NEE could be expressed as one-humped curves with the maximum appeared at 9:00-10:00. The daily length of carbon sequestration from the atmosphere was reduced from 14 hours (5:00-19:00) in June to 9 hours (7:30-16:30) in October. Chinese boreal forest ecosystem was a carbon sink in June, July and August, while a carbon source appeared in September and October. Mean daily NEE in 2007 and 2008 were-1.45 g CO2·m-2·d-1 and-1.37 g CO2·m-2·d-1. NEE was mainly influenced by PAR, and the correlative coefficients were 0.558 and 0.494 in 2007 and 2008, respectively.(4) The intensity of carbon dioxide exchange during growing season in 2007 was stronger than that in 2008. The reason might result from higher mean air temperature (12.46℃in 2007 and 11.04℃in 2008) and higher mean photosynthetically active radiation (697μmol·m-2·s-1 in 2007 and 639μmol·m-2·s-1 in 2008).更多还原