兴安落叶松树干CO_2各通量成分对树干呼吸的贡献及其主要影响因子

CO_2 Flux Components,Their Contributions to Stem Respiration and the Key Impact Factors in Stems of Larch

树干呼吸（Rs）的CO2通量由三部分组成，即液流中CO2运输通量（FT）、储存通量（AS）和树干表面CO2释放通量（EA）。其中木质部液流中CO2的运输（FT）在植物的气体交换中起到非常重要的作用，是茎、枝呼吸作用测定中非常重要且未予说明的组分。为探明兴安落叶松树干各通量成分对树干呼吸的贡献，采用红外气体分析法（IRGA）原位连续测定树干表面CO2释放通量，同时测定树干液流速度及树干温度，通过Arrhenius方程拟合树干呼吸与树干温度的关系，进而通过质量平衡法计算凡和FT、AS。结果表明：EA耳和AS占R。的比例是动态变化的，EA与树干内部CO2通量密切相关，n和△s可影响以，在24h周期内EA占总呼吸量的65．10％～100％，FT占总呼吸量的1．86％～29．46％，储存通量占总呼吸量的0．42％-5．44％。个体之间，树干呼吸的各通量成分所占的比例不同，FT和△s是木本组织呼吸与树干表面CO2释放通量之间差别的重要影响因子，液流速度对液流中CO2运输通量（FT）的影响在树木个体间也存在差异。

According to a mass balance approach, plant stem respiration （Rs） is composed of three parts that accounts for all fluxes of carbon dioxide of stems： transport flux （FT, dissolved CO2 entering and leaving the segment in flowing sap） ; storage flux （ AS, the increase or decrease in mean sap [ CO2] over time） ; efflux to atmosphere （EA , CO2 leaving the segment by diffusion through bark）, in which stem internal CO2 transport in xylem sap flow （ FT） plays a very important role in gas exchange of plant. It is an essential and non - specific component in respiration measurements of stems and branches. To evaluate the contribution of these three flux components to the stem respiration of Larix gmelinii, the stem CO2 efflux was continuously determined using infrared gas analysis method （IRGA） in situ and the sap flow density and stem temperature were simultaneously recorded. The relationship between stem respiration and stem temperature was fitted by Arrhenius equation assumed that the CO2 efflux is equal to the stem respiration rate when the sap flow ceased. Then, the stem respiration rate （Rs）, CO2 transport flux in sap flow （FT） and storage flux （AS） were calculated according to mass balance method. Our results showed that proportions of EA, Fw and AS accountting for Rs are dynamic. CO2 efflux （EA ） on the stem surface closely related with internal CO2 flux of the stem. It means that Fw and AS can affect EA. In 24 h cycle, EA, FT, AS accounted for 65. 10% - 104.45%, 1.86% ~ 29.46%, and 0. 42% ~ 5.44% of the total stem respiration, respectively. Sap flow is the main factor affecting the composition of the three flux components, but the effect is different among the individual trees.