Study on carbon cycle in forest ecosystem using stable oxygen isotopic measurement

利用稳定氧同位素测量研究森林生态系统碳循环

基本信息

批准号：
18510019
负责人：
MURAYAMA Shohei
金额：
$ 2.57万
依托单位：
National Institute of Advanced Industrial Science and Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18510019/
关键词：
stable oxygen isotopic ratio carbon cycle exchange between atmosphere and forest ecosystem hydrological processes isotopic discrimination 大気-森林生態系交換

项目摘要

Systematic measurements of atmospheric CO_2 concentration and its stable oxygen isotopic ratio (δ^<18>O) in and above the forest together with δ^<18>O of CO_2 in soil an, precipitation, soil water, water vapor and leaf water were made in a cool-temperate deciduous forest at Takayama site in central Japan. Using the observed data, temporal variations of δ^<18>O discriminations during photosynthesis and ecosystem respiration were estimated, and possibility of separating these carbon budget components from net ecosystem CO_2 exchange obtained from the eddy covariance flux measurement was examined. δ^<18>O of atmospheric CO_2 showed more complicated diurnal variation than CO_2 concentration, but prominent δ^<18>O increase appeared in the daytime under sunny and dry conditions, reflecting increase of photosynthetic ^<18>O discrimination. Seasonal variation of daytime δ^<18>O of CO_2 above the forest showed scattered but low values in winter and high values in spring. From late spring to early fall, significant year-to-year difference of the variation was seen with low and high values under respective rainy and sunny summer conditions, which may reflect difference of biological and hydrological processes due to that of meteorological conditions associated with the Asian summer monsoon. Comparison with the data at northern mid latitude sites suggested that the rapid decrease of δ^<18>O seen at Takayama in early summer of the rainy summer year is characteristic of the monsoon Asian region. From comparison of the CO^<18>O fluxes associated with photosynthesis and respiration calculated using a simple one-box canopy air model with the variation of the observed δ^<18>O of CO_2, it was found that the model cannot adequately simulate the δ^<18>O variation. The result suggested that analyses of the δ^<18>O data using a multi-layered canopy process model are necessary to precisely separate photosynthetic and respiratory CO_2 fluxes.

系统测量了森林内外大气CO_2浓度及其稳定氧同位素比(δ^18O)以及土壤中CO_2的δ^18O、降水、土壤水、水汽和叶面水等。使用观测数据，估计了光合作用和生态系统呼吸过程中δ^ 18 O辨别的时间变化，以及将它们分开的可能性。大气CO_2涡流协方差通量测量得到的净生态系统CO_2交换的碳收支成分表现出比CO_2浓度更复杂的日变化，但δ^18O增加在白天出现明显。阳光充足且干燥的条件下，反映了光合^<18>O辨别力的增加，森林上方CO_2白天δ^<18>O的季节变化表现出零散但冬季值较低且较高。从春末到初秋，在多雨和晴朗的夏季条件下，年际变化差异显着，这可能反映了由于生物和水文过程的差异。与亚洲夏季风相关的气象条件的比较表明，在多雨的夏季初夏，高山地区δ^ 18 O的快速减少是亚洲季风的特征。从地区比较来看。使用简单的一箱冠层空气模型计算与光合作用和呼吸相关的CO^<18>O通量，并结合观测到的CO_2的δ^<18>O的变化，发现该模型不能充分模拟δ^ 18O变化表明，使用多层冠层过程模型分析δ^18O数据对于精确分离光合和呼吸CO_2通量是必要的。