Inter-annual variability of carbon budget components in an AsiaFlux forest site estimated by long-term flux measurements
Inter-annual variability of carbon budget components in an AsiaFlux forest site estimated by long-term flux measurements
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DOI：
10.1016/j.agrformet.2005.08.016
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发表时间：
2005-11
影响因子：
6.2
通讯作者：
N. Saigusa;S. Yamamoto;S. Murayama;H. Kondo
中科院分区：
文献类型：
--
作者：
N. Saigusa;S. Yamamoto;S. Murayama;H. Kondo
自1993年以来的空气动力学方法和涡度协方差法在日本的冷温带落叶林，这是亚洲通量森林网站之一，自1998年以来的CO2通量进行了测量。在空气动力学方法中，利用CO2浓度的垂直梯度和冠层扩散系数估算CO2通量。感热、水汽和CO2的涡动通量是用声速风速计和闭路红外气体分析仪测量的。涡度相关法估算的CO2通量主要用于分析观测误差以及测量和数据处理过程中产生的不确定性。通过与涡度相关法估算的CO2通量进行比较，验证了空气动力学法估算的CO2通量的有效性。夜间净生态系统CO2交换（NEE）是高度敏感的大气稳定性，因为现场周围的复杂地形。夜间NEE的估计和不校正，取决于摩擦速度。1999年、2000年和2001年的年净生态系统生产力（NEP）值估计分别为198、309和290 gCm − 2 year − 1（经校正）和251、376和342 gCm − 2 year − 1（未经校正）。夜间校正导致该站点的年NEP的不确定度约为50- 70 gCm − 2 year − 1。NEP已经计算了9年，这是亚洲任何特定站点的最长记录，作为通量测量的结果。年NEP估计为237± 92 gCm − 2 year −1（平均值±标准差）。从1994年到2002年，每年的变化很大。年NEP的年际变化与总初级生产力（GPP）相似，而代表生产力的碳收支分量的年际变化比呼吸（生态系统呼吸和土壤呼吸）更显著。1998年和2002年观测到的年净排放量较高（分别为329 gCm-2 year-1和346 gCm-2 year-1），这主要是由于在这两年的生长期前半期观测到的CO2吸收量较高。本研究的结果表明，在1998年和2002年的高GPP是由早期的叶子出现与厄尔尼诺现象的影响下，一个异常温暖的春天。结果还表明，在1998年和2002年的CO2吸收的增加，由于长的生长期比呼吸的增强，在冷温性森林更显着。
The CO2flux has been measured by the aerodynamic method since 1993 and by the eddy covariance method since 1998 over a cool-temperate deciduous forest in Japan, which is one of the AsiaFlux forest sites. In the aerodynamic method, the CO2flux is estimated using the vertical gradient of the CO2concentration and the diffusion coefficient over the canopy. The eddy fluxes of sensible heat, water vapor, and CO2are measured using a sonic anemometer and a closed-path infrared gas analyzer. The CO2flux estimated by the eddy covariance method was mainly used to analyze observational errors and uncertainties caused by measurement and data processing. The CO2flux determined by the aerodynamic method was validated by comparison with that estimated by the eddy covariance method. The nighttime net ecosystem CO2exchange (NEE) was highly sensitive to atmospheric stability because of the complex terrain around the site. The nighttime NEE was estimated with and without correction, depending on the friction velocity. The annual net ecosystem production (NEP) values for 1999, 2000, and 2001 were estimated to be 198, 309, and 290gCm−2year−1with correction and 251, 376, and 342gCm−2year−1without correction, respectively. The nighttime correction is responsible for an uncertainty of approximately 50–70gCm−2year−1in the annual NEP at this site. The NEP has been calculated for 9 years, which is the longest record at any particular site in Asia, as a consequence of the flux measurements. The annual NEP was estimated to be 237±92gCm−2year−1(mean±S.D.) from 1994 to 2002 with a large year-to-year variability. The annual NEP had a similar year-to-year variation to that for gross primary production (GPP), and the carbon budget components representing productivity had more remarkable year-to-year variability than the respiration (ecosystem respiration and soil respiration). A high annual NEP was observed in 1998 (329gCm−2year−1) and in 2002 (346gCm−2year−1), mainly due to the high CO2uptake observed during the first half of the growth period in both years. The results of the present study suggest that the high GPP in 1998 and 2002 was caused by early leaf emergence related to an unusually warm spring under the influence of the El Niño. The results also suggest that the increase in CO2uptake due to the long growth periods in 1998 and 2002 was more marked than the enhancement of respiration in the cool-temperate forest.