Leaf age affects the seasonal pattern of photosynthetic capacity and net ecosystem exchange of carbon in a deciduous forest
Leaf age affects the seasonal pattern of photosynthetic capacity and net ecosystem exchange of carbon in a deciduous forest
复制标题
DOI：
10.1046/j.0016-8025.2001.00706.x
复制
发表时间：
2001-06
影响因子：
7.3
通讯作者：
K. Wilson;D. Baldocchi;P. Hanson
中科院分区：
文献类型：
--
作者：
K. Wilson;D. Baldocchi;P. Hanson
光合能力的时间趋势是决定生态系统碳通量的季节性和大小的关键因素。在美国东南部的落叶混交林（步行者分支流域，橡树岭，TN，美国），我们独立测量光合能力（使用单叶气体交换技术）和整个冠层碳通量（使用涡度协方差法）的季节趋势。土壤呼吸也测量了使用室和冠层下的涡度协方差系统。这些独立的室和涡度协方差测量，沿着与生物物理模型（CANOAK），被用来研究如何叶龄影响的季节性模式的碳吸收在生长季节。当在光合能力的季节性测定代表在CANOAK模拟，有很好的协议与涡度协方差数据的季节性趋势的碳吸收。通过使用整个生长季节的光合能力的早期最大值来去除模拟中的时间趋势，估计年碳吸收量约为300 g C m-2年-1-估计的年净生态系统交换总量的一半。另外，使用光合能力的平均值不正确地模拟了森林碳吸收的季节性。除了与叶片发育和衰老有关的变化外，光合能力在中夏末下降，即使叶片氮基本上是恒定的。当在模型模拟中只忽略这些中、晚夏的减少时，CANOAK仍然高估了碳吸收量，其值相当于年净生态系统交换总量的25%。
Temporal trends in photosynthetic capacity are a critical factorin determining the seasonality and magnitude of ecosystem carbonfluxes. At a mixed deciduous forest in the south-eastern United States (Walker Branch Watershed, Oak Ridge, TN, USA), we independently measured seasonal trends in photosynthetic capacity (using single-leaf gas exchange techniques) and the whole-canopycarbon flux (using the eddy covariance method). Soil respiration was also measured using chambers and an eddy covariance system beneath the canopy. These independent chamber and eddy covariance measurements, along with a biophysical model (CANOAK), areused to examine how leaf age affects the seasonal pattern of carbon uptake during the growing season. When the measured seasonality in photosynthetic capacity is representedin the CANOAK simulations, there is good agreement with the eddy covariance data on the seasonal trends in carbon uptake. Removing the temporal trends in the simulations by using the early season maximum value of photosynthetic capacity over the entire growing season over estimates the annual carbon uptake by about 300 g C m−2 year−1– halfthe total estimated annual net ecosystem exchange. Alternatively, use of the mean value of photosynthetic capacity incorrectly simulates the seasonality in carbon uptake by the forest. In addition to changes related to leaf development and senescence, photosynthetic capacitydecreased in the middle and late summer, even when leaf nitrogenwas essentially constant. When only these middle and late summer reductions were neglected in the model simulations, CANOAK still overestimated the carbon uptake by an amount comparable to 25% ofthe total annual net ecosystem exchange.