State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.
State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing, 100081, China.
Photosynth Res. 2021 Mar;147(3):269-281. doi: 10.1007/s11120-020-00817-9. Epub 2021 Jan 29.
Fluxes of carbon and water along a vertical profile within a canopy, particularly the associations between canopy and ecosystem levels, are not well studied. In this study, gas exchange along the vertical profile in a maize canopy was examined. The relationships between leaf- and ecosystem-level carbon and water fluxes were compared. The results from research conducted over two growing seasons showed that during vegetative growth, the top and middle leaf layers in the canopy contribute most to the carbon and water fluxes of the entire canopy. During the grain-filling stage, gas exchange processes were performed mostly in the middle leaves with and near the ears. Significant relationships were observed between the net ecosystem CO exchange rate (NEE) plus soil respiration and the assumed canopy levels (A) and between evapotranspiration rates at the ecosystem (ET) and assumed canopy levels (E). This highlights the close associations between these parameters by integrating the leaf gas exchange rates measured in a conventional leaf cuvette and those at the ecosystem level via the eddy covariance technique. These results improve our understanding of how carbon assimilation varies vertically within a canopy, highlighting the critical role of ear leaves.
冠层内垂直剖面的碳和水通量，特别是冠层和生态系统之间的关系，研究得还不够充分。本研究考察了玉米冠层中垂直剖面的气体交换情况，并比较了叶片和生态系统水平的碳和水通量之间的关系。两个生长季节的研究结果表明，在营养生长阶段，冠层的顶部和中部叶片层对整个冠层的碳和水通量贡献最大。在灌浆期，气体交换过程主要在中部叶片及其附近进行。净生态系统 CO2 交换率（NEE）加土壤呼吸与假定的冠层水平（A）之间以及生态系统（ET）蒸腾速率与假定的冠层水平（E）之间存在显著关系。这通过整合常规叶片室测量的叶片气体交换率和通过涡度相关技术在生态系统水平上的测量值，突出了这些参数之间的紧密联系。这些结果提高了我们对碳同化如何在冠层内垂直变化的理解，强调了穗叶的关键作用。
