Reconciling leaf physiological traits and canopy flux data: Use of the TRY and FLUXNET databases in the Community Land Model version 4
Reconciling leaf physiological traits and canopy flux data: Use of the TRY and FLUXNET databases in the Community Land Model version 4
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DOI：
10.1029/2011jg001913
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发表时间：
2012-06-20
影响因子：
3.7
通讯作者：
Reichstein, Markus
中科院分区：
文献类型：
--
作者：
Bonan, Gordon B.;Oleson, Keith W.;Reichstein, Markus
与FLUXNET涡度协方差塔的估计值相比，社区土地模型第4版高估了初级生产总值（GPP）。Bonan等人（2011年）的修订模型与FLUXNET一致，但在冠层尺度上产生真实GPP的叶片水平光合参数V-cmax的值低于Kattge等人（2009年）的全球综合中观察到的值，热带阔叶万年青树除外。我们调查V-cmax和冠层通量之间的差异。多层模型与显式计算的光吸收和光合作用的阳光照射和阴影的叶片在树冠深处，让人们了解叶片和树冠之间的规模不匹配。我们评估的模型与光响应曲线在个别FLUXNET塔和经验升级的年度GPP。与标准的两叶冠层和它的低V-cmax相比，在多层冠层中观察到的V-cmax的偏差是相似的，或者是改进的，尽管亚马逊是一个例外。这种差异与两叶冠层中被遮蔽的叶片对光的吸收有关，并且当冠层尺度参数K-n较低时导致较高的光合作用，但观测受到限制。较大的K-n降低了遮荫叶片的光合作用，并缩小了两叶和多层冠层之间的差异。低模型V-cmax是由碳-氮地球化学模拟中GPP的氮还原诊断的。我们的研究结果表明，施加氮减少补偿不足的两叶冠层，产生高GPP。叶性状数据库（V-cmax），光合能力（K-n），塔通量，和经验放大领域的冠层内配置文件提供了重要的补充信息模型评估。
The Community Land Model version 4 overestimates gross primary production (GPP) compared with estimates from FLUXNET eddy covariance towers. The revised model of Bonan et al. (2011) is consistent with FLUXNET, but values for the leaf-level photosynthetic parameter V-cmax that yield realistic GPP at the canopy-scale are lower than observed in the global synthesis of Kattge et al. (2009), except for tropical broadleaf evergreen trees. We investigate this discrepancy between V-cmax and canopy fluxes. A multilayer model with explicit calculation of light absorption and photosynthesis for sunlit and shaded leaves at depths in the canopy gives insight to the scale mismatch between leaf and canopy. We evaluate the model with light-response curves at individual FLUXNET towers and with empirically upscaled annual GPP. Biases in the multilayer canopy with observed V-cmax are similar, or improved, compared with the standard two-leaf canopy and its low V-cmax, though the Amazon is an exception. The difference relates to light absorption by shaded leaves in the two-leaf canopy, and resulting higher photosynthesis when the canopy scaling parameter K-n is low, but observationally constrained. Larger K-n decreases shaded leaf photosynthesis and reduces the difference between the two-leaf and multilayer canopies. The low model V-cmax is diagnosed from nitrogen reduction of GPP in simulations with carbon-nitrogen biogeochemistry. Our results show that the imposed nitrogen reduction compensates for deficiency in the two-leaf canopy that produces high GPP. Leaf trait databases (V-cmax), within-canopy profiles of photosynthetic capacity (K-n), tower fluxes, and empirically upscaled fields provide important complementary information for model evaluation.