Simple scaling of photosynthesis from leaves to canopies without the errors of big-leaf models
Simple scaling of photosynthesis from leaves to canopies without the errors of big-leaf models
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DOI：
10.1111/j.1365-3040.1997.00094.x
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发表时间：
1997-05-01
影响因子：
7.3
通讯作者：
Farquhar, GD
中科院分区：
文献类型：
--
作者：
dePury, DGG;Farquhar, GD
在冠层光合作用的大叶模型中，单位地面积的Rubisco活性被视为冠层内单位叶面积的活动之和，电子传递能力也同样被求和。这些模型高估了光合作用的速率，并需要经验的曲率因子来响应光照，我们表明，对于冠层内任何叶片氮的分布(包括最佳分布)，所需的曲率因子不是恒定的，而是随冠层叶面积指数和叶片氮含量而变化。我们进一步表明，潜在的原因是太阳黑子的穿透和冠层中叶片角度的范围导致的吸收辐照度的时间平均分布和瞬时分布之间的差异，这些误差在按多层处理冠层的模型中是避免的--多层模型。我们提出了一种替代多层模型的方法：通过分别对树冠的日照和遮荫部分进行积分，得到了一种既准确又简单的单层日照/遮荫模型。该模型是叶模型的缩放版本，与综合方法不同。
In big-leaf models of canopy photosynthesis, the Rubisco activity per unit ground area is taken as the sum of activities per unit leaf area within the canopy, and electron transport capacity is similarly summed. Such models overestimate rates of photosynthesis and require empirical curvature factors in the response to irradiance, We show that, with any distribution of leaf nitrogen within the canopy (including optimal), the required curvature factors are not constant but vary with canopy Leaf area index and leaf nitrogen content. We further show that the underlying reason is the difference between the time-averaged and instantaneous distributions of absorbed irradiance, caused by penetration of sunflecks and the range of leaf angles in canopies.These errors are avoided in models that treat the canopy in terms of a number of layers - the multi-layer models. We present an alternative to the multi-layer model: by separately integrating the sunlit and shaded leaf fractions of the canopy, a single layered sun/shade model is obtained, which is as accurate and simpler. The model is a scaled version of a leaf model as distinct from an integrative approach.