PHOTOSYNSAT, photosynthesis from space: Theoretical foundations of a satellite concept and validation from tower and spaceborne data
PHOTOSYNSAT, photosynthesis from space: Theoretical foundations of a satellite concept and validation from tower and spaceborne data
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DOI：
10.1016/j.rse.2011.03.014
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发表时间：
2011-08-15
影响因子：
13.5
通讯作者：
Coops, Nicholas C.
中科院分区：
文献类型：
--
作者：
Hall, Forrest G.;Hilker, Thomas;Coops, Nicholas C.
我们在这里开发的理论基础，一个新的卫星概念，利用多角度，沿着轨道光谱测量，以推断光合作用和总初级生产，在景观水平随着时间的推移。我们验证了理论使用塔和星载传感器。该概念起源于Hall等人（2008）和Hilker等人（2008 a），基于两个原理：（1）光化学反射指数（PRI）相对于传感器偏导数PRI/偏导数alpha（s）观察到的阴影分数的一阶导数与光利用效率c成比例。(2)这种行为可以在理论上和经验上被证明是独立的植被结构和光学特性。这两个原则为鲁棒的光合作用算法提供了基础，该算法可以在空间和时间上一致地应用。我们使用冠层反射率模型开发了一般理论概念，该模型纳入了叶片反射率对光照强度的依赖性，允许531 nm处的叶片反射率取决于光合下调的强度。使用这个模型，我们能够表明，使用PRI单独推断e是混淆的阴影分数所看到的传感器，PRI值在一个非下调的生理状态，和阳光照射的冠层反射率。我们能够证明，通过使用偏导数PRI/偏导数alpha（s）--而不是PRI--作为冠层高度c的主要测量值，这些困难得到了缓解。我们使用三年多来获得的塔和卫星数据在两种不同的生物群落和植被类型中展示了我们的概念，以表明PRI/偏导数α（s）和c与单个函数相关。基于这些想法，我们提出了一个新的卫星概念，可以利用空间和时间上的鲁棒算法来映射光合作用在景观尺度及其时间变化的发展。(C)2011 Elsevier Inc. All rights reserved.
We develop herein the theoretical foundations for a new satellite concept, utilizing multi-angle, along track spectral measurements to infer photosynthesis and gross primary production, at the landscape level over time. We validate the theory using both tower and space-borne sensors. The concept, originated in Hall et al. (2008), and Hilker et al. (2008a) and is based on two principles: (1) The first derivative of the photochemical reflectance index (PRI) with respect to shadow fraction viewed by the sensor partial derivative PRI/partial derivative alpha(s), is proportional to light-use efficiency c. (2) This behavior can be shown both theoretically and empirically to be independent of vegetation structure and optical properties. These two principles provide the basis for a robust photosynthesis algorithm that can be applied consistently both spatially and temporally. We develop the general theoretical concept using a canopy reflectance model that incorporates a dependence of leaf reflectance on illumination strength, permitting the leaf reflectance at 531 nm to depend on the intensity of photosynthetic down-regulation. Using this model we are able to show that using PRI alone to infer e is confounded by the shadow fraction viewed by a sensor, the PRI value in a non-down-regulated physiological state, and the sunlit canopy reflectance. We are able to demonstrate that these difficulties are mitigated by using partial derivative PRI/partial derivative alpha(s)-not PRI-as the primary measure of canopy level c. We demonstrate our concept using tower and satellite data acquired over three years, in two distinct biomes and vegetation types to show that PRI/partial derivative alpha(s) and c are related by a single function. Building on these ideas we propose the development of a new satellite concept that can utilize a spatially and temporally robust algorithm to map photosynthesis at landscape scales and its temporal variation. (C) 2011 Elsevier Inc. All rights reserved.