Dynamics of photosynthetic photon flux density (PPFD) and estimates in coastal northern California
Dynamics of photosynthetic photon flux density (PPFD) and estimates in coastal northern California
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DOI：
10.1007/s00704-010-0368-6
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发表时间：
2011-08-01
影响因子：
3.4
通讯作者：
Carruthers, Raymond I.
中科院分区：
文献类型：
--
作者：
Ge, Shaokui;Smith, Richard G.;Carruthers, Raymond I.
植物需要太阳辐射进行光合作用，假设其他环境参数不受限制，它们的生长与接收的量直接相关。因此，精确估算光合有效辐射（PAR）是提高植物生长模型整体精度的必要条件。本研究的目的是探讨在加州州北方的弗朗西斯科湾区的PAR辐射通量。在生长季节（3月至8月）为2年2007-2008年，光合光子通量密度（PPFD）的现场幅度进行了调查，然后在每小时和每天的时间尺度处理。结合全球太阳辐射（R（S））和模拟的地外太阳辐射，开发了五个PAR相关值，即，基于通量密度的PAR（PPFD）、基于能量的PAR（帕雷）、从通量到能量的转换效率（fFEC）、PAR能量占总太阳辐射的比例（fE）以及一个新发展的太阳辐射从地外系统穿透到地面时的指标--损失的帕雷百分比（LPR）。这些PAR相关值显示了显著的日变化，中午出现高值，上午和下午出现低值。在整个实验季节，fFEC的整体平均每小时的值被认为是2.17 μ mol J（-1），而相应的fE值为0.49。太阳正午时的每小时fFEC和fE的月平均值分别为3月的2.15到8月的2.39 μ mol J（-1）和3月的0.47到7月的0.52。然而，月平均日值相对稳定，它们表现出弱的季节变化，范围从2.02 mol MJ（-1）和0.45（3月）到2.19 mol MJ（-1）和0.48（6月）。在整个生长季中，fFEC和fE在太阳正午的日平均值分别为2.16 mol MJ（-1）和0.47。PPFD和首次报道的LPR都表现出较强的日变化模式。然而，他们有相反的趋势。PPFD在中午左右很高，导致同一时间段LPR的值很低。两者都与太阳总辐射R（S）、太阳高度角h和晴朗指数K（t）高度相关。使用最佳子集选择的变量，两个参数模型，估计PPFD和LPR，这可以很容易地应用于辐射站点，只记录全球太阳辐射测量。发现这两个模型涉及最常测量的全球太阳辐射（R（S））和两个大尺度几何参数，即，地外太阳辐射和太阳高度。因此，这些模型对当地的天气条件（如温度）不敏感。特别是，通过在美国和希腊收集的两个测试数据集，验证了模型可以扩展到不同的地理区域，在那里它们表现良好。因此，这两个基于小时的模型可以用来提供精确的PAR相关值，如开发精确的植被生长模型所需的值。
Plants require solar radiation for photosynthesis and their growth is directly related to the amount received, assuming that other environmental parameters are not limiting. Therefore, precise estimation of photosynthetically active radiation (PAR) is necessary to enhance overall accuracies of plant growth models. This study aimed to explore the PAR radiant flux in the San Francisco Bay Area of northern California. During the growing season (March through August) for 2 years 2007-2008, the on-site magnitudes of photosynthetic photon flux densities (PPFD) were investigated and then processed at both the hourly and daily time scales. Combined with global solar radiation (R (S)) and simulated extraterrestrial solar radiation, five PAR-related values were developed, i.e., flux density-based PAR (PPFD), energy-based PAR (PARE), from-flux-to-energy conversion efficiency (fFEC), and the fraction of PAR energy in the global solar radiation (fE), and a new developed indicator-lost PARE percentages (LPR)-when solar radiation penetrates from the extraterrestrial system to the ground. These PAR-related values indicated significant diurnal variation, high values occurring at midday, with the low values occurring in the morning and afternoon hours. During the entire experimental season, the overall mean hourly value of fFEC was found to be 2.17 mu mol J(-1), while the respective fE value was 0.49. The monthly averages of hourly fFEC and fE at the solar noon time ranged from 2.15 in March to 2.39 mu mol J(-1) in August and from 0.47 in March to 0.52 in July, respectively. However, the monthly average daily values were relatively constant, and they exhibited a weak seasonal variation, ranging from 2.02 mol MJ(-1) and 0.45 (March) to 2.19 mol MJ(-1) and 0.48 (June). The mean daily values of fFEC and fE at the solar noon were 2.16 mol MJ(-1) and 0.47 across the entire growing season, respectively. Both PPFD and the ever first reported LPR showed strong diurnal patterns. However, they had opposite trends. PPFD was high around noon, resulting in low values of LPR during the same time period. Both were found to be highly correlated with global solar radiation R (S), solar elevation angle h, and the clearness index K (t). Using the best subset selection of variables, two parametric models were developed for estimating PPFD and LPR, which can easily be applied in radiometric sites, by recording only global solar radiation measurements. These two models were found to be involved with the most commonly measured global solar radiation (R (S)) and two large-scale geometric parameters, i.e., extraterrestrial solar radiation and solar elevation. The models were therefore insensitive to local weather conditions such as temperature. In particular, with two test data sets collected in USA and Greece, it was verified that the models could be extended across different geographical areas, where they performed well. Therefore, these two hourly based models can be used to provide precise PAR-related values, such as those required for developing precise vegetation growth models.