Quantifying photosynthetic capacity and its relationship to leaf nitrogen content for global-scale terrestrial biosphere models
Quantifying photosynthetic capacity and its relationship to leaf nitrogen content for global-scale terrestrial biosphere models
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DOI：
10.1111/j.1365-2486.2008.01744.x
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发表时间：
2009-04-01
影响因子：
11.6
通讯作者：
Wirth, Christian
中科院分区：
文献类型：
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作者：
Kattge, Jens;Knorr, Wolfgang;Wirth, Christian
光合作用能力及其与叶片含氮量的关系是陆地生物圈模型(TBM)最敏感的两个参数，由于缺乏足够广泛的数据库进行系统分析，该模型在全球尺度模拟中的代表性受到严重阻碍。在这里，我们利用质量性状、气候和土壤数据将陆地植被划分为功能型(PFT)，然后将观测到的羧化能力V-max(723个数据点)和最大光合作用速率A(Max)(776个数据点)同化到Farquhar等人提出的C-3光合作用模型中。限制V-max(25)(V-max归一化到25摄氏度)与每个PFT单位叶面积的叶氮含量的关系。在第二步中，所得到的函数被用来根据自然植被(1966个数据点)中容易测量的叶氮含量值来预测每PFT的V-max(25)。将所得到的V-max(25)的平均值应用到TBM(在气候-植被耦合模式ECHAM5/JSBACH中的Bethy)中，并将模拟的总初级生产力(GPP)与林分尺度上的独立观测结果进行比较。除了提供从更全面的数据中约束的每个PFT的参数范围外，该分析的结果还允许对以前的参数进行几个重大改进。(1)PFT之间的平均V-max(25)值的范围主要取决于光合氮素利用效率的差异(NUE，定义为V-max(25)除以叶片含氮量)，而在每个PFT中，V-max(25)值的分散主要是由叶片含氮量的高变异性决定的。(2)在某些已知缺磷的热带土壤上，我们发现了系统的NUE抑制。(3)本研究得到的热带树木的V-max(25)显著低于目前用于TBM的早期估计值，对模拟的GPP和地表温度有明显的影响。(4)模拟的GPP与观测的GPP之间的均方根差显著减小。
Photosynthetic capacity and its relationship to leaf nitrogen content are two of the most sensitive parameters of terrestrial biosphere models (TBM) whose representation in global-scale simulations has been severely hampered by a lack of systematic analyses using a sufficiently broad database. Here, we use data of qualitative traits, climate and soil to subdivide the terrestrial vegetation into functional types (PFT), and then assimilate observations of carboxylation capacity, V-max (723 data points), and maximum photosynthesis rates, A(max) (776 data points), into the C-3 photosynthesis model proposed by Farquhar et al. to constrain the relationship of V-max(25) (V-max normalised to 25 degrees C) to leaf nitrogen content per unit leaf area for each PFT. In a second step, the resulting functions are used to predict V-max(25) per PFT from easily measurable values of leaf nitrogen content in natural vegetation (1966 data points). Mean values of V-max(25) thus obtained are implemented into a TBM (BETHY within the coupled climate-vegetation model ECHAM5/JSBACH) and modelled gross primary production (GPP) is compared with independent observations on stand scale. Apart from providing parameter ranges per PFT constrained from much more comprehensive data, the results of this analysis enable several major improvements on previous parameterisations. (1) The range of mean V-max(25) between PFTs is dominated by differences of photosynthetic nitrogen use efficiency (NUE, defined as V-max(25) divided by leaf nitrogen content), while within each PFT, the scatter of V-max(25) values is dominated by the high variability of leaf nitrogen content. (2) We find a systematic depression of NUE on certain tropical soils that are known to be deficient in phosphorous. (3) V-max(25) of tropical trees derived by this study is substantially lower than earlier estimates currently used in TBMs, with an obvious effect on modelled GPP and surface temperature. (4) The root-mean-squared difference between modelled and observed GPP is substantially reduced.