De Kauwe Martin G, Lin Yan-Shih, Wright Ian J, Medlyn Belinda E, Crous Kristine Y, Ellsworth David S, Maire Vincent, Prentice I Colin, Atkin Owen K, Rogers Alistair, Niinemets Ülo, Serbin Shawn P, Meir Patrick, Uddling Johan, Togashi Henrique F, Tarvainen Lasse, Weerasinghe Lasantha K, Evans Bradley J, Ishida F Yoko, Domingues Tomas F
Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia.
Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
New Phytol. 2016 May;210(3):1130-44. doi: 10.1111/nph.13815. Epub 2015 Dec 31.
Simulations of photosynthesis by terrestrial biosphere models typically need a specification of the maximum carboxylation rate (Vcmax ). Estimating this parameter using A-Ci curves (net photosynthesis, A, vs intercellular CO2 concentration, Ci ) is laborious, which limits availability of Vcmax data. However, many multispecies field datasets include net photosynthetic rate at saturating irradiance and at ambient atmospheric CO2 concentration (Asat ) measurements, from which Vcmax can be extracted using a 'one-point method'. We used a global dataset of A-Ci curves (564 species from 46 field sites, covering a range of plant functional types) to test the validity of an alternative approach to estimate Vcmax from Asat via this 'one-point method'. If leaf respiration during the day (Rday ) is known exactly, Vcmax can be estimated with an r(2) value of 0.98 and a root-mean-squared error (RMSE) of 8.19 μmol m(-2) s(-1) . However, Rday typically must be estimated. Estimating Rday as 1.5% of Vcmax, we found that Vcmax could be estimated with an r(2) of 0.95 and an RMSE of 17.1 μmol m(-2) s(-1) . The one-point method provides a robust means to expand current databases of field-measured Vcmax , giving new potential to improve vegetation models and quantify the environmental drivers of Vcmax variation.
陆地生物圈模型对光合作用的模拟通常需要指定最大羧化速率（Vcmax）。使用A-Ci曲线（净光合速率A与细胞间二氧化碳浓度Ci）来估算该参数很费力，这限制了Vcmax数据的可用性。然而，许多多物种野外数据集包含饱和光照和环境大气二氧化碳浓度下的净光合速率（Asat）测量值，可通过“单点法”从中提取Vcmax。我们使用了一个A-Ci曲线的全球数据集（来自46个野外站点的564个物种，涵盖一系列植物功能类型）来测试通过这种“单点法”从Asat估算Vcmax的另一种方法的有效性。如果准确知道白天的叶片呼吸（Rday），则可以用r(2)值为0.98和均方根误差（RMSE）为8.19 μmol m(-2) s(-1)来估算Vcmax。然而，Rday通常必须进行估算。将Rday估算为Vcmax的1.5%，我们发现可以用r(2)为0.95和RMSE为17.1 μmol m(-2) s(-1)来估算Vcmax。单点法提供了一种强大的方法来扩展当前实地测量的Vcmax数据库，为改进植被模型和量化Vcmax变化的环境驱动因素带来了新的可能性。
