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Assessing variability of optimum air temperature for photosynthesis across site-years, sites and biomes and their effects on photosynthesis estimation
Agricultural and Forest Meteorology ( IF 5.6 ) Pub Date : 2021-03-01 , DOI: 10.1016/j.agrformet.2020.108277
Qing Chang , Xiangming Xiao , Russell Doughty , Xiaocui Wu , Wenzhe Jiao , Yuanwei Qin

Abstract Gross primary productivity (GPP) of vegetation is affected by air temperature. Biogeochemical models use the optimum air temperature (Topt) parameter, which comes from biome-specific look-up tables ( T opt − b − LT ). Many studies have shown that plants have the capacity to adapt to changes in environmental conditions over time, which suggests that the static T opt − b − LT parameters in the biogeochemical models may poorly represent actual T opt and induce uncertainty in GPP estimates. Here, we estimated biome-specific, site-year-specific, and site-specific optimum air temperature using GPP data from eddy covariance (EC) flux tower sites (GPPEC) ( T opt − b − EC , T opt − sy − EC , T opt − s − EC ), the Enhanced Vegetation Index (EVI) from MODIS images ( T opt − b − EVI , T opt − sy − EVI , T opt − s − EVI ), and mean daytime air temperature (TDT). We evaluated the consistency among the four T opt parameters ( T opt − b , T opt − sy , T opt − s and T opt − b − LT ), and assessed how they affect satellite-based GPP estimates. We find that T opt parameters from MODIS EVI agree well with those from GPPEC, which indicates that EVI can be used as a variable to estimate T opt at individual pixels over large spatial domains. T opt − b , T opt − sy , and T opt − s differed significantly from T opt − b − LT . GPP estimates using T opt − b and T opt − sy were more consistent with GPPEC than when using T opt − b − LT for all the land cover types. Our use of T opt − sy substantially improved 8-day and annual GPP estimates across biomess (from 1% to 34%), especially for cropland, grassland, and open shrubland. Our simple calculation shows that global GPP estimates differ by up to 10 Pg C/yr when using our suggested T opt − sy − EVI instead of using the static T opt − b − LT . Our new approach on estimating Topt has the potential to improve estimates of GPP from satellite-based models, which could lead to better understanding of carbon-climate interactions.

中文翻译:

评估不同地点年份、地点和生物群落的光合作用最佳气温的变化及其对光合作用估计的影响

摘要 植被的总初级生产力(GPP)受气温影响。生物地球化学模型使用最佳气温 (Topt) 参数,该参数来自特定于生物群落的查找表 ( T opt − b − LT )。许多研究表明,植物具有适应环境条件随时间变化的能力,这表明生物地球化学模型中的静态 T opt - b - LT 参数可能无法很好地代表实际 T opt 并导致 GPP 估计的不确定性。在这里,我们使用来自涡流协方差 (EC) 通量塔站点 (GPPEC) ( T opt − b − EC , T opt − sy − EC , T opt − s − EC ), MODIS 图像的增强植被指数 (EVI) ( T opt − b − EVI , T opt − sy − EVI , T opt − s − EVI ), 和平均日间气温 (TDT)。我们评估了四个 T opt 参数(T opt − b 、T opt − sy 、T opt − s 和 T opt − b − LT )之间的一致性,并评估了它们如何影响基于卫星的 GPP 估计。我们发现来自 MODIS EVI 的 T opt 参数与来自 GPPEC 的参数非常吻合,这表明 EVI 可以用作估计大空间域上单个像素的 T opt 的变量。T opt − b 、T opt − sy 和T opt − s 与T opt − b − LT 显着不同。对于所有土地覆盖类型,使用 T opt - b 和 T opt - sy 的 GPP 估计比使用 T opt - b - LT 时更符合 GPPEC。我们对 T opt - sy 的使用大大提高了整个生物群落的 8 天和年度 GPP 估计值(从 1% 到 34%),特别是对于农田、草地和开阔灌木地。我们的简单计算表明,当使用我们建议的 T opt − sy − EVI 而不是使用静态 T opt − b − LT 时,全球 GPP 估计差异高达 10 Pg C/yr。我们估计 Topt 的新方法有可能改进基于卫星模型的 GPP 估计,这可能会导致更好地了解碳-气候相互作用。
更新日期:2021-03-01
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