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散射辐射对青藏高原高寒草地总初级生产力模拟的影响
任小丽,何洪林,张黎,葛蓉,曾纳,李攀,于贵瑞,等
作者单位E-mail
任小丽 中国科学院地理科学与资源研究所 renxl@igsnrr.ac.cn 
何洪林 中国科学院地理科学与资源研究所 hehl@igsnrr.ac.cn 
张黎 中国科学院地理科学与资源研究所  
葛蓉 中国科学院地理科学与资源研究所  
曾纳 中国科学院地理科学与资源研究所  
李攀 中国科学院地球化学研究所  
于贵瑞 中国科学院地理科学与资源研究所  
摘要:
太阳辐射的散射组分能够增强植被冠层LUE(Light Use Efficiency, 光能利用率),因此需要在生产力模型中显式地加入散射辐射的影响,从而更准确地模拟植被冠层光合作用。以青藏高原高寒草地为研究对象,改进光能利用率模型,增加散射辐射模块,利用站点通量观测数据估计模型关键参数;结合区域尺度气象数据和遥感数据,模拟了2003—2008年青藏高原高寒草地区域尺度GPP(Gross Primary Production, 总初级生产力) ,并量化了GPP模拟的不确定性,进而通过分析模型改进前后GPP空间分布及其不确定性的差异量化了散射辐射的作用。结果表明:考虑散射辐射对LUE的影响后,模型参数优化效果明显提升,青藏高原高寒草地GPP的模拟效果得到提升;2003—2008年青藏高原高寒草地GPP模拟值呈现东南部较大,西北部较小的空间格局,与不考虑散射辐射的结果一致,但GPP均值从312.3 g/(m2·a)增至341.7 g/(m2·a),增幅约9.4%,说明不考虑散射辐射会低估青藏高原高寒草地GPP;GPP模拟值不确定性的空间分布与不考虑散射辐射的结果一致,但是平均不确定性大小有所降低,从9.15%降至8.66%。研究显示,若在青藏高原高寒草地的GPP模拟中不考虑散射辐射,虽不会影响其空间格局,但会低估GPP模拟值的大小,同时增加其不确定性。
关键词:  散射辐射  光能利用率  总初级生产力  不确定性分析
DOI:
分类号:
基金项目:国家重点研发计划(2016YFC0500204);国家自然科学基金(41571424);科技基础性工作专项(2015FY110700)
The Effects of Diffuse Radiation on the Estimation of Gross Primary Production of the Alpine Grasslands on the Tibetan Plateau
REN Xiaoli,HE Honglin,ZHANG Li,Ge Rong,曾纳,李攀,于贵瑞,et al
Abstract:
The effect of diffuse radiation on photosynthesis is needed to be involved in ecosystem models to accurately simulate the gross vegetation photosynthesis, since diffuse radiation can enhance vegetation canopy light use efficiency (LUE). In this study, we modified a LUE model by incorporating the effect of diffuse radiation on photosynthesis to simulate the gross primary production (GPP) of alpine grasslands on the Tibetan Plateau during 2003-2008, and quantified the effects of diffuse radiation on the estimation and uncertainty of GPP. Values of key model parameters were estimated using eddy covariance observational data. The results showed that: (1) The performance of the modified model in simulating GPP was improved with considering the impact of diffuse radiation on LUE, with high correlation between the modeled and observed GPP (R2 > 0.80). (2) Compared to the results without considering diffuse radiation, GPP simulated by the modified model kept the same heterogeneous spatial pattern across Tibetan Plateau, i.e., higher in the southeast and lower in the northwest. The mean annual GPP in Tibetan alpine grasslands increased 9.4%, from 312.3 g/(m2·a) to 341.7 g/(m2·a), when incorporating the effects of diffuse radiation. (3) The spatial distribution of the uncertainty in GPP was opposite to that of GPP, with larger uncertainty occurring in regions with lower GPP, which was consistent with the results without considering diffuse radiation. The mean uncertainty decreased from 9.15% to 8.66% when diffuse radiation was considered. These results indicated that the magnitude of GPP will be underestimated and the uncertainty of GPP will be overestimated if the effects of diffuse radiation were not considered in the LUE model. This emphasizes the importance of diffuse radiation in GPP simulation using the LUE model.
Key words:  diffuse radiation, light use efficiency (LUE)  gross primary production (GPP)  uncertainty analysis