植被光能利用率:模型及其不确定性

光能利用率（Light use efficiency： LUE）指植物截获的光能转化为化学能的效率，表示为生产力和吸收光能之比。基于LUE概念的模型对模拟预测全球变化下碳循环、植被生产力及其潜力具有重要意义。全球变化和人类活动影响给植被生产力和碳循环的评估带来了巨大挑战。系统梳理了LUE模型的不确定性并分析其原因，以期提高生产力模拟预测的准确度。分析发现LUE模型准确度仅为62%-70%且模型间差异较大（32%），误差随着植被类型、时间尺度和空间区域的不同存在显著差别。目前计算LUE的误差是模型不确定性的关键，原因主要在于LUE与影响因素尤其是水分的关系并不清楚。一方面不能准确区分水分胁迫指标对LUE的影响机制，另一方面无法准确模拟水分等影响因素与LUE关系的时空演变特征。未来该领域研究的重要方向是发展集成样地和区域尺度的叶绿素荧光、光化学指数等研究方法，厘定LUE与影响因素特别是的水分关系，并分析其时空演变特征。

Light use efficiency of vegetation: model and uncertainty

Light use efficiency (LUE) refers to the efficiency of fixed energy to intercepted energy, which is defined as ratio of productivity to intercepted energy. LUE model could simulate LUE and productivity, which is of implication to the simulation and prediction of carbon cycle, productivity and its greatest potential. The uncertainty of LUE model increased under the influence of global change and human activities which has become big challenge to the evaluation of vegetation productivity and carbon cycling. Thus, a systematic analysis of uncertainty and its causes was conducted to improve the estimation and prediction of vegetation productivity. The analysis indicated that the accuracies of LUE models ranged from 62% to 70% with a large variation (32%). The error of model varied with vegetation types, temporal scales and regional difference. The calculation of LUE in LUE model was the key of model uncertainty, which mainly resulted from unclearness of relation between LUE and its influence factors, particularly water. Firstly, it is not clear how different water indexes affected the LUE. Secondly, the spatiotemporal evolvement of relation between influencing factors and LUE has not been simulated rightly. The important research direction in this field is to determine the relationship between the LUE and water and the spatiotemporal evolution pattern of this relationship. Also, it''s important to develop the integrated experimental techniques and research methods at plot and regional scales.