Ma Wei Ting, Yu Yong Zhi, Wang Xuming, Gong Xiao Ying
Key Laboratory for Subtropical Mountain Ecology (Ministry of Science and Technology and Fujian Province Funded), College of Geographical Sciences, Fujian Normal University, Fuzhou, China.
Key Laboratory for Humid Subtropical Eco-Geographical Processes of the Ministry of Education, Fujian Normal University, Fuzhou, China.
Front Plant Sci. 2023 Jan 12;13:1037972. doi: 10.3389/fpls.2022.1037972. eCollection 2022.
Carbon isotope composition (δC) has been widely used to estimate the intrinsic water-use efficiency (iWUE) of plants in ecosystems around the world, providing an ultimate record of the functional response of plants to climate change. This approach relies on established relationships between leaf gas exchange and isotopic discrimination, which are reflected in different formulations of C-based iWUE models. In the current literature, most studies have utilized the simple, linear equation of photosynthetic discrimination to estimate iWUE. However, recent studies demonstrated that using this linear model for quantitative studies of iWUE could be problematic. Despite these advances, there is a scarcity of review papers that have comprehensively reviewed the theoretical basis, assumptions, and uncertainty of C-based iWUE models. Here, we 1) present the theoretical basis of C-based iWUE models: the classical model (iWUE), the comprehensive model (iWUE), and the model incorporating mesophyll conductance (iWUE); 2) discuss the limitations of the widely used iWUE model; 3) and make suggestions on the application of the iWUE model. Finally, we suggest that a mechanistic understanding of mesophyll conductance associated effects and post-photosynthetic fractionation are the bottlenecks for improving the C-based estimation of iWUE.
碳同位素组成（δC）已被广泛用于估算全球生态系统中植物的内在水分利用效率（iWUE），提供了植物对气候变化功能响应的最终记录。这种方法依赖于叶片气体交换与同位素分馏之间已确立的关系，这在基于C的iWUE模型的不同公式中有所体现。在当前文献中，大多数研究都使用简单的光合分馏线性方程来估算iWUE。然而，最近的研究表明，使用这种线性模型进行iWUE的定量研究可能存在问题。尽管有这些进展，但缺乏全面综述基于C的iWUE模型的理论基础、假设和不确定性的综述文章。在此，我们1）介绍基于C的iWUE模型的理论基础：经典模型（iWUE）、综合模型（iWUE）和纳入叶肉导度的模型（iWUE）；2）讨论广泛使用的iWUE模型的局限性；3）并对iWUE模型的应用提出建议。最后，我们认为对叶肉导度相关效应和光合后分馏的机制理解是改进基于C的iWUE估算的瓶颈。
