Wullschleger Stan D, Epstein Howard E, Box Elgene O, Euskirchen Eugénie S, Goswami Santonu, Iversen Colleen M, Kattge Jens, Norby Richard J, van Bodegom Peter M, Xu Xiaofeng
Environmental Sciences Division, Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6301, USA
Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22904-4123, USA.
Ann Bot. 2014 Jul;114(1):1-16. doi: 10.1093/aob/mcu077. Epub 2014 May 2.
Earth system models describe the physical, chemical and biological processes that govern our global climate. While it is difficult to single out one component as being more important than another in these sophisticated models, terrestrial vegetation is a critical player in the biogeochemical and biophysical dynamics of the Earth system. There is much debate, however, as to how plant diversity and function should be represented in these models.
Plant functional types (PFTs) have been adopted by modellers to represent broad groupings of plant species that share similar characteristics (e.g. growth form) and roles (e.g. photosynthetic pathway) in ecosystem function. In this review, the PFT concept is traced from its origin in the early 1800s to its current use in regional and global dynamic vegetation models (DVMs). Special attention is given to the representation and parameterization of PFTs and to validation and benchmarking of predicted patterns of vegetation distribution in high-latitude ecosystems. These ecosystems are sensitive to changing climate and thus provide a useful test case for model-based simulations of past, current and future distribution of vegetation.
Models that incorporate the PFT concept predict many of the emerging patterns of vegetation change in tundra and boreal forests, given known processes of tree mortality, treeline migration and shrub expansion. However, representation of above- and especially below-ground traits for specific PFTs continues to be problematic. Potential solutions include developing trait databases and replacing fixed parameters for PFTs with formulations based on trait co-variance and empirical trait-environment relationships. Surprisingly, despite being important to land-atmosphere interactions of carbon, water and energy, PFTs such as moss and lichen are largely absent from DVMs. Close collaboration among those involved in modelling with the disciplines of taxonomy, biogeography, ecology and remote sensing will be required if we are to overcome these and other shortcomings.
地球系统模型描述了控制全球气候的物理、化学和生物过程。虽然在这些复杂模型中很难挑出一个组件比另一个更重要，但陆地植被是地球系统生物地球化学和生物物理动态中的关键参与者。然而，关于如何在这些模型中表示植物多样性和功能存在很多争议。
建模者采用植物功能类型（PFTs）来表示在生态系统功能中具有相似特征（如生长形式）和作用（如光合途径）的植物物种的广泛分组。在本综述中，PFT概念从19世纪初的起源追溯到其在区域和全球动态植被模型（DVMs）中的当前应用。特别关注PFTs的表示和参数化，以及高纬度生态系统中植被分布预测模式的验证和基准测试。这些生态系统对气候变化敏感，因此为基于模型的过去、当前和未来植被分布模拟提供了一个有用的测试案例。
考虑到树木死亡、树线迁移和灌木扩张的已知过程，纳入PFT概念的模型预测了苔原和北方森林中许多新出现的植被变化模式。然而，特定PFTs地上尤其是地下性状的表示仍然存在问题。潜在的解决方案包括开发性状数据库，并用基于性状协方差和经验性状-环境关系的公式取代PFTs的固定参数。令人惊讶的是，尽管苔藓和地衣等PFTs对碳、水和能量的陆地-大气相互作用很重要，但在DVMs中基本上没有。如果我们要克服这些及其他缺点，建模人员与分类学、生物地理学、生态学和遥感学科的人员需要密切合作。
