用于全球变化研究的中国植物功能型划分

DEFINING PLANT FUNCTIONAL TYPES IN CHINA FOR GLOBAL CHANGE STUDIES

植物功能型(Plant functional types,PFTs)作为沟通植物的结构和功能与生态系统属性的桥梁,随着全球变 化与植被的关系研究的深入而受到广泛重视。植物功能型的划分依赖于研究的背景、尺度和要解决的问题。为了 区域尺度全球变化研究的需要,该文提出了一个基于植物关键特征的植物功能型划分方法。该方法首先选择了6 项植物特征,包括3项冠层特征:木本-草本、常绿-落叶和针叶-阔叶,以及3项生理特征:光合途径(C3/C4)、植物的 水分需求和热量需求,作为划分植物功能型的关键特征;然后,先根据植物冠层特征划分得到5个基本类型,再根 据水分和热量条件进行详细划分,得到29种备选类型;需要时,再根据研究目的从这29种备选类型中选择所需类 型。根据这个方法,在充分考虑了我国季风气候条件下特有的水热配置和高海拔环境对植物的形态和功能特征影 响的基础上,从备选类型中选择了一套适合中国气候和植被特征的植物功能型体系。这套体系包括18类植物功 能型,其中含7类'树'功能型、6类'灌木'功能型和5类'草'功能型,另根据需要设置2类'裸地'功能型。并且根 据植物的生理生态特征和中国植被的地理分布确定了用于限制植物功能型分布的气候因子,这些气候因子包括绝 对最低温度、最暖月平均温度、有效积温。

Plant functional types (PFTs) bridge the gap between plant physiology and ecosystem processes, providing a powerful tool for studies on global change, vegetation dynamics and vegetation-atmosphere processes . In this paper, a two-stepped hierarchical PFT classification system was proposed based on six key plant attributes. Three of six key attributes were related to plant canopy structure, including permanence of above-ground live biomass ( woody vs. herbaceous ) , leaf longevity ( evergreen vs. deciduous) and leaf structure (broad-leaved vs. needle-leaved) . The other three attributes were related to plant physiological characteristics, including photosynthetic pathway (i.e. C3 vs. C4 grasses) , drought resistance and temperature tolerance (e.g. warm evergreen, cool conifer) . In the first step of the analysis, five basic plant types were derived based on canopy attributes. In the second step, these five basic plant types were sub-divided into 29 types according to their photosynthetic pathways, drought resistance and temperature tolerance. We tested this PFT classification system by simulating the distribution of vegetation in China. A sub-set of 18 plant types was selected from the 29 PFTs that were characteristic of the vegetation in China, especially in relation to the water balance and energy budget as affected by the monsoon climate and the Tibetan Plateau. This set of PFTs contained 7 trees, 6 shrubs and 5 grasses. Two types of bare ground were added for the simulation. Six climatic variables were selected to be used as the distributional constraint of each PFT, which included absolute minimum temperature (Tmin) , mean temperature of the warmest month (Tw) , growing-day degrees (GDDs) , annual range of monthly mean temperature (DTY), moisture index (annual precipitation-annual potential evapo-transpiration, MI), annual precipitation (P). The values of these climatic variables were determined based on the geographical distribution of each plant functional type. Using BIOME1, the distribution of the PFTs across China was then modeled. The simulated map of China's vegetation was in close agreement with the ac- tual vegetation map, indicating that this set of PFTs was capable of simulating the geographical distribution of vegetation in China. This study provides a basis for future studies on climate-vegetation interactions and for developing regional dynamic vegetation models and regional climate models for China.