基于背包LiDAR的半湿润常绿阔叶林及其常见树种的垂直结构特征

Vertical structural characteristics of a semi-humid evergreen broad-leaved forest and common tree species based on a portable backpack LiDAR

森林的垂直结构是地上植被要素在垂直方向上的排列,它影响动植物多样性和生态系统功能,是许多植物生态学家关注的重点。背包激光雷达技术的发展为大面积、高精度扫描三维森林结构提供了基础。直观反映生物量的冠层高度(canopy height,CH)、代表植物光合能力的叶面积指数(leaf area index,LAI)和单木尺度上的特征是森林垂直结构最重要的参数。本研究旨在探索鸡足山半湿润常绿阔叶林样地尺度和单木尺度上的垂直结构特征。本研究基于背包激光雷达,对滇中高原20.16 ha半湿润常绿阔叶林样地群落的CH和LAI进行了精细扫描和点云定量分析,在进行地形校正和群落分类的基础上,精细提取和分析了森林群落的叶面积指数的垂直变化和水平格局,并定量提取了群落常见乔木种的单木形态和垂直结构参数。结果显示:(1)以20 m×20 m标准样方为统计单位的CH和LAI的分布接近正态分布;(2)根据LAI的垂直分布,森林动态监测样地群落冠层由上至下可划分为林冠上层、林冠中层、林冠下层与灌木层4个层次;(3)元江栲(Castanopsisorthacantha)和高山栲(C.delavayi)群落的LAI垂直变化呈单峰格局,峰值高度分别为15m和13m,云南松(Pinusyunnanensis)群落为双峰格局,峰值高度为5 m和10 m;(4)不同树种的各单木参数表现出较大的差异性,但冠幅面积/胸径比表现出相对的稳定性。本研究在国内首次基于激光雷达技术定量分析具有复杂结构的半湿润常绿阔叶林的叶面积指数的三维格局,或可对以后该类型森林生物多样性的研究和不同森林类型之间的比较研究提供数据基础。

Background & Aims:The vertical structure of a forest is the vertical arrangement of aboveground vegetation elements.This feature of the forest affects plant and animal diversity and ecosystem function,and thus has been the focus of many plant ecologists.The development of portable backpack LiDAR technology allows for scanning of 3D forest structure over a large area with high precision.The purpose of this study is to explore the vertical structural characteristics of the semi-humid evergreen broad-leaved forest in Jizu Mountains on the scale of plot and individual tree.Methods:The most important parameters of the vertical forest structure are:the canopy height(CH),the leaf area index(LAI),and the characteristics of individual tree.The CH directly reflects the biomass and the LAI represents photosynthetic capacity of plants.Based on a portable backpack LiDAR,the CH and LAI of a 20.16 ha semi-humid evergreen broad-leaved forest dynamics plot in the Central Yunnan Plateau were carefully scanned and quantitatively analyzed.On the basis of topographic correction and community classification,the vertical change and horizontal pattern of the LAI of the forest community were extracted and analyzed,and the parameters of single tree morphology and vertical structure of common tree species were surveyed quantitatively.Results:The results showed that:(1) the distribution of CH and LAI in a 20 m × 20 m square was close to a normal distribution;(2) according to the vertical distribution of LAI,the canopy of the large plot can be divided into four layers:the upper canopy,the middle canopy,the lower canopy,and the shrub layer;(3) the vertical variation of LAI of the Castanopsis orthacantha community and the C.delavayi community showed a single-peak pattern with peak heights of 15 m and 13 m,respectively,and that of the Pinus yunnanensis community showed a double-peak pattern with peak heights of 5 m and 10 m;(4) the parameters of different tree species showed great variation,but the value of crown area/diameter was relatively uniform.Conclusion:This is the first study in China to quantitatively analyze a 3D pattern of LAI for a semi-humid evergreen broad-leaved forest with a complex structure based on LiDAR technology.This work may provide a useful database for future studies of forest biodiversity of this type and for comparative studies between different forest types.