摘要
叶面积指数(LAI)是量化冠层结构最常用的参数之一,准确估测LAI对森林生态系统结构特性的研究具有重要意义。利用半球摄影图像法和LAI-2000法及半球摄影图像法结合凋落物法估测了小兴安岭白桦次生林LAI及其动态变化。首先对该林型叶凋落末期(11月初)的半球摄影图像进行合理校正(包括木质部分所占比例α,冠层水平集聚指数ΩE),校正值作为该时期常绿树种的真实LAI(LAIt),结合各调查期的凋落物数据,得到落叶季节(7—11月)的LAIt,并以该值为参考值,对比分析了两种光学仪器法估测值。结果表明:两种光学仪器法在LAI最大时期低估(分别低估2.83%、6.20%),其他时期显著高估(平均高估118.13%、89.34%),但两种光学仪器法与探讨方法估测值存在很好的相关性:LAIt=-1.1393+1.0934.LAIHP,R2=0.80;LAIt=-0.1712+0.6259.LAILAI-2000,R2=0.83。研究结果可为将来方便、快捷、准确的估测白桦次生林的LAI提供参考。
Leaf area index （LAI）, defined as the total one-sided leaf area per unit ground surface area （m^2m^-2） , is among the most frequently used parameters for analysis of plant canopy structure. Most ecosystem process models that simulate carbon and water cycles at a stand or regional scale require LAI as an input variable, thus accurate measurement of LAI is essential for conversion of leaf-level processes to the canopy level. The main methods of LAI measurement generally are classifiable into two groups： direct measures, which mainly include destructive sampling and the litterfall method; and indirect measures, which mainly include hemispherical photography and the LAI-2000 plant canopy analyzer. However,using a direct or indirect method alone may not accurately estimate LAI for mixed needle and broadleaf forest or broadleaf forest with a high proportion of evergreen species. Secondary Betula platyphylla is among the most common broadleaf forest types that regenerate naturally after clear cutting of broadleaved-Korean pine forest in the Xiaoxing＇an Mountains in northeast China. In the present study, we estimated LAI and its seasonal dynamics in secondary B. platyphylla forest in the Xiaoxing＇an Mountains using optical methods （hemispherical photography and the LAI-2000 Plant Canopy Analyzer） and a combinational method （hemispherical photography combined with the litterfall method ）. In the combinational method,hemispherical photographs obtained in early November were calibrated with consideration of the woody-to-total ratio （α） as well as the clumping index （for clumping beyond the shoots,ΩE）.The calibrated value was regarded as the true LAI （LAI,） of coniferous species ; the LAI, of the study stand and its seasonal dynamics （ from July to November） were obtained by supplementation of the LAI, of coniferous species by incorporation of litterfall data for each observation. Using this resuh as a reference value, we compared the results obtained with the two optical methods. The
出处
《生态学报》
CAS
CSCD
北大核心
2013年第8期2505-2513,共9页
Acta Ecologica Sinica
基金
国家科技支撑计划(2011BAD37B01)
林业公益性行业科研专项经费项目(200804001)
长江学者和创新团队发展计划(IRT1054)资助
