摘要
叶面积指数(leafarea index,LAI)是定量描述冠层结构的最有效指标之一。鉴于森林冠层三维结构的高度复杂性和异质性,迄今仍没有形成统一标准的LAI测量方法。该文利用LAI-2000冠层分析仪、CI-110冠层分析仪和半球摄影法(digital hemispherical photograph,DHP),对北京东灵山地区以蒙古栎(Quercus mongolica)为主的落叶阔叶林、华北落叶松(Larix gmelinii var.principis-rupprechtii)林和油松(Pinus tabuliformis)林的有效叶面积指数(effective leafarea index,LAIe)进行了动态监测,探寻其季节变化规律。为准确地估算温带山地主要森林类型的LAI,对光学仪器测量值进行了去除木质成分、聚集效应等校正,与基于凋落物收集法的相应实测值进行了比较分析。结果表明:3种典型森林在生长季期间叶片生长均呈现单峰型;3种光学仪器测量方法的同期LAIe数值大小顺序为:LAI-2000冠层分析仪>DHP>CI-110冠层分析仪。光学仪器的直接测量值LAIe包含了木质成分的贡献,钝化了季节动态的变化幅度,这对有明显季节交替的落叶林尤为突出。经校正,LAI-2000冠层分析仪和DHP的测量值与实测值都表现出显著的相关性,其中LAI-2000冠层分析仪最适于采用基于空隙大小的校正方法,而基于空隙度和空隙大小的综合算法则是校正DHP的最佳选择。结合经济成本和野外实际操作等因素考虑,DHP具有更大的推广优势,特别适用于温带山地落叶林。
Aims Leaf area index（LAI）is one of the most frequently used parameters for analysis of canopy structure and forest productivity.It can be determined by direct or indirect methods.Sources of errors in indirect LAI measure-ments with optical instruments include non-photosynthetic components,element clumping,and a topography ef-fect.Our objective was to find an appropriate method for evaluating LAI and its seasonal dynamics in typical temperate montane forest.Methods We examined the applicability of three indirect methods（LAI-2000 plant canopy analyzer,CI-110 plant canopy analyzer and digital hemispherical photograph（DHP））and one direct method（litterfall）to determine the seasonal dynamics of LAI in three typical temperate forests in Dongling Mountain of Beijing.The forests in-cluded a secondary deciduous broad-leaved forest dominated by Quercus mongolica and two plantations（Larix gmelinii var.principis-rupprechtii and Pinus tabuliformis）.These represent deciduous broad-leaved forest,de-ciduous needle-leaved forest and evergreen needle-leaved forest,respectively.The optically-based effective leaf area index（LAIe）values were corrected to eliminate wood elements and clumping effects and then compared with the direct measurement of LAI based on litter collection.Important findings For all the three forests,the LAI seasonal dynamic shows a uni-modal pattern with a peak in July.Optically-based LAIe underestimated the amplitude of the seasonal dynamics.Wood element elimination can strengthen the seasonal sensitivity of LAI,especially in the seasonally distinct deciduous forest.The order of LAIe measured by the three optically-based methods in three stands is LAI-2000 plant canopy analyzerDHP CI-110 plant canopy analyzer.There was good correspondence with the direct measurement LAI for the corrected LAI of LAI-2000 plant canopy analyzer and DHP.The correction method based on gap-size distribution was ap-propriate for the LAI-2000 plant canopy analyzer and the method based on both gap fraction and gap-size distri-bution for DHP.Considering economics and practical convenience,we recommend DHP for LAI evaluation in these temperate montane forests.
出处
《植物生态学报》
CAS
CSCD
北大核心
2012年第3期231-242,共12页
Chinese Journal of Plant Ecology
基金
国家自然科学基金(30900188)
中国科学院知识创新工程重要方向项目(KZCX2-YW-433)资助
关键词
聚集效应
有效叶面积指数
光学测量方法
clumping effects
effective leaf area index
optically-based methods
