利用冠层分析仪测算苹果园叶面积指数及其可靠性分析

以山东省苹果主产区成龄密植园、间伐园和疏枝园苹果树为材料，利用方框取样法（直接法，di）和冠层分析仪法（间接法，in）分别测定了叶面积指数（LAI）。结果表明：冠层分析仪法与方框取样法测量的LAI 平均值分别为3.0±0.2 和4.3±0.2，前者比后者平均低30.2%，且随着LAI 增加，二者相差增大.密植园、间伐园和疏枝园相应偏低32.0%、35.5%和25.0%。统计分析表明，LAIdi 与LAIin 相关性极显著，密植园、间伐园和疏枝园中的相关系数（r）分别为0.91、0.89 和0.92。把冠层分析仪鱼眼摄像头最外圈去掉（平均视天顶角为68º）LAIdi 与LAIin 之间相差在13%以内，校正后密植园、间伐园和疏枝园中二者的相关系数（r）分别为0.93、0.93 和0.94。尽管方框取样法和冠层分析仪法测量的LAI 具有极显著的相关性，但冠层分析仪法的测值偏低，因此，在应用冠层分析仪估计苹果园的LAI 时，要改进冠层分析仪的测量方法，并利用方框取样法测得的结果对其进行校正，以便提高准确性。在本研究中，密植园、间伐园和疏枝园内冠层分析仪的校正系数分别为1.3004、1.2077 和1.1762。

Leaf Area Index Estimated with Plant Canopy Analyzer in Apple Orchards and Analysis of Its Reliability

It was studied that leaf area index(LAIs)were respectively estimated with sampling with a cubic frame(direct method)and using a plant canopy analyzer(indirect method)in more than 40 adult apple orchards(including unthinned,thinned and partially-cut-branch orchards)selected randomly in Shandong Province.The results showed that LAIs estimated with direct and indirect methods in all orchards tested were3.0±0.2 and 4.3 ±0.2,respectively.Compared to LAI with the direct method(LAI_(di)),average underestimation of LAIs with indirect method(LAI_(in))was 30.2%,in which the underestimation of LAIs were32.0%,35.5% and 25.0%,respectively in unthinned,thinned and partially-cut-branch orchards.In addition,the larger LAI was,the more serious underestimation was in various types of orchards.LAIs estimated with direct and indirect methods were strongly and linearly interrelated to each other(r = 0.91,0.89 and 0.92,respectively,in three types of orchards,P＜0.00001).When omitting the reading of the external ring of the plant canopy analyzer and being recalculated,the linear correlation between LAI_(di) and LAI_(in) was more significant(r = 0.93,0.93 and 0.94,respectively,in three types of orchards,P＜0.00001),and the difference became less(less than 13%).When LAI of apple orchards is estimated by a plant canopy analyzer,further correction of the data can improve its performance and produce reliable estimation through being modified by direct reference measurement.At this study,the modified coefficients of plant canopy analyzer were 1.3004,1.2007 and 1.1762,respectively,in three types of orchards,that is to say,real LAIs in three types of orchards were about 1.3,1.2 and 1.2 times respectively,more than estimated values(modified)of plant canopy analyzer.