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生态学杂志

• 技术与方法 • 上一篇    

一种测量林窗面积的改良方法:等角椭圆扇形法

胡理乐1,2;朱教君1;谭辉1,2;于立忠1;胡志斌1;张金鑫1   

  1. 1中国科学院沈阳应用生态研究所, 沈阳 110016;
    2中国科学院研究生院, 北京 100039
  • 收稿日期:2006-10-09 修回日期:1900-01-01 出版日期:2007-03-15 发布日期:2007-03-15

Equiangular elliptic sector method, an improved approach to estimate forest gap size

HU Li-le1,2; ZHU Jiao-jun1; TAN Hui1,2; YU Li-zhong1; HU Zhi-bin1,2; ZHANG Jin-xin1   

  1. 1Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China;
    2Graduate University of Chinese Academy of Sciences, Beijing 100039, China
  • Received:2006-10-09 Revised:1900-01-01 Online:2007-03-15 Published:2007-03-15

摘要: 目前测量林窗面积较精确的方法为:测量从林窗中心沿8或16个罗盘方向到林窗林冠边缘的距离,再将林窗近似成等角8或16边形估测其面积(本文称这类方法为等角多边形法)。研究表明,等角8或16边形法均会低估林窗面积,本文提出一种改良方法:等角椭圆扇形法,野外测量与前者相同,计算时将相邻距离间的部分近似为椭圆扇形,以所有椭圆扇形面积之和估测林窗面积。用配对t检验对等角多边形法和等角椭圆扇形法的林窗面积进行比较,结果表明:(1)等角16边形法与等角8或4边形法存在极显著差异(P<0.001),比后两者,分别高10.96%和61.66%,这表明等角条边形法均会低估林窗面积;(2)等角椭圆扇形16分法比等角16边形法大10.16%,且二者之间存在极显著差异(P<0.001),因此,等角16边形法的测量值位于等角椭圆扇形16分法和等角8边形法之间;由(1)和(2)可推断等角椭圆扇形16分法比等角8边形法更准确;(3)等角椭圆扇形8分法与等角椭圆扇形16分法没有显著差异(P=0.715),但与等角8边形法存在显著差异(P<0.05),因此,等角椭圆扇形8分法比等角8边形法更准确。另外,本文的两个等角8边形法(基于两组不同罗盘方位的测量距离)求得的林窗面积之间存在极显著差异(P<0.01),而两个等角椭圆扇形8分法之间却没有差异(P=0.778),这表明等角椭圆扇形8分法的结果更稳定。

关键词: 棉花, 生理发育时间, 模拟模型

Abstract: Gap size is one of the important characteristics of forest gaps, and an important index for characterizing the light penetration and resource availability within forest gap. Therefore, it is of significance to measure gap size conveniently and accurately. One kind of the most commonly used methods in measuring gap size is to measure the distance from gap center to its edge along eight or sixteen compass directions, and then, estimate gap size approximately as a siogon. In this paper, this kind of method is called siogon methods (SMs), including equiangular octagon method (EOM), equiangular sixteen-gon method (ESM), and equiangular quadrangle method (EQM). Although EOM has less precision, it has been used more universally than ESM, because of its less time-consuming. Previous studies indicated that both EOM and ESM underestimated gap size, and thus, an improved approach was proposed in the present paper, i.e., using the same data sets to calculate the gap size approximating forest gap as 8 or 16 equiangular elliptic sectors. This improved method was named as equiangular elliptic sectors method (EES), which involved 8-equiangular elliptic sector (8-EES) and 16-equiangular elliptic sector (16-EES). Paired t-test indicated that the gap size estimated by ESM was significantly larger than that estimated by EOM and EQM, with an average of 10.96% and 61.66% increment respectively. The gap size estimated by 16-EES was significantly larger than that estimated by ESM, with an average of 1016% increment, while 8-EES had no significant difference with 16-EES, but had significant difference with EOM. Moreover, there was a significant difference between the gap size estimated by EOM with two data sets (the octagons were formed with eight different compass directions), but not for 8-EES. Therefore, it is recommended that gap size could be better estimated by 8-EES.

Key words: Gossypium hirsutum, Physiological development time, Simulation model