不同林分密度指标的比较研究

Comparison of different stand density measures

用28年生杉木造林密度试验林的逐年观测数据,对林分密度指数、相对植距和优势高—营养面积比3个林分密度指标进行比较分析。结果表明:(1)不同造林密度林分达到一定年龄后,相对植距几乎相等,无法体现不同密度之间的区别,不是一个理想的密度指标;(2)利用Statistica统计软件,通过牛顿迭代法,基于Richards方程分别不同造林密度建立了年龄与林分密度指数和优势高—营养面积比的关系模型,并计算其特征参数,结果表明该模型能对这2种密度指数进行正确预估,且方程极限参数a都随着造林密度的增加而增大,体现了不同密度之间的差别;(3)与林分密度指数相比,优势高—营养面积比由于具有不含参数、适用年龄范围较大和速率参数b较稳定等特点而更加理想。

The three stand density measures,including stand density index,relative spacing and ratio of dominant height to nutrient area,were analyzed and compared by using the data obtained year by year during 28-year-old Cunninghamia lanceolata from the different planting density experiment stands.The results show that：（1）The relative spacing of various planting density stands were almost equal after stands reached a certain age,which could not reflect the difference between the different planting densities.So the relative spacing was not an ideal density measure.（2）The models between the age and the stand density measures,including stand density index and ratio of dominant height to nutrient area,were respectively established based on Richards equation by using the Newton iterative method of statistica software,and its characteristic parameters were calculated.The results indicated that these two stand density measures could be properly estimated by these models.And the limit parameters of Richards equation increased with the increase of planting density,which reflected the difference between the different planting densities.（3）Compared with the stand density index,the ratio of dominant height to nutrient area was more ideal because it had the characteristics of without parameter,the larger applicable age range and the stable rate parameter etc.