马尾松纯林叶面积指数和平均树高的协整模型研究

Study on Cointegration Model of Leaf Area Index and Average Height of Pinus massoniana Pure Forest

依据森林资源二类调查,在全面踏查的基础上,分别于2006年、2008年和2012年调查了岳麓山马尾松纯林11块样地,地位指数为16,年龄为12～32年,并对其进行了叶面积指数与平均树高的分析。结果表明,通过ADF检验分析可知,叶面积指数为I(2),平均树高为I(2),它们具有协整关系。采用Engle和Granger提出的两步检验法检验,叶面积指数对平均树高的回归方程非均衡误差是平稳的,它们的长期均衡方程为:lny t=1.246 7 lnx t-0.282 2+εt,根据Hendry提出的方法建立短期误差修正方程为:△lny t=0.750 8+0.030 7△lnx t-1.138 8εt-1。叶面积指数对平均树高的长期弹性系数为1.246 7,短期弹性系数为0.030 7,误差修正系数为-1.138 8,表明平均树高对长期均衡的短暂偏离,要在下一期进行反向修正。该模型系统具有良好的拟合性,模型决定系数R2=0.859 1,模型显著性水平P=0.000 0。从模型分析可以得到林分叶面积指数的适当调整有利于林分平均树高的生长,在马尾松次生林经营中多注重叶面积的培育,有助于叶面积发育和树高的生长,最终促进整个林分的生长。

Based on the data of forest inventory for management plan, combing with the comprehensive transect- walks, eleven sampling sites of Pinus massoniana pure forest located at Yuelu mountain were surveyed. The site in- dex and stand age were 16 and 12 - 32 years old respectively, the leaf index and average tree height were ana- lyzed. The leaf area index and average tree height existed cointegration relationship, the long run relationship can be described by the equation ： lnyt = 1. 246 7 lnxt - 0. 282 2 ＋εt, the flexibility coefficient of the leaf area index to the average tree height was 1. 246 7. The dynamic short run relationship could be described by the equation： △lnyt =0. 750 8 ＋0. 030 7△lnxt - 1. 138 8ε-1 , the short flexibility coefficient of the leaf area index to the aver- age tree height was 0. 030 7, error-correction coefficient was - 1. 138 8. The error-correction coefficient is nega- tive show that the difference between the average and the long balance could be amended in the next term. The fit- ting effect of the model was excellent, with the determining coefficient and the significance level of 0. 859 1 andO. 000. Though model analysis, it was concluded proper adjustment of the leaf area index was benefit for the growth of average tree height. More attention should be paid to the cultivation of leaf area during the management of Pinus massoniana secondary forest, achieving the objective of promoting the growth of the whole stand.