六盘山华北落叶松单木树高对立地因子和林分特征的响应

Response of Individual Height of Larix principis-rupprechtii Plantation to Site Factors and Stand Characteristics in Liupan Mountain Area

[目的]研究宁夏六盘山林区华北落叶松(Larix principis-rupprechtii)人工林内单木树高对立地条件和林分特征的响应,并建立树高生长模型,以便准确预测树高生长,确定适宜立地条件及林分结构,指导优化林分结构的精准经营。[方法]选择建立典型样地,进行每木调查及树干解析,采用外包线法确定树高对单一因子的响应规律和适宜函数形式,然后连乘耦合多因子影响,构成能反映多因子影响的树高生长模型,并利用实测数据检验,获得可准确预测华北落叶松单木树高的最优模型。[结果](1)华北落叶松单木树高随林龄增加的生长过程呈现“S”型曲线。(2)相关分析表明,在除林龄外的各因子中,对单木树高生长影响的大小排序为:海拔>郁闭度>优势度>林分密度>坡向>坡度。(3)最适合华北落叶松生长的海拔范围是2000~2400 m,坡向是阴坡和半阴坡,坡度是20°~25°,郁闭度是0.49~0.64,林分密度是1100~1300株·hm^(−2),单木树高随优势度增加而增大,且增大速率在优势度>0.2后渐趋平缓。(4)建立了耦合主要因素影响的单木树高生长模型,拟合效果很好。[结论]宁夏六盘山区华北落叶松人工林内的单木树高同时受立地条件和林分结构特征影响,主要影响因素为林龄、海拔、郁闭度、优势度等。在考虑综合因素影响下建立的单木树高生长耦合模型可准确预测单木树高的时空变化,将作为华北落叶松林合理经营的科学依据。

[Objective]For the main afforestation species of Larix principis-rupprechtii in the forest area of Liupan Mountains,To study the response of individual tree height in Larix principis-rupprechtii,the main afforestation species in the forest area of Liupan Mountain Area,to site conditions and stand structure,in order to predict tree height growth more accurately,and to determine the suitable site for afforestation and proper stand structure for forest management,so as to guide the accurate and precise management of stand structure.[Method]The tree height growth data of L.principis-rupprechtii were obtained by carrying out the survey of analytic trees of various dominances in selected typical plots with various site conditions and stand structure characters,and the response law and suitable function forms of tree height response to all single factors were determined by the upper boundary line method.Then the tree height growth model which can reflect the influence of multiple factors was formed by a continuous multiplication.The model parameters were fitted using the measured data for getting the optimal tree height growth model.[Result](1)The growth process of individual tree height of L.principis-rupprechtii showed a"S"curve.(2)Correlation analysis showed that the influence on tree height growth by the factors except tree age followed the order of elevation>canopy density>tree dominance>stand density>slope aspect>slope.(3)The most suitable conditions for the height growth of L.principis-rupprechtii are the elevation range of 2000−2400 m,the slope aspect range from shade slope to half shade slope,the slope gradient range of 20°−225°,the canopy density range of 0.49−20.64,the stand density of 1100−21300 trees/hm2.In addition,the height of individual trees increased with rising tree dominance but with a leveling-off increase rate after the dominance is higher than 0.2.(4)The height growth model of individual trees was established by coupling the response functions to the main influencing factors,with a satisfactory fitness.[Conclusion]The individual tree height growth of L.principis-rupprechtii is affected by both site conditions and stand structure characteristics.The main influencing factors are tree age,elevation,canopy density,and tree dominance.When considering the influencing factors,the coupled model of individual tree height growth can predict the spatio-temporal variation of individual tree height more accurately,and benefit the rational management of L.principis-rupprechtii plantation.