新疆野核桃自然保护区分枝成株野核桃胸径树高与冠幅的通径分析

Path analysis between diameter at breast height,height and crown width Juglans regia generating individual plant from branch in Wild Walnut Natural Conservation Area in Xinjiang,China

【目的】研究不同发育期分枝成株野核桃冠幅及胸径、树高对其影响程度,为建立更佳冠幅预测模型及目标树经营提供理论依据,达到优化森林经营管理措施的目的。【方法】对新疆野核桃自然保护区不同坡向分枝成株野核桃生长进程中幼苗期、小树期、中龄期、老龄期的胸径、树高与冠幅关系进行通径分析。【结果】1)分枝成株野核桃的胸径在中龄期前生长缓慢,中龄期后生长较快,阳坡(3.6 cm·a^(-1))平均生长速率大于阴坡(3.3 cm·a^(-1));树高、冠幅在中龄期前生长较快,中龄期后生长缓慢,阳坡平均树高、冠幅生长速率(0.7、0.3 m·a^(-1))小于阴坡(0.9、0.4 m·a^(-1))。2)阳坡和阴坡分枝成株野核桃的胸径、树高、冠幅均随发育期增大而增大,同一坡向不同发育期的平均胸径、平均树高差异显著(P <0.05)。3)阳坡和阴坡同一发育期分枝成株野核桃冠幅级组成结构相似,幼苗期、小树期、中龄期、老龄期的冠幅均分别集中分布于0.1~0.5、0.1~2.0、2.0~4.5、3.0~4.0 m。4)阳坡分枝成株野核桃的胸径仅在幼苗期对冠幅的影响有负向作用,树高对冠幅的影响具有显著正向作用且随发育期增长先增加后减小;阴坡分枝成株野核桃的胸径对冠幅的影响随发育期增长由负向转为正向,树高对冠幅的影响具有正向作用且随发育期增大逐渐增大。【结论】由于分枝成株野核桃自身生长权衡机制,冠幅在不同坡向不同发育期主导因子不同,因此灵活选取生长指标预测冠幅比单一指标预测更准确。

【Objective】In order to establish better crown width prediction model and provide theoretical basis for target tree management,and achieve the ideal structure for forest management,the relationship of crown width in Juglans regia generating individual plant from branch populations among different stand ages and the influence degree of diameter at breast height(DBH)and height on crown width were studied.【Method】We used path analysis to analyze the DBH,height and crown width of four stand ages(seedling,young tree,middle-aged tree,old tree)of J.regia generating individual plant from branch populations in Xinjiang Wild Walnut Nature Reserve,Xinjiang Province.【Result】1)The DBH of J.regia generating individual plant from branch populations were slow-growing before middle-aged tree and fast-growing after middle-aged tree. The average growth rate of DBH in sunny slope (3.6cm·a^(-1)) was higher than that of shady slope (3.3cm·a^(-1)). Height and crown width of J. regia generating individual plant from branch populations were fast-growing before middle-aged tree, and slow-growing after middle-aged tree. The average growth rate of height and crown width on sunny slope (0.7m·a^(-1), 0.3m·a^(-1)) was lower than shady slope (0.9m·a^(-1), 0.4m·a^(-1)). 2)In different slope directions, the DBH, height and crown width of J. regia generating individual plant from branch populations increase with the stand age and have significant differences between growth periods in same slope directions (P < 0.05). 3)The crown width class composition and structure of J. regia generating individual plant from branch populations at different slope direction and same stand stage are similar: seedling, young tree, middle-aged tree and old tree were concentrated at 0.1-0.5m, 0.1-2.0m, 2.0-4.5m, 3.0-4.0m, respectively. 4)In sunny slope, the DBH only had a negative effect on crown width at seedling, and the height of J. regia generating individual plant from branch populations had a significant positive effect on crown width, and this positive effect was gradually decreased with the increase of stand age. In shady slope, with the increment of stand age, the influence of DBH on crown width changed from negative to positive. Height had a positive effect on crown width, which increases as stand age increases.【Conclusion】Due to the different growth trade-off mechanisms, in different slope direction, the dominant factors of crown width is different in different growth stages, so it is more accurate to estimate crown width by flexible selection of growth indexes than by single index at different growth stages.