林分结构对烟台黑松海岸防护林天然更新的影响

为阐明黑松(Pinusthunbergii)海岸防护林天然更新的影响机制,在对烟台2个典型样地6条样带共60个样方(10m×10m)调查的基础上,采用拟合模型和多重回归分析技术,探讨林分结构指标中,垂直结构(树冠指数、小树比例和大树比例)和密度因素(基面积、郁闭度和灌木盖度)对黑松种群天然更新的影响。结果表明在垂直结构变量中,树冠指数(CI)与幼龄植株个数之间存在典型的抛物线关系,在CI5-6范围内,幼龄植株个数达到最高;幼龄植株个数与小树比例关系较弱,但与大树比例表现出显著的正线性关系。在密度变量中,幼龄植株随着郁闭度的增加,个体数呈上升趋势,而随着灌木盖度的增加,则表现出显著的下降倾向;幼龄植株个数与基面积关系不明显。幼龄植株个体数变化取决于垂直结构变量CI和密度变量郁闭度和灌木盖度共同作用的影响。理解这些更新规律,是黑松海岸防护林可持续管理的前提。

Effects of forest structure on natural regeneration of Pinus thunbergii coastal

In order to understand the natural regeneration mechanism of the P. thunbergii coastal shelter forest, we established 60 plots (10 m×10 m) on six transects distributed throughout two stands in Yantai region of Shandong province, China. Using fitting model and multiple techniues, the effects of forest vertical structural indicators (crown index, proportion of small and large trees) and density indicators (basal area, canopy coverage and shrub coverage) on natural regeneration of P. thunbergii coastal shelter forest were studied. The results indicated that a parabolic model could delineate the relationship between crown index and number of juveniles well. The highest number of juveniles occurred when crown index (CI) ranged from 5 to 6. The positive correlation between the number of juveniles and the proportion of large trees was strong, while that between the number of juveniles and the proportion of small trees was not significant. As long as the density indicators, the number of juveniles was positively related to canopy coverage, but negatively to shrub coverage and not apparently to basal area. Regression analysis indicated that the variation of juvenile density was determined by the combined effects of vertical structural indicator (e.g. CI) and density indicators (canopy coverage, shrub coverage). A full understanding of those regeneration rules is a prerequisite for sustainable management of P. thunbergii coastal shelter forest.