常绿阔叶林石栎和青冈种群生活史特征与空间分布格局

Life History and Spatial Patterns of Lithocarpus glaber and Cyclobalanopsis glauca Populations in Evergreen Broad-leaved Forest

以中亚热带低山丘陵常绿阔叶林石栎-青冈群落为研究对象,采用相邻格子法在湖南省长沙县大山冲林场建立1hm2永久性监测样地,通过编制静态生命表绘制种群年龄结构图和存活曲线以及应用Ripley’s K函数,研究了石栎和青冈的生活史动态、空间点格局以及不同生活史的空间关联性。结果显示:(1)两种群的死亡率随径级的增加呈上升趋势,在幼树(Ⅰ级)到小树(Ⅱ级)阶段均达到死亡高峰;两种群均属于增长型年龄结构,生命曲线接近于Ⅰ型(曲线凸型)。(2)分布格局主要呈聚集分布,聚集强度随空间距离的增大而增强,随年龄的增大石栎种群呈下降趋势,青冈种群呈先减弱后增强的趋势。(3)石栎和青冈的幼树、小树在小尺度上与中树、大树显著正关联,且青冈在t>15m的尺度上小树和大树亦显著正关联。研究表明,物种的生物学特征和种内、种间竞争是影响石栎、青冈种群生存力的重要因素;种子扩散、萌芽繁殖、生境特化和负密度效应是维持石栎和青冈种群空间格局的主要驱动因子。

The life history,spatial patterns and spatial associations across life stages of dominant populations Lithocarpus glaber and Cyclobalanopsis glauca were studied in subtropical evergreen broad-leaved forest at Dashanchong forest farm,Changsha County,Hunan Province,sampling a 1 hm2 permanent monitoring plot by contiguous grid quadrate method and making the statistic life tables,figuring age structure and survival curves and using Ripley’s K function.The results showed that（1）：The mortality of the two populations increased with size class and reached death peak at juvenile and young stages.The two populations belonged to growing populations and their survival curves were close to type Ⅰ （clump-shaped curve）.（2）They aggregated across whole stages with scales from 0 to 25 m and their aggregation strength increased with spatial distance.Meanwhile,the aggregation strength of L.glaber decreased and C.glauca showed from decreasing to increasing with age increasing.（3）Spatial associations of L.glaber and C.glauca populations among different life stages were significantly positive at small scales,which were also found between juvenile and old trees of C.glauca population at more than 15 m scales.The biological characteristics,interspecific and intraspecific competition were important factors in determining the survival ability of L.glaber and C.glauca populations and seed dispersal,sprout regeneration,habitat specialization and negative density effect could be the main driving factors in maintaining the spatial patterns of L.glaber and C.glauca populations.