不同林龄阔叶红松林林下簇毛槭的性比格局及雌雄个体的空间分布

为探讨不同发育阶段林分下的雌雄异株植物与性别相关的性比格局和空间分布, 以5.2 ha的中龄林和1.0 ha的老龄林固定监测样地内簇毛槭(Acer barbinerve)雌、雄植株的定位观测数据为基础, 对比分析了长白山不同林龄的阔叶红松林中的已花簇毛槭的性比格局、空间分布及其与环境因子间的关系。研究结果表明: 中龄林和老龄林中雌树的胸径均显著大于雄树, 总体上性比极显著偏离1:1。随着树木的生长, 性比由偏雄性转变为不再偏离1:1, 这可能是因为雄树始花胸径较小所致。O-ring单变量点格局分析显示中龄林样地中的雌树和雄树符合异质性泊松分布, 老龄林样地中的雌树和雄树均完全随机分布。O-ring双变量点格局分析显示, 在随机标签假设下, 中龄林中的雌树和雄树在1-4 m尺度上空间负相关, 在4-100 m尺度上空间独立, 老龄林中的雌树和雄树在所有尺度上空间独立。簇毛槭在中龄林和老龄林中不同的空间分布格局说明中龄林中簇毛槭分布的斑块性相对明显, 随着林分的发育, 郁闭度较高的老龄林样地中环境异质性降低, 环境因子对簇毛槭分布的影响减弱。典范冗余分析(redundancy analysis, RDA)表明在中龄林中, 林分密度只能解释3.73%的雌树分布的变异, 与雄树分布的相关性不显著, 叶面积指数和非生物因子对雌树和雄树的影响均较弱; 老龄林中簇毛槭的分布与生物因子和非生物因子的相关性均不显著。

Sex ratio and spatial patterns of males and females of different ages in the dioecious understory tree,Acer barbinerve,in a broad-leaved Korean pine forest

Acer barbinerve(Aceraceae) is one of several understory tree species which occur in temperate forests in the Changbai Mountain region in Northeast China. We studied sex ratios and the spatial distributions of A. barbinerve and their relationships with environmental factors. In 2009, we mapped and sexed all reproductive A. barbinervetrees within a 5.2-ha (260 m×200 m) middle-aged experimental field plot and a 1.0-ha (100 m × 100 m) old-growth plot. In both plots, the sex ratio of reproductive trees was significantly male-biased. A further analysis revealed that the sex ratio was male-biased in small trees (DBH < 2 cm), and turned to a balanced ratio in larger individuals (DBH ≥ 2 cm), suggesting that males may reach maturity at smaller size than females. A univariate O-ring statistical analysis showed that under the complete spatial randomness (CSR) null model, males and females in the middle-aged plot occurred as clumped distributions at 0-88 m scales and 1-13 m scales, respectively. And both genders were distributed randomly in the old-growth plot. Under the heterogeneous Poisson null model, males and females were distributed randomly at 0-100 m scales in the middle-aged plot. The bivariate O-ring statistics indicated that under the random labeling null model, males and females showed spatial repulsion at 1-4 m scales, and then occurred as spatial independence at 4-100 m scales in the middle-aged plot, and both genders showed spatial independence at 0-50 m scales in the old-growth plot. Apparently, both males and females were influenced more by environmental heterogeneity in the middle-aged plot than in the old-growth one. Stand density were found to have a negative relationship with the distribution of females in the middle-aged plot, but it only explained 3.73% of the total variation, and showed litter effect on males. Environmental factors explained even less in the old-growth plot.