中国红树林北缘区秋茄树种群空间分布格局和结构特征分析

Analyses on spatial distribution pattern and structure characteristics of Kandelia candel population in north marginal region of mangrove,China

对位于中国红树林北缘区福鼎市的秋茄树〔Kandelia candel （ Linn.） Druce〕天然林和人工林的高度结构和径级结构进行了分析，并以“空间替代时间”的方法研究了秋茄树天然林和人工林的空间分布格局以及天然林的种群结构特征。结果表明：不同滩位秋茄树天然林和人工林的高度结构及径级结构明显不一致。天然林中株高0.0~0.5和1.5~2.0 m的个体占多数；而人工林以株高1.5~2.0 m的个体为主，无株高0.0~0.5 m的幼苗，株高超过2.0 m的植株也极少，表明天然林的高度结构均匀而人工林的高度结构极不合理。根据基径（ D）可将秋茄树种群分为13个径级，其中天然林不同径级个体数量随径级增大依次减少，而人工林中径级Ⅲ（6 cm≤D〈10 cm）的植株数量最多，且没有径级Ⅸ（30 cm≤D〈34 cm）以上的个体，表明天然林的径级结构良好。从分布格局看，天然林幼苗群呈现聚集分布，而其小树群、大树群和老树群均为随机分布；人工林无幼苗群和老树群，小树群呈均匀分布，大树群呈聚集分布。种群静态生命表分析结果表明：秋茄树天然林种群的期间死亡率和消失率在龄级1（D〈2 cm）和龄级7（22 cm≤D〈26 cm）达到最大，在其他龄级均较小且处于稳定状态；其个体生存率单调下降、累计死亡率单调上升，仅在龄级1时个体生存率高于累计死亡率，从龄级2（2 cm≤D〈6 cm）开始均表现为累计死亡率高于生存率；其存活曲线属于典型的Deevey-Ⅲ型，表明秋茄树天然林种群中幼苗丰富但期间死亡率较高，成树的期间死亡率相对较低且个体数量稳定。

Height structure and diameter class structure of natural and artificial forests of Kandelia candel （ Linn.） Druce in Fuding City, north marginal region of mangrove, China, were analyzed, and spatial distribution pattern of natural and artificial forests and population structure characteristics of natural forest of K. candel were researched by method of“space replacing time”. The results show that height structure and diameter class structure of natural and artificial forests of K. candel at different beach places are not constant obviously. Height of individuals in natural forest is concentrated in 0. 0-0. 5 and 1. 5-2. 0 m, and that in artificial forest is concentrated in 1 . 5-2 . 0 m without seedling with height of 0 . 0-0 . 5 m and a few individuals with height over 2. 0 m. It is indicated that height structure of natural forest is uniform, while that of artificial forest is obviously unreasonable. Based on basic diameter （ D ） , K. candel population is divided into thirteen diameter classes, in which number of individuals at different diameter classes in natural forest decreases with increasing of diameter class, while there is a peak value at diameter class Ⅲ（6 cm≤D〈10 cm） and no individual at above diameter classⅨ（30 cm≤D〈34 cm） in artificial forest. It is indicated that diameter class structure of natural forest is good. The distribution pattern of seedling group in natural forest is clumped distribution, and that of small, big and old tree groups is random distribution. While in artificial forest there are no seedling and old tree groups, small tree group appears uniform distribution and big tree group appears clumped distribution. The analysis result of static life table of population shows that interval mortality rate and disappearing rate in natural forest population of K. candel reach the maximum at age classes 1 （D〈2 cm） and 7 （22 cm≤D〈26 cm） , and those at other age classes are smaller and stable. Its survival rate of individual decreases monotonically, cumulative mortality rate increases monotonically, and survival rate of individual is higher than cumulative mortality rate only at age class 1 , and cumulative mortality rate is higher than survival rate from age class 2 （2 cm≤D〈6 cm）. Its survival curve belongs to typical Deevey-Ⅲ type, which shows that seedling in natural forest population of K. candel is abundant but interval mortality rate is higher, while interval mortality rate of mature tree is relatively lower and individual number is stable.