南岭大东山长柄双花木群落物种组成与种群结构特征分析

采用样方法以及用基径结构代替年龄结构的方法,对位于南岭大东山不同海拔的3个长柄双花木(Disanthus cercidifolius var.longipes Chang)样带(包括小洞、大洞和鸡子场样带,海拔分别为1 010、1 170和1 260 m)进行了调查,并编制了种群静态生命表和生存曲线,对其群落物种组成、种群年龄结构和生殖力现状进行了分析。结果显示:3个样带群落乔木层优势种数量及种类组成差异明显,共包含26个种类,但共有种仅3种,除长柄双花木外还有多花杜鹃(Rhododendron cavaleriei Lévl.)和两广杨桐(Adinandra glischroloma Hand.-Mazz.)2种;小洞样带长柄双花木种群的重要值(46.116%)明显高于另2个样带。根据基径可将长柄双花木种群分为68个龄级,3个样带的种群年龄结构基本一致,但小洞样带个体数量更多且基径31.0 mm以下的幼体所占比例最高;总体上长柄双花木种群中5 a以下的幼苗数量偏少,其他龄级的个体数量呈现随株龄增大波动但整体下降的趋势。种群的个体死亡率在5~10 a和10~15 a龄级较高(分别为20.30%和20.50%),并随年龄增长总体呈逐渐下降的趋势;且不同龄级个体生命期望值为4.49~0.50,总体偏低。种群生存曲线为Ⅰ型,种群净增殖率、内禀增长率、周限增长率和世代平均周期分别为0.504、-0.018、0.982和38.351 a,显示该种群在当前状态下自我更新不良,属缓慢的负增长型种群。根据研究结果,对该区域长柄双花木种群提出了相应的保护对策和建议。

Analyses on community species composition and population structure characteristics of Disanthus cercidifolius var. Iongipes in Dadongshan of Nauling Mountain

Using the quadrat method and the method of base diameter structure instead of age structure, three sampling transects （including Xiaodong, Dadong and Jizichang with altitudes 1 010, 1 170 and 1 260 m, respectively） of Disanthus cercidifolius var. longipes Chang in Dadongshan of Nanling Mountain were investigated and the static life table and survival curve of population were created, and community species composition, population age structure and fecundity status were also analyzed. Results show that there are obvious differences in dominant species number and species composition of arbor layer among three sampling transects, which contain 26 species but only three common species, those are Rhododendron cavaleriei L6vl. and Adinandra glischroloma Hand.-Mazz. besides D. cercidifolius var. longipes. And the important value （46. 116% ） of D. cercidifolius vat. longipes population at Xiaodong sampling transect are obviously higher than that at other two sampling transects. According to base diameter, D. cercidifolius var. longipes population can be divided into 68 age classes. Population age structure of three sampling transects is basically identical, but the individual number of D. cercidifolius var. longipes is more and proportion of young individuals with base diameter below 31.0 mm is the highest at Xiaodong sampling transect. Generally, number of seedling with age below 5 a is less in the population, and individual number in other age classes appears a trend of fluctuating but generally reducing with increasing of age. Individual mortality rate of population is higher in age classes of 5-10 a and 10- 15 a （ 20.30% and 20.50%, respectively）, and appears generally the trend of gradually reducing with increasing of age. And expectative life of individuals in different age classes is generally low with the value of 4.49-0.50. The survival curve of the population is I type, and net reproductive rate, intrinsic rate, finite rate and generation span is 0. 504, -0. 018, 0. 982 and 38. 351 a, respectively, meaning that itself generation ability is not good at present status and it belongs to slow negative growth population. According to these research results, suitable conservation strategies and proposals of D. cercidifolius var. longipes population in Dadongshan of Nanling Mountain are put forward.