南京老山国家森林公园朴树种群结构与分布格局研究

采用每木调查法、时空互代法和相邻格子样方法对南京老山国家森林公园朴树种群的结构和动态进行研究。(1)大小级结构分析表明:朴树种群以Ⅱ级(幼树)数量最多,Ⅰ级(幼苗)、Ⅲ级(小树)、Ⅳ级(中树)和V级(大树)数量很少或缺失,个别样地内甚至存在2个大小级缺失的情况。朴树种群处于活跃演替阶段的群落中,为不稳定的间歇型种群。(2)对于不同的生境,Ⅰ级数量缺乏甚至缺失基于不同的原因:山坡生境条件下,Ⅰ级缺乏或缺失是由于草本层盖度大,加上朴树幼苗生长缓慢,在激烈的生存竞争中处于不利地位,导致Ⅰ级死亡率高,因而数量较少或缺失;沟谷生境条件下,岩石裸露,土层瘠薄,在雨期受流水冲洗更为严重,影响朴树种子的停留和生根,不合适朴树幼苗生长,导致Ⅰ级缺乏或缺失。(3)生存曲线分析表明:自Ⅱ级向Ⅲ级、Ⅳ级与Ⅴ级的发育过程中,死亡率逐渐降低。(4)朴树的分布格局多为集群分布,在不同生长发育阶段的分布格局不同,朴树种群基本呈现扩散趋势。

Studies on population structure and distribution pattern of Celtis sinensis in Laoshan National Forest Park of Nanjing

By applying the contiguous grid quadrats,the technique of censusing every individual,with the time specific method for life table analysis,the population’s structure and its dynamic change of Celtis sinensis from Laoshan National Forest Park in Nanjing were studied. Based on the analysis of size class structure,the results showed that the saplings of size class Ⅱ were of the biggest abundance. However,the saplings of size class Ⅰ,young trees,median trees and large trees were lacking,or of no individual, and there were even two size classes absent in some plots. It could be concluded that the communities of Celtis sinensis in different plots were in actively successional phase,and Celtis sinensis was an unstable intermittent population. The reasons for the lacking or absence of the saplings of size class Ⅰ would be due to their special habitat situation. In the fields along the hillside,the coverage of the herbaceous layers were large,above 40% at least. Together with the slow growth of Celtis sinensis ,it was disadvantage for the saplings of size class Ⅰ of the plant in the survival competition. Meanwhile,in the fields along the valley,with naked stone of large area,and also little clay,it was difficult for its seeds to stay or take roots,and it would be even more serious if it was in the rain season for the water current. Thus,saplings of size class Ⅰ were also lacking in these fields. The analysis of the survival curve showed that,during the development process,from size class Ⅱ to size class Ⅲ,size class IV and size class V,the death rate shifted rapidly from high to low. The spatial distribution patterns of most plots were of clump. At different developmental stages,the distribution patterns were different. In addition,the population of Celtis sinensis showed a tendency to spread from sapling trees of size class Ⅰ to young trees,median trees,and large trees.