浙江天童常绿阔叶林不同传播方式物种种子雨的基本特征

为了研究不同传播方式物种种子雨的基本特征,以浙江天童常绿阔叶林20 hm2动态监测样地的种子雨为研究对象,分析了种子雨的密度、物种组成以及种子限制的强度.结果表明:(1)种子雨收集器共收集到种子136 38粒,隶属于28科66种,种子雨密度为146粒/m2;(2)样地内有56%的物种未收集到种子,因此种子雨与可繁殖个体物种组成的相似性较低且受不同传播方式影响,风力传播的相似性系数极值(Rmax)最大且距种子收集器距离(d)最远(风力传播:Rmax=0.226,d=20 m;重力传播:Rmax=0.077,d=9 m;鸟类传播:Rmax=0.094,d=13 m),证明通过风力传播的种子在远距离传播上更有优势;(3)样地内存在一定程度的种子限制,有43个物种的种子只在很少的(10)收集器中出现.对于较为优势的物种而言(IV≥1),传播方式可能是影响种子限制的主要因素.另外,群落中通过风力传播的物种种子限制很可能仅仅是由于可繁殖个体的缺少造成的,而通过重力和鸟类传播的物种存在很高的种子限制可能是因为种子的低产量以及种子扩散能力的不足.

Character of seed rain of species with different dispersal modes in Tiantong evergreen broad-leaved forest,Zhejiang Province

To reveal the character of seed rain of species with different dispersal modes, we explored the seed rain in a 20 hm2 evergreen broad leaved forest dynamic plot in Tiantong from Oct.2012 to Sept.2013, then analyzed the density and species composition of seed rain and seed limitation (measured by the proportion of plots that seeds were not dispersed in). The results were showed as follows: (1) A total of 13,638 seeds were collected belonging to 66 species and 28 families.The density of seed rain was 146 seeds/m2during the twelve month period (total trap area = 93.5 m2); (2) 56% of tree species were not found in seed traps which contributed to generally low species similarity between seeds and adult plants. Different dispersal modes also affected the Jaccard similarity coefficient (R). The extreme R coefficient(Rmax) while the maximum distance from the seed collector (d) were caused by wind(Anemochory:Rmax=0.226,d=20 m;Gravity:Rmax=0.077,d=9 m;Zoochory:Rmax=0.094,d=13 m), which indicated that the seeds 〖JP2〗dispersed by wind had an advantage in long distance dispersal;(3)More than 60% of species were distributed among no more than ten seed traps during a year, which exhibited seed limitation in plot. As far as the relatively dominant species(IV≥1) were concerned, dispersal mode could have a great impact on seed limitation. When it comes to anemochory species, it was possible that their seed limitation was just the result of lacking in individuals, and a severe seed limitation in gravity and zoochory species could be attributed to low productivity and incapacity in dispersal.