The Temporal And Spatial Distribution Characteristics Of Seed Rain By Different Dispersal Modes In An Evergreen Broad-leaved Forest In Tiantong, Zhejiang Province, Eastern China

Evergreen broad-leaved forest in Tiantong is one of the most typical vegetation types in subtropical regions.Seed rain is a major source of the forest propagues which can effect on species coexistence and maintain the species diversity in forest. To rev-eal the character of seed rain of species with different dispersal modes, we explored the seed rain in a20ha evergreen broad-leaved forest dynamic plot in Tiantong from Oct.2012to 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 as follows:(1) A total of13,638seeds was collected belonging to66species and28families. The density of seed rain was146seeds/m2during the twelve-month period (total trap area=93.5m2).Zoochory species is the most among the total species which accounted for60.61%.Gravity and anemochory accounted for22.73%and15.15%of species mass,the annual seed production of Liquidambar formosana contributed about19.58%of total seed rain;(2) There was a marked peak in the number of seeds and species in autumn in one year.The annual seed rain by different dispersal modes had a clear temporal dyna-mic.The temporal dynamic of Zoochory and Anemochory species followed a trimodal distribution(with peaks in the late of spring,summer and autumn);In contrast,the gravity showed a irregular mode;(3)The annual seeds of nineteen dominant tree species contributed about91.26%of total seed mass.And it had a clear seed rain dynamic which can classified into tree type as follows:the species had a peak of seed rain in dry season; the species had a peak of seed rain in wet season; the species had two peaks of seed rain in both dry and wet seasons;(4)A11of66species collected from seed traps is recorded in Tiantong dynamic plot,which are accounted for43.40%. Fifty six percent of tree species were not found in seed traps which contributed to generally low species similarity between seeds and adult plants;(5) 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=20m;Gravity:Rmax=0.077, d＝9m;Zoochory:Rmax=0.094, d=13m), which indicated that the seeds dispersed by wind had an advantage in long-distance dispersal;(6) More than60%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 and gravity species, it is possible that their seed limitation was just the result of lacking in individuals, and a severe seed limitation in zoochory species could be attributed to low productivity and incapacity in dispersal of the seeds.