The Population Structure Of Machilus Thunbergii And Effect Of Animals On Its Seed Dispersal

Machilus thunbergii is a vulnerable tree species, distributed in subtropic evergreen broad-leaved forest. Community species diversity, population distribution pattern, population age structure, seed rain,seed bank, and the effect of animals on its seed dispersal and regeneration have beed researched in autumn in 2012 and 2013, in Fujian Meihuashan National Nature Reserve. The results are as follows:Machilus thunbergii plant community appearance showed evergreen throughout the year. All 142 species of plants, belonging to 83 genus and 45 families in community, were recorded which showed a rich species. The vertical structure of plant communities is obvious, can be divided into tree layer, shrub layer and herb layer. Species diversity index showed: shrub layer> tree layer> herb layer. In the bamboo forest, human disturbance have some impact on community, species diversity was significantly lower than other forest types.With size structure replacing the age structure of the population, population structure of Machilus thunbergii was analyzed, the results showed a pyramid-type structure. Population distribution pattern showed that seedlings and saplings of Machilus thunbergii met the cluster distribution generally, while adult individuals distributed randomly. Spreading tendency appeared from seedling to sadult tree. During the growing period from seedlings to saplings, a large number of individuals died, and mortality peak occurred in grade?seedling stage, the survival rate is only 20.75%. However, some individuals still survive and grow to adapt to the environment, showing a strong adaptability. Dynamic analysis of population structure showed slow population growth.The fruits of Machilus thunbergii began to mature in September, the flourishing appeared from the beginning of November. In early December, the amount of fruit drop reduced to a relatively stable amount. As the seeds mature in batches and influenced by wind and rain, seed rain ends of the curve showing low middle high, with multiple peaks in volatility trend, and there are different degrees of relevance and research to humidity and rainfall. The seed rain consisted of six types: mature and complete fruit, immature fruit, gnawed fruit, bare seeds, molded fruit and shrinking fruit. The quality of seed rain was fairly high, which could provide abundant supply of natural seed sources updated.The fruit characteristics suitable to be fed with the spread by animal. Without dormancy, seeds of Machilus thunbergii can germinate after falling to the ground in a suitable environment.There were no living seeds existed in seed bank underground. Therefore, almost the regeneration relied on seeds dropped in current year.There were totally 26 animal species, visting Machilus thunbergii fruit tree, including 18 species of birds, 5 species of rodents and 3 species of ants. Number of bird species and individuals are both the largerest, which means the most important feeder and dispersers. Those six species of bird which swallowed the whole fruit and dispersed the seeds all belong to Pycnonotidae and Corvidae. Black bulbul(Hypsipetes madagascariensis) from Pycnonotidae was the most important feeder, visit frequency account for about 40% of all visits during the two years observation. Corvidae swallowed more fruits in each visit, flew a rather longer distance and carried seeds for much longer time, thus defecating intact seeds away from parent trees through gut. The performance of Pycnonotidae was opposite. The removal experiment showed that the feeding intensity of animals was: bamboo forest>bamboo-broadleaved-mixed forest>broadleaved forest. Birds searching fruits on the ground had an impact on the secondary dispersing of seeds. Rodents were the main consumers of the ground seeds, but the hoarding behavior had some affect on the secondary dispersing too. Ants had little effect on secondary diffusion of Machilus thunbergii seeds.