食果鸟类在红豆杉天然种群形成中的作用

2005年10月初至2006年2月,在南京中山植物园研究了红豆杉(Taxus chinensis)天然更新种群的分布格局,野外定点观察了鸟类对红豆杉种子的取食行为,记录了红豆杉落果的命运,分析了食果鸟类在红豆杉种群形成中的作用。结果表明:红豆杉天然更新种群集中分布于距母树群10m以外面积约0.5hm2的山坡上,全部红豆杉幼苗、幼树共213株,主要分布在中下坡;幼苗和幼树的空间水平格局符合聚集分布特征。"果实"成熟后,一部分被鸟类直接在树上取食,一部分掉落母树下地面。经过对结实母树的定点、连续观察,记录到4种鸟类取食红豆杉"果实",其中红嘴蓝鹊(Urocissa erythrorhyncha)和白头鹎(Pyc-nonotus sinensis)为主要的取食者和传播者。食果鸟类整吞"果实",消化果肉(假种皮)后,种子经消化道随粪便排出,以此过程传播种子。在取食完红豆杉"果实"后,食果鸟类多飞向坡上。坡上排水良好,有适量的荫蔽,生境适宜红豆杉种子萌发和幼苗的成长。因此,食果鸟类将种子传播至适宜萌发和生长的环境中,对该红豆杉种群的天然更新起主要作用。同时,鸟类传播对于红豆杉种群扩散、占据新的生境也有着特殊的意义。

Roles of frugivorous birds in the establishment of naturally regenerated Taxus chinensis population

From October 2005 to February 2006, field work was made in the Nanjing Sun Yat-Sen Botanical Garden to study the spatial pattern of naturally regenerated Taxus chinensis population, fate of its dropped fruits, and feeding behaviors of frugivorous birds. The results showed that the regenerated T. chinensis population was distributed on the hillside >10 m far from its parent trees, with an area of about 0.5 hm2. There were 213 saplings and seedlings in total, mainly distributed on meso-slope and downgrade, and presented a clumped spatial pattern. When the fruits ripened, they were partly eaten by frugivorous birds, and the others dropped under the parent trees. Four kinds of frugivorous birds preying on T. chinensis fruits were observed, of which, Urocissa erythrorhyncha and Pycnonotus sinensis were the most important predators and dispersers. They mostly devoured the whole fruit, digested the red aril, and excreted the seed. After devoured the fruit, the frugivorous birds mostly flied to the hillside, where the circumstance was beneficial for T. chinensis to germinate and survive. The fruits that were not eaten by frugivorous birds dropped under the parent trees, predated by insects or decayed. Frugivorous birds played an important role in T. chinensis regeneration. They dispersed the seeds to new sites, being of significance for the diffusion and invasion of T. chinensis population to new habitats.