斑块生境中啮齿类和蚁类动物对南方红豆杉地面种子的搬运

Understory seed removal of Chinese yew (Taxus chinensis) by rodents and ants in patchy habitats

南方红豆杉(Taxus chinensis)在我国南方地区多分布在村落附近的斑块生境中,成熟后的种子直接落在母树下或被鸟类等动物搬运至其他斑块中。林下地面种子会被地面活动的动物搬运,继而影响种子命运及种群更新。于2016年、2017年南方红豆杉果期,在浙江天目山一个红豆杉种群分布地(临安市桐坑村),采用野外种子摆放实验的方法研究了动物对地面种子的搬运情况。结果表明:啮齿类动物取食是南方红豆杉地面种子消失的主要原因,但种子消失率在斑块间及边缘生境中的差异较大。母树林和竹林是啮齿类动物的主要觅食生境,两种生境的动物取食率明显高于山核桃种植园。边缘生境成为啮齿类斑块间移动的通道,而非觅食场所。4种啮齿类动物中,淡腹松鼠(Callosciurus pygerythrus)在母树林斑块以外的生境中出现频率最高,而其他地面搬运者回避利用山核桃种植园,仅在母树林和竹林斑块中搬运南方红豆杉地面种子。可见,斑块生境中动物改变了南方红豆杉地面种子的空间沉积格局,进而影响植物种群的更新。

Chinese yew(Taxus chinensis)is an endangered species and prone to extinction in China.While the contribution of birds to the recruitment of bird-dispersed trees,the effects of post-dispersal seed removal by rodents and ants were overlooked.In this study,we investigated post-dispersal seed removal by understory animals for T.chinensis in a seed placement experiment.Seven species(four rodent species,i.e.Callosciurus pygerythrus,Tamiops swinhoei,Rattus tanezumi,Niviventor confucianu and three ant species i.e.Aenictus bobaiensis,Monomorium floricola,Odontomachus monticola)could remove seeds in the ground.Seed removal by rodents was the main factor for the disappearance of T.chinensis seeds,with seed disappearance rate varying among patches and edge habitats.Mother tree forest and bamboo forest were main foraging habitats for rodents,with feeding rate in both habitats being significantly higher than that in pecan plantation.The edge habitats were corridors instead of foraging fields for rodents.Callosciurus pygerythrus presented frequently in habitats outside the mother tree patch.For other species,habitat fragment preferred mother tree patch and bamboo forest but evaded pecan plantation.Seed removal by rodents could reduce the density of seed bank in the bamboo patches,thus affect recruitment of T.chinensis.Our results highlight the importance of understory seed removal in the plant recruitment in the patchy environment.