Verification of top-down effects in the tropical forest ecosystems of South-eastern Asia

1)通过观察4种犀鸟、白长臂猿、猪尾猴等食果性动物在树冠上的果实消耗情况，揭示了水果消费者与果实特性之间的关系。泰国考艾国家公园是一片潮湿的热带森林，在259种植物中，只有一粒种子的果实大而富含脂肪的植物被犀鸟捕食和驱散。因此，这些植物可以被称为犀鸟散布植物。白手长臂猿更喜欢含糖量高的水果，而猪尾猴经常吃未成熟的水果，主要充当种子捕食者。2)对散布在犀鸟巢树周围的种子和幼苗进行了为期3年的标记和监测。近巢树苗在3年内大部分消失，但也有部分“犀鸟散植”幼苗存活下来。苗木S遭受严重的种子掠夺，这是由于小兽类被巢树周围高密度的种子和幼苗所吸引。3)用摄像捕捉法研究了地面水果的消耗情况，并用捕获-再捕获法监测了3年来小型兽类、最大食草动物和文昌鱼的种群消长情况。两种主要的种子捕食者--苏菲木和布吉特的生物量(2150克/公顷)是其他热带森林中记录的啮齿动物的两倍和三倍(例如，怀卡坎的616克/公顷)。两种啮齿动物在枯水期中期的种群密度最高。但两种啮齿动物的繁殖季节不同，表明它们的食性、果实和种子之间存在一定的关系。4)总之，犀鸟灭绝的森林中的种子和幼苗将受到更多的种子捕食，因为种子在母树周围积累得更多，因此树木的更新将变得困难，至少对某些树种来说是如此。

1) Fruit consumption on the canopy by 4 species of hornbills, white-handed gibbons, pig-tail monkeys and other frugivores was observed to reveal the relationships between fruit consumers and fruit characteristics in Khao Yai National Park, Thailand, a moist tropical forest Among 259 plant species, plants having a large and lipid-rich fruit with 1-seed were observed to be consumed and be dispersed only by hornbills. So these plants can be called "hornbill dispersed plants". White-handed gibbons preferred sugar-rich fruits, and pig-tailed monkeys often ate unripen fruits and acted mainly as seed predators. 2) Seeds and seedlings dispersed around nest trees of hornbills were marked and monitored during 3 years. Most of seedlings near nest trees disappeared during 3 year, however, some seedlings of "hornbill dispersed plants" had survived. Seedling s were suffered by heavy seed predation, which caused by small mammals attracted by a high density of seeds and seedlings around nest trees. 3) Fruit consumption on the ground was studied by camera trapping, and population fluctuation of small mammals, Maxomys surifer and Niniventer bukit was monitored during 3 years by capture-recapture method. The biomass of two main seed predators, M. surifer and N. bukit (2150 g/ha) was twice and three times as high as rodents recorded in other tropical forests (e.g. 616 g/ha in Huai Kha Khaeng). These two species of rodents showed highest population density in the middle of dry period. But the breeding season of two rodents differed, which suggested some relationships of food fruit/seed of them. 4) In conclusion, the seeds and seedlings in the forests where hornbills are extinct will be suffered by heavier seed predation caused by heavier accumulation of seeds around mother trees, so that the regeneration of trees will become difficult at least for some tree species.