Long-term fluctuation of biological activities in a lowland dipterocarp forest : Does general flowering contribute to maintenance of biodiversity

全开花是亚洲双龙果林特有的一种特有现象，是热带生物学中最壮观、最神秘的现象之一。它的独特之处在于涉及开花的同步，从而在不同的植物群体中结果。GF发生的时间间隔不规律，不到1年到几年不等。我们根据10年的观测表明，这种现象很可能是由不规律的干旱引发的。在东南亚的季节性森林中，干旱往往发生在从拉尼娜到厄尔尼诺的过渡时期，这导致6-7年的不规则周期，包括干旱期有几次干旱和湿润期没有干旱。另一方面，繁殖成功率与一般开花的大小呈正相关。我们对可能受普花期影响的各种昆虫和小型哺乳动物的种群动态进行了监测。光诱法采集的叶甲种群在不同物种间表现出不同的波动模式，但与全盛期显著对应的物种非常罕见，因此我们认为全盛期不是叶甲种群波动的主要驱动力。可能，叶子的潮红可以部分解释这种模式。另一方面，陆生和树栖小型哺乳动物的种群波动主要遵循开花和结果模式。开花后幼虫的丰度更大，因此它们可能依赖于一般开花进行繁殖。由于它们被认为是双龙脑种子的捕食者，同步结果可能有助于减少这类哺乳动物对种子的捕食。

General flowering, one of the most spectacular and mysterious phenomena in tropical biology, is a masting phenomenon unique to Asian dipterocarp forests. It is unique in involving the synchronization of flowering thus fruiting across diverse plant groups. GF occurs at irregular intervals of less than 1 year to several years. We showed that this phenomenon was most likely triggered by irregular droughts based on 10 years of observations. In the aseasonal forests of SE Asia, droughts tend to occur during transition periods from La Nina to El Nino, which results in an irregular 6-7-yr cycle involving a dry period with several droughts and a wet period without droughts. On the other hand, reproductive success was positively correlated with the magnitude of general flowering. We have aim monitored population dynamics of various insects and small mammals, which are likely to be affected by general flowering. Leaf beetles collected by light traps showed various fluctuation patterns depending on species, but species sharply corresponding general flowering were very rare Therefore, we consider that general flowering is not the major driving forces of fluctuation of populations of leaf beetles. Possibly, leaf flushing may explain part of the patterns. On the other hand, population fluctuation of terrestrial and arboreal small mammals largely followed flowering and fruiting patterns. Abundance of young individuals were larger just after flowering event, thus they may depending on general flowering for reproduction. Since they are considered to be predators of dipterocarp seeds, synchronized fruiting may contribute reduction of seed predation by such mammal species.