Climatic Influence on Asian Tropical Rain Forest Dynamics

在亚洲热带，厄尔尼诺事件带来了干旱，而拉尼娜事件则导致了潮湿的气候。研究了厄尔尼诺和拉尼娜两种不同气候事件对东南亚热带雨林森林群落动态的影响。实地考察是在马来西亚的一片低地热带雨林和泰国的一片低山热带雨林中进行的。在马来西亚的现场，一块52公顷的地块内所有活着的树木都被贴上了标签，绘制了地图，鉴定了物种，并于1992年用胸径进行了测量。第二次点算是在1997年进行的。1999年，人们再次观察到这些枯死的树木。在1997年的359965棵活树中，有15798棵树在两年后死亡，死亡率为0.022/年，高于1992年至1997年的0.013/年。死亡率的增加表明厄尔尼诺现象(1997/1998年)和拉尼娜现象(1998/1999年)对森林动态的影响。0.013/年的死亡率给出了1998年和1999年厄尔尼诺现象(El Nino…)时9,359棵死树的估计。莫尔和拉尼娜不可能假想地发生。因此，据估计有6439棵树被厄尔尼诺和拉尼娜杀死。在1999年新增的0.32公顷山泥倾泻范围内，有2235棵树木死亡。因此，厄尔尼诺现象造成的树木死亡相当于4204棵。这些估计表明，厄尔尼诺现象造成的死亡率为0.012，拉尼娜现象造成的死亡率为0.0064。死亡率对地形的依赖很明显，因为山脊上的死亡率比山谷里的高。对沙捞越出口荔枝坚果的多元回归分析表明，沙捞越出口荔枝坚果的数量与选秀概率之间存在很强的相关性，选秀概率是指每月降雨量小于100毫米/月的气象站数量与沙捞越可用气象站总数的比率。在泰国的山地森林中，对壳斗科和樟科的种群动态进行了15公顷的监测。然而，关于森林动态与厄尔尼诺/拉尼娜之间的关系，还没有观察到明显的迹象。虽然在1999年12月25日观察到了零下3.2摄氏度的异常低温，但2000年春季没有开花，这表明另一种开花触发因素与马来西亚的龙脑果不同。较少

In the Asian tropics, an El Nino event brings a draught, while a La Nina induces wet climate. This study investigates the effect of two contrasting climatic events, El Nino and La Nina, on the forest community dynamics of tropical rain forest in Southeast Asia. Field work was conducted in a lowland tropical rain forest in Malaysia and a lower montane tropical rain forest in Thailand. In the Malaysian site, all the living trees>1.0 cm dbh within a 52-hecatre plot were labeled, mapped, identified to species, and measured by dbh in 1992. The second enumeration was conducted in 1997. The dead trees were observed again in 1999. Out of the 359965 living trees in 1997, 15798 trees died after two years, showing a mortality of 0.022/yr, which is greater than 0.013/yr observed in 1992-1997. The increase of mortality suggests the impact of El Nino(1997/1998)and La Nina(1998/1999)on forest dynamics. The mortality rate of 0.013/yr gives an estimate of 9359 dead trees in 1998 and 1999, when El Nino … More and La Nina could not hypothetically occurred. Therefore 6439 trees are estimated to be killed by El Nino and Lanina. The number of dead trees within the new landslide areas of 0.32 ha in 1999 is 2235. Hence the trees killed by El Nino are equivalent to 4204. These estimates suggest the mortality rate of 0.012 due to El Nino and that of 0.0064 due to La Nina. The dependency of mortality rates on topography is clear, since mortality rates are higher on ridges than in valleys. A multiple regression analysis on illipe nut exports from Sarawak showed a strong correlation between exported illipe nut quantities and draft probability, which is defined by the ratio of the monthly number of weather stations with rainfall less than 100 mm/month to the monthly total number of available weather stations in Sarawak. In the montane forest of Thailand, population dynamics of Fagaceae and Lauraceae speices were monitored in a 15 ha plot. However, no clear sympotoms were observed, concerning the relationships between forest dynamics and El Nino/La Nina. Although the unusual cold temperature of minus 3.2 C was observed on 25 December 1999, flowering did not occurred in the spring 2000, suggesting another flowering trigger different from dipterocarps in Malaysia. Less