Here we show that this phenomenon is 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 Niña to El Niño, which results in an irregular 6–7-yr cycle involving a dry period with several droughts and a wet period without droughts.
(Shoko Sakai et al, 2006, American Journal of Botany. 2006;93:1134-1139.)
We witnessed the mass flowering in our forest in early April 2010, after the onset of rain after a prolonged drought of 2 to 3 months. Here are some photos of this phenomenon.