“If you’ve seen one, you’ve seen them all.” It has been a classic fools’ argument put forward in many contexts, often to oppose the preservation of the world’s forests.
But all forests are not alike. Nor are all tropical forests alike. Just how dissimilar one of the Old World’s most spectacular tropical forests, Malaysia’s Lambir Hills National Park, is from Panama’s forests was the topic of Dr. Rhett Harrison’s March 2 presentation at the Smithsonian’s Tupper Center free science lecture series.
Harrison, a Scot by birth and culture, is a post-doctoral fellow at the Smithsonian Tropical Research Institute. He came here to conduct studies at Barro Colorado Island, but before that he worked at Lambir Hills, which is in Sarawak, the Malaysian part of the island of Borneo, which also includes the country of Brunei and part of Indonesia.
It’s “one of the most important research areas in the Asian region,” Harrison said of Lambir Hills, pointing out that in recent years it has drawn more scientists than any other Asian forest park.
Lambir Hills is special because it’s on several biological and geological boundaries.
It’s a lowland bisected by a high jungle ridge, partly covered by the Lambir Foundation, a sandstone formation with deep sandy soil and a covering of raw humus (and thus good drainage), and partly covered by a shale formation from the Miocene epoch, which has topsoil with a high clay content that tends to retain water. The area has more frequent droughts than most other parts of Borneo, which have been more frequent in recent years.
The effect of such droughts on wild figs and the creatures that pollinate them is Harrison’s specialty. His studies at Lambir Hills showed that a severe dry season in 1998 killed off fig wasps which were the only pollinators of certain species of figs, thus causing crashes in the populations of those plants. The figs didn’t start to come back for three or four years, when wasps from other areas moved back in.
Back in the last Ice Age, sea levels were lower and the sea amidst the Malay Peninsula, Java, Sumatra, Borneo and the Riau islands were a continuous land mass. The sea moved back up and the land was once again divided, leaving the Riau Pocket of related and relatively rare flora around widely dispersed parts of the region. Lambir Hills is one of those niches, and thus counts on “more tree species than any other comparable area of the Old World,” according to Harrison.
On the other hand, compared to the New World tropical forests Lambir Hills has few vertebrates, and studies in the 80s and 90s showed that there has been a marked decline in vertebrate species. There have been 23 vertebrate extirpations from the park, including such species as the spectacular Helmeted Hornbill, the Great Slaty Woodpecker and the Banded Langur. These animal declines Harrison attributes to poaching and to the elimination of forests around the park’s boundaries.
Maybe the most unusual biological feature of the park is the phenomenon of general flowering. At irregular intervals of more than one year, there are massive flowerings and fruiting of many species of plants, particularly of canopy trees. Just why this happens is the subject of much study and speculation.
There are population explosions or mass migrations of beetles, bees and other animals that pollinate the trees associated with general flowerings. But are they a cause or an effect?
General flowerings tend to be local rather than regional. “In some cases you can get neighboring valleys out of synch with one another,” Harrison pointed out.
Two hypotheses that have become problematic are that a low temperature spell acts as the trigger for a general flowering; and that the phenomenon occurs in order to provide more seeds than the plants’ predators can eat at one time, and thus allow some of the seedlings to survive.
The first hypothesis is a problem, Harrison said, because there was a general flowering in Lambir Hills National Park in 1998, but this wasn’t associated with a low temperature trigger that has been suggested.
The second hypothesis may be supported by the association of predator population increases with general flowerings, but Harrison believes that there is a lack of good evidence that predator satiation is the driving factor behind the massive flowering and fruitings.
This of course contrasts with Panamanian forests, in which it seems that some canopy species or another is always blooming but rarely do we see many, let alone most, flowering or fruiting at the same time.
Also in this section:
Martian marine past
The trees of a unique Borneo park
WHO targets traffic accidents
The Panama Canal's advancing technology
