Forest first impressions

by Cam Webb, Research Associate
October 14, 2014

A forest view, with a young Livistona rotundifolia palm on right

Forest first impressions

Our Sulawesi team, Han, Acun, Yessi, Opan, Jupli, Hendrik, Herman (N. Park counterpart), on the edge of the Toraut river (raft just visible).

Our Sulawesi team, Han, Acun, Yessi, Opan, Jupli, Hendrik, Herman (N. Park counterpart), on the edge of the Toraut river (raft just visible).

We’re back in Kotamobagu for a weekend, further sampling the joys of this charming town, and catching up on email. The last week or so at Toraut has gone well, aided by good weather, easy logistics, a great field team, and plenty of tasty food. Acun has finished the layout and tree measurement of plots A, B, C, and D, and even begun to collect voucher specimens, wood samples, and DNA samples. Our perennial need for tree climbers has been met yet again here in Sulawesi: thanks on this trip go to Han and Opan. Copra (dried coconut “flesh”) is still a major export crop here (along with cloves) and the vast coconut plantations are full of able climbers, making 40 cents per coconut palm climbed and harvested. I’ve finished the morphotyping of plot A (classing trees into taxonomic units), and Yessi Santika (a counterpart and core project member from the LIPI herbarium) made collections (with photos) of over 80 fertile plants. For once, we seem to have picked a good (i.e., dry) time for fieldwork (both Seram and Flores turned out wetter than expected). However, this August-November dry season could end early, so I have to be careful not to fall behind in my fieldwork, despite the pleasure of having enough time to take the work slowly and pay lots of extra attention to trees, seedlings, and documentation.

Toraut flowers (clockwise from bottom): Morinda (Rubia.), Pterocymbium (Malva.), Averrhoa bilimbi L. (Oxali.), Garuga (Burse.), Knema (Myris.)

Toraut flowers (clockwise from bottom): Morinda (Rubia.), Pterocymbium (Malva.), Averrhoa bilimbi L. (Oxali.), Garuga (Burse.), Knema (Myris.)

A good number of the trees and other plants in the forest are flowering, which is good news for the later process of taxonomic identification: while some species can be identified based just on leaves and twigs, those in large, complex genera usual require flowers or fruits for a confident determination. While I haven’t found any existing information on the general phenology (temporal pattern of flowering and fruiting) of the forests of northern Sulawesi, in a place with a dry season we expect natural selection to have driven plants towards flowering during the dry season, and thus fruiting at the beginning of the wet season. This would maximize the time that seedlings of immediately germinating species (the majority) have to grow and send down deep roots before the next dry season. The lower humidity of the dry season might also minimize flower damage and seed mortality due to fungal pathogens. Finding a tree in flower always gives me a buzz: the floral complexity, color, and fragrance contrast pleasingly with the forest’s broad background of green leaves and brown stems. The most delicious aroma so far belongs to flowers of Averrhoa bilimbi L. (Oxalidaceae), a relative of the starfruit.

I’ll save a quantitative description of the forest for a later report, but my first impression is of a forest that:

  1. Has high species diversity; perhaps only second in richness to our Bornean sample, but I haven’t crunched the numbers yet.
  2. Has a slight to moderate seasonal character: a number of trees are now leafless, making identification particularly challenging! One leafless species that is easy to identify from its abundant fallen flowers is a Pterocymbium (Malva.), a genus common in seasonal forests.
  3. Is on rich soils: the Aglaia and euphorbs appear species-rich, a good indicator of fertility; the soil also looks rich: a light, crumbly nutty-brown!
  4. Is slightly disturbed: while the forest structure is good, with many tall trees, there is a higher density of Macaranga than
    I would expect of a forest that had not experienced disturbance for decades. However, Whitmore and Sidiyasa (1986, citation last week) also noted a high abundance of in Macaranga back in the 1980s, before the forest would have been (selectively) logged, so these particular Macaranga species may be semi-shade-tolerant members of primary forest.
A forest view, with a young Livistona rotundifolia palm on right

A forest view, with a young Livistona rotundifolia palm on right

The large trees are dominated by figs (Ficus spp., both free-standing and strangling), Koordersiodendron pinnatum (Anaca.), Dracontomelon dao (Anaca.), Pometia pinnata (Sapin.), Cananga odorata (Annon.), and Vitex spp. The lack of dipterocarps is expected (given that we are east of Wallace’s line), but is still slightly disconcerting to me (given that we are so close to Borneo). Sulawesi is famous for its ebony wood, but while there are a few species of ebony (Diospyros, Ebena.) here in Toraut, some apparently with narrow, inner cores of black heartwood, the famous Diospyros celebica only occurs on the north and south coastal slopes in North Sulawesi, and not in this central valley. The understory here is fairly open, but with a very high density of juveniles of the the beautiful fan-palm Livistona rotundifolia, as well as young rattans, whose viciously hooked, whip-like leaf stems constantly arrest forward movement. Once snagged, tugging against these strong, sharp hooks is futile, leading only to the tearing of clothes or skin, and one must patiently and carefully relax any tension and release the whips; in Australia these forest rattans are known as “wait-a-while vines!”

Despite the heavy hunting in this forest, the density of large birds seems high, and every fifteen minutes or so there is some nearby activity by either a flock of the awesome Sulawesi red-knobbed hornbills (Rhyticeros cassidix), with their loud “helicopter-whooshing” wing-beats, or musical drongos and coucals, or noisily foraging malkohas. The black macaques are still around and I saw a large troop of perhaps twenty individuals, but they were very wary. They were traveling on the ground but would climb small trees to maybe four metres and lean far out from the trunk and bob and call out, looking at me with alarm; they looked far more like chimpanzees (which I’ve only seen on TV) than the common long-tailed macaques of Borneo and elsewhere. The leaf litter is very dry, loudly betraying the movements of other animals: squirrels (two species so far), skinks, and partridges. This dry leaf litter is also home to the least-beloved residents of these forests, the chiggers! Known here as “gonone,” we had been anticipating an unpleasantly itchy month from these critters (as we had in Seram), especially since they are reportedly worse in dry season. But while we have all got a few, and are forced to scratch madly every now and again, they do not seem to be as irritating as the ones in Seram. All in all, working in this sun-dappled, dry, birdsong-filled forest is a daily delight.

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