A review of dipterocarps - Center for International Forestry Research
A review of dipterocarps - Center for International Forestry Research
A review of dipterocarps - Center for International Forestry Research
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Biogeography and Evolutionary Systematics <strong>of</strong> Dipterocarpaceae<br />
Asian <strong>dipterocarps</strong> deeply imprint the <strong>for</strong>est ecology<br />
and economy <strong>of</strong> the places where they grow. They<br />
constitute prominent elements <strong>of</strong> the lowland rain <strong>for</strong>est<br />
(Whitmore 1988) and are also well represented in the<br />
understorey. As a family they dominate the emergent<br />
stratum. Most belong to the mature phase <strong>of</strong> primary<br />
<strong>for</strong>est, which contains most <strong>of</strong> the entire genetic stock<br />
(Jacobs 1988). All species can colonise secondary<br />
<strong>for</strong>ests during the succession phases provided there is a<br />
seed source; seed dispersal is limited, except among<br />
water dispersed species. However, none seems presently<br />
confined to secondary <strong>for</strong>mations. Certain <strong>dipterocarps</strong><br />
<strong>of</strong> the seasonal regions dominate the fire-climax<br />
deciduous <strong>for</strong>ests <strong>of</strong> northeast India and Indo-Burma.<br />
In Asia, <strong>dipterocarps</strong> occupy a large variety <strong>of</strong> habitats<br />
(Symington 1943, Wyatt-Smith 1963) from coastal to<br />
inland, riverine to swampy and to dry land, undulating to<br />
level terrain, ridges, slopes, valley bottoms, soils deeply<br />
weathered to shallow, well-drained to poorly drained, and<br />
rich to poor in nutrients. In Peninsular Malaysia the<br />
altitudinal zonation <strong>of</strong> their main habitat types ranges<br />
from 0-300 m (low-undulating dipterocarp <strong>for</strong>est), 300-<br />
750 m (hill dipterocarp <strong>for</strong>est), and 750-1200 m (upper<br />
dipterocarp <strong>for</strong>est). Zonation however, differs in Borneo<br />
and Sri Lanka. The freshwater swamps, especially in drier<br />
parts, are rich in species (Corner 1978, in Jacobs 1988)<br />
while true peat-swamp is relatively poor. The dipterocarp<br />
flora is also poor on limestone and riverine fringes.<br />
Asian <strong>dipterocarps</strong> are limited altitudinally<br />
(Symington 1943) by climatic conditions, and the<br />
conjunction <strong>of</strong> altitude and other natural barriers, such<br />
as large rivers and watersheds, have obstructed the<br />
distribution <strong>of</strong> species in Borneo. For example, the<br />
northwest and northeast <strong>of</strong> Kalimantan, Sarawak, Brunei<br />
and Sabah are much richer in species than the rest <strong>of</strong><br />
Kalimantan. The everwet areas are also richer in species<br />
than the seasonal ones as shown in Sri Lanka by the<br />
concentration <strong>of</strong> species in the southwest quarter, or in<br />
the Thai-Malaysian transition belt, or from Java to the<br />
Lesser Sundas (Jacobs 1988).<br />
Distribution <strong>of</strong> Dipterocarps and<br />
Related Taxa<br />
The present distribution patterns <strong>of</strong> <strong>dipterocarps</strong> are<br />
thought to reflect routes <strong>of</strong> colonisation and past climatic<br />
conditions (Fig. 1). Living <strong>dipterocarps</strong> sensu lato are<br />
spread over the tropical belt <strong>of</strong> three continents <strong>of</strong> Asia,<br />
Africa and South America. They occupy several<br />
12<br />
phytogeographical zones that mainly con<strong>for</strong>m to climatic<br />
and ecological factors. However, in southeast Asia,<br />
Wallace’s line where it runs east <strong>of</strong> the Philippines and<br />
between Borneo and Celebes, is a major phytogeographic<br />
boundary <strong>for</strong> <strong>dipterocarps</strong>. It cannot be explained in terms<br />
<strong>of</strong> climatic differences but requires the intervention <strong>of</strong><br />
continental shelf drift.<br />
Phytogeographical Regions <strong>of</strong> Living Taxa<br />
The South American region (Fig. 1, Table 4) corresponds<br />
to Guyana, Venezuela and the part <strong>of</strong> Colombian Amazon<br />
which overlies the Guyana shield.<br />
The African region (Fig. 1, Table 4) includes a<br />
continental area and an insular part in Madagascar. The<br />
<strong>for</strong>mer is in two disjunct areas (Aubreville 1976): a) a<br />
narrow strip in the northern hemisphere from Mali on<br />
the west, to Sudan on the east, neither reaching the<br />
Atlantic nor the Indian Ocean; and b) in the southern<br />
hemisphere the Monotes-Marquesia area covers a semidry<br />
region between the two oceans, south <strong>of</strong> the<br />
Congolese rain <strong>for</strong>est, most <strong>of</strong> which is essentially<br />
central and does not reach the Atlantic or Indian Oceans.<br />
The Asian region (Fig. 1, Table 4) corresponds to the<br />
Indo-Malesian area, which concentrates a high number<br />
<strong>of</strong> genera and species in the equatorial <strong>for</strong>ests. This area<br />
is limited northward by the Himalayan foothills, then<br />
approximately by the borders <strong>of</strong> Assam, Arunachal<br />
Pradesh (India), Burma, Laos and Vietnam, and<br />
penetrating into south China including Hainan Island. On<br />
the extreme southwest the large belt <strong>of</strong> Asian<br />
<strong>dipterocarps</strong> reaches the Seychelles (1 sp. Vateriopsis<br />
seychellarum), and covers India and Sri Lanka. Its eastern<br />
border corresponds to New Guinea. The Sundalands<br />
delimit the most southern part. No dipterocarp species<br />
is found in Australia.<br />
Five main phytogeographical regions are classically<br />
recognised within this distribution area: 1) Malesia:<br />
Peninsular Malaysia, Sumatra, Java, Lesser Sunda Islands,<br />
Borneo, the Philippines, Celebes, the Moluccas, New<br />
Guinea and the Bismarks. The northern frontier <strong>of</strong><br />
Peninsular Malaysia delimits this part; 2) Mainland<br />
southeast Asia: Burma, Thailand, Cambodia, Laos,<br />
Vietnam and south China (Smitinand 1980, Smitinand et<br />
al. 1980, 1990); 3) south Asia: India, Andaman islands,<br />
Bangladesh, Nepal; 4) Sri-Lanka; and 5) Seychelles. In<br />
these Asian phytogeographical areas each dipterocarp<br />
group manifests a more or less distinctive pattern <strong>of</strong><br />
variation at the species level (Ashton 1982).