Flora of Sarawak
It has been acknowledged that Borneo is one of the most important centres of
plant diversity in the world. The flora of Borneo is conservatively
estimated to harbour between 12,000 and 15,000 species of vascular
plants, that is, about 5-6% of the world total. Of these, 40-50% are
endemic to the island, and up to 80% of the endemic species in Borneo
occur in Sabah and Sarawak.
The vascular plant flora of Sarawak comprises more than 8,000 species.
Over 2,000 tree species have been enumerated whereas orchids would number
more than 1000 species each, ferns account for 757 species and palms
make up another 260 species. New species continue to be collected and
recognized.
The complex soil and terrain, together with altitudinal sequence, give
rise to a wide range of habitats for plants in Sarawak. Each of the
forest types is distinctly different in morphological characteristics
and species complexities. Floristically, the mixed dipterocarp forest
and the old secondary forest are among the richest. Old secondary
forests evolved from ex-shifting cultivation areas for more than
100 years and have been studied in Lanjak Entimau Wildlife Sanctuary.
The occurrence of understorey trees below 10 cm dbh
and the non-tree flora are more variable among the
forest types. An example from
Lanjak Entimau Wildlife Sanctuary (LEWS),
the largest sanctuary in Sarawak, is shown below.
| Forest Type | Families | Genera | Species | Average No. of Trees/ha |
| Riparian | 31 | 62 | 70 | 533 |
| Alluvial | 38 | 111 | 265 | 518 |
| Old Secondary | 53 | 144 | 376 | 588 |
| Lowland Dipterocarp | 52 | 152 | 494 | 810 |
| Hill Dipterocarp | 43 | 123 | 368 | 838 |
| Summit Ridge | 48 | 110 | 285 | 1,029 |
| Submontane | 40 | 73 | 123 | 968 |
| Montane | 33 | 55 | 93 | 1,106 |
In the 52 ha Long Term Ecological Plot (LTER) at Lambir National Park, 72 families, 278 genera and 1,083 species have been recorded. Number of trees per hectare for diameter class of 1-10 cm, greater than 10 cm and greater than 50 cm were 6269, 633 and 41 respectively.
Different families dominate the different forest types. A ranking is shown for 6 families in Lanjak Entimau Wildlife Sanctuary.
| Forest Type | Euph | Dipt | Myrt | Clus | Laur | Myri |
| Alluvial (Enserieng) | 2 | 1 | 3 | - | 5 | 4 |
| Old Secondary | 1 | - | 2 | 4 | 3 | 5 |
| Lowland Dipterocarp | 1 | 2 | 3 | - | 5 | 4 |
| Hill Dipterocarp | 2 | 1 | 4 | - | 5 | - |
| Summit Ridge | 2 | 4 | 1 | 3 | - | - |
| Submontane | 3 | 5 | 1 | 2 | 4 | - |
| Montane | 3 | 5 | 1 | 2 | 3 | - |
| Euph=Euphorbiaceae Dipt=Dipterocarpaceae
Myrt=Myrtaceae Clus=Clusiaceae Laur=Lauraceae Myri=Myristicaceae |
The most common families for trees down to 1.0 cm diameter class at Lambir National Park are shown in the table below:
| Family | No. of Genera | No. of Species |
| Euphorbiaceae | 28 | 117 |
| Dipterocarpaceae | 11 | 94 |
| Annonaceae | 12 | 57 |
| Rubiaceae | 22 | 37 |
| Leguminosae | 13 | 36 |
| Tiliaceae | 8 | 36 |
| Anacardiaceae | 13 | 33 |
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