Plant Formations in the Sri Lankan BioProvince
Peter Martin Rhind
Sri Lankan Lowland Rain Forest
Confined to the southwest quarter of Sri Lanka, these multi-storied forests are some of the
richest in the World with a density of species approaching the highest of all the World’s
natural jungles. Above the canopy, is usually an emergent layer of very tall trees, up to 38
m high, such as Dipterocarpus zeylanicus, Doona congestifolia, Pygeum zeylanicum,
(Meliaceae), Shorea stipularis (Dipterocarpaceae), Syzygium makul (Myrtaceae) and
Below the canopy is lower story of medium sized trees principally comprised of
and Wormia triquetra. The endemic trees of this layer include Bridelia moonii
(Euphorbiaceae), Brysophyllum ellipticum, Timonius jambosella (Rubiaceae),
Goniothalamus hookerii (Annonaceae), Litsea longifolia (Lauraceae), Semicarpus moonii
(Anacardiaceae), Syzygium firmum, S. neesianum (Myrtaceae) and Stemonopurus
The shrub layer includes various small trees and shrubs such as Agristitachys longifolia,
layer is usually rich in ferns and aroids, while other common plants include Apama
and the endemic Memycylon arnottianum (Melastomataceae). Lianas, climbers and
epiphytes are well represented. Typical climbers and lianas found on some of the larger
trees include Acacia concinna, Angistrocladus vahlie, Connarus monocarpus, Coscinium
scandens. Ferns, lichens and orchids dominate the epiphyte flora with common epiphytic
orchids including Liparis longipes, Pholidota imbricata and Sarchohilus pulchellus.
Sri Lankan Lower Montane Rain Forest
These forests form a zone between 600 and 1500 m around the central hills and see their
best development in the Knuckles Range and in the central part of the Great Escarpment.
In some respects they are transitional between the lowland and upland rain forest but
some species including endemic trees such as Calophyllum tomentosum (Hypericaceae),
general their species richness is slightly lower than the lowland forests and their structure,
with just three layers, is less complex. The canopy, which reaches heights of 80 feet,
typically comprises Calophyllum soulattri, Carallia calycina, Doona gardneri, Durio
(Elaeocarpaceae) and two endemic palms Loxococcus rupicola and Oncosperma
the most prominent species of these forests. In a lower arborescent storey the main
species are Acronychia peduculata, Actinodaphne ambigua, Amoora rohituka, Celtis
cinnamomea, Cleidon nitidum, Dovyalis hebecarpa, Eleocarpus amoenus, Euodia
roxburghiana, Helica zeylanicus, Lagerstroemea speciosa, Ligustrum walkeri, Meliosma
simplicifolia, Machilus macrantha, Meloechia umbillata, Microtropis wallichiana, Nelitris
jambosella, Neolitsea involucrata, Ouratea zeylanica, Ocophea zeylanica, Schefflera
wallichiana, Villebrunea integrifolia, while endemics at this level include species such as
Aporosa fusiformis (Euphorbiaceae) and Elaeocarpus subvillosus (Elaeocarpaceae).
Despite having a lower overall species diversity, these forests support much greater
numbers of epiphytes, and these are particularly rich in orchids such as Adrorhizon
purpurescens, Dendrobium panduratum, Eria braccata, Josephia lanceolata and Oberonia
longibracteata. The field layer typically includes Allophylus cobbe, Clerodendron
infortunatum, Elettaria involucrata, Mallotus walkerae, Milliusa indica, Ochlandra stridula
and Strobilanthes species.
Sri Lankan Highland or Upper Montane Rain Forest
These forests, sometimes referred to as tropical montane cloud forests, start at about
1500 m but see their best development above 1800 m, and crown the highest mountains
and plateaus of Sri Lanka. The largest single expanse occurs as a crescent extending
from Siripada to Pidurutalagala (across the Nuwara, Eliya and Horton plains).
Pidurutalagala is the highest peak on the island measuring 2524 m and this is still below
the timberline for these forests, and there is no upper conifer zone. Isolated patches can
also be found on Knuckles, Namunukula and Haputale. Floristically they are less rich than
the forests of lower altitudes, but about 50% of all their species are endemic to Sri Lanka.
Their structure is also less complex with all trees more or less arranged in a single layer.
Their canopies normally reach heights of about 30 feet but on rare occasions extreme
dwarf varieties of these jungles occur reaching no higher than about 3 feet. These so-
called pygmy rain forests can be found, for example, on Knuckles Wilderness. Another
unusual feature is the lack of conifers and members of the Fagaceae, which normally play
an important role in the montane forests of Southeast Asia. Conifers, in particular, often
form important emergents, but on Sri Lanka this role is mainly played by endemic species
of Calophyllum (Hypericaceae). The frequency of various species of Symplocos
(Symplocaceae) is a further peculiarity with all but one of them endemic. The tree layer
typically comprises Acronychia pedunculata, Actinodaphne ambigua, Adinandra
lasiopetala, Aporosa latifolia, Elaeocarpus montanus, Euonymus rovolutus, Gordonia
(Hypericaceae), Cinnamomum litsaefolism, Litsea iteodaphne (Lauraceae), Syzygium
with many orchids such as Cirrhopetalum odoratissima, Coelogyne odoratissima,
(Orchidaceae) covering the branches of trees. Mosses and filmy ferns cover many of the
tree trunks and lichens hang from twigs. However, there are fewer climbers, but species
such as Asparagus falcatus, Elaeagnus latifolia and Toddalia asiatica are often prominent.
On the Knuckles range there are a number of rare, endemic species associated with these
forests such as Calophyllum trapezifolium (Hypericaceae), Eugenia lucida, E. phylliroides
(Myrtaceae) and Stemonoporus affinis (Dipterocarpaceae) that are confined to these
mountains. In general the field layer is often densely carpeted with Webera montana,
species of Stenosiphonium and dwarf bamboos such as Indocalamus wightianus,
Oxytenanthera monodelpha and Teinstachyum attenuatum. Other associated species
include Diacalpe aspidioides, Doodia dives Lastraea beddomii, Leptgramme totta, Lomaria
Sri Lankan Monsoon Forest
Unlike the rain forests, the monsoon forests have to contend with periods of drought
sometimes lasting up to six months. They are, however, the main type of forest found in
this BioProvince covering about 75% of Sri Lanka’s forested areas. The trees are a
combination of evergreen, semi-evergreen and semi-deciduous, but the forests as a whole
have a general deciduous character. Not surprisingly, the species diversity of monsoon
forest is not as great as the rain forest and usually has a simple two-storied structure. The
canopy is predominantly composed of Hemicyclia sepiara, while associated species
include Adina cordifolia, Alseodaphne semicarpifolia, Berrya cordifolia, Chloroxylon
species include Aglaia roxburghiana, Alatantia monophylla, Alphonsea sclerocarpa,
the endemic Canthium dicoccum (Rubiaceae). Climbers and creepers are noticeable less
conspicuous but may include Cissus quandrangularis, Columnella trifida, Derris scandens,
Hugonia mystax and Ventilago maderaspalam. Epiphytes, on the other hand, are well
represented and include several orchids such as Habenaria plantaginea, Rhynchostylis
rich field and shrub layers including ferns such as Adiantum caudatum, Cheilanthus
zones between monsoon and rain forest there are forests of intermediate character known
as intermonsoon forests. Among the trees characteristic of these zones is the endemic
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