Sri Lankan Lowland Rainforest
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, Xylopia parvifolia, together with endemics like Cryptocaraya membranaceae (Lauraceae), Canarium zeylanicum (Burseraceae), Diptercarpus hispidus, Hopea discolor, Shorea lissophylla (Dipterocarpaceae), Mangifera zeylanicum (Anacardiaceae) and Palaquium grande (Sapotaceae). The canopy and sub canopy layers typically comprise Adenanthera pavonina, Chaetocarpus castanocarpus, Cullenia excelsa, Cyathocalyx zeylanicus, Ficus callosa, Harpullia arborea, Horsfieldia iriya, Iilex zeylanica, Isonandra lanceolata, Kokoona zeylanicus, Kurrima zeylanica, Lasianthera apicalis, Litsea glutinosa, Mesua ferrea, Mimusops elengi, Pometia exima, Pygeum zeylanicum, Scutinanthe brunnea, Strombosia zeylanica, Trichadenia zeylinica, Urandra apicaulis, and endemics such as Anisophyllea cinnamomoides (Anisophylleaceae), Artocarpus nobilis (Moraceae), Camnosperma zeylanica, Semecarpus gardneri (Anacardiaceae), Carallia calycina (Rhizophoraceae), Chaetocarpus coriaceus (Euphorbiaceae), Diospyros quaesita (Ebenaceae), Horsfieldia iriyaghedhi, Myristica dactyloides (Myristicaceae), Hydnocarpus octandra, Trichadenia zeylanica (Flacourtiaceae), Mastixia tetrandra (Cornaceae), Pseudocarapa championii (Meliaceae), Shorea stipularis (Dipterocarpaceae), Syzygium makul (Myrtaceae) and Terminalia parviflora (Combretaceae).
Below the canopy is lower story of medium sized trees principally comprised of Adenanthera aglaeosperma, Aporosa latifolia, Axinandra lanceolata, Calophyllum pulcherrimum, Chrysophyllum roxburghic, Cinnamomum zeylanicum, Cleidion javanicum, Dillenia retusa, Eleocarpus serratus, Garcinia cambogia, Gironniera cuspidata, Hollarhena mitis, Julostylis angustifolia, Lannea grandis, Litsea cauliflora, Macaranga digyna, Machilus macrantha, Mallotus alba, Ochna wightiana, Pterygota thwaitesii, Rejoua dichotoma, Symplocos cuneata, Syzygium aquem, Trema orientalis, Turpinia malabarica 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 cordifolium (Dipterocarpaceae).
The shrub layer includes various small trees and shrubs such as Agristitachys longifolia, Aporosa lindleyana, Desmos elegans, Diospyros insignia, Gaetnera vaginans, Gyrinops walla, Humboldtii laurifolia, Ixora coccinea, Lasianthus strigosus, Leea sambucina, Schumacheria castaneaefolia, and Symplocos coronata together with endemics such as Semecarpus pubescens (Anacardiaceae) and Sysygium spissum (Myrtaceae). The field layer is usually rich in ferns and aroids, while other common plants include Apama siliquosa, Calamus zeylanicus, Ellettaria cardmomum, Ochlandra stridula, Polyalthia acuminata, Psychotria nigra, Schizostigma hursuta, Symplocos minor, Todalia aculeata 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 fenestratum, Dalbergia championi, Derris scandens, Entada scandens and Tetracera 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 Rainforest
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), Cinnamomum citrodorum, Cryptocarya wightiana, Litsea gardneri (Lauraceae) and Elaeocarpus glandulifer (Elaeocarpaceae) are more characteristic of montane forest. In 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 zeylanicus, Garcinia echinocarpa, Meliosma arnottiana, Nothopegia beddomei, Semecarpus nigro-viridis and endemic species such as Calophyllum cuneifolium, C. tomentosum (Hypericaceae), Doona gardneri (Dipterocarpaceae), Elaeocarpus glandulifer (Elaeocarpaceae) and two endemic palms Loxococcus rupicola and Oncosperma fasciculatum (Arecaceae). In fact, the endemic dipterocarp Doona gardneri can be one of 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 zeylanica, Litsea ovalifolia, Michelia nilagirica, Microtropis ramiflora, Neolitsea fuscata, Olea polygama, Photinia notoniana, Plectronia montana, Pygeum wightianum, Rhamnus arnottianus, Scolopia crenata, Syzygium revolutum, Symplocos spicata and Terstroemia japonica. While among the many endemic species are Calophyllum walkeri (Hypericaceae), Cinnamomum litsaefolism, Litsea iteodaphne (Lauraceae), Syzygium rotundifolium and S. umbrosum (Myrtaceae). Epyphytes continue to be a major element with many orchids such as Cirrhopetalum odoratissima, Coelogyne odoratissima, Dendrobium aureum, Eria bicolor, Oberonia wightiana and the endemic Ipsea speciosa (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 patersoni, Muranta fraxinae and Osmunda javonica.
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 swietenia, Diospyros ebenum, Elaeodendron glaucum, Holoptelia integrifolia, Manilkara hexandra, Mitragyna parvifolia, Pterospermum canescens, Schleichera trijuga, Sterculia foetida, Stereospermum chelonioides, Strychnos nux-vomica, Syzygium cuminii and Vitex pinnata. The subcanopy is usually dominated by Nephilium langana while other common species include Aglaia roxburghiana, Alatantia monophylla, Alphonsea sclerocarpa, Cassia marginata, Cordia domestica, Dimorphocalyx glabellus, Diospyros ovalifolia, Euphorbia antiquorum, Garcinia spicata, Gleniea zeylanica, Grewia polygama, Hesperethusa alata, Holorrhena mitis, Lapisanthes trichocarpa, Morinda tinctoria, Memycylon capitellatum, Phyllochlamys taxoides, Pityranthe verrucosa, Pleurostylia wightii, Premna tomentosa, Walsaru piscidia, Sapindus emarginatus,Tricalysia dalzelli and 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 retusa, Saccolabium guttatum, Vanda spathulata and Vanilla walkeri. They also have very rich field and shrub layers including ferns such as Adiantum caudatum, Cheilanthus mysorensis, Gymnopteris quercifolia, Hemionitis arifolia, Micromelum minutum and Ophioglossum lustanicum, while the shrubs typically include Allangium lamarkii, Allophyllus cobbe, Croton aromaticus, Ehretia buxifolia, Glycosmis pentaphylla, Gmeliana asiatica, Ixora arborea, Murraya koenigii, Polyalthia koronii, Randia dumetorum, Stenosiphonium cordifolium, Tarana asiatica and Webera corymbosa. In the transition 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 Hopea cordifolia (Diperocarpaceae).
Sri Lankan Saltmarsh
The presence of saltmarsh in Sri Lanka seems anomolous since it seems to be outside the recognised global distribution of this habitat. It was thought to be confined to temperate and high latitude zones. In Sri Lanka is mainly confined to arid parts of north-western and south-eastern coasts where it may represent the most southerly saltmarsh in the northern hemisphere.
In a study of saltmarsh on a small islet between Mannar Island and mainland Sri Lanka on the north-western coast several major vegetation types were recognised. In simplified terms these comprised Suaeda Saltmarsh, Arthrocnemum Saltmarsh, Saltmarsh Pasture, Thorny Salt Scrub, Cynodon-Cyperus Depressions and Cyperus Depressions.
This vegetation was found to be composed of two physiognomically but phytosociologically distinct vegetation types, one in low strongly maritime zones (described as the maritime community) and one on more inland areas on damp saltmarsh pasture (decribed as the inland community). The maritime community was dominated by Suaeda maritima, forming shrubs unto 75 cm high, together with sporadic patches of Suaeda monoica and Suaeda nudiflora. Other less common species included Cynodon dactylon, Evolvulus alsinoides, Portulaca tuberosa, Portulaca wightiana and Salicornia brachiata. In the inland communities Suaeda monoica and Suaeda nudiflora were the dominant species forming shrubby vegetation up to 1.5m high. Less common species here included Arthrocnemum indicum, Cynodon dactylon and Salicornia brachiata.
Situated between the inland Suaeda saltmarsh and thorny salt scrub this vegetation largely comprised almost mono-specific stands of Arthrocnemum indicum. However, up to 50% of this zone was bare ground. The few other species included Cynodon dactylon and Salicornia brachiata.
This complex of grass-dominated vegetation could be further divided in dry saltmarsh pasture, damp saltmarsh pasture and mixed saltmarsh pasture.
Dry saltmarsh pasture
These pastures comprise dwarf turf with up to 40% bare ground. It can become very parched during draughts and is rarly influenced by sea water. Other scattered species included Acacia planifrons, Aloe barbadensis, Asparagus racemosus, Coccinia grandis, Calotropis gigantea, Dactyloctenium aegyptium, Dyschoriste madurensis, Enicostema verticillare, Epaltis divaricata, Euphorbia antiquorum, Euphorbia hirta, Evolvolus alsinoides, Grewia tenax, Hybanthus enneaspermus, Ocimum canum, Portulaca tuberosa, Portulaca wightiana, Salvadora persica, Sida retusa and Zornia diphylla.
Damp saltmarsh pasture
Forming in relatively low lying areas this largely comprise closed turf of Cynodon dactylon. The vegetation is generally flooded in wet months and occasionally inundated by sea water. Other species such as Arthrocnemum indicum, Cressa cretica, Cyperus pumilus, Cyperus rotundus and Salicornia brachiata occur sporadically.
Mixed saltmarsh pasture
This vegetation represents a transition zone or ecotone between the main saltmarsh pasture types and other communities. For example, in the transition zone to thorn scrub mixed swards of Cynodon dactylon, Eragrostis tenella and Zoysia matrella were found in association with Acacia eburnea, Acacia planifrons, Aloe barbadensis, Asparagus racemosus, Hibiscus macranthus, Hybanthus enneaspermus, Ocimum canum, Portulaca tuberosa and Portulaca wightiana.
Thorny Salt Scrub
Representing the final stage in saltmarsh succession these scrub zones form an almost continuous belt at the top of the saltmarsh. They are never inundated by seawater but all the species are adapted to the dry maritime conditions. In places they show clear stratification with up to three distinct layers. The uppermost tree layer includes Acacia eburnea, Acacia planifrons, Azima tetracantha, Cassia auriculata and Coccinia grandis. Underneath is a discontinous layer of shrubs mainly comprising Aloe barbadensis, Asparagus racemososus, Calotrophis gigantea, Euphorbia antiquorum and Ocimum canum. The field layer comprises small herbs such as Enicostema verticillare, Evolvulus alsinoides, Hibiscus micranthus, Hybanthus enneaspermus, Portulaca tuberosa Portulaca wightiana and thegrasses Cynodon dactylon and Zoysia matrella.
In stabilised depressions scattered in low-lying regions up to 2 m below the level of other communities and regularly flooded by high tides, the vegetation comprised closed but dwarf swards dominated by Cynodon dactylon, Cyperus pumilus and Cyperus rotundus together with Salicornia brachiata. In the rainy season therophytes such as Cressa cretica and Heliotropium supinum would appear. The presence of tubers on Cyperus rotundus is thought to help it overcome prolonged exposure to floods and tides.
Occupying brackish depressions with the thorn-scrub belts are stands of Cyperus rotundus together with occasional individuals of Cynodon dactylon, Ocimum canum, Portulaca tuberosa and Zoysia matrella.
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