Cullenia exarillata- Mesua ferrea- Palaqium ellipticum – Gluta travancorica type (CMPG) 

This type is confined to south of the Ariankavu Pass, between 8º20’N and 8º 50’ N.  It is mainly defined by the altitudinal preference of Cullenia exarillata.  This speceies is commonly found between 700 and 1400 m and seldom descends to 550 m in some moist valleys.  Its latitudinal distribution goes up to 11º 55’N (Wayanad plateau.)  Mesua ferrea and Palaqium ellipticum are widely distributed in  both the low and medium elevation forests, however they tend to become more dominant at medium elevation. Gluta travancorica, a common canopy species is endemic to the south of the Ariankavu pass.  The association of this species with the other three species (CMP) makes them a distinct medium elevation type. 

There are certain species, which are either exclusive to the CPMG type or rarely found in the other medium elevation type north of Ariankavu pass.  They are represented by Calophyllum austroindicum, Garcinia rubro-echinata, Garcinia imbertii,Garcinia travancorica, Diospyros barberi, Atuna travancorica, Nageia wallichiana  at canopy and subcanopy level; Memecylon subramanii, Popowia beddomeana, Memecylon gracile, Octotropis travancorica, Diotacanthus grandis, Goniothalamus rhynchantherus  and Vernonia travancorica at undergrowth level.

 Nageia wallichiana ( Podocarpus) a sole indigenous Gymnosperm tree species in South India.  In the  WG it is found in the Agasthyamalai region (Periyar plateau) and in Anamalai region.  In the Agasthyamalai region it  is more common towards the eastern side as a canopy tree it forms with CMPG type, at above 1000 m.  In the other two regions, they are rare in the CMP type of forests.

 The species, which are also characteristic in this facies include  Elaeocarpus venustus, Eugenia floccosa, Aglaia bourdilloni, Actinodaphne campanulata and Syzygium microphyllum. Bentinckia codapanna, an endemic palm is often found along the margins of the facies near the cliffs.

Cullenia exarillata –Mesua ferrea – Palaquium ellipticum type (CMP) 

This type occupies the WG of Kerala between the Ariankavu Pass and the Brahmagiri Ghat in Wayanad.  The lower limit of the type on the western side of the Ghats locally varies from 550 to 750 m.  The bioclimatic range of this type is generally similar to CMPG type except in the length of the dry season, which varies from 2 to 4 months.  In the Elaimalai region, the entire CMP type has been converted into cardamom plantations.  In these plantations, cardamom has been grown as undergrowth, while keeping the original canopy intact.  In the dense forests, apart from the type species,other common canopy tree or emergent species are Diospyros sylvatica, Drypetes elata, Cinnamomum keralense, Syzygium gardneri, Dimocarpus longan, Aglaia lawii, Litsea oleoides and all these are widely distributed.  In the second and third ensembles that are also broadly distributed include Agrostistachys meeboldii, Symphilia mallotiformis, Tricalysia apiocarpa, Myristica dactyloides.  Homalium travancoricum and Diospyros paniculata.  However, some species like Drypetes venusta, Semecarpus travancorica, Diospyros nilagirica, Litsea bourdillonii, Litsea keralana, Bhesa indica, Aglaia tomentosa , are found up to the Palghat Gap. Beyond the Gap, these species either disappear or become rare.  In the fourth ensemble Ardisia pauciflora,Goniothalamus wightiana, Tabernaemontana gamblei, Psychotria anamalayana, Lasianthus jackianus are common.

Dipterocarpus indicus – Dipterocarpus bourdillonii - Strombosia ceylanica type (DDS)

This type covers a wide area in the WG between Ariankavu Pass and northern border of the Palaghat Gap (9ºn and11ºN).  Its general bioclimatic conditions are similar to that of the DKS type, except for the mean temperature of the coldest month, which is higher than 20ºC 

Like in the previous type, Dipterocarpus indicus and Strombosia ceylanica are also characteristic species in this area.  However, Kingiodendron pinnatum, which is dominant in the earlier types, has been replaced by gigantic Dipterocarpus bourdillonii.  The distribution of both the Dipterocarpus are patchy due to over exploitation in the past. Dipterocarpus bourdillonii, which generally occurs at lower limits(<450 m), is the most affected species.  Currently it is encountered only along streams and in some inaccessible areas.

 Bulk of the DDS type is in the form of distributed forests.  These forests were logged for several decades for hardwoods and softwoods.  Due to this repeated logging several climax species like Vateria indica, Palaquium ellipticum, Calophyllum polyanthum, Otonephelium stipulaceum, Chrysophyllum roxburghii, Dipterocarpus indicus, Semecarpus auriculata, Poeciloneuron indicum, have become less frequent.  However, species with wider ecological aptitude viz.  Polyalthia fragrans, Pterygota alata, Artocarpus gomezianus, Antiaris toxicaria and Bombax ceiba have become common and taken over the canopy.

 DDS type is also dotted with swamps especially in Ranni (between Plapally and Erumeli) and Kannur Divisions.  Some of these swamps are dominated by Humboldtia vahliana with looping stilt roots along with Myristicaceae members viz. Knema attenuata, Myristica dactyloides and Gymnacranthera canarica

Dry Teak Forest

This sub-type occurs in areas having a rainfall of  900 mm-1300mm.  It is characterized by shallow, porous or clayey soils and heavy grazing combined with frequent fires. 

Floristics: Top canopy trees – Tectona grandis, Anogeissus latifolia, Pterocarpus marsupium, Boswellia serrata,Terminalia tomentosa, T. paniculata, T bellirica 

Second storey trees – Chloroxylon swietenia, Diospyros montana, Hardwickia binata, Cassia fistula, Wrightia tinctoria

1.3 High elevation type

 The high elevation forests are generally confined to altitude between 1400 and 1800 m, where the mean temperature of the coldest month varies 14-16ºC and length of the dry period ranges from 2 to 3 months.  Rainfall in the area varies between 3000 to 5000 mm.  Structurally, the forests are stunted, with two ensembles, and canopy seldom exceeds 15 m.  Two floristic types have been identified in these high elevation forests.

Bhesa indica – Gomphandra coriacea – Litea spp. type (BGL)

In the Western Ghats of Kerala , this type is found between the  Ariyankavu Pass and Palghat gap, between 1400 and 1800 m.  At this elevation range, several species of the lower elevations disappear or become very rare viz Cullenia exarillata, Palaquim ellipticum, Diospyros spp and Agrostistachys meeboldii.  The family Annonaceae which is dominant at lower strata in both low and medium elevations, disappears completely at high elevation.  However, some species that are less important at lower elevations become significant at higher elevation range.  Gomphandra coriacea, vicariant of Gomphandra tetrandra of low elevation forest, become conspicuous at lower strata.  Lauraceae, which tends to become common with the increase of elevation, manifest its highest diversity.  Several other species like Schefflera capitata, Mastixia arborea, Archidendron clyparia, Hydnocarpus alpina, Cocculus laurifolius, Acronychia pedunculata, Isonandra spp. Meliosma spp., Symplocos spp are also common in this type.

Schefflera spp. Meliosma arnottiana - Gordonia obtuse type (SMG)

This type found in north of the Palaghat gap (between 1400 and 1800 m) as a transition between CMP of medium elevation and LSM of montane type.  Compare to its counter part (BGL) type in the south of the Palaghat gap, SMG type requires 3 to 6 months dry period.

Even though the species mentioned in this type is found through out the medium elevation and above, they reach their optimum presence in the above mentioned region.  Among Araliaceae Schefflera capitata, S. micrantha, S.racemosa. S.wallichiana are common.  Lauraceae (Litsea, Cinnamomum, Alseodaphne, Neolitsea) and Myrtaceae (Eugenia, Syzygium, Rhodomyrtus) become conscpious from this type and towards montane type.

Lateritic Semi Evergreen Forest

Distribution: These are forests, which come up in the latteric soils and characterized by the presence of   Xylia xylocarpa.

Floristics: Top Canopy trees – Xylia xylocarpa, Pterocarpus marsupium, Anogeissus latifolia, Grewia tiliifolia,

 Secondary storey trees – Briedelia retusa, Strychnos nuxvomica, Calycopteris floribunda

Shrubs – Adhatoda vasica

Littoral forest

This type of forest occurs along the coast having a fair width of sandy beach.  The most important species is the tall evergreen, light-foliaged casuarina.  In the absence of casuarina, smaller evergreen and deciduous trees form the dominant canopy. 

Locality Factors:  The habitat exhibits pecularities, which needs mention.  The sea sand has adequate lime content, but little nitrogen and mineral nutrients.  Though the beach sand is coarse and porous, a high water table of brackish water is always maintained due to the proximity to the water body.  The high insolation levels and sand-laden winds render the area suitable only to xerophytic plants.    The mean annual temperature ranges from 26-29 degree Celsius.  The rainfall received is around 5000 mm.

 Floristics: Species composition varies in different regions

Low elevation types

The low elevation types are typically ‘Dipterocarp’ Forests.  Structurally, they are all dense forests with four structural ensembles (sense Oldeman, 1974) and an emergent layer.  Canopy height often reaches 35-45 m.  Floristically, low elevation forests are grouped into three main types

Dipterocarpus indicus – Kingiodendron pinnatum – Strombosia ceylanica type (DKS)

This type is confined to south of the Ariankavu Pass (8º 20’N to 9º 00’N), where the length of the dry season varies from 2 to 3 months.  Like in the other two low elevation evergreen forest types, Dipterocarpus indicus is a characteristic canopy species.  Kingiodendron pinnatum, yet another important canopy tree in the type, shows a peculiar distribution pattern.  It is very rare in the low elevation wet evergreen type between the Ariyankavu Pass and the Palaghat Gap, however, becomes prominent again north of the Palaghat Gap.  Strombosia ceylanica has a wide distribution throughout the WG, but is more common among the canopy trees of low elevation types, south of the Palaghat Gap.

The denser part of the DKS type is represented by two facies, which are found above 8 º 40’N.  Below, that, the DKS type is mostly in the form of fragments or in a degraded condition.  Some of the big fragements are close to climax forests with the presence of Vateria indica, Kingiodendron  pinnatum, Hopea parviflora, Mesua ferrea, and Strombosia ceylanica.  Dipterocarpus indicus are rare in these fragments.

The two facies that have been identified under DKS type, one is characterized by the local abundance of otherwise two geographically rare species (Hopea racophloea and Humboldtia decurrens ),and the other corresponds to a particular ecosystem adapted to water logged areas.

(i) Hopea racophloea – Humboldtia decurrens facies

This facies is confined to humid valleys between Kallar and Shendurni Rivers , west of Agastya malai.  Although, the distribution of Hopea racophloea and Humboldtia decurrens goes beyond the Ariankavu Pass, their presence in DKS type is more conscipious than in any other regions.  Hopea racophloea with exfoliating bark is a canopy tree.  Its regeneration is always gregarious.  Humboldtia decurrens, a caulifliorus tree with large winged pinnate leaves, is prominent in the third structural ensemble of the forest.  Other common canopy trees are Vateria Indica, Artocarpus gomezianus, Otonephelium stipulaceum, Holigarna nigra, Cynometra sp. and ficus beddomei.  Poeciloneuron indicum has been found in patches.  semecarpus auriculata and semecarpus travancorica are common towards the lower limit of the type.  Among the species of lower ensembles Diospyros paniculata, Fahrenheitia zeylanica, Diospyros humilis, Hydnocarpus macrocarpa, Knema attenuata, Cynometra bedlomei are important.

Medium elevation types

Medium elevation forests are structurally very similar to low elevation ones especially at the lower limits, they are tall (canopy 35-45 m) with four structural ensembles.  Towards the upper limit, the forests are stunted with two or three ensembles (canopy < 18 m ).  They differ floristically from low elevation types due to disappearance of species like Dipterocarpus spp., Kingiodendron pinnatum etc.  At this elevation range, the relative abundance of certain species like Strombosia ceylanica, Vateria indica, Diospyros bourdillonii etc. have also become less.  Two main types and one facies have been recognized at medium elevation

Moist Teak Bearing Forest

Here, the teak found is usually of second and third quality.  The overwood mostly comprises of deciduous species.

Floristics: Top canopy trees -   Terminalia tomentosa, Dalbergia latifolia, Bombax ceiba, Lannea coromandelica, Albizia lebbeck

Second storey trees – Xylia  xylocarpa, Wrightia tinctoria, Mallotus philippensis

II a – Bambusa bambos, Dendrocalamus strictus

Shrubs – Helicteres isora, Desmodium spp

Montane evergreen forests (Laitsea spp, - Microtropis spp – LSM):

Montane evergreen forests (sholas) are confined to high altitude plateaus, in the regions of Anamalai (Eravikulam and Munnar) ,Vavul malai (North Nilambur) and upper reaches of New Amarambalam RF (South Nilambur) , adjoining the Nilgiri plateau.  These plateaus generally come under high rainfall (>5000mm) zone and the temperature (mean temperature of the coldest month) is less than 13.5ºC.  Here the evergreen forests are found amidst the grasslands in valleys, depressions and on convex mounts.  The tree layer in shoals comprises of short boled evergreen species with canopy height up to 15 m and bark covered with lichens, orchids and moss.

Lauraceae and Myrtaceae families characterize these forests.  Litsea spp. of the former family and Syzygium spp. of the latter are dominant, along with Microtropis spp (Celastraceae).  Other common species in the shola include Symplocos pendula, Elaeocarpus recurvatus, Michelia nilagirica Actinodaphne bourdillonii, generally dominated by subtropical elements like Berberis tinctoria, Daphniphyllum neilgherrense, Photonia notoniana, Rapanea spp., Rhododendron nilagiricum, Rhodomyrtus tomentosa, Symplocos spp., Turpinia cochinchinensis.

Myristica Swamp Forest

They are fairly dense evergreen forests reaching a height of 15-30 m , with clean slender boles.  The undergrowth includes mainly aroids and scitaminae.

Distribution: Restricted to valleys in the tropical evergreen forest of Travancore

Locality Factors: It occurs as fringe forest on slow moving streams.  The soil is sandy alluvium with high humus content.

The soil layer remains inundated from June to January’

Floristics: Top canopy trees & second storey trees- Myristica magnifica , Myristica malabarica, Lagerstroemia

speciosa, Laphopetalum wightianum, Carallia brachiata

Shrubs – Pandanus sp

IV a – Cyperaceae, Scitaminae

Climbers – Calamus sp

Nilgiri Sub-tropical Hill forests

These forests resemble the tropical rain forest except for the stunted growth of trees.  They are less luxuriant and the trees have shapeless boles, often festooned with epiphytes.  Strobilanthes usually forms dense undergrowth.

Distribution: They are seen in the Nilgiris, Anamalai, and Palani Hills of Tamilnadu and Kerala.

Locality Factors: This sub group occurs at altitudes between 1000m and 1700m on the South Indian hills.  The mean annual temperature ranges from 17-22 degree Celsius.  The rainfall recorded is high and varies from 1500-6600mm.  The number of rainy days amounts to a Maximum of 132.

Floristics: Top Canopy trees and  second or secondary storey trees – Calophyllum elatum, Actinodaphne hookeri, Canthium dicoccum, Ficus arnottiana, Persia macrantha

Shrubs – Strobilanthes sp

Climbers – Calamus sp

South Indian Sub Tropical Hill Savannah

An open savannah forest with tall, coarse grass reaching a height of 2-3 m. Scattered trees of deciduous nature are also seen.

Distribution: Found in the Nilgiri and Palani Hills of Tamil nadu and Kerala

Locality factors: The rainfall varies from 1500 mm upwards and is evenly distributed.

Floristics: Top canopy trees- Dalbergia latifolia, Anogeissus latifolia.

Second storey trees – Olea dioica

Shurbs- Phoenix humilis

IV b – Heavy grass

Southern Moist Mixed Deciduous Forest

Top Canopy trees and Second storey trees – Terminalia paniculata, Terminalia tomentosa, Careya arborea, Phyllanthus emblica, Dillenia pentagyna, Sterculia villosa, Albizia odoratissima, Cassia fistula, Gmelina arborea, Saccharum spontaneum (Grass species)

Southern Montane Wet Grasslands

They are seen over large areas on the rolling downlands.  The highest parts of the forest and the forest in the depressions  are subject to annual frost.  Fires are frequent and grazing is heavy.

Floristics: Cymbopogon flexnosus. Eragrostis nigra, Themeda cymbaria

Southern Montane Wet Temperate Forest

They are luxuriant evergreen forests with closed  canopy.  The trees attain considerable girth, but are short boled and branchy.  The leaves exhibit a varying range of colours, which is a distinct feature of  this forests. The wet nature of the forest results in abundance of moss, ferns and other epiphytes.  The canopy differentiation is not discernible.

Distribution & Locality factors:  It occurs in Tamilnadu and Kerala on the Nilgiris, Anamalia, Palani and Thirunelveli hills from about 1500 m upwards.  It is also found in patches of Shola of the sheltered plains.  The mean annual temperature ranges from 14-17 degree Celsius.  The mean annual rainfall varies from 1300-6000 mm.  The soil is reddish or yellowish clay, topped by varying depths of soil rich in humus.

Floristics:  Ternstroemia gymnanthera Syzygium,S.arnottianum,S.tamilnadensus, calophyllifolium, E. arnottiana, E. Montana, Rhododendron nilagiricum, Elaeocarpus spp.

Southern Secondary Moist Mixed Deciduous Forest

Floristics: Top canopy trees – Terminalia paniculata, Mangifera indica, Dalbergia latifolia, Lagerstroemial anceolata, Alstonia scholaris, Xylia xylocarpa.

Second storey trees – Olea dioica, Careya arborea, Phyllanthus emblica, Callicarpa tomentose Phylanthus emblica,  a Bamboo absent

Shurbs -  Clerodendrum Viscosum, Helicteres isora, Glycosmis pentaphylla

Climbers – Calycopteris floribunda, Acacia chesia

Tropical riparian fringing forest (riparian forest)

The forest type is characterized by a few evergreen and semi-evergreen species restricted on the sides of streams forming a narrow fringe.  In the Sanctuary the forest type is restricted mostly along the sides of the Pambar and Chinnar rivers.

 The dominant species are Terminalia arjuna, Hopea parviflora, Bischofia javanica, Mangifera indica, Drypetes roxburghii, Vitex leucoxylon, Pongamia pinnata, Garcinia gummi-gutta, Mallotus stenanthus, Calophyllum calaba, Entada rheedei, Lepisanthes tetraphylla, Syzygium cumini, Schefflera racemosa, Homonoia riparia, Vitex altissima, Salix tetrasperma, Gnetum ula etc

Very Moist Teak Forest

In this type, teak forms only 10 percent of the overwood.  Most of these forests are sub climaxes in semi evergreen forest and are of secondary orgin.

Floristics: Top Canopy trees – Lagerstroemia lanceolata, Grewia tiliifolia

Second Storey trees – Dillenia pentagyna, Kydia calycina 

Bamboos – Bambussa bambos

Shrubs – Clerodendrum viscosum, Glycosmis pentaphylla, Lantana camara

Climbers – Spathalobus roxburghii, Acacia pennata.

 West coast Semi-Evergreen forest

  Being intermediate between the tropical evergreen and moist deciduous forest, these are difficult to define except describing in comparative terms.  They usually include patches of both these types mixed into a mosaic.  It forms a closed high forest, the dominant trees sometimes will grow very large.  Buttressed stems continue to frequent both in evergreen and moist deciduous forests. The general canopy is less dense than in true evergreen and the evergreen undergrowth rather copious; climbers tending to very heavy.  Bamboo is usually found well distributed in the evergreen forest.  Epiphytes are abundant, including many ferns and orchids.

 Locality factors: Rainfall varies from 2000-2500 mm on the plains

 Floristics: Top canopy trees – Terminalia tomentosa, Dalbergia latifolia,Haldina cordifolia, Xylia xylocarpa, Artocarpus hirsutus, Hopea parviflora, Mesua lerrea,

Second storey trees- Hydnocarpus pentandra, Bischofia javanica, Mallotus philippensis, Kydia calycina

Bamboos- Ochlandra sp, Bambusa bambos