Classification of Kerala Forests
Semi-evergreen forests (west coast semi-evergreen forests) are generally considered as a transitional stage between evergreen and moist deciduous forests. It is also found in localities where the evergreen forests are subjected to high disturbances. These forests occur between 600 to 800 m and in some places it extends up to 900 m. Animal species such as lion tailed macaque, Nilgiri langur, Nilgiri marten, small Travancore flying squirrel, brown mongoose, Malabar civet, and many birds such as the great Indian hornbill and the Bourdillon's great eared night jar occupy specific niches in these forests.
The floristic composition is an admixture of both evergreen and deciduous species in the top storey. The prominent evergreen species are Artocarpus heterophyllus, Bischofia javanica, Calophyllum elatum, Euvodia lunuankenda, Hopea ponga, Mangifera indica, Mesua ferrea and Myristica dactyloides. The deciduous floral elements include Acrocarpus fraxinifolius, Bombax ceiba, Chukrasia tabularis, Dalbergia latifolia, Grewia tiliaefolia, Lagerstroemia microcarpa, Pterospermum sp., Terminalia bellirica and Toona ciliata. The species occurring in the lower layer are the same as seen in the evergreen forests.
Southern Hill top Tropical Evergreen Forest
It is an inferior variety of the typical evergreen forest, reaching to a maximum height of only 10 m.
Distribution: This type of forest abounds in the Andamans and Western Ghats. They are usually seen on the slopes and tops of hills.
Locality factors: High winds, less favourable soil and climatic conditions restrict the formation of a climax. Rainfall is usually high, over 4500 mm and humidity is high even during periods of scanty rainfall.
Floristics: Top canopy trees & Second storey trees - Artocarpus heterophyllus, Canarium strictum, Cedrela toona, Cullenia exarillata, Dysoxylum malabaricum, Elaeocarpus seratus, Eugenia species, Holigarna beddomei, Mesua ferrea.
Bamboos :– Ochlandra travancorica
Shrubs: Pandanus spp, Strobilanthes spp
Climbers: – Calamus spp
West coast tropical evergreen Forest
These are dense evergreen forests with lofty trees of 45 m or more height. A large number of species occur mixed together. This makes the canopy extremely dense. Ferns, mosses, aroids and orchids are seen in plenty. The undergrowth consists of cane, creeping bamboo, and palms. With the increase in elevation and rainfall, the height of the forest diminishes, though it remains dense and evergreen, changing into the stunted wet sub-tropical forest.
Distribution: Enjoys a wide distribution over the Western Ghats
Locality Factors : It is seen in an altitudinal range of about 250-1200 m.The rainfall varies from 1500-5000mm.
Floristics: These forests are characteristic in having a high proportion of Mesua ferrea, Palaquium ellipticum, Cullenia exarillata and Calophyllum elatum. The absence of Hopea parviflora and Dipterocarpus indicus needs mention.
Top canopy trees: Artocarpus hirsutus, Bischofia javarnica, Canarium strictum, Calophyllum elatum, and Dysoxylum malabaricum
Second storey trees: Actinodaphne hookeri, Cinnamomum zeylanicum, Euphoria longana, Myristica beddomei, Vateria indica.
Shrubs: Leea indica, Pandanus spp, Strobilanthes spp, Rubiaceae
No grass in undistributed forest.
Climbers :– Climbers on the whole are not woody
Wet evergreen and semi-evergreen climax forests
In Kerala, wet evergreen forests are mostly confined to the windward side of the WG, where the rainfall is above 2000mm. By taking into account the distribution pattern of certain charactristic species, which reflect the climatic variations, the forests are further subdivided into eight main floristic types and three facies. All these types are classified according to low (0-800m), medium (800-1450m) and high (1400-1800m). The medium elevation forests in some places may appear at lower elevation (650 m ) due to local variations in the moisture and exposure.
Based on the moisture regime, moist deciduous forests are divided into primary/climax or secondary moist deciduous forests. The primary moist deciduous forests generally occupy the rainfall zone of 1500 to 1800 mm, as a transition between wet evergreen and dry deciduous forests. The secondary moist deciduous forests occur within the potential area of wet evergreen formations, where the rainfall is more than 2000 mm. Although the floristic composition is almost similar in both the types, the relative dominance of certain species varies.
Secondary Dry Deciduous Forests
These are inferior climax forests predominated by poorly shaped, small sized trees. Sandal is also seen in such forests.
Distribution: They are seen distributed in dry deciduous forests and intruding into the drier parts of moist deciduous forests.
Locality Factors: The soil surface is hard and impervious due to exposure and trampling effected by heavy grazing, fuel and timber collection.
Floristic: Top canopy trees – Bombax ceiba, Grewia tiliaefolia, Schleichera oleosa, Tectona grandis
Second storey – Feronia limonia, Santalum album Shrubs – Dodonaea viscosa, Lantana camara
Southern Dry Deciduous Forests
The sub group differs from the dry teak forest species-wise, though typical plants like Boswellia are conspicuous. Heavy grazing invigorates growth of thorny species. Bamboo is mostly absent and of poor quality, if present. Climbers are rarely seen.
Distribution: It occurs throughout peninsular India, especially in drier localities.
Locality factors: The rainfall varies from 875 mm –1125mm on dry sites and soils. The shallow soiled, well-drained hillsides and the undulating grounds have identical forests, making it difficult to establish the relation of site and climate to the forest in situ.
Floristic: Diospyros tomentosa, Chloroxylon swietenia, Hardwickia binata, Boswellia serrata
Primary moist deciduous forests (Lagerstroemia microcarpa – Tectona grandis – Dillenia pentagyna type – LTD)
Primary deciduous forests are found in isolated patches between the Anamalai and Wayanad plateaus. Denser part of this type is the form of woodland and savanna woodland. Dillenia pentagyna and Tabernaemontana heyneana are characteristic species of this type. Lagerstroemia microcarpa and Tectona grandis, together with other species such as Anogeissus latifolia, Dalbergia paniculata, Pterocarpus marsupium, Terminalia paniculata, Hymenodictyon excelsum, Haldina cordifolia are common.
Secondary moist deciduous forests:
In kerala secondary forests cover larger areas than the primary type, mostly in the form of dense forests and woodland to savanna woodland. Especially on the steep slopes, they are found as tree savanna. Floristically, there are similar to primary moist deciduous however, some deciduous species like Dillenia pentagyna, Tabernaemontana heyneana, Strychnos nux-vomica, and Xylia xylocarpa, are relatively more common than in the primary forests. Tectona grandis, which is extensively planted, has also been found mixed with other species in dense formations. In the dense forests often there is dominance of evergreen species like Ixora brachiata, Olea dioica, Persea macrantha, Dimocarpus longan, Flacourtia montana etc.
Dry Deciduous forests
With in the given rainfall regime, dry deciduous forests in Kerala State are rare. They are confined to northern slope of Anamalai in Chinnar Wild life Sanctuary, eastern part of Mannarkad Division, and South Wayanad Wildlife Sanctuary where the rainfall is less than 1200 mm. The physiognomic structure of these dry deciduous forests is highly variable, due to impoverishment of soil, especially on steep slopes, and also due to anthropogenic pressures including fire and grazing. Three types of dry deciduous forests have been recognized.
Albizia amara –Acacia spp. Gyrocarpus asiaticus type (AAG)
This type is found only in Chinnar Wild life Sanctuary, up to 650 m. On the lower slopes, Acacia chundra and A.leucophloea are characteristic species, particularly in the scrub woodland and thickets. Albizia amara, Erythroxylum monogynum, Dichrostachys cinerea and Chloroxylon swietenia, and Hardwickia binata are the other common species of this type.
On the slopes, especially on skeletal soils, tree savannas are the prominent formations. In such habitat Gyrocarpus asiaticus, with metallic-coloured bark, is the characteristic species, along with other slope-loving species, like Cochlospermum religiosum, Givotia rottleriformis, Sterculia urens and Commiphora caudate.
Anogeissus latifolia – Pterocarpus marsupium – Terminalia spp. type (APT)
This type is found above 600 m in Mannarkad Division (northern part) and Chinnar WLS. As it is generally found on slopes, physiognomy varies from savanna woodland to tree savanna. Apart from the species mentioned in this type Dalbergia paniculata, D.latifolia, Emblica officinalis, Kydia calycina and Grewia tiliifolia are also common.
Anogeissus latifolia – Tectona grandis – Terminalia spp.type (ATT)
This type is found only in the South Wayanad WLS. It is generally represented by dense forest and woodland to savanna woodland. Compared to adjacent primary moist deciduous forests, here the species like Dillenia pentagyna, Alstonia scholaris, Callicarpa tomentosa disappear and the species mentioned in the type become dominant. Other common species include Diospyros melanoxylon, Madhuca latifolia, Emblica officinalis, Lagerstroemia parviflora Careya arborea etc. In some poorly drained low-lying areas Shorea roxburghii become conspicuous.
In Kerala grasslands are generally found above 1500 m. The grasslands, which are also called as ‘shrub-savanna’ are characterised by herbaceous and shrubby species mixed with grasses.
The grasslands below 1800 m that are adjacecnt to medium or high elevation evergreen forests, are often found with sparse trees, represented by Wendlandia thrysoidea, Glochidion spp. Terminalia chebula, Emblica officinalis, Careya arborea, Briedelia crenulata; in some places a dwarf palm. Phoenix is found in patches. At this elevation range, grasses are tall, and reach the height up to 1.5 m. They are commonly represented by Androprogon lividus, Arundinella purpurea, Agrostis peninsularis, Chrysopogon zeylanicus, Eulalia phaeothrix, Sehima nervosum, Heteropogon contortus, Eulalia sp, Themeda sp, Ischaemum indicum, and Tripogon bromoides. In cattle grazed and frequently burnt areas, unpalatable Cymbopogon flexuous and Pteridium, a fern are frequent.
The grasses in this zone are mixed with other herbs like Crotalaria, Desmodium, Hypericum, Knoxia, Leucas, Lobelia, Osbeckia etc. Phlebophyllum kunthianum, a monocarpic shrub species, often dominates the grass land landscape.
At above 1800 m, especially in the Anamalai region (Eravikulam and Munnar) grasslands are more specialised. During the colder months, the minimum temperature often goes below zero degree centigrade. In this zone grass layer is less than 1m and is represented by Andropogon foulkesii, Anthistiria ciliata, Arundinella spp., Arundinaria villosa, Bothriochloa pertusa, Chrysopogon orientalis, Cymbopogon spp.,Eragrostis nigra, Eulalia spp., Heteropogon contortus , Isachne spp., Themeda spp., Tripogon bromoides and Zenkeria elegans.
Among Shrubby elements Berberis tinctoria, Gaultheria frangrantissima, Hypericum mysorense, Lobelia excelsa, Oldenlandia stylosa, Osbeckia wightianum, Pteridium aquiilnum, Rubus fairholmianus, Phlebophyllum kunthianus are particularly frequent. Rhododendron arboreum var. nilagiricum in the form of small tree is also sporadically seen in grasslands.
The common herbaceous elements among grasses include Anaphalis spp., Campanula fulgens, Cassia spp., Crotalaria notonii, Cyanotis spp.,Indigofera pedicellata, Justicia simplex,Knoxia mollis, Leucas suffruticosa, Lilium neilgherrense, Oldenlandia articularis Polygala sibirica, Striga asiatica, Viola patrinii,and Wahlenbergia gracilis. In the swampy pockets Commelina spp., Centella asiatica, Drosera peltata, Fimbristylis uliginosa etc are common. .
Mangroves are wetland ecosystems formed by the assemblage of specialized plants and animals adapted to semi saline swamps along coasts. Mangrove forests of Kerala are highly localized, but the species diversity of these mangroves and its associates are comparatively rich. It is confined to the upper reaches of estuaries, lagoons, backwaters and creeks. In Kerala mangroves are distributed in all the districts except Idukki, Pathanamthitta, Palakkad and Wayanad. Maximum extent is reported from Kannur district. The total extent of mangrove forests in the state is estimated to be less than 50km2 (Mohanan 1997) . Mangroves play an important role in the economy of coastal people through various ways. Mangroves provide excellent habitat for migratory birds, serve as breeding ground for many species of fishes and prawns helps in controlling pollution, rutting of husks etc.
The important mangrove plants are
Acanthus cillicifolius, Acrostichum aurem, Aegiceras corniculatum, Avicennia officinalis, A, rina, Azima tetracantha, Bruguiera gymnorrhiza, B. cylindrica, B sexangula, Excoecaria agallocha, E indica, Kandelia candel, Rhizophora apiculate, R mucronata, Sonneratia caseolaris, Calophyllum etc. Some of these species that disappeared from the Kerala coast are Azima tetracantha an Ceriops tagal, Heritiera littoralis and Flagellaria indica have discourteous distribution. Calamus rotang and Syzygium travancoricum are some of the rare and endangered species found in the mangroves.
The major threats to the mangrove forests are land reclamation for urbanization, intensive aquaculture felling of mangrove trees for fuel and fodder, unsustainable land use, ambiguity in ownership etc.
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
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