West coast tropical evergreen forests
It is the climax vegetation in Kerala and is best represented at 600 to 1200. Earlier records indicate that these forests extended right from the sea level onwards but due to heavy demographic pressures almost all the coastal forests have disappeared except for sacred groves preserved on religious grounds. Physiognamically, the forest type is reaching a height of 0-45 m and are encountered at places where the minimum rainfall is at least 2000 mm./year. In undisturbed areas, stratification is conspicuous and at least three to four strata of vegetation are met with. Most of the trees are buttressed up to about 15m with festooning of trees with mosses, lichens, aroids, ferns, orchids etc. Common trees of the top story include species like Artocarpus heterophyllus, Bischofia javanica, Calophyllum calosa, Calophyllum polyanthum, Canarium strictum, Cullenia exarillata, Drypetes elata, Dysoxylum malabaricum, Elaeocarpus tuberculatus, Holigarna spp. Messua ferrea, Palaquium ellipticum, Persea macrantha, Poiciloneuron indicum, Polyatlhia spp. Vateria indica, etc.
The second storey of the forest formation is about 20 m hight dominated by species like Aglaia elagboidea, Actinodaphne malabaricai, Baccaurea courtallensis, Cinnemomum spp., Garcinia spp, Syzigium spp. The third storey is generally less than 15 m height and are represented by small trees like Agrostachys meeboldii, Evonymus spp., Syzigium spp., Memecylon spp, Turpinia malabarica.
Ecologically, these forests are most advanced and encountered in ‘climax’ conditions. Floristic richness is high and these forests need preservation for both tangible and intangible benefits.
West coast semi-evergreen forests
It is transition type vegetation between evergreen and moist deciduous forests brought about due to disturbances in wet evergreen forest. It is often encountered in places where evergreen forests are subjected to heavy extractions. Ideal altitudinal limit of the vegetation is 600-800 m and at certain places it extends up to 900 m. If given adequate protection for nearly a century it can progress towards evergreens. The top storey of the forest type is composed of an admixture of both evergreen and deciduous species. Prominent evergreen trees are Artocarpus heterophyllus, Bischofia javanica, Calophyllum elatum, Hopea wightiana, Mesua ferrea, Knema attenuata, Myristica dactyloides, etc. while the deciduous elements are Acrocarpus fraxinifolius, Bombax malabarica, Chukrasia tabularis, Dalbergia latifolia, Grewia tilifolia, Lagerstroemia microcarpa, Terminalia bellerica, Toona ciliata, etc.
South Indian moist deciduous forests
From a commercial point of view this is the most productive forest type. The trees are of average height of 35 m and during the dry season from February to April, they are devoid of foliage. Buttressed trees are comparatively few in number and the dominant species are Albizia procera, Bombax malabarica, Dalbergia latifolia, Tectona grandis, Terminalia paniculata, T. tomentosa, T. belleriaca, Tetramelos nudiflora and Xylia xylocarpa. Bamboos and Reeds are quite common and layering of trees is not quite distinct. Giant lianas like Enatada scandens and Spatholobus roxhurghii are also quite frequent. Ground flora consists of many species of medicinal plants.
Although the forest type is in succession towards “climatic climax” very often they are encountered only in seral stages due to repeated annual fires.
The high altitude natural grasslands are located along the northern and eastern boundaries of MSNP. These high altitude grasslands consist of grasses, herbs and shrubs. The dominant species of grasslands are Chrysopogon zeylanicus, Arundinella fuscata, Dichanthium polyptychum, Eulalia pheothrix, etc. The common non-grass species in the grasslands are Anaphallis sp., Swerita sp., Hypericum mysurensis, Phlebophyllum kunthianum, Eupatorium sp. Viola sp. and Pteridium aquilinum.
The extent of vegetation types as well as information on the RET species are not available at present.