The forests of NBR are spread over a vast area and cover various ecotypes. The following pages explain the difference in forest types and its relevance to the culture and ecology of the Nilgiri Biosphere Reserve.
The overall classification of the different forest types are as follows
- Semi Evergreen
- Moist Deciduous
- Dry Deciduous
- Dry Scrub Woodland
These forests form a major portion of the western part of the reserve and are characterized by giant trees, multilayered species variation and luxuriant vegetation.
The giant lofty trees can go upto a height of 150 feet or more and are oftern supported by huge buttresses. These trees offer refuge to a multitude of life forms including mosses, ferns, epiphytes, orchids, birds and often small animals. The annual rainfall is more than 200 mm with a maximum of 4 -5 dry months, and the mean temperature higher than 150 C throughout the year. The soil is loamy laterite. The main NTFPs are wild nutmeg (Myristica spp.), cinnamom (Cinnamonum spp.), cane (Calamus spp.), Piper longum, honey and other herbs. These forest are located in Silent Valley, Attapadi Reserve Forest, New Amarambalam, Nilambur Special Division and small pockets of Coimbatore Division in Tamil Nadu. Its ecology is that of the Cullenia-Mesua-Paaquim series.
These forests are moist and occur as a transition zone between the Evergreen Forests and the Moist Deciduous Forests. The trees are slightly lower in height as compared to Evergreen Forests. They are usually found in the lower or more accessible regions of the Evergreen Forests. Buttressed trees are quite common, lianas are also abundant. There are 2 possible transition zones for these forests – either they secondary forests moving towards the evergreen climax or they are the degraded forms of the Evergreen Forests. In some degraded areas around habitations, bamboo (Bambusa arundinacea) and sandalwood (Santanalis spp.) are also found. Lagerstroemia lanceolata is the predominant deciduous species. The otehr main species are Bischofia javanica, Calophylum polyanthum, Tetrameles nudiflora, Artocarpus gomezianus and Dalbergia sissoides.
These forests are restricted to parts of Nilambur valley and even here they have been mostly converted to teak plantations. Wyanad plateau, the south western part of Nagarhole National Park, and western part of Mudumalai Wildlife Sanctuary also contain remnants of this type. Rainfall is around 3000-4000 mm with a dry season of 3-4 months. The soil is generally red lateritic loam. They are also classified as moist deciduous teak type and under this, the Tectona–Dillenia–Lagerstroemia lanceolata–Terminalia paniculata series.
The undergrowth includes many evergreen shrubs and small trees. The trees reach a height of 25-30 m. Buttresses, lianas and dense undergrowth are common. Some species are common to the dry deciduous forest type also. The common trees include Tetrameles nudiflora, Steriospermum personatum, Dysoxylum binectariferum, Ficus nevosa, Ficus glomerata, Pterocarpus marsupium, Salmalia malabarica, Terminalia bellerica, Terminalia tomentosa.
Sholas are found intensively in the Nilgiri South Division and adjacent areas of Kerala in the upper reaches of Silent Valley, Attapadi and New Amarambalam. They are also highly concentrated in the Western catchment area, forming part of the Mukurthi National Park. They are accompanied by grasslands and are frequently the origin of most of the rivers of the zone. The trees are short to medium height (7-20 m), have small dense leaves and make a thick canopy. There is a thick concentration of mosses and ferns. They have a high water retention capacity. They are also classified as the Shola Montane forest type due to their slow growth, high susceptibility and confined geographical area – they are referred to as `Living Fossils’. The average rainfall is around 1000-1200 m with a maximum dry season of not more than one month. The main trees in this forest are Michellia niligarica, Bischofia javanica, Calophyllum tomentosa, Cedrela toona, Eugenia spp., Ficus glomerata, Mallotus spp., Rhododendron spp., Machilus macarantha, Litea spp., etc.