Silent Valley National Park - Geography
Silent Valley is rectangular, twelve kilometers from north to south and seven from east to west. Located between 11°03' to 11°13' N (latitude) and 76°21' to 76°35' E (longitude) it is separated from the eastern and northern high altitude plateaus of the (Nilgiris Mountains) by high continuous ridges including Sispara Peak (2,206 m) at the north end of the park.
The park gradually slopes southward down to the Palakkad plains and to the west it is bounded by irregular ridges. The altitude varies from 658 m to 2328 m at Anginda Peak, but most of the park lies within the altitude range of 880 m to 1200 m. Soils are blackish and slightly acidic in evergreen forests where there is good accumulation of organic matter. The underlying rock in the area is granite with schists and gneiss, which give rise to the loamy laterite soils on slopes.
Terrain & Geomography
The Silent Valley Plateau, lying at the southwest corner of Nilgiris, sloping towards the south and is practically winged in by hills. Because of the topographic isolation of the plateau, cut off as it is from the east, north, west and south by steep ridges end escarpments; there is little permeating influence from surrounding areas into this stretch of forests.
The terrain is generally undulating with steep escarpments and many hillocks. The elevation ranges from 900 M to 2,300 M above MSL with the highest peak at 2,383 M (Anginda peak). The area lies entirely on a plateau to the north of Mannarkkad, the outer slopes of the hills forming the tableland. The main basin of the Kunthipuzha, which runs from north to south and empties its waters into the Bharathapuzha, is covered by these forests.
The lowest point of the plateau is 685.8 m on the southern boundary, where the Kunthipuzha rushes down the Ghats in a series of rapids. The western edge of the plateau rises gradually from 1127 m at Vannampara on the south west corner to 1163m at Cherambankumban and 1245 m at Valliyamullumalai and culminates at Koyilpara, 1904 m on the northwest corner. To the east of the Kunthipuzha the water shed separating the Bhavani and Kunthipuzha drainage systems starts at Aruvampara in the south and progressively rises northwards to an a elevation of 2383 m in the Anguinda peak on the Nilgiri boundary, the highest point in the tract . The western slopes of this range drain into the Kunthipuzha in a series of parallel valley running east to west and are characterized by extensive grassy blanks.
Soils in general are loam in the surface as well as in deeper layers and strongly acidic in all the three layers with a mean pH value ranging between 5.1-5.4, the mean organic carbon (OC) range between 20.64 and 23.42 g/kg, and total N between 1.08-1.47 g/kg.
In a study conducted in the following plant communities-Palaquium ellipticum-Cullenia exarillata; Palaquium- Mesua ferrea; Palaquium-Poeciloneuron indicum; Mesua-Calophullum elatum; Mesua-Cullenia; Ochlandra (Reed)-Calophyllum; Ochlandra-Peciloneuron - indicates that the soils are strongly acidic in the three layers in all communities except in the surface in Reed-Calophyllum where it is very strongly acidic and in the 40-60 cm layer in Palaqium-Mesua where it is medium acidic.
Soil organic Carbon content decreases with depth in all communities except in Reed - Calophyllum and Reed -Poeciloneuron where no trend is observed. There is sound environment for enzymatic activity. The humus substances decompose to fulvic type in Palaquium-Mesua, Mesua-Calophullum, Mesua-Cullenia and Reed- Calophyllum while in the remaining they decompose to humic type.
There is constant reporting of discovery of new plant species on every exploration. A great network of surface roots in physical contact with moist leaf litter, the root mat having a biomass of 18 g dry weight in 5000 M3. Laurel type leaves with entire margin and with a drip-tip in the mesophyl, thick and leathery for emergent and relatively thin for the under storey species. Very thin bark, less than 6mm in thickness.
Multi layered tree species with stature of more than 60m with a trunk typically slender and often buttressed at the base, the crown depth and width being low compared to the trunk height. Tree density and basal area are comparable to the richest tropical rain forests in other parts of the world. Multi layered nature of the forest with emergent species raising their heads above the general canopy layer, consequently imparting an undulating bumpy look to the surface.
The tree species computed for the Silent Valley (118 vascular plants of 84 species in 0.4 ha) is very high compared to a range of 60 to 140 species that characterize the other known tropical forests. The Alpha Diversity Index is 4.8, which is the same as that of another well known tropical rain forest, Barro Colorado Islands in Panama Canal. Zoological Survey of India had conducted faunal survey in 5 different locations. The specimens were sorted out into species and the groups compared. The levels of diversity in the Silent Valley were found to be much higher than those of the other areas.
The findings of zoological Survey of India indicate that both in terms of species abundance and numerical richness, Silent Valley presents a unique picture in both submergible and non-submergible areas. The limited studies of the fauna of Silent Valley reveals that its rich resources as rare and unique – rare because many species which originally inhabited the entire belt of the Western Ghats have been lost due to destruction of their habitat by human beings or for other reasons.
These faunal resources however are still available in Silent Valley, because of the relatively little human intrusion. It is unique because what little has been collected and studied has already proved to be of immense scientific interest from the taxonomic, zoogeographic and ecological points of view.
A number of species, which were available in the Western Ghats 50 to 100 years ago and which have not been recorded subsequently, still exist in Silent Valley. They include insects, fishes, amphibians, reptiles and mammals. Type specimens of these, described earlier by scientists, have been deposited in museums outside India. Even prototypes are not available in India for referral studies.