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.
Soil
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.
Ecological Significance
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.