The forests are mostly Southern Tropical dry deciduous miscellaneous type 5A/C3 (Champion & Seth 1968) and they are further sub-divisible into Teak, Miscellaneous, Nallamaddi, Yepi and Anogeissus types depending on species preponderance.
NSTR lies astride the river Krishna in the biotic provinces of zone (6) of the Deccan peninsula 6E.
Plant Diversity Niches
The average rainfall for the entire Nallamalais is about 740mm. The forests of Nallamalais are confined to 6480 sq. km, of which, 5937 Sq.KMs is under the tiger reserve, out of which NSTR Andhra Pradesh is having an area of 3727 Sq.Km.
In Nallamalais under the broad classification of the tropical vegetation, three types of forests, viz. Dry Deciduous, Moist Deciduous, and Scrub occur with their subtypes and several micro-climatic niches wherein fidelity plants come up.
Based on the classification of forests by Champion and Seth (1968), the following types have been designated for the Nallamalais:
- Southern Dry Mixed Deciduous forests,
- South Indian Moist Deciduous forests,
- Slightly Moist Teak forests,
- Tropical Riparian Fringing forests,
- Tropical Dry Evergreen forests and
- Scrub —further differentiating this into Euphorbia type, Acacia type, etc.
Intermixed with Dry Deciduous forests are the edaphic climaxes like Boswellia type, calamus forests, Phoenix humilis var. pedunculata type, almost pure formation of Terminalia coriacea type etc.,
It has been estimated that there are 1400 taxa spread over 109 families. Amongst those the following four have been found newly viz., Andrographis nallamalayana Ellis, Euphorbia linearifolia Roth var Nallamalayana Ellis, Crotalaria madurensis Wt. var. kurnoolica Ellis & Swaminathan and Rostellularia vahili, (Roth) Nees var. rupicola Ellis.
The N.S.T.R. is having about 353 species in 88 families that are found to have medicinal properties.
Grass potential in Nallamala is very good and occurs in 90% of the catchment area. Dense grass occurs in 30% of the area and scattered occurrence in 20%. But pure grasslands are scanty in this Reserve. Mostly one can find the woodland savannas. About 66 taxa of grasses are found to exist.
The old trees commonly found are ficus, Terminalias, Hardwickia, Bombax, Tamarindus, Syzigium, Pterocarpus, Albizzia, Tendu, Grewia, Gardenia, Mohawa, Cassias, Buchanania, Neem, Feronia, Ficus and Sizygium etc., species.