Ecoregion
Deccan Thorn
Scrub Forests
Area of the ecoregion
341,000 km2
Altitude
600–900 m
Annual rainfall
500-1000 mm
Temperature
9o C–40o C
Overview
This large, semi-arid region, primarily situated on the Deccan Plateau, is characterised
by sparsely vegetated, thorn forest or savanna like forests. The ecoregion has a
complex and diverse geological history influencing the unique formations in the region.
Strong edaphic factors, a low rainfall and harsh climate has resulted in a specialised
diverse group of plants and animals adapted to the rocky outcrops and hill ranges
and the various basins and biogeographic regions of the scrub ecosystem. This region
houses the floodplains and basins of most of the major rivers of peninsular India. This
area is considered one of the most ancient geological landscapes with a rich biological
and cultural history.
Ecological Restoration Projects in the Ecoregion
Mine restoration in Pandalgudi
Adjoining ecoregions
This large ecoregion transitions into the East Deccan Dry Evergreen forests and the
South Deccan Dry Deciduous Forests towards the southernmost regions. The ecoregion
is flanked by the North Western Ghats Moist Deciduous Forests and the Extension of
Thorn scrub hills: Madanapalle, Andhra pradesh
ERA India | Deccan Thorn Scrub Forests 1
the Narmada Valley Dry deciduous forests. Towards the north, this region transitions
into the Central Deccan Plateau Dry Deciduous forests. The east coast contains tracts
of the Godavari Krishna Mangroves.
Geography
This large ecoregion covers an area 341,000 km2 which includes the majority of
the deccan plateau and the northern deccan traps. With a total length of 1560 km
this region extends from the Tapti river basin down to the tip of the peninsula. The
southernmost reaches form a narrow leg that runs parallel to the coastal profile while
the majority of the expanse is straddled in the land between the Western Ghats and
the northern Eastern Ghats. The Deccan plateau; averaging from 600 to 900 m above
sea level, is characterised by an undulating terrain dominated by erosive processes
and extended networks of small valleys and gorges. This region is home to most of
the major systems of the peninsula including: The Godavari, Indravati, Tungabadhra,
Krishna and Bhima rivers. These rivers are fed by numerous tributaries and streams
both originating from the hill ranges as well as from small fluvial systems that form
over the contours and landforms; and provide a crucial input of water to an otherwise
rain shadowed and arid region.
Geology and Soil
A distinct feature of the deccan plateau is the diverse layered geological mosaics
of basal rock and soil types. These different formations are associated with the rich
historical processes that formed the deccan plateau, and have specific geographic
boundaries and reaches thus playing a dominant role in influencing the biogeography
of the region and its biomes and ecosystem types. Major soil types of the region
include: Nutrient rich volcanic silt and schistic soil along the northern deccan traps,
ferruginous,quartzite rich soils of the central and southern regions and alluvial loam
along the coast and deltas. Bedrock composition also varies from laterite formations
to the west, Basalt to the north , large granitic pediplains or gneissic formations in the
south and stratified laminar granite or ‘Kadapa’ to the southwest.
Climate
The uniform higher elevation of the Deccan and the heavy rain shadow effects that
occur due to the blockade of clouds and depression systems from the west and east
results in low annual rainfall in this region ranging from 500-1000 mm. The southern
ERA India | Deccan Thorn Scrub Forests 2
Trees[left to right]: Albizia amara, Chloroxylon swietenia, Commiphora caudata, Deccania pubescens,
Trees[left to right]: Gardenia gummifera, Givotia moluccana, Premna tomentosa, Ziziphus xylopyrus
Shrubs[left to right]: Benkara malabarica, Cadaba fruticosa, Carissa spinarum, Dodonaea viscosa
Climbers[left to right]: Walsura trifoliata, Phyllanthus polyphyllus, Naringi crenulata, Murraya paniculata
ERA India | Deccan Thorn Scrub Forests 3
extensions of this ecoregion receives a sizable portion of its rainfall from the =northeast
monsoon as well between the months of October to December Annual dry periods
can be 6 months or more with drastic variation in rainfall and drought quite common.
Thorn Scrub thickets structure, Andhra Pradesh
During the drought periods strung duty winds and gusts become a staple and common
feature. Most of the rainfall occurs during the Southwest monsoon between June to
September with convectional thundershowers playing an important role. Temperatures
reach a maximum between the months of March and May reaching as high as 40
degrees celsius and averaging between 33 to 36 degrees. Minimum temperatures can
go as low as 9 degrees during January with an average of 18 degrees celsius across
the region. Maximum and minimum temperatures vary significantly according to the
latitude, elevation and distance from the coast. Higher latitudes, higher elevations have
lower minimum and maximum temperatures.
Natural vegetation
Due to extremes in seasonality, harsh dry periods the vegetation of this region is
predominantly a dense wooded, small leaved-thick leaf and armed group of shrubs
and trees that form a single layered canopy or cover that ranges from 5 - 10 m in
height. The density of this forest type forms dense and interlocked hedge like growths
with sections of barren rocky land and pockets of taller stature dry deciduous trees.
ERA India | Deccan Thorn Scrub Forests 4
Characteristic native plant species
Trees Shrubs
Acacia catechu Syzygium alternifolium Atalantia monophylla Phyllanthus polyphyllus
Albizia amara Syzygium cumini Bauhinia racemosa Pterolobium hexapetalum
Anogeissus latifolia Terminalia alata Benkara malabarica Walsura trifoliata
Buchanania axillaris Terminalia catappa Boswellia serrata Wendlandia tinctoria
Chloroxylon swietenia Vitex altissima Bridelia cinerascens Ziziphus mauritiana
Commiphora caudata Wrightia tinctoria Cadaba fruticosa
Dalbergia lanceolaria Ziziphus xylopyrus Carissa carandas
Deccania pubescens Carrissa spinarum
Diospyros ebenum Catunaregam spinosa
Diospyros melanoxylon Cleistanthus collinus
Dolichandrone atrovirens Cycas beddomei
Ficus amplissima Dendrocalamus strictus
Ficus mollis Dodonaea viscosa
Gardenia gummifera Drypetes sepiaria
Givotia moluccana Erythroxylum monogynum
Hardwickia binata Flueggea leucopyrus
Limonia acidissima Grewia flavescens
Madhuca indica Grewia tiliaefolia
Morinda pubescens Huberantha cerasoides
Phyllanthus emblica Ixora arborea
Premna tomentosa Memecylon umbellatum
Pterocarpus marsupium Murraya paniculata
Sterculia urens Naringi crenulata
Strebulus asper Ochna obtusata
Plant seasonality
J F M A M J J A S O N D
The vegetation composition is predominantly slow growing and short trees and
shrubs both sharing very similar growth strategies, physiological characteristics and
adaptations for this climatic type. Although limited by climate these forest types hold
a large diversity of shrub and tree species with specific distributional boundaries. At
any given section of forest the dominant set of species can make up more around 50
percent of the community composition. However this set of dominant species are very
variable from one geographic zone to another. There is an equal number of deciduous
species as well as evergreen species that have adapted to arid climates. Most of the
vegetation is low growing and extremely hardy to adverse climatic conditions.
Variation within ecoregion
As mentioned earlier, this large ecoregion, majorly influenced by geological processes
and local climate, has distinct boundaries and patterns. It also holds some endemic
species that have adapted to unique habitats within the landscape e.g., Terminalia
pallida, Pterocarpus santalinus, Shorea tumbuggaia, Syzygium alternifolium,
Glochidion tirupathiense.
Topography has a dominant role to play, in a peninsular level there is a gradual sloping
gradient from west to east with higher peaks and flatter undulating areas found
towards the west with an increased density of gaps, gorges and eroded flood-plains
that lead to exposed granitic formations such as inselbergs, castle kopjes, bornhardts
and tors found further east and south. There is significant variance in forest type
between separate parts of the region with areas closer to the hill ranges holding a
greater number of deciduous forest species as carryovers from the adjoining areas.
Proximity to river channels, basins or fluvial system plays a critical role in dictating
forest type, stature and densities.
Plant seasonality
The annual phenology of species broadly follows the patterns of the dry deciduous
forests surrounding this region. However, in this forest type inherent seasonality is
more limited and plant phenology is far more reliant on significant weather events such
as first monsoonal rains or amount or frequency of pre-monsoon showers which can
determine the timings of flushes and flowering. Also the seasonality of plants changes
significantly according to the levels of stress induced by possibly extended droughts
ERA India | Deccan Thorn Scrub Forests 7
or times of plenty as vegetation of this region functions in a tightly balanced energy
budget.
Pollination and seed dispersal ecology
Most flowers are pollinated by insects of the small classes dominated by
Hymenopterans, lepidopterans, and coleopterans. Flowers of plants adapted to harsh
conditions are small and largely pollinated by several groups of insects. Some of the
larger deciduous trees within the region are also pollinated by birds. A large subset
of species use wind dispersal with a few trees and shrubs producing berries primarily
pollinated by birds and small mammals.
Animal life
This region is home to some distinct grazing antelopes such as the chinkara, four-
horned antelope and the gazelle. The rocky outcrops boulder hill slope formations
provide important habitats for sloth bear and leopard populations. This landscape is
one of the last tracts that is home to significant numbers of the Indian wolf and is also
an important habitat for the Indian fox. Characteristic reptiles of the region include
the monitor lizard, rock python, saw-scaled viper, Russell’s kukri, and the common cat
Left to right: Indian wolf, slender loris, saw scaled viper
Left to right: , Eurasian eagle owl, Blue rock thrush, great Indian bustard
ERA India | Deccan Thorn Scrub Forests 8
snake. This landscape is home to 96 species of butterflies. Insect populations are very
seasonal in this ecosystem following an annual cycle. There are a significant group
of more than 200 species of birds that are specialised in these rocky scrub habitats
including the egyptian vulture, blue rock thrush, eurasian eagle owl, yellow-throated
bulbul, Indian nightjar and the Indian courser.
Conservation
These landscapes are one of the most disturbed areas in the subcontinent affected by
grazing, firewood collection, and conversion to agriculture, with fewer, small protected
areas also disturbed by human interventions. Parts have also suffered from ill-advised
tree planting and monoculture plantations of eucalyptus, neem, Melia dubia and other
trees. Historic land use plays a major role in the arid landscape as greater disturbance
increases the abundance and spread of more hardy, and arid thorny species that can
at times replace more diverse and dense floristic compositions in soil types applicable
to their growth following natural successional patterns. For this reason, there is also
intrusion of scrub forest species into disturbed deciduous and dry-evergreen forest
regions.
Important Protected Areas in the Ecoregion
1. Seshachalam Biosphere Reserve
2. Cumbum Forest Range
3. Sri Penusila Narasimha Wildlife Sanctuary
4. Pakkamalai Reserve Forest
5. Gengavaram Reserve Forest
6. Muttukadu Reserve Forest
7. Siruvadi Reserve Forest
8. Koothakudi Reserve Forest
9. Lankamalla Reserved Forest
10. Nagoor Reserved Forest
11. Nakkasalem Reserved Forest
Ecological Restoration Projects in the Ecoregion
Mine restoration in Pandalgudi
ERA India | Deccan Thorn Scrub Forests 9
Acknowledgements
We want to thank the following
individuals and organisations for their
contributions and efforts that helped us
make this document
Text
Madhavan A. P.
Editors
T. R. Shankar Raman
Design
Arjun Singh
Janhavi Rajan
Images (CC-BY / CC-BY-SA via Wikimedia Commons)
[cover] Ecoregion Map: Madhavan A.P.
[Pg 1] Thorn scrub hills: L. Shyamal
[Pg 3] Albizia amara: Dinesh Valke
[Pg 3] Chloroxylon swietenia: Public Domain Dedication
[Pg 3] Commiphora caudata: V. Arun
[Pg 3] Deccania pubescens: V. Arun
[Pg 3] Gardenia gummifera: Vinayaraj
[Pg 3] Givotia moluccana: Public Domain Dedication
[Pg 3] Premna tomentosa: Suresh V Kutty
[Pg 3] Ziziphus xylopyrus: A.J.T Johnsingh
[Pg 3] Benkara malabarica: Renjusplace
[Pg 3] Cadaba fruticosa: J.M Garg
[Pg 3] Carissa spinarum: J.M Garg
[Pg 3] Dodonaea viscosa: Dwergen Paartje
[Pg 3] Walsura trifoliata: V.Arun
[Pg 3] Phyllanthus polyphyllus: Public Domain
Dedication
[Pg 3] Naringi crenulata: Vengolis
[Pg 3] Murraya paniculata: Mokkie
[Pg 4] Thorn scrub thickets structure: Adhitya Madhav
[Pg 8] Indian wolf: Vadya Rupal
[Pg 8] Slender loris: Kalyan Varma
[Pg 8] Saw scaled viper: Hopeland
[Pg 8] Eurasian eagle owl: Sughir Garg
[Pg 8] Blue rock thrush: Artemy Voikhansky
[Pg 8] Great Indian bustard: SVKMBFLY
Icons
[cover] Creative Commons by Austin Condiff from
NounProject.com
[cover] Cc By by H Alberto Gongora from NounProject.com
[Pg 6] Leaf by Arthur Shlain from NounProject.com
[Pg 6] Flower by Eucalyp from NounProject.com
[Pg 6] Orange by Iconic from NounProject.com
ERA India | Deccan Thorn Scrub Forests 10
Key References
Babu, M.V. 2010. Diversity and quantification of trees in
Seshachalam Hill Ranges, Eastern Ghats, India. Indian
Journal of Tropical Biodiversity 18: 143 - 161.
Reddy, C. S., Babar, S., Giriraj, A., Reddy, K.N. & Rao,
K. T. 2008. Structure and floristic composition of tree
diversity in tropical dry deciduous forest of Eastern
Ghats, Southern Andhra Pradesh, India. Asian Journal of
Scientific Research 1: 57-64.
Suresh, H. S. & Sukumar, R. 1999. Phytogeographical
affinities of flora of Nilgiri Biosphere Reserve. Rheedea
9: 1-21.
Tiwari, U. L. & Ravikumar, K. 2018. Floristic diversity,
vegetation analysis and threat status of plants in
various forest types in Dharmapuri Forest Division,
Tamilnadu, Southern India. Notulae Scientia Biologicae
10: 297-304.
Wikramanayake, E., Dinerstein, E., Loucks, C. J., Olson,
D. M., Morrison, J., Lamoreux, J., McKnight, M. & Hedao,
P. 2002. Terrestrial Ecoregions of the Indo-Pacific: A
Conservation Assessment. Island Press, Washington,
DC.
One Earth Ecoregion Snapshot
https://www.oneearth.org/ecoregions/deccan-thorn-
scrub-forests/
ERA India | Deccan Thorn Scrub Forests 11
www.era-india.org
Version 1.0, 5 June 2022
SUGGESTED CITATION
ERAIndia (2022). Ecoregion Profile: Deccan Thorn Scrub
Forests. Version 1.0. Ecological Restoration Alliance,
India. 10 pages.
https://era-india.org/resources/deccan-thorn-scrub-forests
This work is licensed under a Creative Commons
Attribution 4.0 International License.
You are free to copy, distribute, display, remix,
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ERA India | Deccan Thorn Scrub Forests 12
