Indian Savannas

A.S. RaghubanshiBanaras Hindu University

Indian Savanna/Grasslands

• About 400 grass species, 139 endemic• Pastoral nomadism- 200 tribes (6% of India’s total

population)• Grasses- multiuse species (fuel, fodder, thatching

material, craft, rope, medicine, essential oils, etc)• Habitat for wildlife- insects, reptiles, amphibians,

birds (e.g. Lesser Florican), large mammals, wild cats, blackbuck, barasingha, chinkara, wild ass, etc.

Origin• Savannas of the Indian sub-continent are derived

primarily from woodlands through the action of humans (Singh, 1976; Singh e t al., 1983; Gadgil and Meher-Homji, 1985)

• Originated predominantly from woodland ecosystems through deforestation, shifting cultivation, and burning

• Without human disturbance, almost no natural grassland

• Maintained at a subclimax stage by repeated burning & grazing

Distribution & Types

• 8°N-30°N• Savanna types:

1. Sehima-Dichanthium2. Dichanthium-Cenchrus-Lasiurus3. Phragmites-Saccharum-Imperata4. Themeda-Arundinella5. Temperate Alpine

Indian Savanna Types(Dabadghao and Sankarnarayan, 1973)

Grassland Type Climatic Zone

Soil Areal extent(million Km2)

Distribution

Sehima-Dichanthium

Tropical Red, black laterite

1.74 Most of South India, Maharastra, MP, Chhattisgarh, some parts of U.P., Punjab, Gujarat and West Bengal

Dichanthium-Cenchrus-Lesiurus

Sub-tropical, Semi-arid

Alluvial 0.436 North Gujarat, Rajasthan excluding Arawalis, western UP, Delhi, Haryana, Punjab, parts of Jammu

Phragmites-Saccharum-Imperata

Humid, per-humid

various 2.8 Upper UP, NEH, Assam, West Bengal, North Bihar

Themeda-Arundinella

Sub-tropical

Forest hill soils

0.26 NEH, Himanchal Pradesh, J&K, Assam

Temperate-Alpine Temperate, Alpine

- - Himalayan Hill Ranges

Lasiurus sindicus (Sewan) found in western Rajasthan- wonder grass-very high protein content

Sehima-Dichanthium Type• Distribution: Tropical peninsular India, central Indian Plateau, Chhota

Nagpur Plateau, Arawali ranges• Topography: undulating to hilly• Rainfall: 300-6350mm• Maximum cover: 87%

Sehima-Dichanthium Type

• Grasses: Aristida setacea, Borthriochloa pertusa, Dichanthium annulatum, D. caricosum, Sehima nervosum

• Shrubs: Carissa auriculata, Mimosa rubicaulis, Ziziphus nummularia

• Trees: Acacia catechu, A. sandra, Anogessus latifolia, Dalbergia latifolia, Hardwickia binata, Tectona grandis, Terminalia tomentosa

Dichanthium-Cenchrus-Lasiurus• Distribution: subtropical and semi arid regions• Topography: mainly level, occasionally broken by spurs of southern hill

ranges or by sand dunes in Rajasthan• Rainfall: 100-750mm• Maximum cover: 57%

Dichanthium-Cenchrus-Lasiurus• Grasses: Cenchrus ciliaris, C. setigerus, Chrysopogon

monticola, Cynodon dactylon, Dactyloctenium sindicum, Dichanthium annulatum, Eleusine compressa, Lasiurus hirsutus, L. sindicus, Panicum antidotale, Sporobolus marginatus, S. pallidus

• Shrubs: Balanites aegyptica, Calotropis procera, Capparis decidua, Carissa auriculata, C. opaca, Dichrostachys cinerea, Prosopis cineraria, Tamarix dioica, Zizyphus nummularia

• Trees: Acacia catechu, A. leucophloea, A. senegal, Dalbergia sisoo, Prosopis cineraria, Salvadora oleoides

• Dichanthium dominant in protected areas• Cenchrus dominant with moderate grazing

Phragmites-Saccharum-Imperata• Distribution: Gangetic plains, Brahmaputra valley and plains of the Punjab• Topography: level, low lying, ill drained lands• Rainfall: up to 4000mm• Maximum cover: 57%

Phragmites-Saccharum-Imperata• Grasses: Bothriochloa intermedia, Desmostachya

bipinnata, Imperata cylindrica, Phragmites karka, Saccharum arundinaceum, S. bangalense, S. sponteneum, Sporobolus arabicus, S. indicus, Vetiveria zizanioides

• Shrubs: Calotropis gigantea, Clerodendron sp., Dandrocalamus strictus, Lantana camara, Leea indica, Vitex negundo

• Trees: Acacia arabica, Anogeissus latifolia, Butea monosperma, Hydrocarpus laurifolia, Pterocarpus dalbergioides, Tectona grandis, Terminalia procera, Vitex peduncularis

Themeda-Arundinella type• Distribution: northern and north-western montane tract• Topography: mountains ranging from 350-2100 m alt• Rainfall: 1000-2000mm• Maximum cover: 80%

Themeda-Arundinella type• Grasses: Arundinella bengalensis, A. nepalensis,

Bothriochloa intermedia, B. pertusa, Chrysopogon fulvus, C. cerrulatus, Cymbopogon jwarancusa, Eulaliopsis binnata, Heteropogon contortus, Panicum orientale, Themeda anathera

• Shrubs: Berberis lycium, Colebrookia oppositifolia, Daphne oleoides, Desmodium tiliaefolium, Indigofera gerardiana, I. pulchella, Myrsine africana, Prinsepia utilis, Punica granatum, Rhus cotinus, Woodfordia fruticosa

• Trees: Benthamidia capitata, Pinus roxburghii, Pristacia integerrima, Platanus orientalis, Prunus armeniaca, Quercus leucotricchophora, Robinia pseudoacacia

Temperate Alpine Type• Distribution: northern montane tract• Topography: mountains above 1500 and 2100m alt in the east and west,

respectively• Rainfall: 375-3750mm• Maximum cover: 80%

Temperate Alpine Type

• Grasses: Agropyron canaliculatum, Agrostis canina, Calamagrostris epigejos, Chrysopogon gryllus, Dactylis glomerata, Danthonia jacquemontii, Desmostachya bipinnata, Koeleria cristata, Phleum alpinus, Poa pratensis, Stipa sibirica

• Shrubs: Berberis umbellata,Cotoneaster microphylla, Spirarea lindleyana, Viburnum

• Trees: Cedrus deodara, Pinus vallichiana, Quercus leucotrichophora, Rhododendron arboreum

Climate Controls Distribution

• Sehima-Dichanthium – Tropical, dry sub humid

• Dichanthium-Cenchrus-Lasiurus

– Subtropical, semi arid

• Phragmites-Saccharum-Imperata

– Subtropical, moist sub humid

• Themeda-Arundinella– Subtropical, humid montane

Open Forest 28.99 Mha (8.82%)

EarthTrends 2003

Geological Shifts in Forest-Savanna Boundaries

• Palynological studies have shown an increase in the percentage of pollen of savanna species as early as 4000- 3500 BP, remaining almost constant up to the present (Singh et al. 1990; Caratini et al. 1991).

• A recent development of the savanna, linked to a decrease in rainfall.

Geological Shifts in Forest-Savanna Boundaries

• In contrast, Misra (1983) suggested that forests in India are favoured by present climatic conditions

• Pascal (1988) observed that plots protected from fires show increasing woody plant density

• New studies using stable carbon isotope ratio analysis show that change in ecosystem dominance occurred recently (roughly 2000 BP), and that forest has invaded an area occupied previously by a C4 plant community (savanna and cultivated grassland).

Deciduous Forest

Scrub Woodland

Thicket

Pseudosteppe

Scattered Shrubs Discontinuous ThicketShrub Savanna

Tree Savanna

Savanna Woodland

Fire

Tree removal

Furtherdegradation

Overexploitationand over grazing

Overexploitationand over grazing

Exploitation

Furtherexploitationand grazing

Furtherdegradation

Pandey & Singh 1991

Land Use Change

Forest Savanna

Pandey & Singh 1992

Pandey & Singh 1992

Lele & Hegde 1997)

Fine Root Production

• In a tropical forest ecosystem in South India, Sundarapandian & Swamy (1996) reported a similar strongly seasonal pattern in fine-root production, with maximum production occurring during the rainy season and minimum in the dry season.

Fire

• The mean annual canopy and belowground biomass of a Indian dry tropical savanna increases by 40 % and 12%, respectively.

• An increase in mean aboveground net production of 24 % and in belowground net production of 9 %.

• Fire increases the mean concentrations of N and P by 16% and 42% in vegetation and 18% and 17% in soil, respectively.

Effect of BurningSouth Indian Grasslands

NPP 5294-6962 g/m2/yr

Life Forms

• Phanerophytes: 3-10%• Therophytes & Cryptophytes dominate

– Therophytes abundant during rainy season, able to survive through seeds

– Cryptophytes withstand grazing: hidden sub surface position of their perennating buds

• Perennial Species: proportion increases along the gradient of increasing rainfall and grazing protection

Woody plants

• Mostly deciduous or nearly deciduous• The time of leaf fall appears to be related to

water stress• But new leaves emerge during dry phase

itself, much earlier than onset of rainy season

Phenology of Woody Components

The phenological clock of the forest is set during the interphase of winter and summer ensuring full advantage of the short rainy season that follows.

Ombrothermic diagram

fruiting

Flowering

leafing

Leaf-fall Fruit-fall

Solid symbols and curves are for initiation and open symbols and broken curves are for completion of various phenological events.

Sankaran and McNaughton (1999)• In Indian savanna grasslands, resistance to

compositional change was negatively correlated with diversity

• More diverse communities were more stable as measured by resistance to species turnover

• However, no such relationships were observed within communities

• Results are best explained by the ecological history and species characteristics of communities rather than by species diversity in itself

Issues

• Exotic species invasions– Lantana– Parthenium

• Climate Change– C3-C4 balance– Competitive ability

• Defining tree-savanna boundary– PFTs?

• Response to disturbance-PFTs

Current (%) Projected (%) Change (%)Moist savanna 32.52 0.56 -31.97Dry savanna 33.07 4.34 -28.73

Changes in Savanna Biomes under B2 scenario

Relationship of Lantana cover with Different Vegetation Parameters

Lantana cover (%)

0 20 40 60 80 100

Tre

e C

anao

py

cove

r (%

)

0

20

40

60

80

100

0 20 40 60 80 100

Sh

ann

on

H' f

or

Her

bac

eou

s la

yer

0.0

0.2

0.4

0.60.8

1.0

1.21.4

1.6

1.82.0

Lantana cover (%) Lantana cover (%)

0 20 40 60 80 100

Her

b C

ove

r (%

)

0

20

40

60

80

100 y = -0.71x + 83.844R2 = 0.574 P=<0.0001

y = -0.6113x + 71.44

R2 = 0.6991 ; P= 0.0004y = -0.0074x + 1.0603

R2 = 0.4047 : P = <0.0001

Indian Experimental Sites

• Vindhyan Highlands- Biodiversity Park Area, Banaras Hindu University

• Sariska Tiger Reserve- Rajasthan

Soil fertility AridityDry Humid

Eutrophic Ziziphus mauritania(Rhamnaceae)Acacia leucophloea(Mimosoideae)Butea monosperma(Papilionoideae)

Acacia catechu(Mimosoideae)Terminalia tomentosa(Combretaceae)Buchnania lanzan

Dystrophic Acacia nilotica (Mimosoideae)Balanites aegypticea(Balanitaceae)Cordia dichotoma (Boraginaceae)

Anogeissus latifolia(Combretaceae)Hardwickia binata(Caesalpinioideae)Holarrhena antidysenterica(Apocynaceae)

Grass

• Heteropogon contortus (more palatable), Chloris dolichostachya (less unpalatable)

• Questions– Do tree species’ seedlings differ in their ability to

compete with palatable and unpalatable grasses for different resources?

– If there are significant differences in the responsiveness of the tree species, can these be related to plant traits?

Add on Experiment• How tree seedlings grow in response to a number

of different grass species, representing more palatable species that dominate in moderately and undergrazed conditions and less palatable species that replace them in their local environment under heavy grazing?

• Growth response of the different tree species seedlings in competition with palatable and unpalatable grass species at both Indian sites.

• Heteropogon contortus (more palatable), Chloris dolichostachya (less unpalatable)

L1L0

W1

W0

N0G2

N1G1

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N1G0

N0G0

N1G2

2 m1.6 m1 m1.6 m

1.6 m

1 m

1.6 m

2 m

15.6 m

10.4 m

Block

W1DL0

N0G1

N1G2

N0G2

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N0G1

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1.6 m

1 m

Thanks

raghubansh@gmail.com