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Indian Savannas A.S. Raghubanshi Banaras 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. 2. 3. 4. 5. Sehima-Dichanthium Dichanthium-Cenchrus-Lasiurus Phragmites-Saccharum-Imperata Themeda-Arundinella Temperate Alpine Indian Savanna Types (Dabadghao and Sankarnarayan, 1973) Grassland Type Climatic Zone Soil Areal extent (million Km2) Distribution SehimaDichanthium Tropical Red, black laterite 1.74 Most of South India, Maharastra, MP, Chhattisgarh, some parts of U.P., Punjab, Gujarat and West Bengal DichanthiumCenchrusLesiurus Subtropical, Semi-arid Alluvial 0.436 North Gujarat, Rajasthan excluding Arawalis, western UP, Delhi, Haryana, Punjab, parts of Jammu PhragmitesSaccharumImperata Humid, per-humid various 2.8 Upper UP, NEH, Assam, West Bengal, North Bihar ThemedaArundinella Subtropical Forest hill 0.26 soils 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 – • Dichanthium-CenchrusLasiurus – • Subtropical, semi arid Phragmites-SaccharumImperata – • Tropical, dry sub humid 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). Fire Deciduous Forest Savanna Woodland Exploitation Scrub Woodland Further exploitation and grazing Tree removal Tree Savanna Thicket Further degradation Further degradation Shrub Savanna Scattered Shrubs Overexploitation and over grazing Discontinuous Thicket Overexploitation and over grazing Pseudosteppe Pandey & Singh 1991 Land Use Change Forest Savanna Protected Grazed Total Herbaceous Woody Total Herbaceous Woody NPP (Mg ha-1 yr-1) 18 Pandey & Singh 1992 16 14 12 10 8 6 4 ANP BNP 2 0 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 Burning South Indian Grasslands NPP 5294-6962 g/m2/yr 900 Unburned Burned Total Plant Biomass (gm-2) 800 700 600 500 400 300 200 100 0 M J 1992 J A S O N D J 1993 F M A M J J A S O N D J 1994 F M A 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 Ombrothermic diagram leafing Leaf-fall Flowering fruiting 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. 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 Changes in Savanna Biomes under B2 scenario Moist savanna Dry savanna Current (%) 32.52 33.07 Projected (%) 0.56 4.34 Change (%) -31.97 -28.73 100 y = -0.6113x + 71.44 2 R = 0.6991 ; P= 0.0004 80 y = -0.71x + 83.844 R2 = 0.574 P=<0.0001 80 Herb Cover (%) Tree Canaopy cover (%) 100 60 40 20 60 40 20 0 0 20 40 60 Lantana cover (%) 80 100 0 0 20 40 60 Lantana cover (%) 80 100 Shannon H' for Herbaceous layer Relationship of Lantana cover with Different Vegetation Parameters 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 y = -0.0074x + 1.0603 2 R = 0.4047 : P = <0.0001 0 20 40 60 80 Lantana cover (%) 100 Indian Experimental Sites • Vindhyan HighlandsBiodiversity Park Area, Banaras Hindu University • Sariska Tiger ReserveRajasthan Soil fertility Aridity Dry 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) L0 W1 N0 G2 L1 N1 G0 N0 G0 Block N1 G1 1.6 m 1m N1 G1 N0 G0 N1 G0 N0 G1 1.6 m 1m N1 G2 N0 G1 N1 G2 N0 G2 1.6 m 2m W0 N0 G1 N1 G2 N0 G1 N1 G0 N1 G0 N0 G0 N1 G2 N0 G2 N1 G1 N0 G2 N1 G1 N0 G0 1.6 m 1 m 1.6 m 2m 10.4 m W1 D L0 15.6 m Thanks [email protected]