Transcript Indian Savannas

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
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