Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 October 2021 | 13(12): 19702–19713
ISSN 0974-7907 (Online) | ISSN 0974-7893
(Print)
https://doi.org/10.11609/jott.7296.13.12.19702-19713
#7296 | Received 03 April 2021 | Final
received 25 July 2021 | Finally accepted 02 September 2021
Grass species composition in
tropical forest of southern India
M. Ashokkumar
1, S. Swaminathan 2 &
R. Nagarajan 3
1 Bombay Natural History Society,
Hornbill House, S.B. Singh Road, Mumbai, Maharastra
400001, India.
1 Centre for Wildlife Studies,
Kerala Veterinary and Animal Sciences University, Pookode,
Kerala 673576, India.
2 Wildlife SOS, Bannerghatta
National Park, Bengaluru, Karnataka 560083, India.
3 PG and Research Department of
Zoology and Wildlife Biology, A.V.C. College, Mannampandal,
Mayiladuthurai, Tamil Nadu 609305, India.
1 vimalashok7@gmail.com
(corresponding author), 2 swaminathan@wildlifesos.org, 3 r.nagarajan@ex.ac.uk
Editor: P. Ravichandran, Manonmaniam Sundaranar University,
Tirunelveli, India. Date of publication: 26 October
2021 (online & print)
Citation: Ashokkumar,
M., S. Swaminathan & R. Nagarajan (2021). Grass species composition in tropical forest of southern India. Journal of Threatened Taxa 13(12): 19702–19713. https://doi.org/10.11609/jott.7296.13.12.19702-19713
Copyright: © Ashokkumar
et al. 2021. Creative Commons Attribution
4.0 International License. JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by providing adequate credit to the
author(s) and the source of publication.
Funding: Hill Area Development Programme (HADP)/Western Ghats
Development Programme (WGDP), Udhagamandalam,
The Nilgiris.
Competing interests: The authors
declare no competing interests.
Author details: Ashokkumar Mohanarangan (MA) is a wildlife biologist,
completed his master’s and PhD in Wildlife biology, from AVC College. He has
been associated with organizations such as WWF-India, BNHS and AVC college
providing technical support. He is passionate about wild animal ecology and
conservation. Presently he is working as Teaching Assistant at KVASU-CWS. Shanmugavelu Swaminathan (SS) is a wildlife
biologist, who has been working on large mammal populations, carnivore ecology
and wildlife management for more than 30 years in the Western Ghats. Presently he is working as a senior wildlife
biologist at Wildlife SOS. Rajaratinavelu Nagarajan (RN) is the Principal and
professor and head of the Zoology Dept. A.V.C College and Honorary Associate Professor
of Envt. Sc., University of Exeter, UK. He has more than 30 years of research and
teaching experience. He is an eminent
scholar and excellent mentor, who has always been a source of inspiration.
Author contributions: MA developed the concept, formulated
a hypothesis, and carried out data analysis. SS supported in receiving funds,
field data collection and preliminary analysis. Dr. RN provided technical
support and supervised the work. All the authors contributed to the preparation
of the final manuscript.
Acknowledgements: We thank the Tamil Nadu Forest
Department for permission to research within Mudumalai
Tiger Reserve. We thank the Hill Area Development Program (HADP) for funding
the study. We thank the Bombay Natural History Society, Nilgiri
Wildlife and Environment Association, and A.V.C. College Department of Zoology
and Wildlife Biology for their support.
Abstract: Grass composition was assessed by
plot method (1 m2; n= 1,749) in three habitats (dry deciduous-DDF,
moist deciduous-MDF, and thorn forest-TF) at Mudumalai
Tiger Reserve, southern India across different seasons from Jan 2004 to Dec
2007. The grass species richness and availability (per cent composition) varied
significantly with habitats. Seventy-four species of grasses and sedges were
recorded in all three habitats, with a few species common in all habitats.
Grass availability varied significantly in different habitats across seasons
and was positively influenced by precipitation. Among biotic factors,
regeneration and shrub density had a primary influence on grass availability,
followed by herb, sedge and weed density. The principal coordinate analysis
revealed seven major associations in the tropical forest. There were
considerable changes in the composition and association of grasses when
compared to the past. Fire resistant species such as Themeda
triandra, Heteropogan
contortus and T. cymbaria
dominated in the DDF. Grass species Aristida/Eragorstis were recorded in the TF, which were
considered as indicators of heavy grazing pressure. Grass species that were
reported rare and sporadic in the earlier study were not recorded, which
emphasizes better pasture management in the tropical forest. Grass species composition
and availability was threatened by invasion of weeds.
Keywords: Graminae, Mudumalai
Tiger Reserve, influence of fire on grass, Themeda
triandra, Heteropogon
contortus, Themeda cymbaria.
INTRODUCTION
Grasslands are highly dynamic
ecosystems encompassing natural and semi-natural pastures, woodlands and scrubs
dominated by grasses (Blair et al. 2014). Grasses are one of the important
sources of biodiversity and the primary food source for many herbivores that
support ecosystem function, agricultural sustainability, and livelihood for
many pastoral communities (Sala & Paruelo 1997;
White et al. 2000). In India, 1,506 species of grass belonging to 266 genera
were reported (Kellogg et al. 2020). Peninsular India has maximum diversity and
endemism (Karthikeyan 1989). The study of grass species is important since they
are sensitive to global warming and altered precipitation patterns, and exhibit
immediate response to climate change (Knapp & Smith 2001).
Grass species in the Western
Ghats are threatened by domestic livestock, mining, wind-farms, plantations,
canals and dams have led to degradation and loss of grassland habitats (Vanak 2013). The invasion of exotic species into tropical
forest threatens grasslands (Srinivasan 2011; Ashokkumar
et al. 2012). Invasions not only affect
grass composition but also the foraging efficiency of herbivores (Wilson et al.
2013). Pasture management is essential in protected area management strategies
to reduce the human-animal interactions. Although grasses have wide ecological
amplitude and several adaptations to withstand trampling, grazing, fire, flood,
and drought, they face severe competition for light and nutrients from
aggressive wood species and invasive plants in tropical forests.
Mudumalai Tiger Reserve (MTR) is located
in the Western Ghats, one of 34 global biodiversity hotspots (Myers et al.
2000). There were no earlier studies on the dynamics of grass species
composition and diversity in similar tropical forest in Southern India. Though
tree, herb and shrub species were studied in detail (Robert et al. 2002; Nath
et al. 2006) information on grass species is lacking in the tropical ecosystem.
In addition, the study area also has baseline data on grass species composition
studied a decade before (Sivaganesan 1991), which
enabled comparison with the present study. Sivaganesan
(1991) studied grass composition in the study area in the year 1985, and he has
studied grass species composition using strip transects of one kilometer length (n= 20) and laid 1 m2 plots at
every 250 m interval, resulting in sampling of five plots per transect and a
total of 100 plots across different vegetation types.
Seasonal changes in the phenology
of grass species influence herbivore movement, distribution and abundance (Sivaganesan 1991; Baskaran 1998). Cattle grazing and fire
have major impacts on species composition of woody plants (Kodandapani
et al. 2008) and grasses. The present study investigated the effect of
environmental factors on grass availability (grass abundance) and grass
association in tropical forests of Southern India. Studies on the grass association
help to understand the grass communities in tropical forest and their dynamics
due to climatic and anthropogenic factors.
Study area
Mudumalai Tiger Reserve (MTR) is located
in the Nilgiris District of Tamil Nadu (11º 32´ and
11º 42´ N and 76º 20´ and 76º 45´ E ). It extends over an area of 321 km2
and forms a part of the Nilgiris Biosphere Reserve
(Figure 1). It is part of a contiguous
stretch of forest with Bandipur Tiger Reserve to the
north, Segur Reserve forest to the east, Wayanad
Wildlife Sanctuary to the west, and Gudalur forest
division to the South. Altitude varies
from 485 to 1,226 m with a general elevation of about 900 to 1,000 m. The
annual rainfall varies from 1,001 mm to 1,648 mm. The sanctuary receives rain
from both south-west (May to August) and north-east (September to December)
monsoons. Based on climate seasons can be classified into dry season (January
to April), first wet season (south-west monsoon) and second wet season
(north-east monsoon). The three major
forest types in the study area are tropical moist deciduous forest (MDF), dry
deciduous forest (DDF) and tropical thorn forest (TF) (Champion & Seth
1968).
The major tree species
association in MDF is Lagerstoroemia-Terminalia-Tectona. The ground flora mainly composed of Helicteres isora, Desmodium sp., and Curcuma sp. The dominant
grass species are Cyrtococcum accrescens, C. oxyphyllum,
Bothriochloa pertusa,
Oplismensus compositus
and Oryza meyeriana occur. Bamboo Bambusa
arundinacea is very common along the perennial
water sources. Swamp vegetation mainly
consists of tall grass Cenchrus hohenackeri. Tree species in DDF is dominated by Anogesis latifolia,
Terminalia crenulata, Tectona
grandis, Diospyros montana,
and Gmelina arborea.
Shrubs include Helicteres isora, Antidesma diandram, and Pavetta
indica. Grasses species is dominated by tall
perennial rhizomatous grasses such as Themeda
cymbaria, Cymbopogon
flexuosus, and Apluda
mutica in dry deciduous tall grass area. T. triandra, Setaria
intermedia, and Dicanthium caricosum are common in short grass area. TF is
dominated tree species such as Acacia sp., Albizia
sp., Premna tomentosa,
Dalbergia lanceolaria,
and Ziziphus sp. The shrub species
includes Acacia pinnata, Canthium
parviflorum, Rhus
mysorensis, and Mytenus
emarginatus. Grass species in TF includes Aristida adscencsionis,
Heteropogon contortus,
and Tragus mongolorum. The study area is
threatened by habitat degradation from overgrazing and human disturbance.
METHODS
Five transects each of
three-kilometre length were marked in three habitats (DDF 3; MDF 1, and TF 1;
Figure 1). Two transects in Mudumalai range, two
transects in Theppakad range and one in Masinagudi range were marked and sampled. The locations of
transects were given in the georeferenced study area map (Figure 1). A total of
30 plots (1 m2) were laid at an interval of 100m in each transect.
Transects were sampled two times per season in alternate months. A total of 825
plots were laid in all three vegetation types (DDF 493, MDF 169, TF 103) in
different seasons. In addition to this data, grass species composition, which
was collected as part of Gaur Bos gaurus
foraging ecology study was used. A total of 924 plots (DDF 669, MDF 110, TF
145) of 1 m2 were laid in the Gaur foraged areas in different
habitats, to assess the forage plant species including grass species and their
consumption.
A herbarium of grass species that
include both grass and sedges was made for confirmation of the species
identity. All specimen vouchers were deposited in the Center
for Ecological Sciences, Indian Institute of Sciences, Bangalore. Plant species
were identified using Gamble (1935), Saldanha & Nicolson (1976), Saldanha
(1984, 1996), Sharma et al. (1977), and Kellogg et al. (2020). Grass cover in
each quadrat was visually estimated by giving a percent cover. Percent cover
was given according to the proportion of area (within the quadrat) covered by
grass (Giles 1971; Sivaganesan 1991). The other
variables such as grass height, percent green grass, grass texture, and
phenology were recorded (Jarman & Sinclair, 1979;
Menaut and Cesar 1979; Sivaganesan
1991; Baskaran 1998).
Precipitation data was collected
on monthly basis from weather stations located at the different habitats of the
study area maintained by Center for Ecological
Science, Indian Institute of Science. The information on extant and frequency
of fire was collected from forest management plan and studies on fire in the
study area (Kodandapani et al. 2008). Grass species
richness, mean percent availability and grass height were tested using ANOVA.
The effect of environmental and
biotic variable on grass availability was tested using multiple regressions.
The relationship between the percent grass availability and environmental
factors (habitat, season, precipitation and fire) and biotic factors (shrub,
regeneration, herb, sedges, and weed) were investigated using multiple
regression. The variations among the habitats, seasons and fire were controlled
by entering these predictors as a dichotomous variable.
Grass species association was
determined by principal co-ordinate analysis and species association was
plotted in Euclidean space. The variables used in the analysis are percent
composition of grass, height, habitat, elevation, fire, and spatial locations
in the study area. Statistical analyses were performed by using Windows based
statistical package viz. SPSS 21.0 (SPSS Inc., Chicago, IL, USA) and Past
software 3.17 (Hammer et al. 2001).
Results
A total of 74 species of grasses
and sedges were recorded in the MTR with a maximum of species in DDF followed
by TF and MDF (Table 1). MDF had lower grass species diversity (0.6) than other
habitats. Though, species richness was high in TF (3.4), the mean percent
availability of grass was less in TF (12.7%) than DDF (19%) and MDF (17%). The
species richness and mean percent availability of grass varied significantly
among habitats. The equitability of species
was equal in all the habitats. While grass species diversity was higher in TF,
the abundance of grass was higher in deciduous forests (MDF and DDF).
Species composition and
availability
Grass species composition varied
among different habitats. Altogether, 66 grasses and eight species of sedges
were recorded in three habitats. There were 21 species were common in all
habitats, viz., Themeda triandra,
Oplismenus undulatifolius, Setaria intermedia, S. flavidum,
and S. pumila (Table 2). Among different grass
species Perotis indica,
Cymbopogon sp., Cappillipedium
assimile, E. spicatus,
and Kyllinga sp. were recorded only in
DDF. Likewise, species such as Cyrtococcum oxyphyllum, Paspalum conjugatum, and Cenchrus
polystachios in MDF and Bothriochloa
sp. Eragrostis atrovirens,
Pseudanthistiria umbellata,
P. tripheron, and Leersia
hexandra were recorded only in TF.
In DDF dominant grass species
included both tall and short grass species. Tall grass species include T. cymbaria (30%), I. cylindrica
(13%) and S. fertilis (13%) and short grasses
were T. triandra (27%), O. undulatifolius (25%) and S. intermedia (22%). In
MDF, the dominant species were C. oxyphyllum, E. indica, C. patens, P. polystachion
and A. compressus. Swamp areas of both DDF and
MDF were dominated by grass species such as C. polystachyios,
A. compressus, I. cylindrica,
and E. indica. Dominant grass species in TF
were D. bicornis, P. umbellata,
D. caricosum, and A. mutica (Table 2).
The percent grass composition
varied significantly across season (F= 11.6; p <0.001) in different habitats
(F= 13.92; p <0.001). Fire was not recorded in the TF area during the study
period. Grass availability was higher in the MDF during dry season (27.7%). The
mean percent available grass was highest in first wet season in the DDF (46 %)
in the fire burnt areas (Figure 2). Grass availability was low in second wet
season in TF. The three-way interaction among fire, habitats and seasons in
ANOVA on grass availability was significant. The abundance of grass was higher in
the DDF and MDF in wet seasons in the unburnt areas.
The influence of environmental
variables on grass availability
The grass availability had a
linear relationship with predictors. The model was highly significant and
explained 23% variations in grass availability (%). Previous month
precipitation positively influenced grass availability. All the other variables
negatively influenced grass availability. From the Standardized Partial
Regression Coefficients (SPRC), it was inferred that the shrubs had the primary
influence on growth of grasses followed by sedges, regeneration, herbs, and
weed (Table 3; Figure 3). Furthermore,
the co-efficient of habitat and season indicated that the percent availability
of grass reduced significantly among three habitats and seasons. Though, fire
negatively influenced grass availability, it was not statistically significant
in the model.
Grass species association
Principal coordinate analysis
(multidimensional scaling) summarizes inter grass species association based on
dissimilarity in a Euclidean space. There were seven distinct clusters formed.
Among different variables elevation, height and percent composition
collectively contributed 87% of the variance. There were four distinct clusters
identified based on elevation and further separation was based on habitat and
microhabitat (Figure 4). The first cluster consisted of grass species such as Themeda triandra, Setaria intermedia, Enteropogon
dolichostachyus and Oplismenus
undulatifolius in DDF. The second cluster
consisted of Axonopus sp. (Image 1e) and Bothriochloa bladhii
in riverine forest. The third cluster consisted of thorn forest species such as
Arthraxon, Chrysopogon,
Psudanthistiria, and Cynodon
sp. Forth cluster consisted of Cenchrus, Sporobolus, Centotheca,
and Eragrostis sp. in dry deciduous tall grass
at 1,000 m elevation. Fifth cluster composed of T. cymbaria,
Ischaemum, Cyrtococcum,
and Kyllinga species in the moist deciduous
forest. The sixth cluster composed of Imperata,
Echinochloa, and Cenchrus
hohenackeri in swamp areas of MDF. Dry deciduous
higher elevation regions composed of Arthraxon,
Cappillipedium, and Setaria
species.
Discussion
A total of 66 species of grasses
and eight sedges were recorded in the Mudumalai Tiger
Reserve. The number of species recorded was lower than earlier report (75
species) in the study area (Sivaganesan 1991). The
marginal variation in the species composition could be due to difference in the
area of sampling, earlier study covered greater area of sampling. Sivaganesan (1991) divided the tiger reserve into five
zones and did sampling in five transects with 30 plots in each transects with
250 m interval. The number of transect in Moist deciduous forest is less than
earlier study. Further, there were invasion of exotic weed species such as Lantana
camera and Chromolena odorata in the study area (Ashokkumar
et al. 2012; Wilson et al. 2013), which were less and restricted to tourism
zone in the study area. Whereas the growth of weeds was extensive and occupied
all the grassland patches of DDF and MDF.
Grass species richness,
composition varied among habitats, with maximum number of species recorded in
DDF followed by TF. Cymbopogon sp. found in
hill slopes of DDF in the elevation range of 2,000–3,000 m, P. polystachyon recorded in swamp areas of MDF in the
elevation of above 1,000 m, and A. adscensionis
found in TF in the elevation less than 600 m. Grass species such as C. polystachios, L. hexandra,
and I. cylindrica were observed in the swamps
of MDF and DDF in MTR. This might have been influenced by high moisture content
and nutrients of the soil (Skerman & Riveros 1990). Amarasinghe & Pemadasa (1982) have also concluded that the complex
interaction of edaphic factors, altitude, precipitation and human disturbance
were responsible for a variation on Montane grasslands in Sri Lanka. Thus, the
grass composition varied depending on altitudes and moisture content of the
soil.
Factors influencing grass
composition
Shrubs had the primary influence
on the grass growth followed by sedges, regeneration, herbs and weeds. Studies
done in Prairie grasslands in Canada indicated that shrubs strongly reduced
available soil nitrogen and the secondary growth of shrubs allowed them to
accumulate more biomass and height that eventually displaced the grass species
(Kochy & Wilson 2000). The grass species Axonopus sp. was recorded only in L. camara invaded areas. This grass species was originated
in United States and this species itself considered as weed (Skerman & Riveros 1990).
Therefore, it competes well with weed species. In addition, both L. camara and Axonopus
sp. grow well in humid areas and thus, they do have similar microhabitat
preference. The microhabitat preference and weed resistance properties of Axonopus sp. enabled successful survival in L. camara invaded areas. Grass species that were recorded
in C. odorata invaded areas (Cenchrus, Setaria,
and Chrysopogon) seem to have high
alkaline tolerance (Skerman & Riveros
1990). Thus, grass species had species-specific interaction with weed species.
The percent availability of grass varied significantly among three habitats and
seasons. The seasonal variation in grass availability was due to phenological
changes of grass species due to senescence. The phenology of tropical grasses
are moisture driven, with germination occurring shortly after the rains of
first wet season. Grass senescence occurs in the end of the second wet season
or in the early dry season. Both the reproduction and senescence have been
influenced by multiple factors such as temperature, rainfall and photoperiod
(Blair et al. 2014). Hence the availability of grass was higher in the wet
seasons.
The percent grass available was
significantly positively correlated with precipitation. Rainfall varied
spatiotemporally across vegetation types in the study area. Such a rainfall
pattern is ecologically significant and perhaps a boon to the dynamics of the
study area. Elephant habitat preference was related to the rainfall in the
study area (Sivaganesan 1991). In Africa, several
ecologists (Leuthold & Sale 1973; Caughley &
Goddard 1975; Leuthold 1976; Eltringham 1979;
McNaughton 1985) documented the significance of the rainfall on the habitats
and distribution pattern of the larger herbivores. The western part of the
study area with MDF receives rainfall during south-west monsoon and eastern
part (TF) during north-east monsoon. The grass growth and phenological changes
can be seen depending on the precipitation.
Variation in grass composition in
the study area
Comparison of grass species
composition with earlier study Sivaganesan (1991)
revealed that though, there were no changes in the dominant grass species there
were considerable changes in the minor grass species composition. The principal
coordinate analysis revealed seven distinct clusters of grass species
association. Sivaganesan (1991) reported four
distinct clusters of grass association in the study area: Themeda-Cymbopogon-Imperata
in the dry deciduous tall grass area (Image 1a), Cenchrus-Themeda-Imperata
in the swamp area (Image 1c), Cyrtococcum-Apluda-Arthraxon
in MDF, and Themeda-Heteropogon-Digitaria-Apluda
in the TF area. Changes occurred in the grass species composition in all
habitats. The percent availability of grass was reduced when compared to past,
possibly due to greater extent of invasion of exotic species.
Sivaganesan (1991) indicated that annual
fire seems to influence the species association and succession of species at Mudumalai. He reported that fire-resistant species such as T.
triandra, H. contortus,
and T. cymbaria have survived and dominated
the dry deciduous forest. This is unison with his finding that the above species
also dominated in DDF based on the present study. The fire frequency was also
high (22 incidences per annum), and more area was burnt in DDF (56%) than other
habitats (Ashokkumar 2011). Grass species which were
reported rare and sporadic in the earlier study were not reported in the
present survey, for example Chionachne koenigii in DDF and Oryza meyeriana
in MDF were not recorded. Similarly, percent composition of Apluda
sp. and Arthraxon sp. were less in MDF.
Fewer species were recorded in MDF, but the mean percent available grass was
more in MDF. The dominant grasses in MDF
were tall grass species in the swamp areas which grow up to 3 m, and thus their
percent composition was higher. Earlier TF was dominated by T. triandra and H. contortus (Sivaganesan 1991) and these species were poorly represented
during the present survey and TF is dominated by Digitaria
sp., Pseudanthistiria umbellata.
TFs facing severe pressure due to cattle grazing and removal of cattle dung
from the forest floor had severely affected the forest regeneration and
nutrient cycle. Earlier studies on
livestock populations reported 7,248 cattle in the fringe areas (Silori & Mishra 2001) allowed to free graze in the
reserve. Continued grazing affects grass availability and species composition.
Protection from cattle grazing
Grass species Aristida-Eragrostis
were recorded in the TF which were considered as an indicator species of
deteriorated grassland (Skerman & Riveros 1990). Grass species such as Themeda-Heteropogon-Digitaria-Apluda
were dominant species in thorn forest reported in the past. At present, the
quality of grass pastures was too poor to provide any grazing. Severe cattle
grazing should be stopped for four or five years to allow the succession to
progress towards fair condition represented by Cynodon
dactylon as the first step toward improvement.
Thus grasslands of TF required protection of pasture from cattle grazing or at
least reduction of cattle pressure for at least four to five years to recover.
Species reduced by overgrazing can recover if there were no change in the
physical environment.
Influence of fire on grass
availability
In the study area during the peak
of dry season wildfire was common. These, wildfires were set by the villagers
to get fresh fodder for their cattle and easy to move around in burnt areas.
Fire in grass patches last only for a short time and high temperatures were
maintained for only a few seconds.
Temperatures at soil level rise steeply to 175–200 °C depending on wind,
height and density, and usually return to ambient temperature within a few
minutes (Mondal & Sukumar 2014). The soil temperature at a depth of about
two centimeters changes little, varying at most by 14
C. The effect of subterranean portions
of grasses is thus slight.
The study area as a whole had a
fire-return interval of 3.3 years (Ashokkumar 2011).
The vegetation type with the highest mean area burnt was at DDF (Shorea sp. dominant) with 56.6%, whereas, TF had the
lowest mean area burnt with 14.6%. Forest fires burnt an average of 30% (98 km2/year)
of the forests in each year. Grass biomass was significantly low in burnt
areas. Distance from the park boundary was reported as an important factor that
predicts the fire-return interval in the study area (Kodandapani
et al. 2008). Grass biomass was significantly low in the fire burnt areas of
DDF and MDF. Sivaganesan (1991) indicated that the
effect of annual fire seems to influence the grass species association and
succession of species. On other hand, the annual fire plays an important role
in the maintenance of forest stands at deciduous forest and seedling growth.
The forest fire scorches the tree seeds of Tectona
grandis and facilitates the growth by removing a
portion of the seed coat (Seth & Kaul 1978). But overall tree species
diversity, structure and regeneration were reduced by fire in tropical forest (Kodandapani et al. 2008), further, the results suggest both
grass availability and composition altered by fire.
Conclusions
The present study provides
baseline information on grass species composition in the tropical forest of
southern India. There were considerable changes occurred in the grass species
composition when compared to past. Grass association revealed seven major types
of association in the tropical deciduous forest. Grasslands of TF were
dominated by Aristida-Eragrostis indicators
of heavy gazing and require protection of pasture from cattle grazing or at
least reduction of cattle pressure to recover. Grass composition and
availability was positively influenced by rainfall and reduced by fire in the
tropical deciduous forest. Further grass availability and composition is
threatened by invasion of weeds.
Table 1. Mean percent grass
available (±SD), species richness per plot, diversity and equitability of grass
(and sedges) in different habitats of Mudumalai Tiger
Reserve.
Habitata |
Total number of species |
Species richness (S) / plot (±SD) |
Mean percent (%) ± SD |
Index value |
||
Shannon Weiner Diversity (H') |
Equitability (J') |
|||||
DDF (n= 1,162) |
61 |
2.9 ± 1.30 |
18.8 ± 22.45 |
0.65 ± 0.40 |
0.68 ± 0.22 |
|
MDF (n= 279) |
33 |
2.7 ± 1.34 |
17.5 ± 21.67 |
0.60 ± 0.42 |
0.69 ± 0.21 |
|
TF (n= 248) |
53 |
3.4 ± 1.79 |
12.7 ± 16.79 |
0.80 ± 0.45 |
0.72 ± 0.21 |
|
Overall (n= 1,749) |
74 |
3.0 ± 1.42 |
17.3 ± 21.40 |
0.67 ± 0.42 |
0.69 ± 0.22 |
|
ANOVA |
F |
|
F1645= 20.3 |
F 2,821= 14.04 |
F 1645= 20.5 |
F 1432= 5.18 |
P |
|
p <0.001 |
p <0.001 |
p <0.001 |
p <0.001 |
a -DDF—Dry
Deciduous Forest | MDF—Moist Deciduous Forest | TF—Thorn forest.
Table 2. Percent grass (grass and sedges) available in
different habitats of Mudumalai Tiger Reserve during
the study period (Data sorted in descending order based on total percent).
|
Species |
Habitats |
Total |
||
DDF |
MDF |
TF |
|||
|
Grass |
|
|
|
|
1 |
Axonopus compressus |
45.7 ± 39 |
28.2 ± 31.67 |
- |
33.4 ± 34.34 |
2 |
Cyrtococcum oxyphyllum |
- |
33.4 ± 22.19 |
- |
33.1 ± 22.3 |
3 |
Cenchrus hohenackeri |
27.4 ± 24.17 |
36.3 ± 33.65 |
- |
33.1 ± 30.6 |
4 |
Themeda cymbaria |
30.4 ± 22.45 |
25 ± 17.32 |
- |
30.1 ± 22.15 |
5 |
Themeda triandra |
27.2 ± 21.53 |
20.2 ± 20.17 |
23 ± 26.08 |
26.7 ± 21.68 |
6 |
Oplismenus undulatifolius |
25.1 ± 24.99 |
4.3 ± 4.27 |
26.7 ± 24.9 |
25.3 ± 24.9 |
7 |
Axonopus sp. |
28.4 ± 31.12 |
|
6.5 ± 5.58 |
23.9 ± 29.19 |
8 |
Setaria intermedia |
22.3 ± 22.06 |
25 ± 7.07 |
31.4 ± 26.1 |
23.6 ± 22.78 |
9 |
Pseudanthistiria umbellata |
- |
- |
23.4 ± 20.47 |
23.4 ± 20.47 |
10 |
Centotheca lappacea |
- |
- |
40 ± 0.01 |
20.5 ± 27.58 |
11 |
Setraria flavidum |
17.5 ± 18.03 |
2 ± 0.01 |
25.9 ± 16.92 |
18.9 ± 18.06 |
12 |
Setaria pumila |
18.5 ± 21.39 |
28 ± 0.01 |
17.3 ± 16.38 |
18.5 ± 21 |
13 |
Enteropogon dolichostachyus |
16.2 ± 18.84 |
14.1 ± 14.95 |
20.7 ± 24.35 |
16.6 ± 19.42 |
14 |
Eleusine indica |
22.4 ± 31.09 |
14 ± 13.86 |
7.4 ± 7.16 |
16.3 ± 22.74 |
15 |
Cenchrus polystachios |
- |
15.6 ± 13.53 |
- |
15.6 ± 13.53 |
16 |
Heteropogon contortus |
19.2 ± 20.03 |
- |
10 ± 13 |
15.3 ± 17.93 |
17 |
Cyrtococcum accrescens |
8.7 ± 13.06 |
20.1 ± 21.69 |
- |
15.1 ± 19.3 |
18 |
Setaria verticillata |
- |
|
15 ± 0.1 |
15 ± 0.1 |
19 |
Imperata cylindrica |
13 ± 13.9 |
16.2 ± 28.06 |
- |
13.9 ± 18.92 |
20 |
Digitaria sp. |
11.6 ± 12.51 |
12.3 ± 15.37 |
16.9 ± 12.8 |
13.6 ± 12.82 |
21 |
Bothriochloa sp. |
- |
- |
13.6 ± 7.47 |
13.6 ± 7.47 |
22 |
Panicum sp. |
14.4 ± 8.46 |
- |
1 ± 0.01 |
13.1 ± 9.04 |
23 |
Digitaria bicornis |
13.8 ± 21.91 |
4 ± 1.73 |
9.8 ± 15.84 |
12.2 ± 19.82 |
24 |
Digitaria griffithii |
11.9 ± 13.2 |
5 ± 0.01 |
12 ± 6.35 |
11.9 ± 12.65 |
25 |
Perotis indica |
11.9 ± 17.94 |
- |
- |
11.9 ± 17.94 |
26 |
Panicum tripheron |
7.8 ± 11.67 |
- |
15.2 ± 14.85 |
11.8 ± 13.87 |
27 |
Urochloa distachya |
12.2 ± 11.92 |
12.5 ± 10.61 |
10.6 ± 9.93 |
11.8 ± 11.23 |
28 |
Apluda mutica |
9.4 ± 11.32 |
9.2 ± 13.09 |
18 ± 18.37 |
11.8 ± 14.16 |
29 |
Dichanthium caricosum |
10 ± 0.01 |
5 ± 0.01 |
13 ± 9.08 |
11.4 ± 8.02 |
30 |
Eragrostis tenuifolia |
15.8 ± 23.01 |
- |
3.1 ± 2.77 |
11.4 ± 19.53 |
31 |
Sporobolus fertilis |
13 ± 12.75 |
- |
1 ± 0 |
11.4 ± 12.54 |
32 |
Ischaemum ciliare |
10.2 ± 10.98 |
11 ± 15.25 |
- |
10.9 ± 14.7 |
33 |
Setaria palmifolia |
10.8 ± 12.59 |
1 ± 0.01 |
10 ± 0.01 |
10.5 ± 12.33 |
34 |
Eragrosteilla sp. |
11.8 ± 8.67 |
- |
8.2 ± 13.66 |
10.1 ± 11.39 |
35 |
Eragrosits atrovirens |
- |
- |
10 ± 7.07 |
10 ± 7.07 |
36 |
Oplismenus compositus |
6.3 ± 10.4 |
13.2 ± 13.87 |
- |
9.9 ± 12.79 |
37 |
Paspalum conjugatum |
- |
9 ± 9.64 |
- |
9 ± 9.64 |
38 |
Aristida adscensionis |
8.4 ± 7.6 |
- |
8.8 ± 10.18 |
8.7 ± 9.89 |
39 |
Cynodon radiatus |
15 ± 0.1 |
- |
2 ± 0.01 |
8.5 ± 9.19 |
40 |
Echinochloa colona |
6.3 ± 7.51 |
15 ± 0.1 |
- |
8.5 ± 7.51 |
41 |
Themeda tremula |
7.2 ± 3.13 |
5 ± 0.1 |
20 ± 0.1 |
8.5 ± 5.4 |
42 |
Dactyloctenium aegyptium |
13.9 ± 16.5 |
- |
5.3 ± 7.09 |
8.5 ± 11.8 |
43 |
Sehima sp. |
7.3 ± 15.34 |
- |
11.5 ± 15.73 |
8.2 ± 15.23 |
44 |
Tragus mongolorum |
1 ± 0.01 |
- |
8.1 ± 7.74 |
8 ± 7.73 |
45 |
Sporobolus sp. |
7.8 ± 9.15 |
7.5 ± 11.22 |
4.2 ± 3.49 |
7.5 ± 9.01 |
46 |
Alloteropsis cimicina |
5.4 ± 8.93 |
|
24.9 ± 25.6 |
7.5 ± 13.38 |
47 |
Chrysopogon sp. |
- |
- |
7.5 ± 9.46 |
7.5 ± 9.46 |
48 |
Cymbopogon sp. |
7.2 ± 5.18 |
- |
- |
7.2 ± 5.18 |
49 |
Cappillipedium assimile |
6.8 ± 3.95 |
- |
- |
6.8 ± 3.95 |
50 |
Cynodon dactylon |
7.1 ± 5.73 |
1 ± 0.01 |
3.3 ± 2.08 |
6.4 ± 5.54 |
51 |
Eragrostis sp. |
1 ± 0.01 |
- |
6.6 ± 12.56 |
6.3 ± 12.22 |
52 |
Oryza meyeriana |
7.3 ± 10.01 |
4.7 ± 9.64 |
10 ± 0.1 |
5.8 ± 9.74 |
53 |
Sporobolus diandrus |
4.8 ± 3.77 |
10 ± 0.1 |
- |
5.8 ± 4.02 |
54 |
Digitaria abludens |
20 ± 0.1 |
- |
4.5 ± 4.96 |
5.1 ± 5.65 |
55 |
Elytrophorus spicatus |
5 ± 0.1 |
- |
- |
5 ± 0.1 |
56 |
Eragrosits abludens |
- |
- |
5 ± 0.1 |
5 ± 0.1 |
57 |
Cenchrus purpureus |
5 ± 0.1 |
|
- |
5 ± 0.1 |
58 |
Bambusa arundinacea |
5.4 ± 2.88 |
4.5 ± 4.37 |
1.7 ± 0.58 |
4.3 ± 3.74 |
59 |
Arthraxon sp. |
7.3 ± 8.62 |
- |
2.5 ± 1.9 |
3.1 ± 3.58 |
60 |
Panicum notatum |
- |
- |
3 ± 0.1 |
3 ± 0.1 |
61 |
Bothriochloa bladhii |
2 ± 0.1 |
- |
- |
2 ± 0.1 |
62 |
Isachne elegance |
2 ± 0 |
- |
- |
2 ± 0 |
63 |
Leersia hexandra |
- |
- |
2 ± 0.1 |
2 ± 0.1 |
64 |
Arthraxon lancifolia |
- |
- |
1.5 ± 0.58 |
1.5 ± 0.58 |
65 |
Mnesithea granularis |
1 ± 0.1 |
- |
1.5 ± 0.55 |
1.4 ± 0.53 |
66 |
Chrysopogon lawsonii |
1 ± 0.1 |
- |
- |
1 ± 0.1 |
|
Sedges |
|
|
|
|
67 |
Kyllinga melanosperma |
15.2 ± 22.46 |
7.1 ± 7.22 |
6.2 ± 7.95 |
12 ± 18.59 |
68 |
Mariscus madraspatanus |
6 ± 8.37 |
17.4 ± 26.83 |
2.5 ± 1.22 |
9.8 ± 17.98 |
69 |
Fimbristylis aestivallis |
7.4 ± 5.87 |
- |
6.2 ± 6.02 |
7 ± 5.73 |
70 |
Cyperus distans |
4.2 ± 4.91 |
8.1 ± 13.59 |
5 ± 0 |
4.9 ± 7.42 |
71 |
Cyperus rubicundus |
6.2 ± 5 |
- |
3.2 ± 3.75 |
4.2 ± 4.41 |
72 |
Fimbristylis sp. |
3.7 ± 2.36 |
- |
2.6 ± 2.4 |
3 ± 2.41 |
73 |
Kyllinga sp. |
2.6 ± 2.78 |
- |
- |
2.6 ± 2.78 |
74 |
Kyllinga tenuifolia |
2 ± 0.1 |
- |
1 ± 0 |
1.3 ± 0.58 |
DDF—Dry deciduous forest |
MDF—Moist deciduous forest | TF—Thorn forest | –—Species were not recorded.
Table 3. Multiple regression equation to investigate
the effect of environmental (habitat, fire and precipitation) and vegetation
factors on the grass availability (%) in Mudumalai
Tiger Reserve.
Independent variable |
Predictor |
Coefficients ± SE |
SPRC* |
t |
p |
Model (r2) |
Model (p) |
Grass (%) |
(Constant) |
38.17 ± 2.535 |
|
15.059 |
<0.001 |
23.1 |
p<0.001 |
Fire |
-0.76 ± 1.100 |
-0.015 |
-.694 |
0.488 |
|||
Habitat |
-3.59 ± 0.414 |
-0.191 |
-8.653 |
<0.001 |
|||
Season |
-2.60 ± 0.598 |
-0.138 |
-4.353 |
<0.001 |
|||
Previous month precipitation (mm) |
2.82 ± 0.403 |
0.229 |
6.998 |
<0.001 |
|||
Herb (%) |
-0.31 ± 0.042 |
-0.161 |
-7.286 |
<0.001 |
|||
Regeneration (%) |
-0.52 ± 0.063 |
-0.179 |
-8.206 |
<0.001 |
|||
Sedges (%) |
-0.37 ± 0.039 |
-0.200 |
-9.341 |
<0.001 |
|||
Shrub (%) |
-0.46 ± 0.038 |
-0.268 |
-12.096 |
<0.001 |
|||
Weed (%) |
-0.23 ± 0.043 |
-0.112 |
-5.254 |
<0.001 |
*—Standardized partial regression
coefficient.
For
figures & images - - click here
References
Amarasinghe, L. & M.A. Pemadasa (1982). The ecology of Montane grassland
in Sri Lanka, II- The pattern of four major species. Journal of Ecology
70: 17–23.
Ashokkumar, M. (2011). Population, foraging and activity
pattern of Gaur (Bos gaurus H. Smith, 1827) in
Mudumalai Tiger Reserve, Southern India. Ph.D.
Thesis, Bharathidasan University, Tiruchirappalli, Tamil Nadu, India, 159pp.
Ashokkumar, M., R. Nagarajan, S. Ilayaraja, S. Swaminathan & A.A. Desai (2012). Impact of plant weeds on grass
availability in Gaur (Bos gaurus H. Smith,
1827) foraging areas of Mudumalai Tiger Reserve,
Southern India. Indian Forester 138(12): 1131–1140.
Baskaran, N.
(1998). Ranging and
Resource utilization by Asian elephant (Elephas maximus Linnaeus) in Nilgiri Biosphere Reserve, South India. Ph.D. Thesis,
Bharathidasan University, Thiruchirappalli, India.
Blair, J., J.
Nippert & J. Briggs (2014). Grassland Ecology. In: Monson,
R.K. (ed). Ecology and the Environment, The Plant
Sciences, 8. https://doi.org/10.1007/978-1-4614-7501-9_14
Caughley, G. & J. Goddard (1975). Abundance and distribution of
elephants in Luangwa Valley, Zambia. East African Wildlife Journal 13:
39–48.
Champion,
H.G. & S.K. Seth (1968). Revised survey of forest types in India, Manager of Publication, New
Delhi. 404pp.
Eltringham, S.K. (1979). The ecology and conservation of
large African mammals. University Park Press, Baltimore, 286pp.
Gamble, J.S.
(1935). The Flora of
the Presidency of Madras. Adlard and Son’s Ltd., London, 143pp.
Giles, R.H.
(1971). Wildlife
Management Techniques. The Wildlife Society, Washington, 623pp.
Hammer, O.,
D.A.T. Harper & P.D. Ryan (2001). PAST: Paleontological Statistics
software package for education and data analysis. Palaeontol
Electron 4(1): 9
Jarman, P.J. & A.R.E. Sinclair
(1979). Feeding
strategy and the pattern of resource-partitioning in ungulates,pp.
130–163. In: Sinclair, A.R.E. & M. Norton-Griffiths (eds).
Serengeti: Dynamics of an ecosystem, University of Chicago Press,
Chicago, 397pp.
Karthikeyan,
S., S.K. Jain, M.P. Nayar & M. Sanjappa (1989). Florae Indicae
Enumaratio: Monocotyledonae. Botanical Survey of India,
Calcutta, 435pp.
Kellogg,
E.A., J.R. Abbott, K.S. Bawa, K.N. Gandhi, B.R.
Kailash, K.N. Ganeshaiah, U.B. Shrestha & P.
Raven (2020). Checklist
of the grasses of India. Check List 163: 1–560.
Knapp, A.K.
& M.D. Smith (2001). Variation among biomes in temporal dynamics of aboveground primary
production. Science 291: 481–484.
Kodandapani, N., M.A. Cochrane & R.
Sukumar (2008). A
comparative analysis of spatial, temporal and ecological characteristics of
forest fires in seasonally dry tropical ecosystem in the Western Ghats, India, Forest
Ecology and Management 256: 607–617.
Kochy, M. & S.D. Wilson (2000). Competitive effects of shrubs
and grasses in prairie. Oikos 91(2): 385–395. https://doi.org/10.1034/j.1600-0706.2000.910219.x
Leuthold, W.
& J.B. Sale (1973). Movements and patterns of habitat utilization of elephants in Tsavo
National Park, Kenya. East African Wildlife Journal 11: 369–384.
Leuthold, W.
(1976). Group size
in elephants of Tsavo National Park and possible factors influencing it. Journal
of Animal Ecology 45(2): 425–439.
McNaughton,
S.J. (1985). Ecology of
a grazing ecosystem: The Serengeti. Ecological Monograph 55: 259–294.
Menaut, J.C. & J. Cesar (1979). Structure and primary
productivity of Lamto savannas, Ivory Coast. Ecology
60(6): 1197–1210.
Mondal, N.
& R. Sukumar (2014). Fire and soil temperatures during controlled burns in seasonally dry
tropical forests of southern India. Current Science 107: 1590–1594.
Myers, N.,
R.A. Mittermeier, C.G. Mittermeier, G.A.B. Fonseca & J. Kent (2000). Biodiversity hotspots for
conservation priorities. Nature 403(6772): 853–858.
Nath, C.D.,
H.S. Dattaraja, H.S. Suresh, N.V. Joshi & R. Sukumar
(2006). Patterns of
tree growth in relation to environmental variability in the tropical dry
deciduous forest at Mudumalai, Southern India. Journal
of Bioscience 31(5): 651–669.
Robert, J.,
H.S. Dattaraja, H.S. Suresh & R. Sukumar (2002). Density-dependence in common
tree species in a tropical dry forest in Mudumalai,
southern India. Journal of Vegetation Science 13(1): 45–46.
Sala, O.E.
& J.M. Paruelo (1997). Ecosystem services in
grasslands, pp. 237–252. In: Daily, G.C. (ed.). Nature’s Services: Societal
Dependence on Natural Ecosystem. Island Press, Washington, DC, USA, 412pp.
Saldanha,
C.J. & D.H. Nicolson (1976). Flora of Hassan District, Karnataka, India.
Amerind Publishing Company, New Delhi, 915pp.
Saldanha,
C.J. (1984, 1996). Flora of Karnataka - Vol. (1 & 2). Oxford & IBH Publishing Company, New
Delhi, 535pp.
Seth, S.K.
& O.N. Kaul (1978). Tropical forest ecosystem of India: the teak forests (as a case study
of silviculture and management),pp. 628–640. In: Tropical Forest Ecosystem:
A State of Knowledge. Report by UNESCO/UNEP/FAO, Vendome, France, 683pp.
Sharma, B.D.,
B.V. Shetty, K. Vivekanathan & N.C. Rathakrishnan (1977). Flora of Mudumalai
wildlife sanctuary, Tamil Nadu. Journal of the Bombay Natural History
Society 75(1): 13-42.
Silori, C.S. & B.K. Mishra (2001). Assessment of livestock grazing
pressure in and around the elephant corridors in Mudumalai
Wildlife Sanctuary, South India. Biodiversity and Conservation 10:
2181–2195.
Sivaganesan, N. (1991). Ecology and conservation of Asian
Elephant (Elephas maximus) with special reference to habitat utilization
in Mudumalai Wildlife Sanctuary, Tamil Nadu, South
India, Ph.D. Thesis, Bharathidasan University, Thiruchirappalli,
Tamil Nadu, India, 115pp.
Skerman, P.J. & F. Riveros (1990). Tropical Grasses. Scientific Publishers, Jodhpur,
India, 832pp.
Srinivasan,
M.P. (2011). The Ecology
of disturbances and global change in the montane grasslands of the Nilgiris, South India. PhD Thesis, Department of biology at
the University of Kentucky, USA, 107pp.
Vanak, A.T. (2013). Conservation and sustainable use
of the dry grassland ecosystem in Peninsular India: a quantitative framework
for conservation and landscape planning. Report submitted to Ministry of
Environment and forest, Government of India, Ashoka Trust for Research in
Ecology and Environment, 40pp.
White, R.P.,
S. Murray & M. Rohweder (2000). Pilot analysis of global
ecosystems: Grassland ecosystems, World Resources Institute, Washington, DC, 69pp.
Wilson, G., A.A. Desai, D. Sim
& W.L. Linklater (2013). The influence of the invasive weed Lantana camara
on elephant habitat use in Mudumalai Tiger Reserve,
Southern India. Journal of Tropical Ecology 29(3): 199–207.