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.
Highlights
Grasslands are highly dynamic ecosystems encompassing natural and semi-natural pastures, woodlands and scrubs dominated by grasses (Blair et al 2014)
The present study investigated the effect of environmental factors on grass availability and grass association in tropical forests of Southern India
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
Summary
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). The invasion of exotic species into tropical forest threatens grasslands (Srinivasan 2011; Ashokkumar et al 2012). Invasions affect grass composition and the foraging efficiency of herbivores (Wilson et al 2013). 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
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