Theses and Dissertations
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Item Investigating the roles of fire and cattle grazing on vegetation, invasives, and their implications on Bengal Florican (Houbaropsis bengalensis) breeding habitat use(Wildlife Institute of India, Dehradun, 2025) Thammaiah, Aadya; Nath, Anukul; Dutta, SutirthaGrasslands, though ecologically important, are often overlooked in conservation. These ecosystems are shaped by land-use practices such as fire and grazing, which can help maintain open habitats when appropriately applied. Mismanagement, however, can promote invasive species, threatening native biodiversity. The Bengal Florican (Houbaropsis bengalensis), a critically endangered grassland specialist, highlights the need for targeted conservation in such systems. This study assessed the combined effects of fire and grazing on grassland plant communities, including invasive plants, and Bengal Florican breeding habitat selection in Manas National Park. 2. For the vegetation survey, I selected study sites along gradients of fire frequency (based on 23 years of FIRMS data) and grazing intensity (using distance from human settlements as a proxy). At each site, I used circular plots to sample vegetation and assess species composition. To examine drivers of plant and invasive species abundance, I applied linear models (LMs), incorporating key covariates such as distance to forests, roads, and climate moisture index (CMI). I then used Indicator Species Analysis (ISA) to identify species associated with different fire-grazing regimes. I also performed a Linear Discriminant Analysis (LDA) to assess how well vegetation communities and structure could distinguish between different fire conditions. For Bengal Florican habitat assessment, I quantified vegetation structure visually and insect abundance using sweep netting in display and paired control sites. I used Binomial Generalised 8 Linear Models (GLMs) and Conditional Logistic Regression modelling to evaluate habitat selection by the species. 3. Tree and sapling densities peaked under intermediate fire, whereas shrubs and herbs had the highest density in low fire regimes. Saplings, shrub as well as grass cover peaked in low grazing regimes, but herb cover was highest in low grazing conditions. Among invasives, Leea asiatica and Chromolaena odorata were more frequent in intermediate fire, while Mikania micrantha and Ageratum conyzoides thrived under low fire. Grazing showed significant effects only on Mikania micrantha. ISA identified native species such as Dillenia pentagyna as indicators of low grazing and Cymbopogon flexuosus for medium and high fire regimes, among others. Bengal Florican selected sites with higher insect abundance, shorter vegetation (25–50 cm), with low (outside the PA) and high fire frequency (within the PA). 4. My results showed that plant communities showed species-specific responses to fire and grazing conditions. Bengal Florican habitat-use reflected a preference for open, short grasslands with high insect abundance. In conclusion, my study found that effective conservation requires tailored fire and grazing strategies that sustain open structure and control invasives, especially for the conservation of species such as the Bengal Florican.Item Nutrients and Metals in Soils and Vegetation of Araku, Andhra Pradesh, India(SACON, 2010) Chandra, Rachna; Azeez, P.A.Industrialization and urbanization in past few decades have caused tremendous ecological repercussions, which could be best seen in mining/extractive industry. India is endowed with a wide range of mineral wealth, and large scale mining activities are happening in various places in the country. Some important effects due to mining activities are the change in land use pattern and the associated changes in distribution of plants, animals, water bodies and soil system. Reclamation and reforestation of mined out areas have become necessary due to stern environmental laws in effect in the country, although exceptions are widely seen. The vegetation grown in mine sites is anticipated to accumulate or selectively exclude/tolerate high levels of toxic metals. Several of the soil characteristics can be playing important role in mobility of nutrients and metals in soil system. Thus, knowledge about these soil properties becomes obligatory as assessment of their distribution on a spatio-temporal scale would help better understand their likely mobility and bioavailability. The present investigation undertaken in three proposed mining locations at Araku, Andhra Pradesh, India during 2006 through 2008 is an attempt to examine the nutrients, alkali and alkaline earth metals, select heavy metals across the soil layers, and also alkali and alkaline earth metals, and select heavy metals in organs of select predominant plant species in the area. These species were primarily screened out on the basis of their ability so that they can be used during the initial stages of mine restoration programme, after the mining activities are ceased. As hyperaccumulators take up particularly high amounts of metals in their shoots, an attempt was made to assess the trace and heavy metal from view point of Transportation index (Ti = (metal concentration in leaf] / [metal concentration in root]) in various organs/compartments of the select plant species naturally occurring in the area.Item Factors that Shape Vegetation in the Arid Zone of India(Wildlife Institute of India, Dehradun, 2019) Gayathri, S. Aaranya; Onial, Malvika; Page, Navendu V.In the current era of Anthropocene, it has become increasingly important to make predictions in plant-animal distributions as a function of the predicted changing conditions. Thus, the need to determine what shapes different vegetation structures are recognised, but, the results are often scale specific and rarely single factor determined. We investigate what causes a vegetation structure shift from a grassland to savanna and their possible intermediate transitions in the Thar Desert, North-Western Rajasthan, India. We sampled for vegetation in 67 one km2 grids spread across a 10,235 km2 study area capturing heterogeneity in precipitation. We analysed soil samples collected from sampled grids for soil texture, water holding capacity, total organic carbon, rodded and loose bulk densities. We collared three types of livestock (n=28) to determine potential grazing pressure in the sampled grids as one of the determinants. We used generalized linear models and non-metric multidimensional scaling to determine the determinants of vegetation structure and community. Our results show a clear scale dependence on how the determinants act– precipitation defines the larger community attributes such as species richness (R2=0.39, p= 1.029e-06); soil compaction under the precipitation umbrella defines the vegetation structure (and hence shift from grassland to savanna etc.) and grazing pressure (especially from the smaller livestock) defines the proportion of the life forms within each vegetation structure. The role of environmental determinants in determine vegetation shifts assures that the transitions are going to be gradual. This precludes the frequent finding of grasslands shifting to a shrubland or forest due to livestock grazing. This could be attributed to our finding of livestock having no forage preference to any particular species (χ2=25.76,df=18,p=0.1003) or life forms (χ2= 5.1939, df = 2, p = 0.0745) or possibly due to the low variation in livestock grazing in this landscape. We also found that change in the environmental determinants, however, can lead to two or three possible structure types. A predictive modelling shows the presence of mixed grassland, soft grassland, tree savanna, and tree shrub savanna in the study area. However, the map also indicates that 62.7% of it is already lost agriculture/settlement. Enclosures of Desert National Park protects only one vegetation structure type and covers less than 1%. We emphasize the urgent need to delineate conservation areas based on requirements of faunal species of interest and its habitat requirements before a complete wipe-out of vegetation structure types occur.