Theses and Dissertations

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Author: search.filters.author.Onial, Malvika

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    Making the Urban Matrix Matter : Characteristics of the Avifaunal Community of the Urban Matrix Relative to the Urban Green Spaces of Dehradun
    (Wildlife Institute of India, Dehradun, 2021) Coutinho, Jason Bismarck; Onial, Malvika; Kaushik, Monika
    Urban ecology is a field in science which deals with understanding the ecological synergies within urban systems. This is a relatively new field which started out when ecologists recognized the importance of quantifying human impacts on ecosystems globally. This field is ever so pertinent now that no ecosystem remains which doesn’t have human induced changes. 2. Urban ecosystems are dynamic ecosystems with interactions similar to those of natural ecosystems, but they are also directly influenced by the culture, politics, economics and social organization of human society. Urban has different definitions all over the world with no single consensus and such disparities make it impossible to compare ‘what is urban’ across the globe. Simply urban areas are cities and suburban areas with the landscape being called as the ‘built environment’. Urbanization and the urban sprawl have impacted not only the land covers across an urban area, but also the biodiversity in it. This urbanization filters the biological community at various levels and it is pertinent that we understand this filtering. 3. The urban landscape can be divided into two major categories for simplicity. The urban green spaces are terrestrial areas, both public and private covered with vegetation, made available to users. These are very important to the health of the city. They enhance the wellbeing of the people in the city and also are habitats for urban wildlife. The urban grey on the other hand is the ‘built’ or ‘artificial’ environment. This is usually seen increasing as we reach the center of a city or urban area. 4. The urban matrix is a mix of the greens and the grey and has no clear definition. It is all the habitat patches in the urban landscape that lie outside the urban green spaces. This urban matrix is highly dynamic and every urban area has its own unique habitat mosaic. This important matrix however has not been studied extensively. In most areas of urban ecological research, the matrix’s relevance is undervalued. The current study was conducted in the city of Dehradun from March 2021 to April 2021. To understand the importance of the urban matrix’s contribution in maintaining an urban areas biological diversity, this study aims to quantify the avifaunal community in the urban matrix. Further it looks to understand the relevance of the avifaunal assemblage characteristics of the urban matrix relative to that of the urban green spaces. 5. To study this, the patterns of the avifaunal community in Dehradun were explored. Fundamental properties of biological communities like species richness, abundance, density and composition were looked at the habitat scale. At the landscape scale, potential habitat correlates of the species richness and density were studied so as to shed some light on the factors and processes that might be driving the community assembly in the urban matrix. The comparison of the avifaunal assemblage was done by comparing the overall richness, density and composition in the urban matrix and urban green spaces. 6. In the urban matrix, 109 sampling units were laid and then sampled using a variable radius point count method. A total of 3775 individuals belonging to 81 species were recorded. Feral Pigeon was the most dominant species, habitat-wise species richness was maximum in the built – up areas (54 species) and species density was maximum in scrublands (13.12mean ± 4.35SD per hectare). Ordination graphs showed that plots of green cover were dissimilar from the other habitats. The species richness in the urban matrix was positively influenced by the increasing proportions of open areas and scrublands. Built – up had negative influence on the species richness but showed peaking at moderate levels of human development. Density in the matrix was positively influenced by increasing proportion of scrublands and the landscape heterogeneity. It was negatively influenced by increasing proportions of built – up and green cover. Comparisons of the richness and density of the urban matrix and urban green spaces showed that there was a huge difference in both the parameters, with urban green spaces showing higher values for both. The species composition Venn diagram showed that the matrix and urban green spaces share 64 species among them, with the urban green spaces and urban matrix showing 50 and 17 unique species respectively. 7. In general, the current study shows the relative importance of the urban matrix in maintaining the urban biodiversity and the need of conserving the habitats in the matrix to boost the urban biodiversity.
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    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.