M Sc Dissertation(WII)

Permanent URI for this collectionhttp://192.168.202.180:4000/handle/123456789/3

Browse

Author: search.filters.author.Page, Navendu V.Has files: Yes

Search Results

Now showing 1 - 8 of 8
  • No Thumbnail Available
    Item
    Effects of Local- and Landscape-level Drivers in Influencing Bird Diversity and Persistence in Cashew Plantations of the Northern Western Ghats
    (Wildlife Institute of India, Dehradun, 2024) Madhu, Nandita; Jayapal, Rajah; Page, Navendu V.; Naniwadekar, Rohit
    Agricultural expansion is a significant driver of deforestation and biodiversity loss, particularly in the tropics. The Western Ghats-Sri Lanka biodiversity hotspot is no exception. Most forest patches in the northern Western Ghats are being cleared for cashew cultivation. However, here, cashew plantations host varying proportions of cashew and native trees and have varying extents of ambient forest cover. Investigating the effects of such local and landscape-level drivers across land use types on taxonomic, functional, and phylogenetic diversities, as well as species- and trait-specific responses of birds, as implemented in this study, can give comprehensive insights on the impacts of forest conversion. I conducted this study in the low-elevation forests and cashew plantation landscape of Tillari, Maharashtra. I compared tree species diversity and vegetation structural attributes across land use types using Hill-Shannon diversity and linear models (LMs). To assess how land use type affects bird species composition and taxonomic diversity, I used non-metric multidimensional sampling (NMDS) and Hill-Shannon diversity. To compare functional and phylogenetic impacts across land use types, I used SES (Standardised Effect Size) values of fMPD (functional Mean Pairwise Distance) and pMPD (phylogenetic Mean Pairwise Distance) for LMs and Tukey’s post-hoc analysis. Using Hierarchical Modelling of Species Communities (HMSC), I looked for 1) bird species responses, 2) trait responses, and 3) a phylogenetic signal in the residuals. I collected bird and vegetation data from 100 points distributed across forest, mixed cashew plantations, and pure cashew plantations. My field collaborator (Vishal Sadekar) and I sampled vegetation within a 10 m radius of circular plots around all points. We sampled birds, implementing 10-minute point counts at a point, replicated 5 times across 4 months between January to May 2024. Vegetation differed significantly across all three land use types in terms of tree species diversity and tree height, where the forest had the highest estimates followed by mixed cashew. NMDS showed that the community in mixed cashew plantations overlapped with that of pure cashew plantations. There was no significant effect of land use type on functional diversity. But taxonomic and phylogenetic diversities were lowest in pure cashew. The HMSC model revealed a low explained variation (Tjur R2 = 0.1372), but I found land use type, a site-level variable, to exhibit the highest explained variation of 58% compared to the landscape-level variables. Forest species like Malabar Trogon (Harpactes fasciatus) and Black-naped Monarch (Hypothymis azurea) responded negatively to mixed and pure cashew plantations. Species like Golden-fronted Leafbird (Chloropsis auriforns) and Tickell’s Blue Flycatcher (Cyornis tickelliae) benefitted from mixed cashew and open country species like Indian Peafowl (Pavo cristatus) and Plain Prinia (Prinia inornata) responded positively to pure cashew. Trait response analysis revealed that evergreen species responded positively to the forest and negatively to both cashew habitats. Sedentary species responded positively to forest cover in 800 m. No evidence of a phylogenetic signal was found in the residuals (⍴ = 0.23, 95% CI: 0 - 0.68). This study highlights the value of mixed cashew plantations which are more habitable than pure cashew plantations due to native tree prevalence. However, this study also emphasises that even mixed cashew plantations cannot replace forests as habitats for evergreen forest species. This message is now more crucial than ever in the light of ongoing forest clearance in the northern Western Ghats.
  • No Thumbnail Available
    Item
    Intra-specific variation in seed dispersal effectiveness of Lion-tailed Macaques Macaca silenus
    (Wildlife Institute of India, Dehradun, 2024) Bindu, K.; Kumar, H.N. Dr. H. N. Kumara Dr. Navendu Page Dr. Rohit Naniwadekar; Page, Navendu V.; Naniwadekar, Rohit
    1. Tropical forests are one of the most biodiverse ecosystems on Earth. Seed dispersal is one of the important interactions that maintains species richness and ecosystem functions. Vertebrate frugivores, especially birds and mammals, play a crucial role in dispersing seeds. The dispersal effectiveness of these dispersers is influenced by factors such as size, age, sex, dominance hierarchy and behaviour types. Invasive species pose significant threats to tropical ecosystems, rapidly forming mutualistic relations with native dispersers. This study focuses on the lion-tailed macaques Macaca silenus in the Western Ghats to explore how age-sex categories influence seed dispersal of native and exotic species in terms of diversity and quantity of fruits consumed, quantity of seeds dispersed, daily distance travelled and seed deposition site. 2. I employed non-invasive behavioural sampling on four troops of the lion-tailed macaques for four months. Focal animal sampling of 375.9 hours was employed on individuals belonging to three age sex categories, including adult males, adult females and subadults. Faecal samples were collected to assess quantity of seeds dispersed, and the substrate at seed deposition site was recorded. The movement of focal individual was tracked for the entire duration of the observation. 3. Subadults consumed higher diversity of fruits than females and males. Subadults also consumed more native fruits, while females consumed more non-native fruits. The pairwise dietary overlap between all age-sex categories was high. The rate of consumption of nonnative fruits increased as day progressed. Subadults dispersed significantly less Ficus seeds than the other age-sex categories. Daily movements showed no significant differences across age-sex categories. However, I found weak evidence of males being more likely to disperse seeds on trees, which could be more suitable for Ficus germination. The differences in 7 feeding patterns also highlight the greater importance of subadults in the dispersal of a greater diversity of fruit plant species. 4. The invasives Coffea spp. and Lantana camara constituted up to 90% of the diet of the three age-sex categories. There was difference in the relative proportions of these two species. Males consumed more Coffea spp., whereas subadults and females consumed more Lantana fruits. The macaques dispersed Ficus seeds in clumps, increasing the risk of predation or microbial infection. 5. This study generates novel information on intra-specific variation in seed dispersal, a relatively understudied topic. It also highlights lion-tailed macaques' significant role in dispersing alien invasive species in degraded rainforests and provides valuable insights into their understudied role as seed dispersers.
  • No Thumbnail Available
    Item
    Influence of Forest Cover on Fruit and Frugivore Richness and Abundance in Southern Western Ghats
    (Wildlife Institute of India, Dehradun, 2021) Takorbhai, Patel Zankhnaben; Page, Navendu V.; Kumar, Amit
    Habitat fragmentation is a pervasive threat to ecosystem processes like seed dispersal, which is vital for biodiversity maintenance in tropical forests. Habitat fragmentation negatively impacts the richness, abundance and composition of plants and animals, thereby disrupting the interactions between them, with cascading impacts on biodiversity. However, the remnant fragments continue to harbour biodiversity. However, it is critical to determine the functional value of the fragments in terms of fruit resource diversity and availability and prevalence of frugivores across different size classes. To this end, I conducted the study in the Valparai plateau and adjacent contiguous patches of rainforests in the Western Ghats. I first determined the organization of plant-seed disperser community and identified key frugivores and plants in the landscape using network analysis. Using mixed models and the recently developed Joint Species Distribution Modelling approach called HMSC (hierarchical modelling of species communities), I investigated 1) the relationship between the amount of forest cover and richness of fruiting plants across different seed size classes, 2) the relationship between the amount of forest cover and availability of fruit s across different seed size classes 3) the relationship between richness and presence of all the avian frugivores and, amount of forest cover, and richness and availability of fruits. I recorded the frugivores and fruiting plants from 33 trails distributed in 12 fragments and 2 sites in contiguous area during four months of sampling. I also recorded plant-frugivore interactions. I documented 49 species of fruiting plants and 17 species of avian frugivores
  • No Thumbnail Available
    Item
    Functional Trait Variation within and Across Woody Plant Species Along an Elevation Gradient
    (Wildlife Institute of India, Dehradun, 2021) Nambiar, Ashish; Page, Navendu V.
    Plant phenotypes are defined by a set of traits that have been theorized to be closely linked to the fitness of individuals. These traits have an impact on their ability to grow and compete given the local environment. Variability (intra-specific or inter-specific) in the values of these functional traits is thought to be associated with the ability of an individual to survive in highly variable environments or a wide range of environments. Elevation gradients represent a change in environmental factors within a short spatial scale and hence offers the ideal context to examine functional trait variation. This study seeks to understand the extent of intraspecific trait variation and theorize the drivers of this variation in five woody plant species in response to a change in elevation in a tropical evergreen forest. I focused on three different functional traits i.e Specific leaf area (SLA), leaf dry matter content (LDMC), and Stem specific density (SSD) which represent leaf resource acquisition as wells as stem differentiation. When examining the trends of functional trait values for the entire data set irrespective of species identity, it was seen that differences in mean trait values drove the across-species trends. This highlights the role of the environment in selecting for species with specific mean trait values. Contrary to this, intra-specific trait values did not show directional selection in response to elevation, however, the percentage of the total variation associated with the intra-specific scale was significant. This indicates the occurrence of simultaneous counter gradients which may be leading to there being a lack of signal in functional trait values in response to elevation. I failed to establish a correlation between intra-specific trait variation and the elevation range of occurrence. The results highlight the high functional trait variation seen at the intra-specific scale and emphasizes the importance of considering intra-specific trait variation especially at the scales of high environmental heterogeneity.
  • No Thumbnail Available
    Item
    Effect of Grazing on the Community Structure and Functional Diversity of Grazing Lawns in Sathyamangalam Tiger Reserve
    (Wildlife Institute of India, Dehradun, 2021) Malagi, Aaroha; Adhikari, B.S.; Page, Navendu V.; Ramesh, K.
    Understanding the effects of grazing (by both livestock and wild ungulates) on grasslands is paramount to come up with more robust managerial actions to conserve, and increase the ecosystem function of these valuable ecosystems. In the current study, we investigate the effects of grazing on a highly productive, mesic grassland ecosystem, viz. grazing lawn in Sathyamangalam Tiger Reserve, Tamil Nadu, India. We examined how species richness and composition of a grassland patch change across a grazing gradient by carrying out plot-based vegetation sampling in the grazing lawns of Sathyamangalam Tiger Reserve. We also looked at how trait composition and functional diversity changed across the grazing gradient, to better understand the plant functional response and resilience of the grazing lawn complex. We used a Linear Mixed Effect Model (LMM) to investigate the impact of grazing intensity on species richness, and a Non-metric Multidimensional Scaling (NMDS) to look at the differences in species composition between different grazing treatments. Functional composition and diversity were measured using Lavorel and Villeger’s index in the ‘FD’ package of R (4.0.2). We found that grazing lawns were minimally affected by grazing intensity in terms of species richness and trait composition, but showed a significant change in species composition and functional diversity across the grazing gradient.
  • No Thumbnail Available
    Item
    Patterns of Bird Community Structure in Relation to Land-Use Driven Habitat Changes in the Arid Grasslands of Thar Desert
    (Wildlife Institute of India, Dehradun, 2019) Kher, Varun; Dutta, Sutirtha; Uniyal, V.P.; Page, Navendu V.
    The Indian Thar desert has seen a massive loss of grassland habitat in the last few decades. The main driver of this habitat loss has been the large-scale change in landuse from pastoralism to agriculture, leading to expansion of cultivated land over grasslands. This expansion, further compounded by a simultaneous rise in livestock population has drastically increased grazing pressure on the remaining rangelands. To complicate things further, irrigation schemes (notably the Indira Gandhi Canal) have led to intensification of agriculture in many areas. Protected area network in this landscape is minimal and ineffective, making the multiple-use agro-pastoral landscapes very important for conservation of wildlife. The largest protected area in the landscape – the “DNP WLS” – is also a multiple-use landscape and home to more than 50k people whose livelihood is tied to the federal mandate of conservation in the sanctuary. 1. Understanding the impact of land use change on native biodiversity is thus very important for conservation of biodiversity in this critical habitat. In this context, my study tries to find effects of land-use change on community structure of birds in the arid grassland of Jaisalmer district in the Thar Desert. 2. Understanding ecology or distribution and abundance of species is incomplete without holistically understanding the patterns and processes occurring at the community level. To this end, I explored the patterns of bird community structure in the Thar Desert and tried to understand how these properties change with land-use driven habitat change, by comparing fundamental properties of biological communities like species richness, abundance and composition. Additionally, I tried to find out potential habitat correlates of these properties, so as to shed some light on the processes that might be driving community assembly in response to land-use change. 3. Bird community structure: My results indicate that local-scale species richness,abundance and composition did not differ significantly between protected grasslands, rangelands and extensive rain-fed croplands, during either of the seasons. However, intensive irrigated croplands had a notably different community structure with higher species richness and abundance, during both winter and summer. The change is community structure of intensive croplands was influenced by the change in native species along with ingression of newly colonised species. Most of the newly colonised species were restricted to areas with intensive agriculture where their survival was potentially facilitated by the new microhabitats created by irrigation and associated changes (Rahmani & Soni, 1997). 4. Regional species pool: Intensive agriculture increased the overall species of birds in the region by sustaining newly colonised bird species; while the number of native species in this pool was only marginally lower than protected grasslands and comparable to all the other land-uses in both the seasons. Considering both the seasons together, protected grasslands had the highest naïve and estimated number of native species while the naïve and estimated number of native species in other three land-uses – Rangelands, extensive croplands and intensive croplands – was only marginally lower. This signifies that most species found in the region can use the entire gradient of land-use types at their current levels of intensification. Although this result by itself does not indicate that, all land-use types can sustain all the native species. 5. Seasonality of patterns: In winter, protected grasslands, rangelands and extensive croplands had similar bird communities, which together were significantly different from the communities in intensive croplands. The same pattern repeated in summer, but the magnitude of difference between bird communities in intensive agriculture and other land-uses was much lower. This pattern was correlated to the pattern shown by vegetation structure of intensive agriculture, which also became more similar to other land-uses after harvesting of crops in the summer. This potentially suggests that bird communities are influenced by vegetation structure and areas with similar vegetation structure would have similar bird communities. 6. Habitat correlates of species richness and bird community composition: In both the seasons, species richness was positively associated with the foliar volume of woody vegetation and negatively associated with forb volume (which in turn was negatively correlated with grass volume). During winter, species richness was positively related to crop volume and during summer, with compositional diversity of vegetation. Community composition like richness was influenced significantly by woody plant foliar biomass in both the seasons. Crop volume also had a significant influence on bird communities during both winter and summer, whereas grass volume was significantly influential only in winters. Conservation implications: This study corroborates many others in indicating that low-impact land-uses are important secondary habitats for conservation of grassland species (Dutta & Jhala, 2014; Wright, Lake, & Dolman, 2012). The inferences further support the commonly advocated approach of conserving grasslands at a landscape scale by strategically placing them as mosaics of low-impact agro pastoral land-use with small protected areas embedded within them (Dutta & Jhala, 2014; Dutta, Rahmani, & Jhala, 2011; Singh et al., 2006).
  • No Thumbnail Available
    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.
  • No Thumbnail Available
    Item
    Patterns in plant species richness and diversity in the forest fragments of Western Ghats, Karnataka.
    (Wildlife Institute of India, Dehradun, 2007) Page, Navendu V.; Qureshi, Qamar; Rawat, G.S.
    Patterns of species richness diversity and distribution, and the factors affecting these patterns have always attracted the attention of many ecologists. Degree of fragmentation is one such factor affecting the species richness and composition also of great importance to conservation biology in light of rapid loss of biodiversity. The study examined the patterns of distribution and species richness and its correlates in a fragmented landscape in Kodagu district, Western Ghats, Karnataka. The study also examined some of the factors affecting distribution of epiphytes such as distribution along the tree height gradient and host specificity. A total of 129 species of trees, 29 species of Iians as and 68 species of vascular epiphytes were recorded in 56, 25m x 25m square plots. 60 species of shrubs were recorded in 90, 5m x 5m square plots. Patch area was found to be significantly correlated with tree species richness, but area was not correlated with shrub, liana and epiphyte species richness. However plant density used as measure of site specific productivity along with area were significantly correlated with lianas and epiphyte richness. Neither of these could explain the variation in shrub species richness. Lianas and shrubs did not show any such trend but epiphyte richness showed a negative trend in rarefied species richness with increase in area. Rank abundance curves indicated that Reserve forest had the most equitable distribution of abundance classes and also more number of rare species. Species composition was found to differ significantly across different size classes. All the plant communities showed moderate levels of nestedness. Distribution of an epiphyte along the tree was not influenced by the mode of dispersal alone. There was no strong evidence in support of host specificity however some selective host species were found to be favoured by epiphytes.