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Abstract
Geo-Spatial Mapping of Higher Plant Species Distribution in Bhabha Valley in Western Himalaya
Amit Chawla
Research Fellow
Institute of Himalayan Bioresource Technology,
Email: amit.chawla@rediffmail.com
Amit Kumar
Institute of Himalayan Bioresource Technology
Bhabha valley (31.54 N and 77.95 E to 31.78 N and 78.05 E and 1483 m to 5500 m above msl), situated in the east of the river Sutlej in the district Kinnaur of Himachal Pradesh, presents an extensive heterogeneity of habitats and thus harbours a rich plant species diversity, owing to the elevation gradient it provides. On account of its difficult terrain and remote location, the valley has been hitherto an unexplored area with regard to its biodiversity and ecological aspects. The objective of the present study is to characterize the higher plant species diversity of this pristine valley using remote sensing and GIS. IRS 1D LISS III satellite images were used to prepare the land use and vegetation maps of the valley. Field sampling along an altitudinal gradient, segregated into 6 classes of 500m intervals each, was performed in the representative vegetation types to assess the higher plant species diversity along with recording of related environmental factors. The surface and two dimensional areas were measured for each class from Digital Elevational Model (DEM) using ArcGIS 8.3 software. Soil samples collected from the area were analysed for physico-chemical characteristics and for availability of macro- and micro-nutrients. A geo-spatial database for the field data was prepared and linked to maps in a GIS environment. Statistical analysis was performed to assess the biodiversity pattern of species along the altitudinal gradient. The species distribution, life form, uniqueness were calculated for each class. The relationship between species richness with elevation gradient and distributional range of species was analyzed statistically using non-linear regression. Terrain analysis was performed using digital terrain model. Species diversity was correlated with surface area of the valley along the altitudinal gradient. The number of species plotted against the altitudinal gradient showed a hump shaped curve. The higher elevation gradients have less habitat diversity compared to mid elevation gradients. Further, the mid elevation gradients are inhabited by arboreal forests, with a larger diversity of shrubs and climbers, which contributed to increased plant diversity. Above the timberline, only a few patches of shrubaceous vegetation and alpine meadows were found as the area lacks moist environmental conditions required to harbour rich plant diversity. A total of 18 plant species from Bhabha valley, accounting for 5.75 % of the total species found in the valley, are included in the Red Data lists. Many other plant species are facing different categories of threats and some are on the verge of extinction. Vegetation, soil and species distribution maps were generated in GIS domain by overlaying ecological data for the entire study area. The analysed ecological data for the representative LSE types in conjunction with satellite imageries were extrapolated over whole of the area and evaluated spatially in a stack of overlaid layers in the GIS software. Thus, this study highlights the biotic and abiotic interactions in shaping the spatial distribution of plant communities across the diversified landscape in the Bhabha valley. The study provided the range of species adaptability, species diversity, population status, phytosociological attributes and species distribution patterns in relation to different ecological variables in various vegetation types, which is of immense significant for the conservation measures. Gap areas and species/habitat relationships can be identified for planning of conservation strategies for the area. A major deliverable of the study is the reporting of quantitative data for most of the threatened plant species of Bhabha valley over a wide range of habitats.
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