Impact of Coal Mining on Vegetation: A Case Study in Jaintia Hills ...

IMPACT OF COAL MINING ON VEGETATION: A CASE STUDY IN JAINTIA HILLS DISTRICT OF MEGHALAYA, INDIA3.3.3.1. Radiometric CorrectionFirst order corrections were done by dark pixel subtraction technique followed by Lilles and Kiefer(1999).3.3.3.2. Visual InterpretationStudying changes in land use pattern using remotely sensed data is based on the comparison <strong>of</strong> thetime sequential data. Differences in surface phenomenon over time can be determined and evaluatedby visual interpretation with local knowledge (Garg et al., 1988; SAC, 1999). For the present purposevisual interpretation technique was used for land use/ land cover mapping for four different yearsremote sensing data <strong>of</strong> the study area.3.3.3.3. Change AnalysisThe land use/ land cover maps <strong>of</strong> 1975, 1987, 1999 and 2001 were converted into grid format usingIntergraph MGE Grid Analyst. Maps <strong>of</strong> different time periods were overlaid to find changes. Theincrease or decrease in different land use/ land cover is obtained by intersecting and generating thematrices <strong>of</strong> change-no change for different years.3.3.3.4. Forest Fragmentation AnalysisIt was measured by calculating the amount <strong>of</strong> forest patches occurring in a landscape with respect tonon-forest patches. In the programme, Bio_CAP the area was reclassified into three categories viz.,non-forest, high fragmentation and low fragmentation.3.3.3.5. Phytosociological AnalysisThe community characteristics <strong>of</strong> vegetation in coal mining areas <strong>of</strong> Jaintia Hills district <strong>of</strong> Meghalayawere studied during the last week <strong>of</strong> October, 2004. To find out the impact <strong>of</strong> coal mining onvegetation distant gradient analysis was carried out. In this method, from the center <strong>of</strong> the study area,i.e., Lad Rymbai, structure and composition <strong>of</strong> vegetation is observed in four different zones. Theradius <strong>of</strong> the first circle i.e., zone-I is 2 km. The distance from the periphery <strong>of</strong> the first circle to theperiphery <strong>of</strong> the second circle is also 2 km and is considered as zone-II. Likewise, zone-III and zone-IV are delineated (Figure 3.5). In each circle 24 sample plots each for tree, shrub and herbs were laid.Each sample plot was supported by 3 replicas. The total number <strong>of</strong> sample plots for tree, shrub andherbs came to 72 each in each zone. The overall number <strong>of</strong> sample plots for tree, shrub and herbspecies was 288 each in the mining areas, i.e., in all the four zones. The vegetation characteristics <strong>of</strong>the mined areas were compared with that <strong>of</strong> an adjacent undisturbed forest, i.e., Tubre Sacred Grove.The total number <strong>of</strong> quadrats laid in the control site was 10.For tree component a quadrat <strong>of</strong> 10m x 10m size was laid while for the shrub species it was 5m x 5m.For the herbaceous species the size <strong>of</strong> the quadrat was 1m x 1m. The species found in the quadratswere identified with the help <strong>of</strong> the herbaria <strong>of</strong> Botany Department, North-Eastern Hill University,Shillong and Botanical Survey <strong>of</strong> India, North-Eastern Circle, Shillong. The plants having CBH>15cm was considered as tree, stem diameter 5-15cm at basal level was considered as shrubs and stemdiameter