Seasonal and Altitudinal Changes in Population Density of 20 Species of Drosophila in Chamundi Hill

A year long study was conducted to analyze the altitudinal and seasonal variation in a population of Drosophila (Diptera: Drosophilidae) on Chamundi hill of Mysore, Karnataka State, India. A total of 16,671 Drosophila flies belonging to 20 species of 4 subgenera were collected at altitudes of 680 m, 780 m, 880 m and 980 m. The subgenus Sophophora was predominant with 14 species and the subgenus Drosilopha was least represented with only a single species. Cluster analysis and constancy methods were used to analyze the species occurrence qualitatively. Altitudinal changes in the population density, and relative abundance of the different species at different seasons were also studied. The diversity of the Drosophila community was assessed by applying the Simpson and Berger-Parker indices. At 680 m the Simpson Index was low at 0.129 and the Berger- Parker index was high at 1.1 at 980 m. Linear regression showed that the Drosophila community was positively correlated with rainfall but not elevation, Furthermore the density of Drosophila changed significantly in different seasons (F = 11.20, df 2, 9; P<0.004). The distributional pattern of a species or related group of species was uneven in space and time. D. malerkotliana and D. nasuta were found at all altitudes and can be considered as dominant species

Effect of cell height and infill density on the performance of geocell-reinforced beds of Brahmaputra River sand

© Springer Nature Singapore Pte Ltd 2020. Geocells, which are three-dimensional interconnected cells, are laid over foundation bases to provide lateral confinement to the infill material and thus improve the load-bearing capacity of the bases. Some experimental and mathematical studies have been reported in the literature in this regard. In this research, a laboratory experimental program was undertaken to study the improvement of bearing capacity of geocell-reinforced granular bases made from Brahmaputra river sand. In a laboratory model test, a steel tank was filled with Brahmaputra river sand, reinforced with geocell of different heights (made from woven geotextile), and progressively loaded to record the load versus settlement response. The infill density of sand was also varied to evaluate the effect on performance of geocell-reinforced sand beds. A square steel plate placed on the geocell-reinforced sand bed was incrementally loaded till failure to quantify the positive effects of geocell height and density of infill soil on the resultant bearing capacity. Enhancement of bearing capacity of geocell-reinforced sand bed with the increase in geocell height and density of infill material was evident from the test results. The bearing capacity of the geocell-reinforced bed, as compared to an unreinforced bed, is found to be increased by 1.8–4.3 times for normalized height of 0.33–1, having infill soil relative density of 70%, and 4.3–8.6 times for normalized height of 0.33–1, having infill soil relative density of 90%. The test results also show that significant reduction of settlement is achieved by the use of geocell reinforcement