RESEARCH COMMUNICATIONS CURRENT SCIENCE, VOL. 101, NO. 2, 25 JULY 2011 218 *For correspondence. (e-mail: skray45@yahoo.co.in) 13. Steinbauer, G. P. and Grigsby, B., Interactions of temperature, light and moistening agent in the germination of weed seeds. Weeds, 1957, 5, 681–688. 14. Probert, R. J., The role of temperature in the regulation of seed dormancy and germination. In Seeds: The Ecology of Regenera- tion in Plant Communities (ed. Fenner, M.), CABI Publishing, New York, 2000, pp. 261–292. 15. Baskin, C. C. and Baskin, J. M., Seeds. Ecology, Biogeography, and Evolution of Dormancy and Germination, Academic Press, San Diego, USA, 1998. ACKNOWLEDGEMENT. The research was supported by the Minis- try of Economic Affairs in the framework of the action Research in Brussels (postdoc grant RIB2001-006). Received 24 August 2010; revised accepted 1 June 2011 Coseismic uplift, slow plant mortality and ecological impact in North Andaman following the December 2004 (M w > 9.2) earthquake Sumit Kumar Ray 1, * and Anshuman Acharyya 2 1 Department of Geology, Presidency University, College Street, Kolkata 700 073, India 2 Geological Survey of India, CHQ, 27 J. L. Nehru Road, Kolkata 700 016, India We present here the phenomenon of gradual decay leading to plant mortality in vast stretches (measuring several square kilometres) of vibrant mangrove forests in the coastal wetlands of North and Middle Andaman. We interpret the phenomenon as an effect of static ground uplift following the 26 December 2004 Sumatra–Andaman earthquake. The decimetre to metre scale uplift has cut-off tidal water flow into those parts of the wetlands that were elevated from intertidal to supratidal levels. The consequent thermal shock, desiccation and gradual depletion of soil salin- ity affected the plants in the elevated parts. However, desiccation due to lack of tidal-water inflow caused the plant mortality which took the proportions of an ecological disaster about three to four years after the earthquake. The voluminous forest debris produced by the withered plants is likely to be preserved in the coastal sedimentary sequences as peat beds and serve as palaeoseismic indicators. Keywords: Coseismic uplift, earthquake, ecological impact, mangrove swamp, plant mortality. WHILE discussing ground uplift in North and Middle Andaman Islands following the great Sumatra–Andaman earthquake of December 2004, we had predicted that the intertidal flora of the coastal mangrove forests that were coseismically uplifted from intertidal to supratidal levels would perish within a few years 1 . We further predicted colonization of the perished intertidal forests by sweet- water plants. To test the validity of the predictions that point to a distinct type of ecological disaster, we carried out repeat surveys of the coastal wetlands of North Andaman more than four years after the earthquake. Here we give a brief introduction to the tectonic setting of the Andaman and Nicobar Islands, and an account of what we observed in the context of our prediction. The survey revealed widespread plant mortality affecting the pristine mangrove forests of the coastal wetlands. The 800-km-long Andaman–Nicobar chain of islands delineates the arcuate axial zone of the forearc ridge of the Indonesian subduction complex 2 . The chain of islands is broadly parallel to the subduction zone trench, known as the Sunda–Java trench 2 , that represents a trace of the interface along which the Indian–Australian plate is sub- ducting beneath the Eurasian–South East Asian plate (Figure 1). A general northeasterly convergence of the plates has been inferred 2 . Sediments deposited on the down-going oceanic plate have been scraped, and piled up by thrust faults to build up the accretionary prism and Figure 1. Map showing the location of the Sunda–Java trench 2 and distribution of coseismic vertical ground movement in the Andaman region, caused by the 26 December 2004 megathrust earthquake 1,12,13 . The dashed lines represent the contours of vertical ground movement. Values assigned to the contour lines give the estimated vertical offset in metres. The ‘+’ and ‘–’ signs indicate ground uplift and subsidence respectively. The ‘0’ value contour represents the neutral line 1 . (Insets) Pre-earthquake extent of the Kishorinagar and Radhanagar wetlands. The grass symbol marks the tidal swamps (wetlands) that support dense mangrove forests. The grey shade shows the land areas. IS., Island.