Ramesh Thakur

Gene expression responses of paper birch (Betula papyrifera) to elevated CO2 and O3 during leaf maturation and senescence

Gene expression responses of paper birch (Betula papyrifera) leaves to elevated concentrations of CO(2) and O(3) were studied with microarray analyses from three time points during the summer of 2004 at Aspen FACE. Microarray data were analyzed with clustering techniques, self-organizing maps, K-means clustering and Sammons mappings, to detect similar gene expression patterns within sampling times and treatments. Most of the alterations in gene expression were caused by O(3), alone or in combination with CO(2). O(3) induced defensive reactions to oxidative stress and earlier leaf senescence, seen as decreased expression of photosynthesis- and carbon fixation-related genes, and increased expression of senescence-associated genes. The effects of elevated CO(2) reflected surplus of carbon that was directed to synthesis of secondary compounds. The combined CO(2)+O(3) treatment resulted in differential gene expression than with individual gas treatments or in changes similar to O(3) treatment, indicating that CO(2) cannot totally alleviate the harmful effects of O(3).

Air pollution and global change: a double challenge to forest ecosystems

Abstract The worlds forests provide a host of wood products, and non-wood resources, and they are critically important in conserving plant, animal, insect and microbial diversity, maintaining soil and water resources, and providing opportunities for employment and recreation. Only recently have we started to value forests for their ability to sequester carbon from the atmosphere. The rapidly changing atmospheric environment with its mix of increasing anthropogenic emissions means that the future worlds forests will be faced with unprecedented levels of carbon dioxide and other greenhouse gases, and rising temperatures due to the trapping of radiative heating by the greenhouse gases. In addition, large expanses of these ecosystems will be concurrently exposed to elevated levels of tropospheric ozone, particulates, nitrogen oxides, and acidic rainfall or other air pollutants. Finally, increasing demand for forest products and expanding development pressures from our rapidly growing world population will mean continued land use change and forest habitat loss. Thus, it is very difficult to predict the condition or productivity of forests in this century. In this book, a number of forest and atmospheric scientists summarize what is known on the impacts of air pollution and climate change on forest ecosystems.