Change in atmospheric deposition during last half century and its impact on lichen community structure in Eastern Himalaya

Climatic fluctuations largely affects species turnover and cause major shifts of terrestrial ecosystem. In the present study the five decade old herbarium specimens of lichens were compared with recent collection from Darjeeling district with respect to elements, PAHs accumulation and carbon isotope composition (delta C-13) to explore the changes in climatic conditions and its impact on lichen flora. The delta C-13 has increased in recent specimens which is in contrast to the assumption that anthropogenic emission leads to delta C-13 depletion in air and increased carbon discrimination in flora. Study clearly demonstrated an increase in anthropogenic pollution and drastic decrease in precipitation while temperature showed abrupt changes during the past five decades resulting in significant change in lichen community structure. The Usneoid and Pertusorioid communities increased, while Physcioid and Cyanophycean decreased, drastically. Lobarian abolished from the study area, however, Calcicoid has been introduced in the recent past. Probably, post-industrial revolution, the abrupt changes in the environment has influenced CO2 diffusion and/C fixation of (lower) plants either as an adaptation strategy or due to toxicity of pollutants. Thus, the short term studies (<= 5 decades) might reflect recent micro-environmental condition and lichen community structure can be used as model to study the global climate change.