Abstract
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 (δ13C) to explore the changes in climatic conditions and its impact on lichen flora. The δ13C has increased in recent specimens which is in contrast to the assumption that anthropogenic emission leads to δ13C 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.
Highlights
Extraterrestrial solar UV and cosmic radiation[19]
Zschau et al.[38] correlated the atmospheric deposition of trace elements on lichen genus Xanthoparmelia with specimens preserve in the herbaria and concluded that the trace elements were increased in Arizona due to various anthropogenic activities
We investigated the changes in atmospheric deposition, in terms of elemental composition and Polycyclic aromatic hydrocarbons (PAHs) accumulation, as well as in δ13C as a representative of global CO2 increase and the impact on lichen community structure to study the global climate/ microclimate change during last half century using herbarium specimens
Summary
Extraterrestrial solar UV and cosmic radiation[19]. The lack of vascular system and dependence to absorb water and nutrients passively from their environment make lichens sensitive to environmental factors such as temperature, water availability and air pollutants[20,21]. During the last decades several studies have used herbarium lichen specimens as a tool for determining the early twentieth century environmental conditions to compare with present atmospheric pollution[26,33]. In the view of above, it may be assumed that metals concentrations in the herbarium lichen samples correlate with atmospheric inputs for the corresponding period, herbarium specimens can be safely used in environmental studies provided the disruptive factors such as sampling contamination, preservatives and storage condition can be excluded[39]. We investigated the changes in atmospheric deposition, in terms of elemental composition and PAHs accumulation, as well as in δ13C as a representative of global CO2 increase and the impact on lichen community structure to study the global climate/ microclimate change during last half century using herbarium specimens
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