Microclimatic variations and their effects on photosynthetic efficiencies and lichen species distribution along elevational gradients in Garhwal Himalayas

Climate change effects on Himalayas are expectedly more pronounced than any other mountainous ecoregion of the world with expected threat of meltdown by the year 2100 if effective checks are not imposed. The impacts of this climate warming in the geologically fragile Himalayas has started to show its effects on shifting precipitation patterns, increasing temperatures, glaciers meltdown, species richness patterns and overall unpredictable microclimatic conditions. For measuring such impacts of current climate warming in Himalayan ecosystems, need of ecological substitutes has been stressed on by different United Nation conventions. Lichens in contrast to vascular flora have long been proved to act as cost effective global indicators for measuring ecosystems responses to environmental climate. The variations in microclimatic attributes and their effects on photosynthetic efficiency and distribution were studied in geologically fragile ecosystem of Govind Pashu Vihar National Park in Garhwal Himalayas. Total 217 species of lichens comprising 80 genera and 35 families were found along different elevations. Among the different habitat groups, corticolous lichens showed their dominance (123 species) followed by saxicolous (65 species) and terricolous (29 species) lichens. Corticolous forms were dominated by crustose while saxicolous and terricolous were mostly fruticose growth forms. Mostly large number of species showed a narrow distribution with maximum species richness observed in mid elevation zones (1950–2200 m) followed by a gradual decline towards higher elevations. Phaeophyscia hispidula, Parmotrema reticulatum and Flavoparmelia caperata showed wider ecological amplitude. Out of these species, P. hispidula and F. caperata were further subjected to chlorophyll fluorescence measurements with a pulse amplified modulated fluorometer to access photosynthetic quenching efficiencies. Maximum electron transport rates (ETR; 96 ± 5.76 μmol e⁻ m⁻² s⁻¹) were observed in Phaeophyscia hispidula (1550 m) while F. caperata showed nearly 21% lower ETR. Photochemical quenching (qP; 0.5 ± 0.01) was maximum at 1550 m elevation in F. caperata while P. hispidula showed maximum qP values at 2200 m elevation, showing it’s higher tolerances towards extreme light stresses. F. caperata showed higher (0.102 ± 0.003) non photochemical quenching (NPQ) in comparison to P. hispidula (0.062 ± 0.001) at extreme elevations of 3508 m. P. hispidula overall showed more toxitolerant nature towards abiotic stresses as compared to F. caperata. Higher photosynthetically active radiation (PAR; 1600–2350 µmol m⁻² s⁻¹), thallus hydration levels and extreme variations in air temperature (5.75–31.65 °C), ambient humidity along elevations were imperative in controlling species richness, distribution and photosynthetic quenching of lichen flora in the region.