Effect of Climate on Carbon Isotope Composition of Modern Vegetation

Behera, Padmasini (2015) Effect of Climate on Carbon Isotope Composition of Modern Vegetation. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MS dissertation of Padmasini Behera (10MS87)) Padmasini_Behera_10MS87.pdf - Submitted Version Restricted to Repository staff only Download (1MB)

Abstract

Based on carbon isotope ratio (δ¹³C) plants community can be broadly divided into C₃ and C₄ group. The δ¹³C values of C₃ plants vary from -20 to -33 ‰ whereas for C₄ plants the range is -10 to -14 ‰. The wide range of variations in δ¹³C values in both C₃ and C₄ plants have been attributed to climatic factor as well morphology of plants. This study aims to constrain the δ¹³C values of modern plants (both C₃ and C₄) from the lower Gangetic plain. To investigate this, the δ¹³C values of both C₃ and C₄ plant species was analyzed from Mohanpur, West Bengal, in eastern part of India during summer monsoon period. The δ¹³C value of C₃ plant ranges from -33 to -26‰ with an average of -29.7±1.3‰ (n = 36) and for C₄ plant value ranges from -11 to -14‰ with an average of -12.6±0.7‰ (n = 16). The spread in isotopic value of C₃ plant is much higher than the C₄ plant type. Also the average δ¹³C value of C₃ plants is lower by ~2 ‰ compared to δ¹³C values of C₃ plants globally. In C₃ plants the individual plant parts have different δ¹³C value. The leaves are on average 1.0‰ and 1.7‰ more depleted than woody stem and roots respectively but the flower is only 0.3‰ enriched than leaf. The difference in δ¹³C value of plant parts is not significant in C₄ plant type. Comparison of average δ¹³C value of plant leaves of both C₃ and C₄ with mean annual precipitation (MAP) of three year from same location shows that lowering in δ¹³C value with increase in MAP. The stomatal conductance of the leaf was measured to check the effect of MAP on δ¹³C value of modern vegetation. By comparing the common plant species from Indian subcontinent (Mohanpur location) with other places of Globe, it gives that the δ¹³C value of common plant species is more depleted in Indian subcontinent than other part of Globe. This more depleted value in Indian subcontinent can change the interpretation of paleovegetation reconstruction.

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