Environmental Gradient and its Effect on Isotopic Fractionation in Plant Leaves: A Case Study from the Himalaya with a Biomolecular Approach

Hirave, Pranav Dnyaneshwar (2016) Environmental Gradient and its Effect on Isotopic Fractionation in Plant Leaves: A Case Study from the Himalaya with a Biomolecular Approach. Masters thesis, Indian Institute of Science Education and Research Kolkata.

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Abstract

Plant performance along environmental gradients offers a way to evaluate its potential responses to the effects of climate change such as variations in temperature, precipitation and elevated CO₂ concentration. Isotopic measurements linked to plant performance allow multiple observations along the climatic gradients such as those produced by elevation. Water availability is the most influential factor affecting plant carbon (δ13C) and nitrogen (δ15N) isotope composition in arid and semi-arid environments. This study reports stable carbon and nitrogen isotopic values of bulk leaves and Caron isotopic vaues of leaf wax n-alkanes as well as n-alkanes abundances and chain length distribution of 6 gymnosperm (Cedrus deodara, Pinus wallichiana, Pinus roxburghi, Pinus gerardiana, Abies pindrow and Picea smithiana) and 3 angiosperm (Betula utilis, Quercus incana and Eucalyptus globulus) species collected along an altitude gradient in the Himalayan mountain ranges. The studied sites covers ca. 3.5 km elevation transect and an annual precipitation range of 900 mm. This study gives important information about effect of different nitrogen transport mechanisms in plants. Leaf nitrogen content and δ15Nleaf values do not show consistent relationship with water availability for a particular plant species or type as local variation in soil nitrogen dynamics and fungal association plays important role in defining nitrogen characteristics of a plant. The abundances of n-alkanes of different chain-lengths, show consistent differences between two major plant groups. Angiosperms produce significantly higher concentrations of n-alkanes than gymnosperms in general. Hence this study puts a strong argument that the n-alkane biomarker record will largely (but not exclusively) represent angiosperms if both groups are present and independent fossil data will be essential to assess the paleo-ecological conditions. ACL values of n-alkanes derived from angiosperms also show considerable sensitivity to water availability however detailed analysis is necessary in order to firmly understand this correlation.

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