1. Tropical Leaf Wax n‐Alkane and n‐Alkanoic Acid Reflect δD of Precipitation During Early Stages of Leaf Growth: Insights From an Isotope Labeling Experiment.
- Author
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Saishree, Amrita, Managave, Shreyas, Yadava, M. G., Devi, Salam Maheshwori, and Sanyal, Prasanta
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HYDROGEN isotopes ,DEUTERIUM oxide ,LEAF growth ,CIRCULATION models ,ATMOSPHERIC circulation - Abstract
The hydrogen isotopic compositions of leaf‐wax n‐alkanes (δDalk) and n‐alkanoic acids (δDacid) reflect ambient climatic conditions (including precipitation δD values, δDprecip). However, the understanding of climatic conditions of exactly which period (i.e., early or entire period of the leaf's lifespan) these biomarkers preserve is still evolving. Previous studies on the δDalk and δDacid values, done only in extra‐tropical regions, mostly indicate that δDalk values are biased toward the early growing season whereas δDacid values are not biased toward any season. To decipher the seasonal bias in δDalk and δDacid records from tropics, we conducted a long‐duration experiment wherein deciduous and evergreen species were grown using normal water (δD = −2‰) during early stages of the leaf growth and later using isotopically labeled water (δD = 1,000‰). Our experiment revealed (a) in deciduous and evergreen species, δDalk and δDacid values reflect δDprecip during early stages of the leaf growth, (b) synchronous synthesis of n‐alkanes and n‐alkanoic acids, and (c) in deciduous species, minor incorporation of the previous year's photosynthates in leaf wax pool of the current year's mature leaves. Our study suggests that δDalk and δDacid records in the tropics are biased toward the climatic conditions prevailing during early stages of leaf growth. This bias should be considered while comparing the δDprecip values generated from leaf wax proxy records and isotope‐enabled atmospheric circulation models. Plain Language Summary: The hydrogen isotopic composition of leaf wax n‐alkanes and n‐alkanoic acids preserved in sediments have been used extensively for reconstructing past climate variability. However, whether these records reflect a climate of a specific season or an entire year is not known. In our experiment, we grew various tropical plants using normal water during early growing season and heavy water during later growing season. Lack of isotopic signal associated with the heavy water in leaf wax compounds suggested that the bulk of leaf wax production occurred during the early growing season of the leaves. As the hydrogen isotopic composition of the leaf wax compounds reflects ambient climatic conditions, our results suggested that the hydrogen isotope record of tropical leaf wax compounds reflects the climatic conditions prevailing during the early stages of leaf growth. Key Points: Hydrogen isotope records of leaf wax n‐alkane and n‐alkanoic acid from the tropics reflect climatic conditions during the early leaf growthBoth deciduous and evergreen leaf wax hydrogen isotope records are biased toward the early stages of the leaf growthThis bias should be considered while comparing the hydrogen isotope of precipitation generated from climate models and leaf wax records [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
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