Examining the response of needle carbohydrates from Siberian larch trees to climate using compound‐specific δ¹³C and concentration analyses

Abstract

Little is known about the dynamics of concentrations and carbon isotope ratios of individual carbohydrates in leaves in response to climatic and physiological factors. Improved knowledge of the isotopic ratio in sugars will enhance our understanding of the tree ring isotope ratio and will help to decipher environmental conditions in retrospect more reliably. Carbohydrate samples from larch (Larix gmelinii) needles of two sites in the continuous permafrost zone of Siberia with differing growth conditions were analysed with the Compound-Specific Isotope Analysis (CSIA). We compared concentrations and carbon isotope values (δ(13) C) of sucrose, fructose, glucose and pinitol combined with phenological data. The results for the variability of the needle carbohydrates show high dynamics with distinct seasonal characteristics between and within the studied years with a clear link to the climatic conditions, particularly vapour pressure deficit. Compound-specific differences in δ(13) C values as a response to climate were detected. The δ(13) C of pinitol, which contributes up to 50% of total soluble carbohydrates, was almost invariant during the whole growing season. Our study provides the first in-depth characterization of compound-specific needle carbohydrate isotope variability, identifies involved mechanisms and shows the potential of such results for linking tree physiological responses to different climatic conditions.

Compound-Specific Carbon Isotopes and Concentrations of Carbohydrates and Organic Acids as Indicators of Tree Decline in Mountain Pine

“…More detailed information can be derived from the individual carbohydrates (sucrose, glucose, and fructose), and sugar alcohols (e.g., pinitol), but also from compounds like organic acids (malate and citrate) that are involved in more "downstream metabolic processes" leading to systematic but varying 13 C-enrichment of sink organs (such as stem) in comparison to leaves [20]. Thus far, there have been few investigations analyzing δ 13 C of individual carbohydrates and organic acids [19][20][21][22][23][24][25][26] using high-performance liquid chromatography (HPLC). However, even fewer investigations were applied in natural forest ecosystems to address questions of tree eco-physiology [19,22,23,26,27].…”

“…Due to its importance, changes in δ 13 C values and sucrose concentrations are assumed to show strong responses to changing weather conditions [19]. Other soluble carbohydrates, like glucose and fructose, are also synthesized in considerable amounts in almost all plant tissues, often reflecting a carbon pool supplying all ongoing processes in a tissue such as biosynthesis of compounds, maintenance of cell structure, and respiration.…”

“…The traditional δ 13 C bulk isotope analysis of soluble carbohydrates has limitations in determining the response of plants to environmental variations because compounds with slow turnover rates, like pinitol, can strongly dampen the signal [19]. More detailed information can be derived from the individual carbohydrates (sucrose, glucose, and fructose), and sugar alcohols (e.g., pinitol), but also from compounds like organic acids (malate and citrate) that are involved in more "downstream metabolic processes" leading to systematic but varying 13 C-enrichment of sink organs (such as stem) in comparison to leaves [20].…”

“…Sugar alcohols have a very slow turnover compared to other plant sugars and are therefore not expected to reflect seasonal changes [19]. However, some studies suggested that pinitol plays a role in tolerance to low temperature and drought [19,28].…”

“…Thus far, there have been few investigations analyzing δ 13 C of individual carbohydrates and organic acids [19][20][21][22][23][24][25][26] using high-performance liquid chromatography (HPLC). However, even fewer investigations were applied in natural forest ecosystems to address questions of tree eco-physiology [19,22,23,26,27]. Therefore, further studies are needed to understand how environmental changes impact δ 13 C values and concentrations of individual compounds at the leaf level in declining trees.…”