SREL Reprint #3698

Seasonal non-structural carbohydrate dynamics differ between twig bark and xylem tissues

Liyuan Gao1,2, Doug P. Aubrey3,4, Xingchang Wang1,2, and Huizhen Sun1,2

1Center for Ecological Research, Northeast Forestry University, 26 Hexing Road, Xiangfang District,
Harbin 150040, People’s Republic of China
2Key Laboratory of Sustainable Forest Ecosystem Management-Ministry of Education,
Northeast Forestry University, Harbin 150040, People’s Republic of China
3Savannah River Ecology Laboratory, University of Georgia, Aiken, SC 29802, USA
4Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA

Abstract: Despite extensive research on non-structural carbohydrates (NSC), the distribution of total NSC (TNC) and its primary components (sugar and starch) to the bark and xylem of twigs remains poorly understood. We determined seasonal NSC dynamics in twig bark and xylem in seven temperate tree species exhibiting different xylem anatomies and leaf habits. Seasonal trends in sugar were similar across species with concentrations peaking at least 15 days earlier in the spring for xylem than bark. However, evergreens exhibited maximum bark starch concentrations in early spring, followed by declines throughout the growing season, whereas deciduous species exhibited early spring declines in bark starch, followed by late growing season increases. Evergreens exhibited limited seasonal variation in xylem starch concentrations, whereas deciduous species exhibited variation in xylem starch concentrations that was similar to variation in bark starch. With a few exceptions, concentrations and seasonal amplitudes for sugar, starch, and TNC were generally higher in bark than xylem. Sugar concentrations were generally higher than starch, especially in the bark, which resulted in variability of TNC concentrations in bark or xylem. NSC concentrations varied significantly between xylem and the entire twig when bark was not explicitly considered. Averaged across species, sugar, starch, and TNC content in bark accounted for 66%, 54%, and 61% of total twig content, respectively, even though bark only accounted for 53% of the total twig mass. We recommend quantifying bark sugar and starch separately from xylem when determining twig NSC concentration and content.

Keywords: Non-structural carbohydrate, Bark, Xylem, Twigs, Temperate tree species

SREL Reprint #3698

Gao, L., D. P. Aubrey, X. Wang, and S. Huizhen. 2022. Seasonal non-structural carbohydrate dynamics differ between twig bark and xylem tissues. Trees 36(4): 1231-1245.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).