Upside down and the game of C allocation

Negar Rezaie; Ettore D'Andrea; Andrea Scartazza; Jožica Gričar; Peter Prislan; Carlo Calfapietra; Alberto Battistelli; Stefano Moscatello; Simona Proietti; Giorgio Matteucci

doi:10.1093/treephys/tpad034

Upside down and the game of C allocation

Tree Physiol. 2023 Mar 14:tpad034. doi: 10.1093/treephys/tpad034. Online ahead of print.

Authors

Negar Rezaie¹, Ettore D'Andrea^{2

3}, Andrea Scartazza^{4

3}, Jožica Gričar⁵, Peter Prislan⁵, Carlo Calfapietra^{2

3}, Alberto Battistelli², Stefano Moscatello², Simona Proietti², Giorgio Matteucci^{6

3}

Affiliations

¹ Research Institute on Terrestrial Ecosystems, National Research Council of Italy (CNR-IRET), Via P. Castellino n. 111, 80131 Napoli, Italy.
² Research Institute on Terrestrial Ecosystems, National Research Council of Italy (CNR-IRET), via Marconi 2, 05010 Porano (TR), Italy.
³ National Biodiversity Future Center (NBFC), Palermo, Italy.
⁴ Research Institute on Terrestrial Ecosystems, National Research Council of Italy (CNR-IRET), Via Moruzzi 1, 56124 Pisa, Italy.
⁵ Slovenian Forestry Institute, Večna pot 2, 1000 Ljubljana, Slovenia.
⁶ Institute for BioEconomy, National Research Council of Italy (CNR-IBE), via Madonna del Piano, 10 - 50019 Sesto Fiorentino (FI), Italy.

PMID: 36917230
DOI: 10.1093/treephys/tpad034

Abstract

Non-structural carbohydrates (NSCs) represent the primary carbon (C) reserves and play a crucial role for plant functioning and resilience. Indeed, these compounds are involved in the regulation between C supply and demand, and in the maintenance of hydraulic efficiency. NSCs are stored in parenchyma of woody organs, which is recognized as a proxy for reserve storage capacity of tree. Notwithstanding the importance of NSCs for tree physiology, their long-term regulation and trade-offs against growth were not deeply investigated. This work evaluated the long-term dynamics of mature tree reserves in stem and root, proxied by parenchyma features, and focusing on the trade off and interplay between the resources allocation in radial growth and reserves in stem and coarse root. In a Mediterranean beech forest, NSCs content, stem and root wood anatomy analysis, and eddy covariance data, were combined. The parenchyma fraction (RAP) of beech root and stem was different, due to differences in axial parenchyma (AP) and narrow ray parenchyma (nRP) fractions. However, these parenchyma components and radial growth showed synchronous inter-annual dynamics between the two organs. In beech stem, positive correlations were found among soluble sugars content and nRP, and among starch content and the AP. Positive correlations were found among Net Ecosystem Exchange (NEE) and AP of both organs. In contrast, NEE was negatively correlated to radial growth of root and stem. Our results suggest a different contribution of stem and roots to reserves storage, and a putative partitioning in the functional roles of parenchyma components. Moreover, a long-term trade-off of C allocation between growth and reserve pool was evidenced. Indeed, in case of C source reduction, trees preferentially allocate C towards reserves pool. Conversely, in high productive years, growth represents the major C sink.

Keywords: Eddy covariance; Fagus sylvatica (beech); Mediterranean forest; non-structural carbohydrates (NSCs); wood anatomy.