Patterns and dynamics of canopy–root coupling in tropical tree saplings vary with light intensity but not with root depth

Israel Oren, Neringa Mannerheim, Rita Dumbur, Andreas Fangmeier, Nina Buchmann, José M. Grünzweig*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Carbon (C) dynamics in canopy and roots influence whole-tree carbon fluxes, but little is known about canopy regulation of tree-root activity. Here, the patterns and dynamics of canopy–root C coupling are assessed in tropical trees. Large aeroponics facility was used to study the root systems of Ceiba pentandra and Khaya anthotheca saplings directly at different light intensities. In Ceiba, root respiration (Rr) co-varied with photosynthesis (An) in large saplings (3-to-7-m canopy–root axis) at high-light, but showed no consistent pattern at low-light. At medium-light and in small saplings (c. 1-m axis), Rr tended to decrease transiently towards midday. Proximal roots had higher Rr and nonstructural carbohydrate concentrations than distal roots, but canopy–root coupling was unaffected by root location. In medium-sized Khaya, no Rr pattern was observed, and in both species, Rr was unrelated to temperature. The early-afternoon increase in Rr suggests that canopy–root coupling is based on mass flow of newly fixed C in the phloem, whereas the early-morning rise in Rr with An indicates an additional coupling signal that travels faster than the phloem sap. In large saplings and potentially also in higher trees, light and possibly additional environmental factors control the diurnal patterns of canopy–root coupling, irrespective of root location.

Original languageAmerican English
Pages (from-to)727-739
Number of pages13
JournalNew Phytologist
Volume225
Issue number2
DOIs
StatePublished - 1 Jan 2020

Bibliographical note

Publisher Copyright:
© 2019 The Authors. New Phytologist © 2019 New Phytologist Trust

Keywords

  • Ceiba pentandra
  • Khaya anthotheca
  • canopy–root coupling mechanisms
  • nonstructural carbohydrates
  • phloem sap flow velocity
  • photosynthesis
  • pressure concentration wave
  • root respiration

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