Direct uptake of canopy rainwater causes turgor-driven growth spurts in the mangrove Avicennia marina

Kathy Steppe, Maurits W. Vandegehuchte, Bart A. E. Van de Wal, Pieter Hoste, Adrien Guyot, Catherine E. Lovelock, David A. Lockington

Research output: Contribution to journalArticleResearchpeer-review

33 Citations (Scopus)

Abstract

Mangrove forests depend on a dense structure of sufficiently large trees to fulfil their essential functions as providers of food and wood for animals and people, CO2 sinks and protection from storms. Growth of these forests is known to be dependent on the salinity of soil water, but the influence of foliar uptake of rainwater as a freshwater source, additional to soil water, has hardly been investigated. Under field conditions in Australia, stem diameter variation, sap flow and stem water potential of the grey mangrove (Avicennia marina (Forssk.) Vierh.) were simultaneously measured during alternating dry and rainy periods. We found that sap flow in A. marina was reversed, from canopy to roots, during and shortly after rainfall events. Simultaneously, stem diameters rapidly increased with growth rates up to 70 μmh-1, which is about 25-75 times the normal growth rate reported in temperate trees. A mechanistic tree model was applied to provide evidence that A. marina trees take up water through their leaves, and that this water contributes to turgor-driven stem growth. Our results indicate that direct uptake of freshwater by the canopy during rainfall supports mangrove tree growth and serve as a call to consider this water uptake pathway if we aspire to correctly assess influences of changing rainfall patterns on mangrove tree growth.

Original languageEnglish
Pages (from-to)979-991
Number of pages13
JournalTree Physiology
Volume38
Issue number7
DOIs
Publication statusPublished - 1 Jul 2018

Keywords

  • Dendrometer
  • Foliar absorption of intercepted rainfall
  • Foliar water uptake
  • Hydraulic redistribution
  • Mangrove
  • Mechanistic tree modelling
  • Sap flow
  • Soil-plant-atmosphere continuum
  • Stem diameter variations
  • Turgor-driven radial stem growth

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