Kathy Steppe(1,6), Maurits W. Vandegehuchte(1), Bart A.E. Van de Wal(1), Pieter Hoste(1), Adrien Guyot(2,3,4), Catherine E. Lovelock(2,5) and David A. Lockington(2,3)
1. Laboratory of Plant Ecology, Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000 Ghent, Belgium;
2. National Centre for Groundwater Research and Training, Flinders University, Adelaide, South Australia 5042, Australia;
3. School of Civil Engineering, The University of Queensland, St. Lucia, Queensland 4072, Australia;
4. Department of Civil Engineering, Monash University, Clayton, Victoria 3168, Australia;
5. School of Biological Sciences, The University of Queensland, St. Lucia, Queensland 4072, Australia;
6. Corresponding author ([email protected])
(Received November 9, 2017; accepted February 13, 2018; published online March 17, 2018; handling Editor Roberto Tognetti)
Mangrove forests depend on a dense structure of sufficiently large trees to fulfill their essential functions as providers of food and wood for animals and people, CO2 sinks, and protection from storms.
The 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 serves as a call to consider this water uptake pathway if we aspire to correctly assess influences of changing rainfall patterns on mangrove tree growth.
Keywords: dendrometer, foliar absorption of intercepted rainfall, foliar water uptake, hydraulic redistribution, mangrove, mechanistic tree modeling, sap flow, soil–plant–atmosphere continuum, stem diameter variations, turgor-driven radial stem growth.