Night and day: Shrinking and swelling of stems of diverse mangrove species growing along environmental gradients.

Maria P Vilas,Matthew P Adams,Catherine E Lovelock,Nadia S Santini,Andrew Swales,Marilyn C Ball,Jan-Olaf Meynecke

doi:10.1371/journal.pone.0221950

Abstract

Tree stems swell and shrink daily, which is thought to reflect changes in the volume of water within stem tissues. We observed these daily patterns using automatic dendrometer bands in a diverse group of mangrove species over five mangrove forests across Australia and New Caledonia. We found that mangrove stems swelled during the day and shrank at night. Maximum swelling was highly correlated with daily maxima in air temperature. Variation in soil salinity and levels of tidal inundation did not influence the timing of stem swelling over all species. Medium-term increases in stem circumference were highly sensitive to rainfall. We defoliated trees to assess the role of foliar transpiration in stem swelling and shrinking. Defoliated trees showed maintenance of the pattern of daytime swelling, indicating that processes other than canopy transpiration influence the temporary stem diameter increments, which could include thermal swelling of stems. More research is required to understand the processes contributing to stem shrinking and swelling. Automatic Dendrometer Bands could provide a useful tool for monitoring the response of mangroves to extreme climatic events as they provide high-frequency, long-term, and large-scale information on tree water status.

Highlights

Mangrove forests are of major ecological and socio-economic importance for the functioning of coastal systems in the tropics and sub-tropics [1], and have been broadly recognised as a significant contributor of carbon sequestration to the global carbon balance [2,3]
Daytime stem swelling is a widespread trait across mangrove species and environments and analysis, decision to publish, or preparation of the manuscript
This diel pattern of daytime swelling and overnight shrinking is not the same as that observed in other studies of A. marina [11,13] or in other trees in which maximum shrinking was typically observed during the day when it is proposed that transpiration from the canopy results in depletion of stem water storage [10,15,38]

Summary

Introduction

Mangrove forests are of major ecological and socio-economic importance for the functioning of coastal systems in the tropics and sub-tropics [1], and have been broadly recognised as a significant contributor of carbon sequestration to the global carbon balance [2,3]. Global warming and associated rise in sea level are inducing changes in the structure, function and distribution of these forests. Higher temperature minima reducing exposure to frosts have. Daytime stem swelling is a widespread trait across mangrove species and environments and analysis, decision to publish, or preparation of the manuscript

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Results

Discussion

Conclusion