Plant Sensors and Process-based Models in Tropical Ecohydrology

Abstract:

Mangrove forests are important for food and wood production, but also as CO₂ sink. To fulfill these essential functions, a dense structure of sufficiently large trees is necessary. Mangrove forest structure and carbon gain is highly dependent on the salinity of soil water. So far, only the impact of water available in soils has been considered in mangrove growth studies. In this work, we discovered, by the use of a combination of plant sensors, clear growth spurts in the mangrove Avicennia marina by direct uptake of rainwater by the canopy. Under field conditions in Australia we found that sap flow in Avicennia marina was reversed, from canopy to roots, during and shortly after rainfall events. Simultaneously, stem diameters rapidly increased with growth rates up to 90 µm h^-1. Furthermore, stem water potentials became more positive during rain events. These findings demonstrate how direct uptake of freshwater during rainfall may be essential for mangrove growth, despite their adaptations to the saline, (almost) saturated soils in which they root. These results point to the importance of using plant sensors in tropical ecohydrology. As the intensity and frequency of rain events is predicted to dramatically change with global climate change, we speculate that mangrove growth will alter much more drastically than anticipated before. Hence, inclusion of this water pathway and coupled growth (Steppe et al. 2015) in hydrological, ecological and global models needs to be considered.

References

Steppe K, Sterck F, Deslauriers A (2015) Diel growth dynamics in tree stems: linking anatomy and ecophysiology. Trends in Plant Science 20: 335-343.