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Enabling better global research outcomes in soil, plant & environmental monitoring.

Mangrove Case Studies

Modelling reveals endogenous osmotic adaptation of storage tissue water potential as an important driver determining different stem diameter variation patterns in the mangrove species Avicennia marina and Rhizophora stylosa

Maurits W. Vandegehuchte, Adrien Guyot, Michiel Hubeau, Tom De Swaef, David A. Lockington and Kathy Steppe.

  • Background: Stem diameter variations are mainly determined by the radial water transport between xylem and storage tissues. This radial transport results from the water potential difference between these tissues, which is influenced by both hydraulic and carbon related processes. Measurements have shown that when subjected to the same environmental conditions, the co-occurring mangrove species Avicennia marina and Rhizophora stylosa unexpectedly show a totally different pattern in daily stem diameter variation.
  • Methods: Using in situ measurements of stem diameter variation, stem water potential and sap flow, a mechanistic flow and storage model based on the cohesion–tension theory was applied to assess the differences in osmotic storage water potential between Avicennia marina and Rhizophora stylosa.
  • Key results: Both species, subjected to the same environmental conditions, showed a resembling daily pattern in simulated osmotic storage water potential. However, the osmotic storage water potential of R. stylosa started to decrease slightly after that of A. marina in the morning and increased again slightly later in the evening. This small shift in osmotic storage water potential likely underlaid the marked differences in daily stem diameter variation pattern between the two species.
  • Conclusions: The results show that in addition to environmental dynamics, endogenous changes in the osmotic storage water potential must be taken into account in order to accurately predict stem diameter variations, and hence growth.

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Long-term versus daily stem diameter variation in co-occurring mangrove species: Environmental versus ecophysiological drivers

Maurits W. Vandegehuchte, Adrien Guyot, Michiel Hubau, Stefanie R.E. De Groote, Niels J.F. De Baerdemaeker, Matthew Hayes, Nina Welti, Catherine E. Lovelock, David A. Lockington, Kathy Steppe.

Abstract:

High temporal resolution stem diameter variation (SDV) patterns have been widely recognized as a tool to study fundamental plant physiological mechanisms underlying whole-plant functioning and growth. As an integrative response to hydraulic and carbon related processes, SDV research has greatly improved insights in plant functioning of several herbaceous and woody species. Nevertheless, to date little detailed information on SDV and related physiological processes is available for mangrove species. By measuring continuous tree physiological variables such as stem diameter variations, sap flow and stem water potential in relation to the microclimatic conditions, the water use strategies of two co-occurring mangrove species, Avicennia marina (Forssk.) Vierh. and Rhizophora stylosa Griff. were investigated. Even though both species showed a similar long-term growth trend, closely linked to the environmental conditions, their daily SDV pattern was markedly different. While for Avicennia marina the SDV showed the standard daily pattern of morning decline and evening rise, the opposite daily SDV pattern was observed for Rhizophora stylosa. The contrasting patterns of SDV in both species thriving in the same environment indicates the importance and complexity of physiological endogenous mechanisms in addition to environmental conditions in controlling SDV and radial stem growth.

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Impact of dew and rain on the water relations of the mangrove species Avicennia marina (Forssk.) Vierh.

Stefanie De Groote

Abstract:

Mangroves are unique ecosystems thriving in extreme conditions on the interface between land and sea. They manage to survive in areas with high salinities and limited freshwater availability due to salt ultrafiltration techniques at root level as well as morphological and anatomical adaptations to conserve water. A recent study indicated the possibility of foliar water uptake as an extra mechanism used by the mangrove species Avicennia marina in order to meet its water needs. The primary goal of this research was to evaluate the impact of both dew and rain on the water relations of A. marina. Necessary ecophysiological measurements were conducted in a mangrove forest at North Stradbrooke Island, Australia and coupled to environmental data. Results revealed that this mangrove species transpired at night and that nighttime water loss had a major effect on the whole plant-water balance. Dew was assumed to contribute positively to the plant-water status in two ways: (1) the presence of dew on the leaf surfaces suppressed nighttime transpiration; and (2) foliar absorption of dew reduced local water deficits. Since soil osmotic potential was hardly influenced by the input of fresh rain water, foliar absorption of intercepted rain was believed to be the mechanism used by Avicennia marina to make optimal use of the fresh rain water.

Full Text Available from the University of Gent