Response of Juniperus phoenicea on sandy dunes in the Camargue (France) to water and saline constraint in summer
✍ Scribed by Berger, A. ;Heurteaux, P.
- Publisher
- Springer-Verlag
- Year
- 1985
- Tongue
- English
- Weight
- 507 KB
- Volume
- 62
- Category
- Article
- ISSN
- 1573-5052
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✦ Synopsis
The'Bois des Ridges' woodland occurs on the relic littoral dunes in the National Reserve of the Camargue. Although surrounded by brackish ponds and saline lands with very salt groundwater close to the surface, the dunes are covered with non-halophytic vegetation of herbaceous shrubs and trees, including the dominant shrub Juniperus phoenicea. This is due to the presence of a freshwater lens beneath the dunes supplied by rains, and floating in hydrodynamic equilibrium upon the saline aquifer. The importance and duration of the freshwater stock depends on the precipitation-evapotranspiration balance as well as on the size of the dune.
From the end of the spring to the autumn rain period this freshwater stock is considerably reduced, while the capillary potential in the zone of aeration of soil and the osmotic potential of the soil solution, influenced by capillary rise of the brackish groundwater, decrease. In summer the vegetation is thus subjected to severe drought caused by lack of water or salt excess, to which it must adjust its biological activity.
The water relationships in the soil-plant system have been studied along a transect between the top and the borders of a dune surrounded by saline lands. Using simultaneous water potential measurements of the sunny and shady sides of Juniperus trees daily and seasonal transpiration regulations were studied. The preliminary results indicate that trees on the border of the dune as well as on tops are absorbing water from the same freshwater lens in the middle of the dune.