Spatial partitioning of the soil water resource between grass and shrub components in a West African humid savanna

Most savanna water balance models assume water partitioning between grasses and shrubs in a two-layer hypothesis, but this hypothesis has not been tested for humid savanna environments. Spatial partitioning of soil water between grasses and shrubs was investigated in a West African humid savanna by...

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Bibliographic Details
Published in:Oecologia 1995-10, Vol.104 (2), p.147-155
Main Authors: Le Roux, X., T. Bariac, Mariotti, A.
Format: Article
Language:English
Subjects:
absorcion de agua
absorption d' eau
Animal and plant ecology
Animal, plant and microbial ecology
arbuste
arbustos
balance hidrico del suelo
bilan hydrique du sol
Biological and medical sciences
Fundamental and applied biological sciences. Psychology
gramineas
graminee
Grasses
humid zones
Plant roots
Plants
sabanas
savane
Savanna soils
Savannas
Shrubs
Soil composition
Soil water
soil water balance
Soil water content
Synecology
Terrestrial ecosystems
Water uptake
zona humeda
zone humide
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Summary:Most savanna water balance models assume water partitioning between grasses and shrubs in a two-layer hypothesis, but this hypothesis has not been tested for humid savanna environments. Spatial partitioning of soil water between grasses and shrubs was investigated in a West African humid savanna by comparing the isotopic composition (oxygen-18 and deuterium) of soil water and plant stem water during rainy and dry conditions. Both grass and shrub species acquire most of their water from the top soil layer during both rainy and dry periods. A shift of water uptake pattern towards deeper horizons was observed only at the end of the dry season after shrub defoliation. The mean depth of water uptake, as determined by the isotopic signature of stem water, was consistent with grass and shrub root profiles and with changes in soil water content profiles as surveyed by a neutron probe. This provides evidence for potentially strong competition between shrubs and grasses for soil water in these humid savannas. Limited nutrient availability may explain these competitive interactions. These results enhance our understanding of shrub-grass interactions, and will contribute to models of ecosystem functioning in humid savannas.
ISSN:0029-8549
1432-1939
DOI:10.1007/BF00328579