Title: Converging patterns of uptake and hydraulic redistribution of soil water in contrasting woody vegetation types.
Author: Meinzer, F.C.; Brooks, J.R.; Bucci, S.; Goldstein, G.; Scholz, F.G.; Arren, J.M.;
Source: Tree Physiology. 24: 919-928
Publication Series: Miscellaneous Publication
Description: We used concurrent measurements of soil water content and soil water potential (Ψsoil) to assess the effects of Ψsoil on uptake and hydraulic redistribution (HR) of soil water by roots during seasonal drought cycles at six sites characterized by differences in the types and amounts of woody vegetations and in climate. The six sites included a semi-arid old-growth ponderosa pine (Pinus ponderosa Dougl. ex P. Laws & C. Laws) forest, a moist old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forest, a 24-year-old Douglas-fir forest and three Brazilian savanna sites differing in tree density. At all of the sites Hr was confined largely to the upper 60 cm of soil. There was a common threshold relationship between the relative magnitude of HR and Ψsoil among the six study sites. Below a threshold Ψsoil of about -0.4 Mpa, evernight recharge of soil water storage increased sharply, and reached a maximum value of 80-90% over a range of Ψsoil frin ~ -1.2 to -1.5 Mpa. Although amounts of water hydraulically redistributed to the upper 60 cm of soil were relatively small (0 to 0.4 mm day-1), they greatly reduced the rates of seasonal decline in Ψsoil. The effectivenesss of HR in delaying soil trying diminished with increasing sapwood area per ground area. The relationship between soil water utilization and Ψsoil in the 20-60-cm layer was nearly identical for all six sites. Soil water utilization varied with a surrogate measure of rhizosphere conductance in a similar manner at all six sites. The similarities in relationships between Ψsoil and HR, soil water utilization and relative rhizosphere conductance among the six sites, suggests that, despite probable differences in maximum rooting depth and density, there was a convergence in biophysical controls on soil water utilization and redistribution in the upper soil layers where the density of finer roots is greatest.
Keywords: Coniferous forest, Pinus ponderosa, Pseudotsuga menziesii, rhizosphere, roots, soil water potential, tropical savanna
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Meinzer, F.C.; Brooks, J.R.; Bucci, S.; Goldstein, G.; Scholz, F.G.; Arren, J.M. 2004. Converging patterns of uptake and hydraulic redistribution of soil water in contrasting woody vegetation types. Tree Physiology. 24: 919-928
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