PARENT SESSION
Poster Session #9: Water Relations.
Monday, August 6, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall
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Water dynamics in four water-limited plant communities.
Ryel, Ronald1, Caldwell, Martyn1, Yoder, Carolyn1, Leffler, A. Joshua1, 1
ABSTRACT- Dynamics of water availability was assessed during the growing seasons of 1999-2000 in four near-monoculture plant communities where water is considered a limiting resource. The four communities (Bromus tectorum--annual grass, Agropyron desertorum--perennial grass, Artemisia tridentata--shrub and Juniperus osteosperma--evergreen tree) are widespread in the Intermountain West region of the United States. Soil water potentials (MPa) were measured at nine depths (to 3 m) using screen-cage thermocouple psychrometers. Despite water being a limiting resource, the pattern of water availability differed greatly among these communities. Community differences in water-use dynamics were related to differences in plant phenology, root distribution, and hydraulic redistribution of soil and rain water by roots. The annual Bromus tectorum community had the least water use in the soil column with water uptake only in the upper 60 cm. In contrast, the Artemisia tridentata shrub community had the greatest total water uptake, with water extraction to 180 cm depth. Hydraulic redistribution of water was observed in all communities, especially following rainfall events. The Bromus tectorum community showed water redistribution by roots after above-ground foliage had senesced. Unlike the other communities, the Artemisia tridentata community tended to homogenize the water content in the soil column, both through hydraulic redistribution and temporal changes in the water uptake capacity of roots. Differences in water availability among these communities suggests functional differences in both water and nutrient dynamics.
KEY WORDS: soil water dynamics, hdyraulic redistribution, redistribution of rainfall, steppeland plant communities