Influence of Water Relations on the Limited Expansion of Pinus Monophylla into Adjacent Cercocarpus Ledifolius Communities in the Central Great Basin
Abstract:We investigated the influence of plant water relations on the limited expansion and dominance of Pinus monophylla (an arid land coniferous tree) into adjacent Cercocarpus ledifolius (an evergreen nonconiferous shrub or small tree) communities. Water relations and growth of both species were monitored during 2 growing seasons on a P. monophylla dominated, alluvial fan (2070 m) and a C. ledifolius dominated, exposed ridge (2745 m). In 1990, the influence of supplemental water at the lower site was investigated. Carbon isotope composition was determined from material collected in August 1990. Predawn and midday xylem pressure potentials and transpiration rates suggested that P. monophylla was more water-use efficient than C. ledifolius. Cercocarpus ledifolius had higher transpiration rates throughout the growing season and reached lower xylem pressure potentials late in the season. This suggests C. ledifolius is better able to take advantage of available water for recharging plant moisture and rapid water use. Supplemental water's only effect was a significant increase in C. ledifolius transpiration. Carbon isotope ratios (∂13C) were more negative for C. ledifolius than P. monophylla and with increasing soil water availability. Lower rates of growth and water-use patterns by P. monophylla are not an advantage in the C. ledifolius zone and contribute to its limited expansion into this zone. For. Sci. 39(4): 629-643.
Document Type: Journal Article
Affiliations: Professor, Department of Rangeland Resources, Oregon State University, Corvallis, OR 97331
Publication date: November 1, 1993
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