Water Relations of High-Elevation 'Salix' Phreatophytes in Wyoming

摘要

High-elevation phreatophytes were studied to identify environmental parameters influencing daily and seasonal water consumption. The water relations of Salix planifolia, S. wolfii, and Betula occidentalis at 2865 m were similar throughout the day. Transpiration was reduced before 1,000 h as a result of dew on the leaves, but high stomatal conductances to water vapor diffusion and transpiration flux densities occurred from 1,000 to 1,600 h, resulting in a daily water loss. The period of significant water consumption was from 10 July through 20 September. For comparison, a site at lower elevation (2,225 m) was examined. The growth season at the low-elevation site was estimated to be from 15 June to 30 September. Although differences between the two sites occurred, the data suggest that for both sites and all species examined, stomatal conductance and seasonal water use were most influenced by solar irradiance, dew on leaves, minimum air temperatures in spring and fall, and phenology.