Leaf conductance and transpiration of winterfat associated with 2 species of wheatgrass on disturbed sites

Abstract

Competitive relations between a half-shrub and 2 wheatgrasses were determined on 2 disturbed sites in northwestern Colorado. Leaf conductance and transpiration of winterfat [Eurotia lanata (Pursh) Moq., also known as Ceratoides lanata] were measured in association with a neighboring plant of either winterfat, beardless bluebunch wheatgrass [Pseudoroegneria spicata subsp. inermis (Scribn. and Smith A. Löve], or western wheatgrass [Pascopyrum smithii Rydb.) A. Löve] and as affected by a shallow disturbance of soil to a depth of 30 cm or a deep disturbance of soil to a depth of 1 m. Reduced leaf conductance was associated with advancing phenology and plant water stress as soil water was depleted during the growing season. Leaf conductance and transpiration of winterfat was often lower when it was associated with the 2 grasses than when growing adjacent to another winterfat plant. Lowest transpiration rates of winterfat were found when it was growing adjacent to beardless bluebunch wheatgrass. Thus, the intensity of competition for soil water may be greater for winterfat when associated with wheatgrasses than when growing adjacent to another winterfat plant.