Consequences of Surface and Subsurface Water Use on Wetland Graminoids of Different Geographic Origin

Abstract

We evaluated growth and physiology of three wetland graminoids (Distichlis spicata, Leymus triticoides, and Juncus arcticus) as affected by surface and subsurface water. These species are common in western USA and were collected from two areas: Bishop, California and Burns, Oregon. Our hypotheses were: 1) the use of surface water by plants is higher than the use of subsurface water and 2) there are population differences in the response of the species to available water. The species of study were grown in two-layer pots with soil water content in the upper and lower layers independently controlled. The first hypothesis was partially supported by our results, but variability existed among species. However, when all species had equal access to both surface soil water and subsurface water plants tended to preferentially use surface water. We also found that J. arcticus can display reverse hydraulic lift when growing with no subsurface water. The second hypothesis was clearly supported by results. Although the mechanism is not clear, it is possible that an area with periodic and predictable shallow groundwater underlying a dry or saline soil layer, such as the California site, might favor plant populations with high proficiency in water uptake by deeper roots.