Soil water availability and plant growth in relation to diversity of restored plant communities. Marchant, Luke ^*,1, Roundy, Bruce ^*,, Allen, Phil ^*,1, ¹ Integrative Biology, Provo, UT

ABSTRACT- Competition among different range plant species for a common resource such as soil water often determines a plants growth and ultimately, the composition of a community. Greater plant community diversity should reduce resource availability in time and space. This could increase resistance to weed invasion. To determine effects of diversity on soil water availability we measured soil and plant water potential and plant growth in constructed communities including perennial grasses only, grass and forbs, and grass, forbs, and shrubs. Midsummer plant water potentials and late summer growth of Elymus spicatus was reduced when grown with forbs (Chrysopsis villosa and Hedysarum boreale) and shrubs (Chrysothamnus nauseosus and Artemisia tridentata) compared to that when grown by itself or with Elymus elymoides. Increased density from 3.6 to 5.4 plants/m2 did not affect days of available soil water from March through July. However, time of soil water availability during that period was 16 to 57 days less in mixed communities with grasses and shrubs, grasses and forbs, or grasses, forbs, and shrubs than in monocultures of Elymus elymoides, depending on the soil depth.

KEY WORDS: Water, Plant Growth, Diversity of Restored Plant Communities