D. Nernberg et Mrt. Dale, COMPETITION OF 5 NATIVE PRAIRIE GRASSES WITH BROMUS-INERMIS UNDER 3 MOISTURE REGIMES, Canadian journal of botany, 75(12), 1997, pp. 2140-2145
We examined the effect of moisture on the competitive ability of five
native grasses (Agropyron and Stipa) in competition with the non-nativ
e grass Bromus inermis Leyss. The plants were grown in Large pots in g
rowth rooms, and the moisture treatment was imposed by the frequency o
f watering. The competitive ability of the five native grasses, as mea
sured by shoot biomass ratio, increased with reduced water availabilit
y, but even under the driest conditions, they competed poorly with B.
inermis. The order of competitive ability found in this experiment did
not match the order predicted from field observations based on the hy
pothesis of a strict reciprocal relationship between stress tolerance
and competitive ability. Stipa viridula Trin. was the best competitor
of the five, and Stipa curtiseta (A.S. Hitchc.) Barkworth was consiste
ntly the least competitive. The order of competitive ability was more
variable when measured by the effect on Bromus than when measured by t
he effect on the native grasses themselves. The results suggest that t
olerance of abiotic stress is less important than competitive exclusio
n in determining species distributions on environmental gradients.