Comparative plant responses of Puccinellia distans and Puccinellia nuttalliana to sodic versus normal soil types

In the Grande Ronde Valley of eastern Oregon, two perennial grass species within the genus Puccinellia; Puccinellia distans (L.) Parl. (weeping alkaligrass) and Puccinellia nuttalliana Hitchc. (Nuttallʹs alkaligrass), are weeds that occupy distinct sodic soil patches within agriculturally productive fields. These two species were studied to determine if, under non-competitive conditions, either species exhibited attributes that could allow for the movement of populations into productive soils. Both species had high germination on either sodic or normal soil types. Yet, on both soil types, P. distans grew larger and produced up to 4 times the number of viable seed than did P. nuttalliana. Growth rates and seed production of P. nuttalliana were not affected by soil type; yet, P. distans benefited from the normal soil condition through increased biomass accumulation and seed production. While the phenological development of either species was not affected by soil type; P. distans was able to continue tiller production through out the growing season whereas P. nuttalliana ceased tiller development soon after onset of reproduction. Pucinellia distans adjusted osmotically to a much lower solute potential (−3.6 MPa) than P. nuttalliana (−2.3 MPa) under sodic soils. Under normal soil conditions, P. distans maintained a higher relative water content (80%) than P. nuttalliana (60%) at the same osmotic potential (−2.3 MPa).