GRASS–WOODY PLANT RELATIONSHIPS

Bromegrass (Bromus inermis Leyss. cult Carlton) was grown alone or with aspen (Populus tremuloides Michx.), silverberry (Elaeagnus commutata Bernh.), or western snowberry (Symphoricarpos occidentalis Hook.) in the greenhouse for 90 days. Competition reduced the yields of grass and woody plants compared with yields obtained when either was grown alone. Bromegrass grown alone or with aspen or snowberry produced similar total yields, but when grown with high density silverberry, the total yields were significantly greater. The yield of oat forage obtained from soil that had grown a previous crop of woody plants was reduced by previous high production of aspen or snowberry, but oat yield increased with previous high production of silverberry. It is known that another species of the genus Elaeagnus is a nitrogen-fixer and the silverberry plants used in this study were nodulated. The beneficial effects of silverberry on the grass may have been due to nitrogen fixation.