Quantifying competitive ability of perennial grasses to inhibit Scotch broom

Abstract

Greenhouse pot studies were conducted to quantify the competitive abilities of three native perennial grass species to inhibit development of Scotch broom (Cytisus scoparius (L.) Link ) seedlings: spike bentgrass (Agrostis exarata Trin. ), blue wildrye (Elymus glaucus Buckley), and western fescue (Festuca occidentalis Hook. ). In single-species stands (1) soil water content decreased with increasing grass density, (2) soil water depletion per plant differed among species as ratios of 2.4:1.3:1 for bentgrass, fescue, and wildrye, respectively, and (3) average percentage of ground cover per plant was ranked by species as bentgrass (14 percent), wildrye (8 percent), broom (8 percent), and fescue (5 percent). Regression models predicted 90, 85, and 72 percent reductions in average biomass per plant of broom when grown with approximately 250 plants/m2 of bentgrass, wildrye, and fescue, respectively. Bentgrass and wildrye were more competitive than fescue because of their early-season depletion of soil water and rapid development of cover.

Citation

Harrington, Timothy, B. 2011. Quantifying competitive ability of perennial grasses to inhibit Scotch broom. Res. Pap. PNW-RP-587. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 15 p.