Patterns of Seedling Emergence from North Dakota Grazing Lands Invaded by Kentucky Bluegrass

Abstract

Kentucky bluegrass (Poa pratensis, POPR) is a dominant invader of the northern Great Plains, but little is known about its impact on seedbanks. We quantified patterns of seedling emergence from samples of litter, thatch, and mineral soil collected from invaded grassland sites, hypothesizing that POPR would be the dominant emergent species, but that composition of seedling populations would differ between the layers with a higher incidence of native species in mineral soil. POPR accounted for 84% of the emergent seedlings, and curves, fit with a Hill model, indicated that 50% of cumulative emergence was reached after 40.5 d. Rank-abundance diagrams were highly skewed and strongly dominated by POPR but indicated differences among litter, thatch, and soil layers. POPR accounted for 94.3%, 71.9%, and 69.9% of emergent seedlings from litter, thatch, and soil layers, respectively. More POPR seedlings emerged from litter material than the other layers. Management of POPR by fire or grazing should consider their possible effects on seed production, distribution, and longevity of buried seeds.