Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/23/2009
Publication Date: 3/1/2010
Citation: Espeland, E.K., Perkins, L.B., Leger, E.A. 2010. Comparison of seed bank estimation techniques using six weed species in two soil types. Rangeland Ecology and Management. 63(2): 243-247.
Interpretive Summary: How many weed seeds lie dormant in the soil? What species of weeds will appear in the spring? How can farmers and ranchers plan for weed control in the coming growing season? We can estimate how many weed seeds are in the soil by taking a sample and watering it, and then counting the number of weeds that grow from this soil sample. This study examines how good an estimate we can get with this technique. We tested different watering methods (top-misting vs. top-misting and bottom-wicking) to see if watering method changed our estimate. We also examined the effect of soil water holding capacity on our weed seed estimates. By placing known quantities of common weed seeds (cheatgrass, silvergrass, field pepperweed, kochia, lambsquarters and pigweed) in two soil types, we were able to look at the effects of soil and watering method on our estimates of weed seed numbers. We also germinated these seeds on filter paper in darkness to examine differences in germination (breaking of the seed coat and the extension of a preliminary root, or radicle) and emergence (preliminary leaves, or cotyledons, break through the soil surface). Each soil type produced the same estimates for each weed species, even though their water-holding capacities were different. The two watering methods produced different estimates, with the top-only method severely underestimating the number of weed seeds in the soil. Not only were the numerical estimates of weed seeds different, but the order of species’ abundances changed between the two methods.
Technical Abstract: Tests of three different seed bank estimation techniques were performed on six different weed species. Petri plate germination was compared to two emergence methods, each on two different soil types (stony loam vs. silt loam). Soil types produced equal emergence proportions, however both emergence techniques produced smaller seed bank estimates than the germination technique. The two emergence techniques produced different estimated relative abundances of half the species in the seed bank, thus caution is required when comparing emergence-based seed bank estimates across studies, particularly when methods and their comparability are not fully described.