Author
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Bushman, Shaun |
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Johnson, Douglas |
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Connors, Kevin |
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Jones, Thomas |
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Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/10/2015 Publication Date: 11/1/2015 Citation: Bushman, B.S., Johnson, D.A., Connors, K.J., Jones, T.A. 2015. Germination and seedling emergence of three western North American rangeland legumes. Rangeland Ecology and Management. 68:501-506. Interpretive Summary: Few seed sources of North American forbs are available for revegetation/restoration of degraded western rangelands adapted to precipitation zones less than 300 mm, and those that are available are mainly wildland-collected. The amount of time and resources necessary to make wildland collections in quantity results in high seed prices and variable seed quality, such that forbs have been under-represented in rangeland seeding mixes. We have previously identified basalt milkvetch (Astragalus filipes), western prairie clover (Dalea ornata), and Searls' prairie clover (Dalea searlsiae) as native species adapted to the western USA low precipitation zones for which field-grown seed production would potentially reduce seed costs and increase availability. A series of glasshouse experiments were conducted to determine the effects of scarification, planting depth, and soil composition on germination and seedling emergence of these species. All three species were characterizedd by hard seeds, such that scarification was necessary to increase germination and seedling emergence. A planting depth of 19 mm retarded the rate of emergence for all species and reduced the total seedling emergence in basalt milkvetch. Higher clay content in soils caused crusting that reduced emergence of prairie clovers, but resulted in increased emergence of basalt milkvetch. With seed scarification in sandy soils, prairie clover germination and seedling emergence approached 100% while basalt milkvetch was considerably lower. Along with enhancing stand establishment in seed production fields, these data will assist land managers in planning for optimal establishment of these species in rangeland revegetation/restoration projects. Technical Abstract: Few seed sources of North American forbs are available for revegetation/restoration of degraded western rangelands adapted to precipitation zones less than 300 mm, and those that are available are mainly wildland-collected. The amount of time and resources necessary to make wildland collections in quantity results in high seed prices and variable seed quality, such that forbs have been under-represented in rangeland seeding mixes. We have previously identified basalt milkvetch (Astragalus filipes), western prairie clover (Dalea ornata), and Searls' prairie clover (Dalea searlsiae) as native species adapted to the western USA low precipitation zones for which field-grown seed production would potentially reduce seed costs and increase availability. A series of glasshouse experiments were conducted to determine the effects of scarification, planting depth, and soil composition on germination and seedling emergence of these species. All three species were characterized by hard seeds, such that scarification was necessary to increase germination and seedling emergence. A planting depth of 19 mm retarded the rate of emergence for all species and reduced the total seedling emergence in basalt milkvetch. Higher clay content in soils caused crusting that reduced emergence of prairie clovers, but resulted in increased emergence of basalt milkvetch. With seed scarification in sandy soils, prairie clover germination and seedling emergence approached 100% while basalt milkvetch was considerably lower. Along with enhancing stand establishment in seed production fields, these data will assist land managers in planning for optimal establishment of these species in rangeland revegetation/restoration projects. |
