Defoliation effects on Bromus tectorum seed production: Implications for grazing
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Authors: K. Hempy-Mayer, and D. A. Pyke
Date: 2008
Journal: Rangeland Ecology & Management
Volume: 61
Number: 1
Pages: 116-123
Summary of Methods: A clipping study was set up to examine the optimal defoliation timing, intensity (stubble height), and frequency for maximum seed reduction and to prepare an effective seedbed for native reseeding projects in semiarid environments. The two study sites chosen are located in Malheur County, Oregon, referred to as Lincoln Bench (lat 43° 54' N, long 117° 9' W) and Succor Creek (lat 43° 34' N, long 117° 6' W). At both sites, treatments included clipping at two phonological stages, boot (the moment when inflorescences were beginning to emerge from the sheath) and purple (the moment when caryopses and/or glumes turned red or purple), at two heights, 2.5 cm and 7.6 cm, and either once or twice in the season. Clipping at the boot stage occurred on 26 April for the first clipping and 10 May for the second. At the purple stage, clipping occurred on 24 May and there was no second clipping. Seed density was estimated at midseason and end-of-season. Mid-season estimates were collected at the times of clippings. End-of-season estimates were collected on 31 May by clippings and collecting all plants retaining an inflorescence in the center of each treatment plot and also by taking litter samples and soil samples to a depth of 3 cm. Seed viability tests were conducted 4 months after collection.
Article Summary / Main Points:
• All treatments produced viable seed at the end of the season.
• Clipping to the shortest height at the initial boot and purple stage were most effective at reducing cheatgrass seed densities.
• Clipping plants to a height of 7.6 cm and clipping once at the boot stage were ineffective at reducing cheatgrass seed production.
• No treatment achieved 100% inflorescence removal but the short clipped plots were more successful.
• The most effective treatment was clipping plants twice at 2.5 cm when the majority of the plants are in the boot stage and 2 weeks later when they are in the postboot stages.
• Grazing sheep once in late spring and again when new inflorescences have developed is most likely the best option to reduce cheatgrass seed production; whereas, grazing once with sheep or as much as twice with cattle may not be adequate.Vegetation Types: California Grasslands (including all annual grasslands) Sagebrush Steppe
MLRA Ecoregions: 23 Malheur High Plateau
Agrovoc Control Words: Bromus tectorum Grazing Weed control
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: cheatgrass, cheatgrass control, clipping, grazing, livestock, native plant restoration, weed control
Annotation: This article describes the feasibility of using grazing as a tool for managing cheatgrass infestation. It is important to note that the authors mention that although proper targeted grazing can reduce the amount of cheatgrass seeds produced it is likely that the establishment of native plants through artificial seeding is also needed for long-term management of infestations. The authors also point out that it might be difficult to achieve uniform grazing of all cheatgrass plants and confining animals to smaller spaces with fencing might be necessary. Also, variation in annual precipitation and other environmental factors could influence results. Other integrated approaches such as herbicides and prescribed fire might also need to be incorporated under some circumstances.
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