Author: Alexis Vertolli Robertson

Publisher:

Published: 2012

Total Pages:

ISBN-13: 9781267759900

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California's annual rangelands support thousands of species, yet the relative stability of this highly invaded ecosystem is being threatened by a new wave of invasive species such as medusahead (Taeniatherum caput-medusae) and yellow starthistle (Centaurea solstitialis). Livestock grazing is commonly proposed as a cost effective tool to manage these weedy species. Substantial small scale experimental evidence exists to support planned grazing as an effective management tool to manage these noxious weeds. However, there is little published work examining the effectiveness of ranch-scale implementation of grazing to control invasive weeds. I studied the effectiveness of grazing to control medusahead and yellow starthistle across 7000 acres on the Bureau of Land Management (BLM) Bear Creek Unit grazing allotment in western Colusa County, California. After 4 years exclusion from livestock grazing, the BLM reintroduced grazing on the unit in 2006 with the intent of expanding medusahead and yellow starthistle populations. From 2006 through 2011, a moderately stocked rotational cattle grazing system was annually implemented across 11 paddocks which ranged from 80 to 600 acres in size. The grazing season was January through May during these 6 years. To detect the effects of grazing on the plant community, herbaceous plant community composition and structure were measured in 2006, 2009, and 2011 at 11 permanently located, paired grazed and ungrazed (control) plots. Plant community composition significantly diverged between the grazed and ungrazed plots over the course of the case study. The grazing treatment implemented at Bear Creek Management unit reduced medusahead cover from 45% to 15% cover. Results indicate that better medusahead control could have occurred if the timing of grazing was adapted annually to late spring rainfall patterns and medusahed phenology. Results indicate that grazing had no effect on yellow starthistle, which we hypothesize is because of the mismatch between timing of control and yellow starthistle phenology. It is possible that grazing would have been more effective if the timing of grazing better matched the target weed species phenology which varies often by late season rainfall. After 10 years, the ungrazed plant communities began to shift and medusahead was replaced by other non-desirable species such as ripgut brome and red brome, indicating continued exclusion of grazed did not lead to an ecologically valuable plant community.

Download or read book Plant Community Responses to Cattle Grazing in a Noxious Weed- Dominated Rangeland written by Alexis Vertolli Robertson and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: California's annual rangelands support thousands of species, yet the relative stability of this highly invaded ecosystem is being threatened by a new wave of invasive species such as medusahead (Taeniatherum caput-medusae) and yellow starthistle (Centaurea solstitialis). Livestock grazing is commonly proposed as a cost effective tool to manage these weedy species. Substantial small scale experimental evidence exists to support planned grazing as an effective management tool to manage these noxious weeds. However, there is little published work examining the effectiveness of ranch-scale implementation of grazing to control invasive weeds. I studied the effectiveness of grazing to control medusahead and yellow starthistle across 7000 acres on the Bureau of Land Management (BLM) Bear Creek Unit grazing allotment in western Colusa County, California. After 4 years exclusion from livestock grazing, the BLM reintroduced grazing on the unit in 2006 with the intent of expanding medusahead and yellow starthistle populations. From 2006 through 2011, a moderately stocked rotational cattle grazing system was annually implemented across 11 paddocks which ranged from 80 to 600 acres in size. The grazing season was January through May during these 6 years. To detect the effects of grazing on the plant community, herbaceous plant community composition and structure were measured in 2006, 2009, and 2011 at 11 permanently located, paired grazed and ungrazed (control) plots. Plant community composition significantly diverged between the grazed and ungrazed plots over the course of the case study. The grazing treatment implemented at Bear Creek Management unit reduced medusahead cover from 45% to 15% cover. Results indicate that better medusahead control could have occurred if the timing of grazing was adapted annually to late spring rainfall patterns and medusahed phenology. Results indicate that grazing had no effect on yellow starthistle, which we hypothesize is because of the mismatch between timing of control and yellow starthistle phenology. It is possible that grazing would have been more effective if the timing of grazing better matched the target weed species phenology which varies often by late season rainfall. After 10 years, the ungrazed plant communities began to shift and medusahead was replaced by other non-desirable species such as ripgut brome and red brome, indicating continued exclusion of grazed did not lead to an ecologically valuable plant community.