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United States Department of Agriculture

Agricultural Research Service

Research Project: REDUCING THE IMPACT OF INVASIVE WEEDS IN NORTHERN GREAT PLAINS RANGELANDS THROUGH BIOLOGICAL CONTROL AND COMMUNITY RESTORATION

Location: Pest Management Research Unit

Title: Three California annual forbs show little response to neighbor removal

Author
item Espeland, Erin

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 3, 2012
Publication Date: January 1, 2013
Repository URL: http://handle.nal.usda.gov/10113/56109
Citation: Espeland, E.K. 2013. Three California annual forbs show little response to neighbor removal. Journal of Arid Environments. 88: 121-124.

Interpretive Summary: Competition from other plants is one of the main environmental factors limiting plant performance. When we conduct weed control activities, we expect to see an improvement in the growth of desirable species. In this field study, competitor removal mid-way through the growing season did not result in greater growth for any of the three species (Plantago erecta, Micropus californicus, Clarkia purpurea) in the first year. In the second year, two species (P. erecta and M. californica) had greater growth when competitors where removed early in the growing season and the third species never benefited from competitor removal. Conservation and management strategies of desirable plant species are often predicated on the theory of competitive suppression, and competitor removal is presumed to increase plant growth. Yet, I show with three annual forb species that there are narrow, or even no, windows of opportunity wherein growth of target species increases as a result of competitor removal.

Technical Abstract: Competition is one of the main environmental factors limiting plant performance. When direct competition for resources drives plant growth, we expect to see compensatory growth in annual plants released from competition. In this field study, competitor removal mid-way through the growing season did not result in compensatory growth for any of the three species in the first year. In the second year, two species had greater biomass when competitors were removed early in the growing season and the third species never benefited from competitor removal. Again, in year two, when competitors were removed mid-way in the growing season, target plants did not exhibit compensatory growth. Conservation and management strategies of desirable plant species are often predicated on the theory of competitive suppression, and competitor removal is presumed to increase plant growth. Yet, I show with three annual forb species that there are narrow, or even no, windows of opportunity wherein growth of target species increases as a result of competitor removal.

Last Modified: 10/30/2014
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