Maculosa or c biebersteinii had 47 less forage for elk

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Unformatted text preview: eas dominated by another knapweed (spotted knapweed, C. maculosa , or C. biebersteinii ) had 47% less forage for elk than did areas where the weed was controlled. Heyer winter Yellow star thistle ( Centaurea solstitialis) — “knapweed ” family Native to Mediterranean Europe/N. Africa. Probably arrived in California in contaminated alfalfa seed. Becomes dominant and appears to displace native bunchgrasses in western grasslands. Spiny & toxic to most grazers/browsers. Changed vegetation structure • Comparison of the fibrous, soil-holding roots of the native wheatgrass and the thin taproot of the spotted knapweed. 13 Community Ecology Changed vegetation structure Changed vegetation structure African Cape Ivy English Ivy Ivy plants escape from artificial landscapes to overgrow forests in California & Oregon • Knapweed-dominated habitats have higher runoff than native bunchgrass communities. Runoff increases depletion of the soil and sediment load in local streams. Escalating invasion cycle: 1. Pink passionflower vines overgrow Hawai ’ian forests 2. Pink passionfruits attract and feed invasive feral pigs. 3. Pigs uproot native vegetation. 4. Pigs spread pink passionflower seeds. 5. Back to 1. – “light parasites ” – Trees become top-heavy and topple more easily A...
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This note was uploaded on 09/02/2011 for the course BIOL 6C taught by Professor Sundram during the Spring '09 term at DeAnza College.

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