[PDF] The Decline Of Diffuse Knapweed In British Columbia eBook

Author : Reg F. Newman
Publisher :
Page : 28 pages
File Size : 35,35 MB
Release : 2011
Category : Science
ISBN :

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There are literature reports of a decline in diffuse knapweed population beginning in the early 2000s at several locations on western North American rangeland. To document changes in certain diffuse knapweed populations in British Columbia, we selected five previously monitored diffuse knapweed-invaded sites located on low-elevation grasslands in the Bunchgrass and Ponderosa Pine BEC zones in the southern interior and sampled these for plant species cover, and abundance of biological control insects. Diffuse knapweed populations and soil seed reserves were shown to decline by an average of 74% and 78%, respectively, at five sites in British Columbia from the 1990s to 2009. Three factors were discussed as possible causes for the decline of diffuse knapweed at the five sites. Climate warming/drying was shown to have occurred over the same period as the reported decline in diffuse knapweed at three Kamloops sites and is a possible contributing factor. Increased plant competition, particularly from bluebunch wheatgrass, may also be a contributing factor; however, the small number of sampling sites in this study cannot provide firm conclusions in this regard. The ubiquitous nature of biological control insects at the five sites, combined with their known abilities to damage knapweed, also places biological control as a possible contributing factor for the decline of diffuse knapweed. It is also possible that two or more of the three factors are acting in concert to reduce diffuse knapweed. The demonstrated decrease in diffuse knapweed at the five sampled sites provides baseline data that may contribute to a better understanding of how biological control agents, climate warming/drying, and improved grazing management may be interacting on weed-invaded sites in British Columbia.

Author : R. Sforza
Publisher : CABI
Page : 768 pages
File Size : 25,2 MB
Release : 2008
Category : Weeds
ISBN : 1845935071

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Covering the research findings in various aspects of weed biocontrol, this volume explores weed biology and ecology and the economic impacts, effectiveness and practical implications of weed management strategies. It is of interest to researchers and students in plant and environmental sciences.

Author : Charles Vincent
Publisher : CABI
Page : 468 pages
File Size : 42,83 MB
Release : 2007-08-20
Category : Electronic books
ISBN : 1845932668

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Biological control, the management of pests by the use of living organisms, has a long history of application to agriculture around the world. However, the effective use of beneficial organisms is constrained by environmental, legal, and economic restrictions, forcing researchers to adopt increasingly multi-disciplinary techniques in order to deploy successful biological control programs. It is this complex process, including the mindset and the social environment of the researcher as well as the science being pursued, that this book seeks to capture. Chapters reveal the experiences of scientists from the initial search for suitable control agents, to their release into ecosystems and finally to the beneficial outcomes which demonstrate the great success of biological control across diverse agro-ecosystems. Drawing together historical perspectives and approaches used in the development of biological control as well as outlining current debates surrounding terminology and differential techniques, Biological Control: A Global Perspective will be a valuable resource.

Author : Yuying Kuang
Publisher :
Page : pages
File Size : 48,45 MB
Release : 2015
Category :
ISBN :

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In British Columbia, grasslands provide critical habitat for a wide variety of species and are a significant forage base for BC's ranching industry. Grasslands in BC are threatened from several human-caused stressors, including urban development, over-grazing, climate change and the introduction of non-native invasive species. Spotted knapweed (Centaurea stoebe L.), is an invasive plant introduced to North America from Europe. It can establish large monocultures in BC's grasslands which can cause a reduction in wildlife and livestock forage production, a lowering of native biodiversity, and an alteration in soil nutrient composition. I investigated the carry over effects immediately following removal of large and small spotted knapweed patches on soil mineral nutrients (nitrogen (N), phosphorus (P), carbon (C) and volumetric water content) and the growth of an important native grass, rough fescue (Festuca campestris Rydb.), in grasslands within Lac du Bois Provincial Park, located to the northwest of the city of Kamloops, British Columbia. The results of field experiments showed that soil total nitrogen, total carbon, volumetric water content and biomass of rough fescue were lower in former spotted knapweed patches, but there was no significant difference in soil total phosphorus. In addition, there was no measureable difference between large and small spotted knapweed patches in soil mineral nutrients and plant growth. In a greenhouse experiment I manipulated N:P ratios (1:1, 15:1 and 30:1) and biochar (10g/pot or none) to test their effect on competitive performance between spotted knapweed and rough fescue. The experimental design included five plant combinations: spotted knapweed alone, rough fescue alone, two spotted knapweed, two rough fescue, one spotted knapweed and one rough fescue. The results of the greenhouse experiment showed that total biomass of spotted knapweed was greater than rough fescue at each N:P ratio when they were grown alone or grown under intraspecific condition. Also, results showed that the competitive effect of spotted knapweed was -0.136 ± 0.052 SE; while rough fescue has a facilitation effect of 0.020 ± 0.007 SE. Biochar addition had no effect on plant growth of spotted knapweed or rough fescue, or competitive interactions within and between the two plant species.