Overgrazing and invasive species pose significant threats to the livelihood of British Columbia (B.C.) ranchers. Spotted knapweed (Centaurea stoebe), in particular, can reduce native plant diversity, form dense monocultures and overwhelm the native seed bank. Integrated land management strategies are therefore needed to suppress weeds and restore ecological function as a whole. Recent research suggests that short-duration, light to moderate grazing may aid in restoring grasslands. My primary research objective was to test management-intensive grazing (MiG), extensive grazing, and targeted cattle grazing for their effects on: a) plant community structure and productivity, b) soil chemical and physical properties, and c) the storage of soil carbon in a semi-arid grassland. A secondary objective was to determine the efficacy of targeted cattle grazing to suppress C. stoebe seed production. Electric fence enclosures were established in C. stoebe dominated grassland in Merritt, BC. Cattle numbers and timing were controlled such that MiG was ten cow/calf pairs for one day at the end of the summer growing season, extensive was one cow/calf pair for ten days at the end of the summer growing season and targeted was ten cow/calf pairs for one day at the height of spotted knapweed flowering. Results demonstrated that MiG improved native grass cover and productivity,but total productivity, diversity indices or soil properties did not differ from extensive grazing.Targeted cattle grazing was effective in controlling C. stoebe seed production; cattle readily consumed C. stoebe at the late bud-flowering stage and reduced the number of mature seeds by 88% and seed heads by 79%. At the point of targeted grazing, C. stoebe also contained more crude protein and total digestible nutrients than the grass community. This research helped demonstrate that intensive grazing practices have the potential to create productive invasive-free grasslands in B.C.’s southern interior and beyond. Research results generated recommendations for implementing MiG on natural semi-arid grasslands, as well as for targeted cattle grazing for C. stoebe control.
