Effects of defoliation, shading and competition on spotted knapweed and bluebunch wheatgrass
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Authors: G. A. Kennett, J. R. Lacey, C. A. Butt, K. Olson-Rutz, and M. R. Haferkamp
Date: 1992
Journal: Journal of Range Management
Volume: 45
Number: 4
Pages: 363-369
Summary of Methods: A short term greenhouse study was used to examine the vegetative effects of spotted knapweed (Centaurea maculosa) when grown in different light and competitive conditions and clipped at varying intensities. Two inter-specific and 2 intra-specific competitions were created in the green house by planting the pots to 4 different plant combinations. Each pot was subjected to three levels of light intensity (full, 2/3, and 1/2) and 7 defoliation treatments (varied in frequency, severity and stage of growth).
Article Summary / Main Points:
• Spotted Knapweed roots and crown growth were negatively affected by increasing levels of bluebunch wheatgrass competition.
• As light intensity increased from half light to full there was an increase in spotted knapweed crown and root growth.
• Frequent defoliations reduced root biomass of spotted knapweed; however, crown growth was not affected.
• Total harvested foliage was not significantly affected by any of the defoliation treatments, but there was a decline in root, crown and final harvest forage with treatments at the higher utilization and frequency levels.
• Spotted knapweed plants clipped at a heavy intensity once produced more foliage than control plants.Vegetation Types: All Vegetation Types
MLRA Ecoregions: Not Applicable
Agrovoc Control Words: Weeds Rangelands Grazing
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: centaurea maculosa, pseudoroegneria spicata, clipping, weed management, controlled environment, grazing management strategy, targeted grazing
Annotation: Grazing intensity in this study were applied to spotted knapweed and bluebunch wheatgrass plants. Results indicate that livestock grazing of spotted knapweed would not be an effective management tool, unless the plants were repeatedly selected for throughout a growing season.
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