Relationships among Idaho fescue defoliation, soil water, and spotted knapweed emergence and growth
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Authors: J. S. Jacobs, and R. L. Sheley
Date: 1997
Journal: Journal of Range Management
Volume: 50
Number: 3
Pages: 258-262
Summary of Methods: This short-term greenhouse study in Montana examined the effects of clipping the native Idaho fescue and soil water content on seedling emergence and growth of spotted knapweed. Clipping treatments, simulating utilization, used in this study were 0, 30, 60 and 90% and frequency (1, 2 or 3 times in 14-day intervals). Two watering regimes were also examined (50 ml, three times a week or 150 ml once a week) yielding nine total treatments replicated twice. Experiment was conducted twice. After initial defoliation treatments spotted knapweed seed was evenly broadcast seeded across all plots. Pots were then placed into a growth chamber. After 50 days in the growth camber, all plant material was harvested. Spotted knapweed plants were counted and weighed. Soil plugs were taken of each pot and died at a constant temperature to determine what content. Spotted knapweed and Idaho fescue shoots and roots were separated and measured for total production and root length.
Article Summary / Main Points: Idaho fescue production decreased with increased clipping intensity and frequency. A single defoliation at 30% and 90% increased the number and weight of spotted knapweed as compared to non-defoliated pots. As frequency of defoliation increased the level of defoliation was lower to enhance to establishment of spotted knapweed. As frequency and level of defoliation increased, spotted knapweed establishment and growth increased in direct relation to the increased level of soil moisture. Spotted knapweed plants had greater weights and leaf area in pots watered more frequently than those only watered once a week. Management of mountainous rangelands should account for grazing infrequently, at a moderate rate, to allow Idaho fescue plants to utilize soil water and inhibit the invasion of spotted knapweed.
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, festuca idahoensis, weed invasion, grazing management, plant competition, soil water
Annotation: A limitation of this greenhouse study was competition of Idaho fescue was only species examined and season of grazing was also not examined.
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