Demographic responses of Bromus tectorum and seedlings of Agropyron spicatum to grazing by small mammals: The influence of grazing frequency and plant age
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Authors: D. A. Pyke
Date: 1987
Journal: Journal of Ecology
Volume: 75
Number: 3
Pages: 825-835
Summary of Methods: Pyke investigated the influence of Montane meadow mouse (Microtus montanus) grazing on the population biology of the annual Bromus tectorum and on seedlings of the perennial Agropyron spicatum using four grazing frequencies and ungrazed controls, initiated at four plant ages in an unheated glasshouse. The proportional survival of both species rose with decreased grazing frequency and with increased age at initial grazing. The age-by-species interaction showed that B. tectorum increased survival from 17% for plants grazed at 7 days old to 69% for plants grazed at 30 days old or older. For A. spicatum, survival remained at 5% when plants were grazed at 30 days or younger but increased to 57% as grazing was delayed until plants were older. For both species weekly grazing significantly reduced survival. For B. tectorum, the other three less frequent grazing classes did not significantly differ among themselves in survival whereas for A. spicatum as frequency of grazing decreased, survival increased. Frequency of grazing and age at initial grazing had no significant effects on seed production of Bromus tectorum. The concludes that in the steppe of eastern Washington, small mammals can play a major role in shaping the plant communities.
Article Summary / Main Points: None
Vegetation Types:
MLRA Ecoregions:
Agrovoc Control Words: Riparian zones Rangelands Wildlife
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: bromus tectorum, agropyron spicatum, grazing, frequency, plant age, demographic
Annotation: For each plant species there were 2 ungrazed controls and 16 treatments consisting of all combinations of 2 factors: 1) age of the plants at initial grazing (7, 30, 9, 150 days old) and 2) frequency of grazing (grazed once, weekly, biweekly, or monthly). Grazing experiments began on October 24, 1981. On April 16, 1982 grazing was stopped for the duration of the experiment because of insufficient numbers of mice. The grazing period, did, however, include winter to early spring, the time that mice grazing in the field was most severe. All plants were allowed to complete one growing season. B. tectorum plants were harvested individually at ground level in late June 1982 before seed dispersal.
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