Annual replacement of the tillers of Agropyron desertorum following grazing
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Authors: B. E. Olson, and J. H. Richards
Date: 1988
Journal: Oecologia
Volume: 76
Number: 1
Pages: 1-6
Summary of Methods: In Utah, heavy grazing of a grazing-tolerant Eurasian tussock grass, Agropyron desertorum, before internode elongation seldom affected tiller replacement. Heavy grazing during or after internode elongation increased overwinter mortality of fall-produced tillers and reduced the number and heights of these replacement tillers. Tussocks grazed twice within the spring growing season tended to have lower overwinter tiller mortality, greater tiller replacement, and larger replacement tillers than tussocks grazed only once in spring. The presence of ungrazed tillers on partially grazed tussocks did not increase the replacement of associated grazed tillers relative to tillers on uniformly grazed plants. This result indicates that resource sharing among tillers, if present, is short-lived or ecologically unimportant in this species. Although A. desertorum is considered grazing-tolerant, tiller replacement on heavily grazed tussocks, particularly those grazed during or after internode elongation when apical meristems were removed, was usually inadequate for tussock maintenance. Olson and Richards conclude that chronic reduction in tiller replacement will reduce a tussock's competitive ability, and increase the probability of its death.
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: tussock grass, agropyron desertorum, annual tiller replacement, grazing effects
Annotation: The authors controlled the time of grazing with a grazing system that incorporated frequent (2-3 days) of movement of cattle through the ten 8.5 ha paddocks. In 1983 and 1984, cattle were rotated twice (30 day cycles) through the ten 8.5 ha pastures. In 1985, these animals were rotated 3 times through the system (20 day cycles). They used temporary exclosures to ensure that some tussocks were grazed only once during the first cycle at the pre-, early-, late-, and post-internode elongation developmental stage of tillers.,With uniform grazing, all tillers were grazed to a similar height; with partial grazing, about 50% of the canopy was grazed. Heavy grazing left a 5-6 cm stubble height, whereas moderate grazing left a 10-12 cm stubble height. Adjacent to grazed tussocks were ungrazed control tussocks that were located within a fenced exclosure. They censuses the autumn-produced tillers in November.
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