Plant competition, abiotic, and long- and short-term effects of large herbivores on demography of opportunistic species in a semiarid grassland
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Authors: D. G. Milchunas, W. K. Lauenroth, and P. L. Chapman
Date: 1992
Journal: Oecologia
Volume: 92
Number: 4
Pages: 520-531
Summary of Methods: Establishment and survival of five weeds were examined across a gradient from uplands to lowlands with 5 combinations of disturbances (long-term grazed, and grazed during experiment, long-term grazed and ungrazed during experiment, long-term ungrazed and ungrazed during experiment, vegetation killed by herbicide and ungrazed during experiment, vegetation removed with soil disturbed and ungrazed during experiment) on the Central Plains Experimental Range (40Ëš 49' N, 104Ëš 46' W) in Northern Colorado. Permanently located quadrats were established in each subplot and assigned to one of six weed species seeding treatments (unseeded, or sown with 500 seed of Kochia scoparia, or Salsola iberica, or Sisymbrium altissimum, or Lepidium densiflorum or Cirsium arvense). Seeds were broadcast sown in April before the last snow. Seedling emergence was recorded in early June and sampled once every month though September, with phonologic state was also recorded.
Article Summary / Main Points: Long-term effects of grazing had a more significant effect on seedling emergence than the effects of removal of competition. Very few individual weeds emerged on sites that had a long-term grazing history with or without current season grazing. None of the seeded individuals survived through the growing season on the site was grazed with a long-term grazing history. Seedling emergence was greatest on the site with vegetation removed with soil disturbance. Productivity varied across topography, but there was little or no effect on seedling emergence across the topographic gradient.
Vegetation Types: Shortgrass Prairie
MLRA Ecoregions: 67B Central High Plains, Southern Part
Agrovoc Control Words: Weeds Rangelands Grazing
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: herbivory, compensatory growth, disturbance, establishment, landscape topography, kochia scoparia, salsola iberica, sisymbrium altissimum, lepidium densiflorum, cirsium arvense
Annotation: Grazing intensity ranged from 55-86% utilization on these plots. Invasibility of this particular grassland by weed seeds was limited.
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