Seasonal browsing of Douglas-fir seedlings by sheep
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Authors: W. C. Leininger, and S. H. Sharrow
Date: 1989
Journal: Western Journal of Applied Forestry
Volume: 4
Number: 3
Pages: 73-76
Summary of Methods: Leininger and Sharrow evaluated sheep browsing of Douglas-fir (Pseudotsuga menziesii) seedlings in 1981 and 1982, on the Coast Range of Oregon. Most sheep browsing of Douglas-fir seedlings was confined to spring when new, succulent growth was present. Sheep removed some lateral foliage from 75 to 100% of all study trees in both May-grazed plantations each year. The number of trees that received lateral browsing from sheep was lower during July and August than during May. Consumption of Douglas-fir current annual growth (CAG) by sheep was highest both years of the study in Y-My where it averaged 40%. In contrast, sheep only consumed 1% of the CAG of the study trees in the 2-year-old plantation grazed in July (Y-Jy) and the two older plantations grazed in July and August. Although 96% of the seedlings 50 cm or less in height had terminal leaders browsed by sheep, only 15% in the 111- to 120-cm height class had terminals browsed. Mechanical impacts of sheep on Douglas-fir seedlings were very low during all seasons regardless of plantation age. In neither year did sheep mechanically impact more than 3% of the trees in any plantation. Sheep primarily impact planted regeneration by browsing their foliage rather than by trampling. Data suggest that Douglas-fir forests can be grazed by sheep with little to no damage to conifer regeneration, except in younger plantations in spring.
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: douglas-fir, pseudotsuga menziesii, sheep, browsing, mechanical impacts, seedlings, conifers
Annotation: The five study plantations will be referred to as follows: (1) a 4-year-old plantation grazed in May (O-My); (2) a 6-year-old plantation grazed in July (O-Jy); (3) a 5-year-old plantation grazed in August (O-Ag); (4) a 2-year-old plantation grazed in May (Y-My); and (5) a 2-year-old plantation grazed in July (Y-Jy). A series of small plantations, ranging in size from 10-40 ha were grazed by sheep. Stocking rate averaged 125 ewe with lamb days/ha in 1981 and 143 yearling days/ha in 1982. Sheep were allowed to graze on the study plots until they consumed ~50% of the available ground vegetation. Current annual growth was separated within clipped plots by species.
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