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Variation in shrub and herb cover and production on ungrazed pine and sagebrush sites in eastern Oregon: a 27-year photomonitoring study.Author(s): Frederick C. Hall
Source: Gen. Tech. Rep. PNW-GTR-704 Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 44 p
Publication Series: General Technical Report (GTR)
Station: Pacific Northwest Research Station
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DescriptionStudy objectives were to evaluate yearly fluctuations in herbage canopy cover and production to aid in defining characteristics of range condition guides. Sites are located in the forested Blue Mountains of central Oregon. They were selected from those used to develop range condition guides where soil, topographic, and vegetation parameters were measured as a characterization of best range condition. Plant community dominants were ponderosa pine/pinegrass, ponderosa pine/bitterbrush/Idaho fescue savanna, low sagebrush/bluebunch wheatgrass, and rigid sagebrush scabland. None of the sites were grazed during the previous 30 years or during the 27-year study. Each location was permanently marked by fence posts, and a meter board was placed 10 m down an established transect line. Photographs (color slides) were taken down the transect with closeups left and right of the meter board. Sampling was limited to August 1–4 each year when canopy cover and herbage production were determined. Both total canopy cover and herbage production varied by about a 2.4-fold difference on each site over the 27 years. Apparently "good range condition" may be something of a "running target" and lacks a well-defined set of parameters. Canopy cover is a poor parameter for characterizing range condition. Three of the four plant communities were dominated by bunchgrasses. Abundance of seedheads is commonly used to indicate good range health. But on these sites, seedheads were not produced about half the time. Because these sites were in "good range condition," lack of seedhead production may indicate maximum competition in the community. Maximum competition and maximum vigor do not seem to be synonymous. These bunchgrass communities varied in their greenness on the first of August each year from cured brown to rather vibrant green suggesting important annual differences in phenology. The pinegrass community, being dominated by rhizomatous species, showed surprising variance in seedhead production. Pinegrass did not flower, but Wheeler’s bluegrass, lupine, and Scouler's woolyweed were quite variable, averaging inflorescences only 75 percent of the time.
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CitationHall, Frederick C. 2007. Variation in shrub and herb cover and production on ungrazed pine and sagebrush sites in eastern Oregon: a 27-year photomonitoring study. Gen. Tech. Rep. PNW-GTR-704 Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 44 p
KeywordsRange condition, flowering, canopy cover, herbage production, bunchgrass, yearly variability
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