Browsing Journal of Range Management, Volume 52, Number 1 (January 1999) by Subjects
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Aerial films and solar angles: influences on silver sagebrush inventoryAerial photos in Alberta are generally acquired according to topographic mapping and forestry specifications. The parameters for interpreting rangeland vegetation, such as silver sagebrush (Artemisia cana-Pursch), need to be explored and condensed into an operational specification. Five aerial films and 3 solar angles were evaluated by 7 photo interpreters to determine the optimal conditions for interpreting silver sagebrush at a scale of 1:20,000. Interpreter accuracy and preference are determined for the 2 experimental conditions as to determine operational specifications. Kodak Panatomic-X 2412 achieved the highest interpretation accuracies for silver sagebrush cover detection and plant density estimation (91.0% and 94.4% respectively), while Kodak Aerochrome Infrared 2443 and Agfa Avicolor H100 performed best for estimating plant vigor (92.7% and 93.7% respectively). Photo interpreters also chose Kodak Panatomic-X 2412 as the preferred film for interpreting silver sagebrush (7.7 on a scale of 10). Positive correlations were obtained between combinations of interpretation accuracy, interpreter film preference and photographic density range measurements, indicating the trends for higher accuracy and preference are associated with higher density ranges. Solar angles of 20 degrees, 37 degrees and 54 degrees were evaluated by photo interpreters with significant preference shown for 20(.). Recommendations for modifying Alberta's air photo operational specifications to include high resolution (Kodak Panatomic-X) imagery and decreasing the acceptable lower boundary for the operational solar angle from 30 to 20 degrees for interpreting silver sagebrush at the 1:20000 scale are proposed.
Yield and feeding of prairie grasses in east-central AlbertaInformation on the yield of grasses as the plants mature is useful to optimize grazing potential and quality hay production. The objectives of this study were to compare the yield and feeding value of 11 common prairie grasses over 2 yearly cycles of growth and determine which of the grasses may require supplementation to meet nutrient requirements of grazing cattle. Dry matter yield (DM), crude protein (CP), acid detergent fiber (ADF), calcium (Ca), and phosphorus (P) values were obtained for brome (Bromus inermis [L.]), creeping red fescue (Festuca rubra [L.]), crested wheatgrass (Agropyron cristatum [L.] Gaertn), intermediate wheatgrass (Agropyron intermedium (host) Beauv), meadow foxtail (Alopecurus pratensis [L.]), orchardgrass (Dactylis glomerata [L.]), pubescent wheatgrass (Agropyron trichophorum Link. richt), streambank wheatgrass (Agropyron riparium Scriba &Smith), slender wheatgrass (Agropyron trachycaulum Link Malte), tall fescue (Festuca arundinacea Schreb), and timothy (Phleum pratense [L.]) at weekly intervals from June to September, in 1992 and 1993. Most grasses reached maximum yields at week 8 in 1992 (drought year) and week 12 in 1993 (normal year). Herbage mass yields (g/0.25m2 at week 8 in 1992 (highest to lowest yielding) were crested wheatgrass (235), intermediate wheatgrass(210), pubescent wheatgrass(173), brome(161), slender wheatgrass(152), meadow foxtail(114), Tall fescue(110), timothy(101), orchardgrass(83), creeping red fescue(56), and streambank wheatgrass(50). Herbage mass yields pattern of the grasses in 1993 was similar to that in 1992 except for crested wheatgrass and brome which ranked first and fourth in 1992 but ranked fifth and second, in 1993, respectively. Quality declined in all grasses as they matured. The average CP content of grasses declined from 24% to 13% in 1992 and from 21.5% to 12.1% in 1993 but were adequate to meet crude protein requirements of growing, pregnant or lactating grazing cattle. The Ca levels in all grasses were adequate for all classes of cattle on pasture but the low P levels of 0.11% in both years indicate that growing, pregnant or lactating cattle grazing on these pastures would require P supplementation.