The variability in miserotoxin concentration of 120 individual timber milkvetch plants was determined in the bud, flower, and pod stages of growth on rough fescue grassland, parkland, and Douglasfir zone locations. Although a broad dispersion in miserotoxin levels was evident within each sampling unit of ten plants, the grassland samples exhibited the greatest toxicity with an exceptional level (10.17 +/- 1.13%) occurring during the bud stage. The bud stage of the parkland samples yielded intermediate concentrations (5.22 +/- 1.18%) while forest plants contained lower miserotoxin levels (4.08 +/- 0.95% to 2.49 +/- 0.47%). A decline in miserotoxin levels occurred during the bud-to-pod interval at the grassland and parkland sites, but significant differences were not apparent between the progressive stages of growth at the forest locations. The timber milkvetch toxicity patterns based on the variability of individual plants confirmed previously described trends derived from composite sampling.

Accumulation of acidity in spiny and spineless Opuntia joints fluctuated daily due to crassulacean acid metabolism (CAM) in Golan Height and coastal plain. The acidity reached higher concentrations in the young joints, especially during early morning hours, before the plants were exposed to sunlight. Changes in acidity were more pronounced in the chlorenchyma than in the water-accumulating tissues. These findings provide information on the rate and time of photosynthesis of these plants and may enable the feeding of livestock on Opuntia, while acid levels taken in by livestock are kept low to reduce a cause of diarrhea. The acidity is lower on sunny warm days, during late afternoons, in shriveled, old joints which had been exposed to full sunlight or were excised and stored in light. It may, therefore, be better to let cattle feed on the shriveled Opuntia before the start of the rainy season and use shrubs such as Atriplex halimus, which is better suited after onset of the first rain, as complementary perennial feed.

Seedlings of Pathfinder, Nebr. 28, and experimental ey switchgrass (Panicum virgatum L.) strains were grown in a growth chamber and harvested 1, 2, 3, 4, 6, 8, and 10 weeks following emergence for detection of seedling growth differences among strains. Leaf areas and dry weights of leaf blade and stem axis (stem and leaf sheath) generally increased significantly with each harvest from 4 to 10 weeks. Stem axis and leaf blade dry weights were significantly greater with Pathfinder and ey, respectively, than with Nebr. 28. Final leaf area was significantly greater with ey than with the other strains. Thus, Nebr. 28 (early-maturing) would be less competitive with weeds during establishment than Pathfinder or ey (both are late-maturing). Relative growth rate (RGR), net assimilation rate (NAR), and leaf area ratio (LAR) were similar for all strains, although at the first harvest Nebr. 28 had a lower LAR than the other two strains. RGR, NAR, and LAR generally declined with each successive harvest. The strains appeared to have the same capacity to produce above ground biomass but photosynthate partitioning differed as indicated by leaf and stem comparisons.

Sap velocities in pinyon (Pinus edulis Engelm.) and juniper (Juniperus osteosperma (Torr.) Little) trees in southeastern and southwestern Utah were studied for 1 year using the heat-pulse technique. Measured velocities were related to nearby environmental factors and Dalton's simplified aerodynamic method for estimating evaporation from water. Sap velocity was independent of the dry weight of green biomass within both pinyon and juniper trees. From 90.5 to 99.0% and from 66.0 to 99.0% of the variability in diurnal sap velocities in pinyon and juniper trees, respectively, could be accounted for by using an 8-variable multiple regression equation. Dalton's equation accounted for 4.0 to 86.0% of the variability in diurnal sap velocities for both tree species on select days. Amount of variability in sap velocities explained by multiple regression equations was reduced markedly when sap velocities and environmental data were pooled over all sampling dates.

Runoff and reservoir waters from the Pierre Shale Plains in southeastern Montana were fresh (< 1,000 mg/liter of TDS) to slightly saline (1,000 to 3,000 mg/liter of TDS) and were rated good to fair for livestock use. However, as water levels drop, mainly through evaporation, waters in some reservoirs could become moderately saline (3,000 to 10,000 mg/liter of TDS) and should not be used if other waters are available.

A burned private forest was revegetated by seeding to grasses, legumes, shrubs, and trees. The sequence of events in carrying out this stabilization program provides a guideline for others handling similar situations; timeliness and ecological adaptation of species used is important. A field study (1969-72) compared results obtained on three ecological sites. A satisfactory vegetational cover was established by seeded grass the first year after seeding on all three sites, whereas natural revegetation did not provide satisfactory cover on an unseeded area in 4 years. Common legumes seeded for deer forage did not survive, indicating the need for additional study of species adaptation. Broadcasting tree seed was a failure. Seeded grasses apparently suppressed development of some native shrubs, which was detrimental to wildlife habitat. Herbage production on seeded areas was about four times greater than on the unseeded area. Two years of soil loss from seeded watersheds totaled less than 5 tons per acre as measured by the amount of sediment in debris basins. Fire-killed ponderosa pine snags were most susceptible to windthrow; grand fir was the least.

Sheep diet was examined in the spring season on sagebrush-grass range in northeastern Idaho. Balsamroot and bluegrasses were the preferred plant species. The number of esophageal fistula samples needed for estimating the botanical and chemical components was determined. Botanical samples were more variable than chemical samples indicating a greater number of botanical samples for the same precision.

Grazing intensities of light, moderate, and heavy by cattle did not affect the protein content of blue grama herbage in northeastern Colorado. Crude protein content of live herbage changed with phenological development and with season, but no change occurred in dead herbage. During the early vegetative growth period, a high of 18% crude protein occurred in the plant tissues. Additional precipitation during the growing season did not appear to affect the content of protein in herbage.

During 1972 and 1973, the effects of nitrogen fertilization, burning, and grazing on total nonstructural carbohydrate (TNC) and nitrogen reserves of big bluestem (Andropogon gerardi Vitman) were studied in the Kansas Flint Hills. TNC and nitrogen reserves were lowered when growth exceeded photosynthetic production and nutrient assimilation. TNC reserves were lowest in unburned, heavily fertilized, pastures; nitrogen in storage organs increased linearly as nitrogen fertilization was increased. TNC was higher in burned than in unburned pastures, regardless of fertilization rate. Increasing the grazing rate when nitrogen fertilization was increased had little effect on reserves at senescence.

Protein content of selected native range grass and sedge species was followed during the course of the growing season over a 6-year period on four major range sites in western North Dakota. The study included three rates of nitrogen fertilizer plus some added treatments of phosphorus alone and in combination with nitrogen during the study. Protein content varied appreciably between the same species on different sites, different species on the same site, and between the same species on the same site due to fertilization. Certain species were inherently high in protein content (Agropyron smithii), while others were intermediate (Stipa comata and Stipa viridula), and still another was comparatively low (Bouteloua gracilis). The presence of nitrogen fertilizer generally increased protein content of all species regardless of level of treatment or site; the magnitude of increase, however, varied greatly between sites and species. Decline in protein content is progressive in all species with the advance in maturity regardless of fertilizer treatment level or site. However, the rate of protein loss is accelerated with fertilization and becomes more rapid with a decline in summer moisture. Cool-season species show a more rapid protein loss than was observed from warm-season Bouteloua gracilis. The length of the grazing period when forage values remain near the minimum protein requirement is appreciably extended on some sites with certain species, especially Bouteloua gracilis. Proper range management must take into consideration the potential of each major range site and the inherent species capabilities to produce and maintain a high level of protein for an extended period of grazing.