• Density and Production of Seeded Range Grasses in Southeastern Arizona (1970-1982)

      Cox, J. R.; Jordan, G. L. (Society for Range Management, 1983-09-01)
      Accessions A-68, L-11, L-19, L-28, and L-38 of Lehmann lovegrass (Eragrostis lehmanniana Nees); P-15608 Cochise lovegrass (E. lehmanniana Nees X E. trichophora Coss & Dur.); A-84 and Catalina boer lovegrass (E. curvula var. conferta Nees); Palar Wilman lovegrass (E. superba Peyr.) and P-15630 blue panicgrass (Panicum antidotale Retz.) were seeded at a study site near San Simon, Ariz., in spring 1970 and 1971. Seedbeds were prepared by root plowing and furrow pitting immediately before planting. Growing season precipitation was 136 mm in 1970 and 218 mm in 1971. Mean accession densities in the fall after the initial growing seasons were 18 plants/m2 for both the 1970 and the 1971 plantings. Between fall 1971 and 1972 mean accession densities declined 44% and forage production was unchanged on the 1970 plantings. Accession densities declined 22% and forage production increased 250% on the 1971 plantings. Between fall 1972 and 1982 the majority of seeded plants died and forage production declined 90% on the 1970 plantings. Accession densities declined 78% and forage production declined 84% on the 1971 plantings.
    • Effects of Long-term Grazing on Cryptogam Crust Cover in Navajo National Monument, Arizona

      Brotherson, J. D.; Rushforth, S. R.; Johansen, J. R. (Society for Range Management, 1983-09-01)
      The effects of long-term grazing (40 years) on cryptogamic crusts of Navajo National Monument were investigated. Both vascular and nonvascular communities were heavily impacted with the cryptogamic community showing the greatest reduction in cover. Lichens and mosses were the most damaged, while the algae were much more tolerant. Individual cryptogam species were affected in similar patterns with all identifiable species showing reduced cover. Vascular plant species were also affected with grasses showing the greatest reduction under grazing pressure.
    • Responses of Semidesert Grasses and Shrubs to Fall Burning

      Martin, S. C. (Society for Range Management, 1983-09-01)
      Four 0.8-ha plots south of Tucson, Ariz., were burned November 12, 1975, in a pasture where cattle had not grazed for 12 months. The fire top-killed most small mesquites, killed almost all of the burroweed and much of the cactus, except in unburned patches. Within 5 years regrowth of mesquite and newly established stands of burroweed equalled or exceeded pre-burn levels. Lehmann lovegrass increased following the burn; most other perennial grasses were not greatly affected. Results suggest that periodic burning can maintain a grassland aspect if the intensity and frequency of grazing allow enough dry herbage for an effective fire to accumulate between burns.
    • State of Dry Matter and Nutrients of Soil-Plant Systems of Arizona Fescue and Mountain Muhly

      Klemmedson, J. O. (Society for Range Management, 1983-09-01)
      The state of dry matter, C, N, S and P for soil-plant systems of Arizona fescue and mountain muhly in the Arizona pine-bunchgrass community was determined as a first step to quantification of mineral cycles. These bunchgrass systems differed in stature, structure and accumulation of dry matter and nutrients, both on an absolute and per unit basal area basis for several components of the soil-plant systems. Dry matter/unit area was greater in fescue because of accumulation of standing dead vegetation and litter; weight of live shoots was 18% less in fescue than muhly. All 4 nutrients were present in greater concentrations and amounts in fescue than in muhly biomass, but accumulation patterns and influence on soil differed among nutrients. The standing state data suggest more rapid loss of dry matter and nutrients from muhly than fescue during senescence and decomposition.