• Effects of prescribed fire on Chamaespartium tridentatum ((L.)P. Gibbs) in Pinus pinaster (Aiton) forests

      Rego, F. C.; Bunting, S. C.; Barreira, M. G. (Society for Range Management, 1988-09-01)
      Prescribed burning in Pinus pinaster forests was evaluated in terms of the effects on Chamaespartium tridentatum. Postfire forage quantity and quality were studied. Total biomass production, current year's shoot production, and nutritive value were studied in relation to time since fire. Chamaespartium, a vigorous resprouter, achieved 50% of its preburn biomass level in 2 years. Current year's shoot production reached a maximum 3 to 4 years after fire. Nutritive value of Chamaespartium was briefly enhanced by burning but returned to preburn levels. Seasonal variations of forage quality were very important with lower values in summer or fall. Short-lived increases in protein, cellulose, and hemi-cellulose contents after fire in Chamaespartium shoots returned to preburn levels in 4 years. This supported the traditional fire frequency in the shrublands of 3 to 7 in order to maintain forage quality and productivity.
    • Effects of burning on germinability of Lehmann lovegrass

      Ruyle, G. B.; Roundy, B. A.; Cox, J. R. (Society for Range Management, 1988-09-01)
      Lehmann lovegrass (Eragostis lehmanniana Nees) may be viewed as either an undesirable exotic invader or an important ground cover and forage plant on southwestern rangelands, depending on management goals. Successional responses to management practices intended to control or enhance this grass are highly dependent on the processes of natural revegetation. The effect of seasonal burning on germinability of Lehmann lovegrass in the seedbank was investigated on the Santa Rita Experimental Range in southern Arizona. Samples of surface soil were taken for bioassay immediately after burning in February, June, July, and November for 2 years. Nearly 40% more seedlings emerged from bioassay samples taken from burned than unburned plots. The increase in germinability of Lehmann lovegrass seeds associated with fire may be one of several factors important in its observed ability to re-establish after mature plants are killed by burning.
    • Economic comparison of aerial and ground ignition for rangeland prescribed fires

      Rasmussen, G. A.; McPherson, G. R.; Wright, H. A. (Society for Range Management, 1988-09-01)
      Average ignition costs per ha for aerial and ground ignited prescribed burns in redberry juniper (Juniperus pinchotii)-mixed grass communities were compared to determine the feasibility of using aerial ignition on rangelands. Aerial ignition techniques had greater total costs than ground ignition because of higher fixed costs. However, if greater than 4,000 ha could be burned, as a single or multiple unit, aerial ignition costs are $1.36/ha less than estimated ground ignition costs.
    • Dehydration effects on seedling development of four range species

      Bassiri, M.; Wilson, A. M.; Grami, B. (Society for Range Management, 1988-09-01)
      The effects of temporary drought periods of semiarid regions were simulated by dehydration of germinating seeds of crested wheatgrass (Agropyron desertorum), Russian wildrye (Elymus junceus), alfalfa (Medicago sativa), and cicer milkvetch (Astragalus cicer) in 8 constant humidity environments, ranging from -10 to -220 MPa for 4 days. Combined effects of root excision and temporary dehydration at -22 to -160 MPa were also studied. Subsequent growth of seedlings was evaluated in growth performance tests under favorable soil moisture conditions. When the initial roots were killed by dehydration, survival of grasses depended on the development of seminal lateral root(s) from the scutellar nodes, and survival of legumes depended on development of a new meristem at the distal end or along the side of hypocotyl-root axis. The effect of dehydration was more drastic on the legumes than on the grasses, particularly at more severe conditions. While temporary dehydration of -59 MPa had little effect on grasses, it reduced the percent emergence of the legumes by about 70%. In the -220 MPa treatment, emergence percentages of crested wheatgrass, Russian wildrye, alfalfa, and cicer milkvetch were 59, 35, 6, and 1, respectively, and percentages of rooted seedlings were 58, 12, 3, and 1, respectively. Under combined effects of excision and dehydration at -160 MPa, emergence percentages of the 4 species were 50, 34, 14, and 0, respectively, and their root lengths decreased by 37, 42, 44, and 100%, respectively. Within species variation in tolerance of dehydration suggested opportunities to select and breed for this characteristic.
    • Comparative chemical composition of armed saltbush and fourwing saltbush

      Garza, A.; Fulbright, T. E. (Society for Range Management, 1988-09-01)
      Armed saltbush [Atriplex acanthocarpa (Torr.) Wats.] and fourwing saltbush [A. canescens (Pursh) Nutt.] are browsed by livestock and white-tailed deer (Odocoileus virginianus Raf.). The objective of this study was to compare the chemical composition of these 2 shrubs growing together in south Texas. Leaves and stems from the outer 5 cm of current year's growth of each species were randomly collected from each of 5 stands in November 1985 and February, May, and August 1986. Samples were analyzed for crude protein (CP), calcium, potassium (K), magnesium (Mg), sodium (Na), phosphorus (P), and in vitro organic matter digestibility (IVOMD). Height and standing crop were also determined. Crude protein of armed saltbush leaves ranged from 32% in February to 19% in August. Fourwing saltbush leaf CP ranged from 24% in February to 12% in August. Armed saltbush leaves and stems generally had greater P concentrations than fourwing saltbush. Calcium, K, and Mg concentrations and leaf IVOMD of the 2 species were similar. Fourwing saltbush had lower Na concentrations and greater leaf standing crop than armed saltbush. Laboratory-determined values suggest that both species may provide nutritious browse for cattle and deer on saline rangeland.
    • Atrazine dissipation and off-plot movement in a Nebraska sandhills subirrigated meadow

      Brejda, J. J.; Shea, P. J.; Moser, L. E.; Waller, S. S. (Society for Range Management, 1988-09-01)
      Atrazine [6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine] can be used to modify species composition of naturally subirrigated Sandhills meadows. The potential for ground water contamination exists as the water table depth ranges from 0 to 3 m. Atrazine was applied at 2.2 and 3.4 kg ha-1 in May 1984, August 1984, or May 1985 to a Gannett fine sandy loam (Typic Haplaquoll, coarse-loamy, mixed, mesic) in a Nebraska Sandhills subirrigated meadow. Residues of atrazine applied in 1984 and 1985 carried over into 1985 and 1986, respectively. Herbicide dissipation and off-plot movement were monitored in 1985 by sampling soil at 0 to 5 cm and 5 to 15 cm depths within and outside the experimental areas. Atrazine dissipation initially approached zero-order kinetics after May 1985 application, but generally followed first-order kinetics during the entire 320-day sampling period. Atrazine half-life in the entire 0 to 15 cm sampling zone was 46 +/- 7 days. Herbicide concentrations at the 5 to 15 cm sampling depth did not exceed levels measured at 5 days after application. Low and highly variable atrazine concentrations detected in some of the untreated plots and in some off-plot soil samples indicated minimal lateral movement of the herbicide.