31 research outputs found
Plenary Session—Welcome and Opening Remarks
I vastly appreciate the opportunity of being with you all today to help launch what, I am certain, will prove an extraordinary workshop. I bring you specific greetings and words of welcome from colleagues in eastern Washington and elsewhere in the interior Pacific Northwest and particularly from the organization that John Munn and I work for, the College of Agriculture and Home Economics and Cooperative Extension, Washington State University. We are delighted indeed to have this meeting in our corner of the world this year
Gas Exchange of Three Cool Semi-Desert Species in Relation to Temperature and Water Stress
Three plant species prominent in cool shrub-steppe communities of western North America, Artemisia tridentata ssp. tridentata (true shrub), Gutierrezia sarothrae (half-shrub) and Agropyron spicatum var. inerme (perennial bunchgrass), were studied with the aim of defining interspecific differences in gas exchange response to temperature and plant water potential during the course of the year. These differences in patterns and magnitudes of gas exchange in relation to variations in physical factors were taken as evidence of differing adaptive strategies. Different morphological and phenological features of these three species were also correlated with gas exchange response to physical factors. Rates of net assimilation were found to be lowest for the true shrub Artemisia tridentata and much higher in the suffrutescent Gutierrezia sarothrae and the perennial bunchgrass Agropyron spicatum var. inerme. Variations in temperature exerted a pronounced effect on net assimilation rates of all three species with clearly marked optima for photosynthesis of 16-20° C for the two shrub species and 20-25° C for the grass. Dark respiration rates for all three species increased consistently with increases in temperature. On a seasonal basis, net assimilation rates for all three species were highest during spring and early summer, when water supply was least limiting and temperatures were closest to optimal. During periods of drought and higher temperatures in late summer, the Agropyron became photosynthetically dormant, and the shrubs exhibited much lower rates of net photosynthesis; those of Artemisia were far more reduced than those of Gutierrezia, particularly at higher temperatures, when net assimilation for Artemisia frequently became negative during the afternoon periods. Stomatal diffusion resistances to CO2 assimilation (r\u27s) were much higher for Artemisia than for Gutierrezia under all conditions, and r\u27s increased much more rapidly with increases in temperature and water stress for Artemisia. This greater sensitivity of r\u27s of Artemisia is viewed as an adaptation to curb excessive leaf water loss during hot, dry, late summer periods, allowing maintenance of greater quantities of leaves during such periods. Gutierrezia, which exhibited less effective stomatal control of water loss, shed most of its leaves during drought periods. Under conditions of water stress, residual resistances to CO2 assimilation (r\u27r) for Artemisia were much higher than those of Gutierrezia, although r\u27r for both species tended to increase with decreasing plant water potentials. One major reason for the higher r\u27r values of Artemisia at low water potentials is thought to be linked to the fact that decline of respiration rates with decreasing water potential was less rapid than the concurrent decline in photosynthesis. This might also help to explain the negative net assimilation often noted for Artemisia under conditions of high temperatures and low water potentials. Gutierrezia, conversely, exhibited a less pronounced decline in photosynthetic rates and a more rapid decline in respiration rates with decreasing water potential, and no negative net photosynthesis was observed for this species during daylight hours even though plant water potentials were generally lower than those of Artemisia
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Legume Establishment on Strip Mined Lands in Southeastern Montana
Research was conducted on topsoiled strip mined lands at Colstrip, Mon., over a 6-year period to evaluate germination, survival, productivity, and cover characteristics of Eski sainfoin (Onobrychis viciaefolia), Lutana cicer milkvetch (Astragalus cicer), birdsfoot trefoil (Lotus corniculatus), and ranger and spreader alfalfa (Medicago sativa). Nitrogen and phosphorus fertilizer were applied at a low rate during the first year of study. None of the experimental units received irrigation. Lutana cicer milkvetch and both varieties of alfalfa demonstrated good establishment, survival, canopy cover, and productivity characteristics. Eski sainfoin showed good initial establishment but declined in following years. Birdsfoot trefoil appeared to be unsuitable for revegetation of mined lands at Colstrip. Spreader alfalfa was superior to ranger alfalfa in the parameters evaluated. Lutana cicer milkvetch showed much potential for mined lands revegetation in the study area because of site stabilization, persistence, palatability, nitrogen fixation, and productivity characteristics.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202
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Long-Term Plant Establishment on Mined Lands in Southeastern Montana
Research was conducted on strip mined lands at Colstrip, Mon., over a 6-year period to evaluate germination, survival and cover characteristics of fairway crested wheatgrass (Agropyron cristatum), critana thickspike wheatgrass (Agropgron dasystachyum), ranger alfalfa (Medicago sativa), and fourwing saltbush (Atriplex canescens). All 4 species showed good initial establishment and long-term survival/growth even though subjected to 2 consecutive years of drought when growing season precipitation was less than 50% of the mean. Nitrogen and phosphorus fertilizer application after emergence had no effect on initial or long-term survival of any species. However plant canopy and litter cover were increased for all species except fourwing saltbush by fertilizer application. There was little invasion of native species into the study area. Critana thickspike wheatgrass is a native species that appears well suited for seeding mixtures on mined lands in the study area. However, because of aggressiveness, the use of fairway crested wheatgrass is not recommended in mixtures from which a diversity of native species is the vegetation goal.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202
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Effects of Two Years of Irrigation on Revegetation of Coal Surface-Mined Land in Southeastern Montana
Responses of reseeded vegetation in the first two growing seasons (1978 and 1979) to irrigation on topsoiled sodic mine spoils are presented. In terms of above-ground productivity and stand composition, irrigation significantly promoted growth of seeded perennial grasses and legumes in total. This stimulation was most pronounced in 1979 for the cool-season grasses, slender wheatgrass, smooth bromegrass and western wheatgrass and the invading cool-season legume yellow sweetclover. Other cool-season grasses and warm-season grasses were stimulated by initial irrigation, but were either unaffected or retarded (due to competitive relationships) by continued irrigation. Productivity of invading annual weeds was significantly curtailed by irrigation by 1979. Although differences in composition occurred, total stand productivity was similar for irrigated and nonirrigated plots in 1978, a year of above-average precipitation. In 1979, a drier year, total stand productivity was nearly three times higher under irrigation than nonirrigation. In the first year of study (1978), a higher measured index of stand structural diversity occurred under irrigation. This relationship became reversed in 1979, with higher structural diversity in nonirrigated plots. Root biomass was significantly higher in nonirrigated than in irrigated plots. This difference between irrigation and nonirrigation was most pronounced in the applied topsoil zone. Root distribution was skewed towards shallowest soil depths under irrigation to a far greater extent than under nonirrigation.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202
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Plant community development on petroleum drill sites in northwestern Wyoming
Plant community and soil development were investigated on oil/gas drilling sites occupying both sagebrush and coniferous forest vegetation types in northwestern Wyoming. Sites ranged from 3 to 33 years in age since abandonment. Some sites were seeded at abandonment, while others revegetated naturally. Vegetation and soils were sampled and compared on disturbed and adjacent undisturbed sites. Both soils and vegetation were altered by drilling activities. Disturbed soils generally had higher bulk density and pH and lower organic matter content than undisturbed soils. All disturbed sites were vegetationally dissimilar to adjacent native sites. However, sagebrush disturbances were progressing toward undisturbed conditions more rapidly than coniferous forest disturbances. Seeding accelerated vegetation development, although at different rates between sagebrush and coniferous forest disturbances. Seeding and establishment of introduced grass species on disturbed sites did not prevent natural recolonization of native species.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202
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Plant responses to gypsum amendment of sodic bentonite mine spoil
Abandoned bentonite mine spoils are extremely difficult to revegetate because of their high clay content, salinity, sodicity, low permeability, and the semiarid climate of the area where bentonite mining occurs. Recent research has led to the development of technology utilizing sawmill wastes (chips, bark, and sawdust) to enable the successful revegetation of these lands. The use of wood residue amendments increased water infiltration, leaching of soluble salts, and vegetation establishment; however, sodicity continued to be a problem and threatened to destroy the established vegetation. Surface application of gypsum was evaluated to determine its effectiveness in ameliorating the spoil sodicity and its effect on plant growth. In a 3-year field study, surficial gypsum amendment resulted in significant increases in perennial grass biomass (150%) and canopy cover (140%). These changes were not evident until the second or third year after gypsum amendment. Annual forb biomass did not respond to gypsum amendment; however, canopy cover did exhibit a significant increase in the second year at lower wood residue amendment rates. This research demonstrates that surface applied gypsum can be effective in ameliorating bentonite spoil sodicity when applied to established plant communities.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202