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Articles 1 - 12 of 12
Full-Text Articles in Other Earth Sciences
Changing Fields: Agricultural Land Use Changes In Nebraska 1925-1974, Donald A. Wilhite
Changing Fields: Agricultural Land Use Changes In Nebraska 1925-1974, Donald A. Wilhite
National Drought Mitigation Center: Faculty Publications
The series of graphs and maps which follow illustrate agricultural land use changes in Nebraska from 1925 to 1974. With these graphs and maps, the major agronomic crops of corn (dryland and irrigated), wheat, sorghum and soybeans are analyzed. The purpose of this analysis is to provide a pictorial history of Nebraska's ever-changing cropping system and, hopefully, to stimulate ideas and discussion with regard to trends and future directions. The Nebraska Water Resources Center is deeply interested in both the past and the future of Nebraska's agriculture because of the demands which agriculture places on the state's water resources. An …
A Search For Phytotoxins Influencing Germination And Early Growth Of Ponderosa Pine, United States Department Of Agriculture, Forest Service
A Search For Phytotoxins Influencing Germination And Early Growth Of Ponderosa Pine, United States Department Of Agriculture, Forest Service
Forestry
A series of laboratory and field experiments were conducted to determine if mature ponderosa pines produce a substance (phytotoxin) that inhibits the germination and growth of seedlings directly under the tree crown. Neither live nor dead materials collected from ponderosa pines produced either volatile or water-soluble phytotoxins that drastically inhibited germination of seeds or growth of seedlings. Seed overwintering beneath the canopy of mature pine, or planted in soils collected there, showed reduced germination. Exact cause of the reduction was not determined. If weak phytotoxins were responsible, they did not inhibit growth of seedlings that germinated.
Influence Of Some Environmental Factors On Initial Establishment And Growth Of Ponderosa Pine Seedlings, United States Department Of Agriculture, Forest Service
Influence Of Some Environmental Factors On Initial Establishment And Growth Of Ponderosa Pine Seedlings, United States Department Of Agriculture, Forest Service
Forestry
Study plots were established to determine the effects of various environmental factors on ponderosa pine seed germination and initial seedling establishment and growth. A series of soil surface treatments were performed on plots in two locations: within or under the influence of overstory pine trees and in openings away from the pine influence. Seed germination was significantly greater in the opening plots. The overstory canopy and forest floor restricted the amounts of precipitation, light, and heat reaching the soil and probably decreased germination. Cutworms, birds, and small mammals caused the greatest seedling mortality. The largest seedlings occurred in the fire-treated …
Quaking Aspen - Seed Germination And Early Seedling Growth, United States Department Of Agriculture, Forest Service
Quaking Aspen - Seed Germination And Early Seedling Growth, United States Department Of Agriculture, Forest Service
Forestry
The suckering of aspen (Populus tremuliodes Michx.) as a highly effective means of vegetative propagation is well known and has been widely studied (Baker 1918; Day 1944; Maini 1967; Schier 1974). Less is known about seed propagation, sometimes viewed as having only minor importance because early research (Baker 1918) had indicated that rare seedling establishment was due to low or nonexistent germinability.
Nutrient Losses From Timber Harvesting In A Larch/Douglas-Fir Forest, United States Department Of Agriculture, Forest Service
Nutrient Losses From Timber Harvesting In A Larch/Douglas-Fir Forest, United States Department Of Agriculture, Forest Service
Forestry
Nutrient levels as a result of experimental clearcutting, shelterwood cutting, and group selection cutting--each with three levels of harvesting intensity--were studied in a larch-fir forest in northwest Montana, experimentally logged with a skyline system. None of the treatments altered nutrient levels in an intermittent stream, nor were excessive amounts of nutrients lost in soil below the root zone. Under conditions on this site, skyline logging did not result in surface erosion or nutrient losses that would affect forest management.
Sucker Regeneration In A Utah Aspen Clone After Clearcutting, Partial Cutting, Scarification, And Girdling, United States Department Of Agriculture, Forest Service
Sucker Regeneration In A Utah Aspen Clone After Clearcutting, Partial Cutting, Scarification, And Girdling, United States Department Of Agriculture, Forest Service
Forestry
Clearcutting, partial cutting, scarification, and girdling were used to stimulate root suckering in a Utah aspen clone. Regeneration was inventoried yearly during the first 4 years after treatment and again after 12 years. Clearcutting resulted in the greatest number of suckers. In most years, partial cuts (cuts that removed 67 percent of the basal area) had less than 50 percent as much regeneration as the clearcut plots. Girdling stimulated suckering to a lesser degree than cutting. Mortality was high on girdled plots and by the 12th year after treatment few suckers had survived. Scarification had no apparent effect on sucker …
Heat Content Of Bark, Twigs, And Foliage Of Nine Species Of Western Conifers, United States Department Of Agriculture, Forest Service
Heat Content Of Bark, Twigs, And Foliage Of Nine Species Of Western Conifers, United States Department Of Agriculture, Forest Service
Forestry
Comparative combustion tests showed that bark, twigs, and foliage of nine commercial timber species in the Northern Rocky Mountains generally produce more heat than equal volumes of their ovendry wood and that these parts of harvested trees could be profitably utilized as a source of energy.
A Model For Predicting Lightning-Fire Ignition In Wildland Fuels, United States Department Of Agriculture, Forest Service
A Model For Predicting Lightning-Fire Ignition In Wildland Fuels, United States Department Of Agriculture, Forest Service
Wildfires
A model has been developed for predicting the number of lightning-fire ignitions in wildland fuels. The model is based on both stochastic and physical processes. Stochastic methods are used to generalize the lightning storm characteristics and site conditions that affect the potential for ignition. Physical processes are involved in determining the ignition probability of woody fuels by individual lightning events. Input required to operate the model includes lightning activity, upper air windspeed (storm movement), fuel moisture, and fuel bulk density. The model can be used either to predict ignitions at some future time by using forecast data or to estimate …
Fire Behavior In Nonuniform Fuels, United States Department Of Agriculture, Forest Service
Fire Behavior In Nonuniform Fuels, United States Department Of Agriculture, Forest Service
Wildfires
For the purposes of this study, nonuniform fire behavior is predicted by modeling fire spread through a hexagonal network of fuel cells. Fire spread is assumed to be a process of contagious growth between cells. Fuel properties are allowed to vary from cell to cell in a prescribed manner but have uniform properties within the cell. Consequently, the nonuniformity of the actual fuel array is simulated through cell to cell variations and has a resolution limited by the cell size. Because of the nature of the modeling process, it is necessary to devise a scheme for collecting data describing nonuniformity …
Fire - Decay: Interactive Roles Regulating Wood Accumulation And Soil Development In The Northern Rocky Mountains, United States Department Of Agriculture, Forest Service
Fire - Decay: Interactive Roles Regulating Wood Accumulation And Soil Development In The Northern Rocky Mountains, United States Department Of Agriculture, Forest Service
Wildfires
Decay and fire play interactive roles in recycling wood and other organic materials in forest ecosystems, and contribute to the development of high quality soils in the Northern Rocky Mountains. Decayed wood, charcoal, and other decomposed organic matter are the principal media for ectomycorrhizal and nonsymbiotic nitrogen fixing microbes. The activities of these microbes are critical to the growth of forest trees. The balance between decay and fire, as it affects the amount, distribution, and type of organic matter, controls the ability of forest soils to support the growth of trees.
Turbulence Spectra Above A Vegetated Surface Under Conditions Of Sensible Heat Advection, Raymond P. Motha, Shashi B. Verma, Norman J. Rosenberg
Turbulence Spectra Above A Vegetated Surface Under Conditions Of Sensible Heat Advection, Raymond P. Motha, Shashi B. Verma, Norman J. Rosenberg
National Drought Mitigation Center: Faculty Publications
Spectra of vertical and horizontal velocity, air temperature and humidity fluctuations were analyzed from measurements made over a well-watered alfalfa crop under conditions of sensible heat advection. Vertical velocity and air temperature spectra as well as cospectra of momentum, sensible heat and water vapor were found to be dependent on atmospheric thermal stratification. These spectra and cospectra were shifted toward higher frequencies under advective as compared to lapse conditions. These results indicate that the predominant eddy sizes are relatively smaller under advective conditions. Humidity spectra, on the other hand, were independent of daytime thermal stratification conditions but were influenced by …
Uranium Transport In The Walker River Basin, California And Nevada, Larry Benson, D. L. Leach
Uranium Transport In The Walker River Basin, California And Nevada, Larry Benson, D. L. Leach
United States Geological Survey: Staff Publications
During the summer of 1976 waters from tributaries, rivers, springs and wells were sampled in the Walker River Basin. Snow and sediments from selected sites were also sampled. All samples were analyzed for uranium and other elements. The resulting data provide an understanding of the transport of uranium within a closed hydrologic basin as well as providing a basis for the design of geochemical reconnaissance studies for the Basin and Range Province of the Western United States. Spring and tributary data are useful in locating areas containing anomalous concentrations of uranium. However, agricultural practices obscure the presence of known uranium …