No description available.

No description available.

No description available.

No description available.

No description available.

The purposes of this study were to compare Soil Conservation Service and Forest Service methods for determining range condition, to develop a method for determining range condition using plant frequency data and to develop range condition guides using Sorensen's coefficient of similarity. The final objective was to compare condition scores based on frequency data to Soil Conservation Service and Forest Service condition scores. Loamy upland and sandy loam upland range sites in the Empire Valley and Santa Rita Experimental Range of southeastern Arizona were sampled. Three prominent soil series of upland range sites within the study area were selected for study. Within each soil series, areas of apparent high, medium and low levels of past and present livestock use were sampled at three locations. Soil profile descriptions were made for each of the 27 sample areas and soil characteristics were used to confirm soil series sampled. Plant communities were sampled by weight estimates, Parker 3-step transects and 40 x 40 cm frequency plots. Forest Service and Soil Conservation Service condition scores did not correlate well within the loamy upland or sandy loam upland range sites. Condition scores by both methods, especially for Forest Service data, are confounded with site potential. Cluster and factor analysis procedures identified plant groups associated with soil series, range site and sample location. Range condition was not identified as a criterion of plant group association. Sorensen's coefficient of similarity scores for frequency data based on a specific "high condition" reference area had a high coefficient of determination value when correlated with Soil Conservation Service condition scores for loamy upland range sites. Forest Service condition scores had a very low coefficient of determination value for the same comparison. Soil Conservation Service and Forest Service condition scores compared to similarity scores for frequency data for the sandy loam upland range site had positive but low coefficient of determination. Sorensen's coefficient of similarity, using frequency data as an index of condition, can be used to develop a range site condition guide for a homogeneous range site.

Demography of nocturnal desert rodents was monitored for nine years. Three dissimilar areas were sampled with three distinct trapping configurations and time regimes. All three areas contained similar rodent species. Increased plant growth and seed production resulting from variations in rainfall seemed to have the most profound effect on both rodent densities and species composition. Deviations from the bimodal rainfall pattern occurred in the latter parts of 1972, 1977, and 1978 and early 1973, 1978, and 1979. During these times there was a 2-4 fold increase in rainfall. This pattern produced "desert blooms" in the spring of 1973, 1978, and to some extent 1979. In addition, 1972 and 1978 were years of high rainfall. The reaction of the rodents to the increased plant production was rapid and dramatic. Heteromyid numbers increased approximately six fold with some species increasing twelve fold within a matter of five months. The smaller heteromyids, Perognathus amplus and P. penicillatus, were the first to increase substantially, while the larger rodents reached peak populations in the following year. The resulting population crash that followed the high densities was as dramatic as the increase. Neotoma albigula populations did not increase substantially after the first rainfall phenomenon but did so dramatically after the second period of aberrant rains. The densities of N. albigula remained high long after the heteromyid populations decreased to "normal" levels. The three areas were found to be dominated by different species while the overall rodent densities in the three areas were very similar within the same time frame.

A gravity station network was established over the Tucson Basin on a nominal one mile spacing for the purpose of determining major hydrologic boundaries. Gravity data were supplemented by magnetic, seismic, and borehole geophysical data. Gravity data reveal a marked linearity of pattern which in general correlates with structural trends previously noted in the area. Based on surface geological data, radiometric dating, and the present survey, it is suggested that the Tucson basin began to form in mid-Tertiary time under tensional stresses. As the circum-basin mountain blocks rose, the Tucson basin was gradually filled by the Pantano formation and its equivalents. Around the margins these were alluvial fan deposits which graded laterally into each other and into playa deposits in the central basin. During the Pliocene Epoch this pattern of internal drainage was disrupted and Pantano deposition ended with the inception of a period of erosion. Deposition of later sediments coincided with external drainage and throughflowing streams. The late-Tertiary and Quaternary sediments probably have been faulted to a minor degree by continuing movement along basement structures or by differential compaction over basement topography. The extent to which this affects groundwater gradients is a function of the percentage of coarse material in the aquifer. Further complications in development of these upper aquifers may be due to igneous dikes and to buried glide blocks of relatively impermeable sediments. The Pantano aquifers are probably broken into relatively small, autonomous hydrologic units by near-vertical fault systems. During this study two new applications of geophysical data were used to analyze basin hydrology. Using Gauss' Theorem the total mass deficiency of the basin was determined and from this a total water content of 129 cubic miles was calculated. The second application involved the use of a borehole density log to calculate the aquifer storage coefficient and revealed a probable value of 0.05, much lower than previously estimated.

Integrated geophysical methods, in combination with available well and geologic data, were used for the purpose of defining the subsurface hydrologic and geologic conditions beneath the Walnut Gulch Experimental Watershed and its peripheral area near Tombstone, Arizona. The 58-square mile watershed, within the 290-square mile area covered by portions of this study, was chosen by the U. S. Department of Agricuiture for intensive research relating to the water and sediment yields from a semiarid range land watershed, Surface geology of the watershed reveals an alluvial fandike area between igneous intrusive and sedimentary rocks that support the Tombstone gills o the southwest and the Dragoon Mountains on the northeast, An interface between the Cenozoic alluvium and volcanic rocks, and the igneous intrusive and sedimentary rocks which are noted as the basement complex, was based on velocity determinations from several seismic refraction profiles, and density determinations of 127 surface samples from 75 sites in 19 different formations, Average values of 2.26 gm/cm3 (grams per cubic centimeter) for the Cenozoic alluvium and volcanic rocks and 2.65 gm/cm3 for the intrusive igneous and sedimentary rocks established a density contrast across the interface of 0.39 gm/cm3, A network of 360 gravity stations established over the watershed and its peripheral area aided in defining configuration of the basement complex, provided depth approximations of the alluvium, and controlled the bearings for subsequent seismic traverses. Magnetic profiles over deep, alluvium-filled areas and the surrounding exposed bedrock was postulated to be useful in deducing source areas and depositional patterns within the alluvium. Structural control of groundwater flow to the northwest was suggested through a combined study of dominant trends on the gravity and magnetic maps. A gravity profile north of the watershed across the largest negative anomaly, with the regional gradient removed, was interpreted as an alluvium-filled graben having a width of ten miles, and a depth of 3500 feet east of its center. Toward the southeast, several parallel gravity profiles indicated a decrease in width and depth of the structure. A total of 54 seismic refraction profiles, aggregating a length of 120,000 feet of in-line seismic profiling, was conducted in 13 areas, Velocities derived from reversed seismic profiles, and profiles conducted over outcrops, averaged 2200 feet per second for channel fill, 5000 feet per second for unconsolidated alluvial deposits, 8800 feet per second for conglomerates, and depending on the particular unit, 12,300 to 15,600 feet per second for basement-type rocks. Mapping of the water table in many areas revealed depths from near zero at the confluence of Walnut Gulch and San Pedro River, to 475 feet in the central portion of the watershed. The accuracy of predicting the depth to either groundwater or basement was ± 6 percent, while that for groundwater alone was ± 10 percent. Analysis of the timedistance data, and correlations with surface geology, grayity, and well data provided a basis for the interpretation of the hydrogeology and recent alluvial history. Finally, a new application of velocities was used in this study to analyze a part of the hydrologic cycle. Based on 23 pairs of observation, a prediction equation was derived through linear regression analysis of density versus velocity. Using seismic velocities, the prediction equation, and relationships between density and porosity, areas of maximum transmission losses within the channel were estimated.

No description available.