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Soil under the crown of mesquite trees was compared to soil from adjacent openings at three depths for several physical and chemical properties near Tucson, Ariz. Bulk density was lower in soil under mesquite but increased with depth in that location. Organic matter, total nitrogen, total sulfur, and total soluble salts were up to three times greater in the surface 0 to 4.5 cm of mesquite soil than in open soil but declined with increasing depth to levels approximately the same as in open soil. Total potassium was higher under mesquite but increased with depth. Total phosphorus and hydrogen ion concentrations were the same in soil under mesquite as in soil from open areas. Results suggest that mesquite trees function...
Three mixed prairie sites at Mandan, N.D. were grazed heavily (0.9 ha ), moderately (2.6 ha ), or left ungrazed (exclosure) since 1916. These sites provided treatments to study the effects of long-term grazing on soil organic carbon and nitrogen content and to relate changes in soil carbon and nitrogen to grazing induced changes in species composition. Blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Griffiths] accounted for the greatest change in species composition for both grazing treatments. Relative foliar cover of blue grama was 25% in 1916 and 86% in 1994 in the heavily grazed pasture and 15% in 1916 to 16% in 1994 in the moderately grazed pasture. Total soil nitrogen content was higher in the exclosure (1.44...
(PGBE) esters of 2,4,5-T and silvex were applied to Arizona chaparal at zero, one, two and four pounds per acre in the spring, spring-fall (of the same year), spring-spring, and springfall- spring, beginning in May, 1959. In a second experiment 2,4,5-T and silvex were applied at zero, two and four pounds as the alkanolamine salt, as PGBE esters in Kuron and Esteron form, and as PGBE esters of 2,4,5-T and silvex in Forron formulation in the spring of 1959 and 1960. All tests were made on replicated 25' x 50' plots. The treatments resulted in varying degrees of topkilling of shrub live oak but most plants resprouted from the base or live branches. Treatment effects were recorded in terms of visual estimates of damage...
A 20-year set of cover data on sagebrush semi-desert plant communities responding to wildfire and livestock grazing near Mills in central Utah provided an opportunity to compare the assumptions and adaptability of classical and state-and-transition models for describing secondary succession. Cover data were organized and analyzed by plant species, growth forms, and other ground cover classes. Graphical analysis, ordination (employing semi-strong hybrid multi-dimensional scaling), regression, and analysis-of-variance were used to determine whether the patterns observed were best described as community change (tightly linked species) or individualistic change (each species acting independently). Distinct differences...
Off-road military vehicle traffic is a major consideration in the management of military lands. The objective of this study was to determine the impacts of military tracked M1A1 heavy combat tank vehicles on sediment loss from runoff, surface plant cover, and surface microtopography in a desert military training environment. A randomized block design was used which had 10 blocks with 4 plots in each block. Each block had randomly selected treatments that included an untreated control, 1 pass by a M1A1 tank under wet seasonal conditions, 3 passes by a M1A1 tank under wet seasonal conditions, 1 pass by a M1A1 tank under dry seasonal conditions, and 3 passes by a M1A1 tank under dry seasonal conditions. Data were analyzed...
Relationships between vegetal and edaphic factors and infiltration rates and erosion as measured on 550 infiltrometer plots at chained pinyon-juniper sites in Utah were analyzed by multiple regression analysis. Those factors most important for predicting infiltration rates (regardless of time interval) included total porosity in the O-3 inch layer of soil, percent bare soil surface, soil texture in the O-3 inch layer of soil, and crown cover (percent or tons per acre). The ability to predict infiltration rates (as determined by R2) varied with time and geographic location. Not only did predictive ability vary, but independent variables explaining such variance also changed with time and location. Factors that influence...


    map background search result map search result map Effect of Mesquite on Physical and Chemical Properties of the Soil Effect of Mesquite on Physical and Chemical Properties of the Soil