<p>White-tailed deer (<i>Odocoileus virginianus</i>) are aesthetically and economically important to landowners in Texas. Deer herd health, productivity and survivability decline when population size exceeds the available forage. During stressful times, such as dry winter periods, nutrition is limited and forage availability decreases drastically. White-tailed deer winter diets are mainly comprised of browse species because herbaceous production decreases as winter progresses. The objective of this study was to determine the influence of winter progression on nitrogen (N) and fiber concentration as well in-vitro organic matter disappearance (IVOMD) (using white-tailed deer rumen liquid) of six browse species of moderate to high forage importance. Woody plant samples were collected during pre-frost, mid-winter, and late winter from four (replications) properties in the Cross Timbers of Texas, USA over 2 years. There was a difference between years (P &le; 0.05). There was an interaction (P &le; 0.05) between species and season for all forage values. Nitrogen, a desirable nutrient, decreased as winter progressed, IVOMD decreased as fiber increased with winter progression in five of the six browse species. The only exception was evergreen live oak (<i>Quercus virginiana</i> Mill.) which kept its leaves throughout winter and maintained an average 1.33% N with lowest fiber levels and highest IVOMD in late winter. Results confirm that nutritional value of browse, especially N and fiber, decreases after the first freeze when most browse species shed leaves. It also supports the need for plant biodiversity in white-tailed habitat that supports adequate year-round white-tailed deer nutrition. </p>

Multiobjective decision support systems (DSS) are gaining acceptance as tools to evaluate resource management systems. Before applying a DSS, a matrix of decision criteria and alternative management systems is populated using information from measured data, expert opinion or simulation models. As each information source exhibits differences in data availability and accuracy, the extent to which outcomes from the DSS are influenced by the source of information remains an important issue. A conceptual framework links the Prototype Decision Support System (P-DSS) developed by the USDA-ARS Southwest Watershed Research Center in Tucson, Arizona, to a conservation practice physical effects matrix. Four rangeland practices of yearlong (YL) and rotation (ROT) grazing, with mesquite trees retained (+M) and removed (-M), are evaluated against eight decision variables that consider soil, water, plants and wildlife habitat. Each decision variable is quantified using data from four experimental watersheds on the Santa Rita Experimental Range, expert opinions, and two simulation modeling approaches. The simple approach uses the Curve Number method, RUSLE and MUSLE, while the complex approach uses the CREAMS hydrology and erosion models. Outcomes from the P-DSS are sensitive to the source of information. When measured data and complex models quantify the decision variables, the YL-M and ROT-M management systems dominate the current system of YL+M. The simple modeling approach identifies ROT+M in addition to YL-M and ROT-M. However, when a frequency of rank methodology is used, the simple and complex modeling approaches identify ROT-M as the preferred system, while the measured data and expert opinion identify YL-M. Ranking the four management systems quantified by simple models matches the ranking obtained from the expert survey. Rank ordering using the complex models agrees with the opinion of the most knowledgeable expert. Simple and complex modeling estimates of sediment yield are significantly different, as are estimates of peak runoff rate. The results suggest that model complexity improved information accuracy but had limited effect on the outcomes from the P-DSS. The effect of information sources on the outcomes from the P-DSS may become more pronounced if the evaluation changes from a relative assessment to one involving quality standards.

Johnsongrass (Sorshum halepense (L.) Pers.) occurred in nearly pure stands on the Patagonia-Sonoita Creek Preserve, Santa Cruz County, Arizona prior to grazing. This study investigated the use of grazing, mowing and herbicides to decrease the abundance of johnsongrass, and increase the diversity of other plant species. The grazed only treatment allowed remaining overstory and limited grazing access. Mowing lowered the overstory and provided accessibility to grazing attracting animal utilization of the areas. The herbicided and grazed treatment reduced total johnsongrass productivity, tiller numbers and impacted tiller growth form. Lower percent botanical composition and tiller emergence of johnsongrass plants occurred in 1995 than in 1994. The number of other plant species increased between study years.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

No description available.

Dissertation (PhD (Agric))--University of Stellenbosch, 2006. / Bibliography. Also available via the Internet.

<p> Watersheds are complex systems that are influenced by many factors including geomorphology, climate, soil, vegetation, and land management. Due to this complexity, a watershed assessment that evaluates both the riparian and upland areas has yet to be developed. We proposed investigating a combination of plant community composition within the greenline, upland ecological site function assessment with the Interpreting Indicators of Rangeland Health (IIRH) protocol, and stream morphological parameters. Stream parameters investigated were Rosgen&rsquo;s classification method, bank erosion hazard index (BEHI) and bank height ratio (BHR). This research was conducted on five intermittent streams in southwestern North Dakota. We found that facultative wetland species offered the most protection to intermittent streambanks as a result of hydrology. When assessing the uplands it was determined that there is a positive correlation between rangeland health and riparian health. The stream parameter that showed the strongest relationship was the BEHI.</p><p>

No description available.

Revegetation of semi-desert rangeland is dependent on rainfall, weather, and soil factors affecting seed germination and seedling establishment. To aid in predicting seed zone temperature and moisture following rainfall, a weather driven one-dimensional computer model was developed to simulate the simultaneous flow of heat and water within a bare semi-desert soil. The Newton-Raphson method was used to solve the surface energy budget equation for surface temperature. The coupled soil heat and water flow equations were then solved numerically using the weighted average finite-difference method to calculate the subsurface temperature (T(s)) and water content (θᵥ) profiles. Weather data and soil thermal and hydraulic properties were the only required inputs to the model. The model was tested using two data sets collected in the Altar Valley of Arizona during the summer rainy season of 1988. Data set 1, collected from calendar day (CD) 198 to 205, was used to calibrate the model. Calibration tests revealed that the model markedly underestimated T(s) when measured values exceeded 37°C. Underestimation of T(s) was found to be related to overestimation of latent heat flux. Therefore, the modelled latent heat flux was reduced as a linear function of air temperature (Tₐᵢᵣ) when Tₐᵢᵣ > 30°C. Also, soil thermal conductivity values predicted by the de Vries model had to be reduced 80% in order to achieve acceptable agreement between measured and modelled T(s). Data set 2, from CD 191 to 195, was then used to validate the calibrated (modified) model. Results obtained with data set 2 indicated that the modified model accurately simulated T(s) at 0.01 m depth even when the measured T(s) at that depth exceeded 50°C. Simulated T(s) values for the soil profile were generally within ± 3°C of the measured values. Results also showed good agreement between modelled and measured net radiation flux densities. In addition, the modified model predicted surface layer (0-0.03 m) moisture content remained wet enough for seed germination, i.e. θᵥ > 0.09 m³ m⁻³, about 24 to 36 hours longer than indicated by measured (resistance block) θᵥ values.

Presence and composition of Eragrostis Lehmanniana was measured on 75 permanent transects every 3-8 years between 1958-1989 on the Santa Rita Experimental Range, Arizona. The number of transects occupied and average composition increased rapidly over this period. A repeated measures analysis of two soil groups with different water holding capacity and permeability revealed that the rate of increase of E. Lehmanniana was different between the groups. Repeated measures analysis of five grazing intensities revealed that the rate of E. Lehmanniana increase was different among intensities. It appears that the highest intensity had the highest rate of increase. The influence of grazing on E. Lehmanniana spread was also expressed by the lack of difference in relative composition measured in 1989 between ten livestock enclosures and adjacent grazed areas. This research suggests that E. Lehmanniana will spread and dominate with an average of 89 mm of summer precipitation in 40 days; a lower regime than estimated by other research.