The objectives of this dissertation were to identify soil and vegetation changes due to grazing by livestock and to develop guidelines for monitoring the impact of livestock in the Sahelian zone of Africa. The study was conducted in eastern Senegal during 1983 to 1985. The basic methodology was a study of the process of degradation (retrogression) through the collection of data on soils and vegetation along a gradient of increasing livestock pressure. Two gradients were selected along piospheres. Each gradient was placed on a range site that had homogeneous state factors (climate, geology, and rainfall). The results show that the changes in the soil were confined to the top soil horizon. There was a negative correlation between livestock pressure and factors such as infiltration, percent nitrogen, and percent carbon, and a positive correlation between livestock pressure and the factors of bulk density, and phosphorous content. Changes in the vegetation community were dependent on the range site. On the sandy site, there was a linear, negative correlation between livestock pressure and the factors of plant density, plant cover and biomass. On the loamy range site, the changes in these factors along the gradient had a 2nd or 3rd order polynomial relationship. The effects of bush fires and short term droughts on the vegetation were also studied. Drought, in particular, has an impact that is similar to that of livestock pressure, and may compound the results. Multiple regression analysis and a Twinspan ordination program were used to select parameters and plant species that were highly correlated with the gradient, and could act as indicators of each stage of degradation. These indicators can be used to monitor the impact of livestock on rangelands. General parameters, such as total plant density, are less sensitive to drought-induced changes than the composition of indicator species, but the latter are easier to monitor. Both types of indicators can form the basis for a monitoring methodology that can be used in Africa at three management levels: the individual herder, extension agents and regional branches of the division concerned with rangelands, and policy makers at the ministerial level.

Most livestock and range management projects in the Sahelian countries of Africa have failed to achieve their objectives. Many reasons have been given to explain the failure, but these reasons usually fall short of covering the whole environmental picture and concentrate on the factors internal to the projects. They do not provide complete explanations of why pastoral programs fail because they tend to over-emphasize the isolation of pastoral communities from their wider societies and do not take into consideration the whole socio-economic and political environment. The purpose of this study was to more constructively explain why pastoral development projects succeed or fail. Pastoral projects funded by World Bank and USAID in six Sahelian countries of Africa were studied. Metaevaluation was used to study all of the factors affecting the outcome of pastoral projects. A survey of project evaluators and summaries of project reports and evaluation activities were used as the main sources of data. The results indicate that outcomes of pastoral projects do depend upon the technological, sociocultural, and environmental dimensions of the development situation. But the outcomes are more affected by the policies of governments and their institutions than by any other factor. Factors such as uncertain funding, conflicting goals and objectives, and complicated bureaucratic procedures, generally mean that projects are not implemented as planned, changes are made as the projects are implemented, or implementation never occurs.

The objective of this research was development and testing of a method for estimating cattle carrying capacities. A series of studies were conducted in developing this method. Range site and vegetation production data were grouped by topographic position and multiple linear regression equations were calculated for predicting vegetation production as a site deviated from the average case of a given range site. Overstory-understory relationships from the literature were adapted into overstory canopy cover classes for predicting understory production and tested on a variety of range sites. Use of these classes produced understory biomass estimates within 13% of measured biomass. Range condition class and understory aspect dominance by forage vs. non-forage species were investigated as estimators of forage value of the understory vegetation. Both were significantly related to amount of forage in the understory. However, understory aspect proved to be a better estimator when individual comparisons were examined. The previous findings, along with Soil Conservation Service range site guides, were used to calculate resource value ratings. Adjustment factors to be applied to the resource value ratings were calculated, using data from the literature, to account for the effects of slope and distance from water on forage utilization by cattle. These resource value ratings and adjustment factors form the basis of the carrying capacity estimation method. Pastures identified as properly utilized were used in testing the method developed. Pastures were mapped for range site, vegetation, slope and water location. Maps were converted to digital form and analyzed using the Map Analysis Package (MAP) computer program (Tomlin, 1975). Construction of a final range site-vegetation-slope-distance from water map, assigning of resource value ratings and adjustment factors, and computation of final carrying capacity estimates were accomplished using MAP. Carrying capacity estimates from the developed method were well correlated to estimates from ocular reconnaissance and area allowable use methods, r = .87 and .97, respectively, and with the actual use (perceived proper use), r = .95. These estimates were accomplished without intensive field sampling. The only information required was range site designation, amount of overstory canopy cover, understory aspect class, percent slope and water location.

No description available.

No description available.

I investigated whether rapid-maturing medics (genus Medicago) could establish and produce seed under the relatively dry winter conditions of southern Arizona. Hardseededness is common in many medics and may limit germination before fall rains. Therefore, I was also interested in the amount of medic germination that occurred following summer rainfall. Five accessions from four Medicago species (laciniata, polymorpha, truncatula and littoralis) were sown with or without a companion grass (Oryzopsis hymenoides) and grown with or without weekly 2 cm irrigation. While single-plant forage yields were over 8 times higher with irrigation, each accession established and produced up to 14 seeds for every seed sown under rainfed conditions. The companion grass had no influence on medic performance. Natural reestablishment occurred in all accessions from pods. Seedlings established in summer did not survive to flowering. M. littoralis appeared particularly well adapted to establishment under rainfed conditions in this environment. (Abstract shortened with permission of author.)

I measured digestible protein consumed by 4 (2 M, 2 F) captive desert mule deer (Odocoileus hemionus crooki). Deer were fed native forage collected from the Belmont Mountains, Arizona. Intake of forage differed significantly (P < 0.05) between sexes in every season. Intake of digestible protein for both sexes was highest in fall, lowest in the spring and summer for males and females, respectively. Significant (P < 0.05) differences of forage biomass were recorded among all vegetation associations and seasons in the Belmont Mountains. The most forage biomass was available in winter, the least in spring. Desert mule deer in the Belmont Mountains are close to the nutritional carrying capacity of the range. Other efforts to increase the deer population may not be effective if the forage base is not increased.

Germination of 10 native and exotic grasses was compared for temperature regimes representing abruptly and gradually fluctuating minimum and maximum wet seedbed temperatures in summer, spring, and winter, respectively, in the desert grassland. Gradually fluctuating temperatures produced similar total percent germination but more rapid germination than abruptly alternating temperatures and constant 25 degrees C. Lehmann lovegrass (Eragrostis lehmanniana) and 7 native grasses were sown into stands of Lehmann lovegrass that were left intact, burned, sprayed with herbicide and left standing, or sprayed and mowed. In 1992 mow and dead standing treatments reduced Lehmann lovegrass seedling density and improved establishment of cane beardgrass (Bothriochloa barbinodis), Arizona cottontop (Digitaria californica), green sprangletop (Leptochloa dubia), and plains bristlegrass (Setaria leucopila) compared to burn and control treatments. In 1993 the burn treatment reduced mature Lehmann lovegrass and enhanced establishment of sideoats grama (Bouteloua curtipendula), Arizona cottontop, green sprangletop, and plains bristlegrass compared to the other treatments.

A nearly monospecific stand of Lehmann lovegrass (Eragrostis lehmanniana Nees.) was grazed by cattle during two summer growing seasons to simulate short duration grazing. Grazing treatments were timed to coincide with preboot, boot to early inflorescence and hard seed phenological stages. During each treatment, grazing intensity on individual plants included heavy, moderate or light intensities. In 1990 maximum regrowth occurred when plants were grazed during boot to early inflorescence and at a light grazing intensity. In 1991, plants grazed during preboot or boot to early inflorescence and at a light or moderate intensity produced higher regrowth amounts than the other treatments. Plants grazed during boot to early inflorescence recovered significantly faster than plants grazed during preboot in 1990 and 1991. In 1990 lightly grazed plants recovered biomass faster than plants grazed at heavier intensities. In 1991 plants grazed at light and moderate grazing intensities recovered significantly faster than heavily grazed plants. Heavily grazed plants never produced enough regrowth to resemble moderately or lightly grazed plants within one growing season.

<p> Ranching social-ecological systems (SESs) in the semi-arid, western Great Plains persist under highly variable inter- and intra-annual weather conditions and globally influenced markets. Ranch spatial scales and manager decision-making processes have traditionally been excluded from conventional grazing experiments, leading to considerable debate between scientists and land mangers about grazing strategies to achieve both beef production and biodiversity conservation outcomes on rangelands. In this dissertation I use collaborative, interdisciplinary methodologies to link rangeland and grazing management decision-making processes and learning with ecological outcomes in the semi-arid rangeland social-ecological systems (SESs) of Wyoming and Colorado. </p><p> Chapter 2 analyzes relationships between ranchers and rangeland ecosystems, inspired by the rise of adaptive management discourses in the natural resource management literature and informed by post-colonial and feminist scholarship. Rancher decision-making processes during and after drought can be understood through an ethic of care, as ranchers try to reduce social and ecological vulnerability through adaptation, learning, and respect over long-term (generations-long) time frames. Chapter 3 follows a participatory grazing research project, the Collaborative Adaptive Rangeland Management (CARM) experiment, for four years (2012-2016). I track the social learning processes of a group of 11 stakeholders representing 3 groups: ranchers, conservation NGOs, and public agencies. These stakeholders manage 10 experimental pastures in the shortgrass steppe with comparison to the traditional grazing management practice. These pastures are managed to maintain or improve a viable cattle operation, grassland bird diversity, and rangeland vegetation structure, composition, and cover. Decisions by the stakeholder group about grazing and prescribed burning illustrate the complex role of existing management knowledge in social learning and the outcomes of participatory rangeland research. </p><p> In Chapter 4, I use repeated interviews and ecological monitoring on 17 family-owned and operated ranches in eastern Colorado and eastern Wyoming to categorize different grazing management strategies and compare plant species composition outcomes across those different strategies, accounting for environmental factors. After accounting for environmental influences, using non-metric multidimensional scaling and linear mixed models, I found a reduction of perennial cool-season grasses on ranches in higher grazing stocking rates and on cow-calf/yearling operations compared to cow-calf operations, but no significant differences in plant species composition on ranches with different grazing rotation strategies or different planning styles (tacit vs. explicit planners). I classified ranches into adaptive cycle trajectories to interpret ranch decision-making in terms of ranch SES-scale resilience. In Chapter 5, I review critical social literature to reflect on my positionality as a researcher, as well as the importance of consent and respect in social-ecological research. </p><p> Findings in this dissertation provide useful information for understanding the adaptation of ranch-scale rangeland SESs. Future research or outreach projects seeking to engage with rancher stakeholders may be improved by considering complex decision-making processes, caring practices, and the stewardship ethic of ranchers. Future efforts to bring multiple public-lands stakeholder groups with different management perspectives together for adaptive management will be improved if they consider the important role of stakeholder practices and experiences with rangeland management in social learning, and commit to building trust and knowledge through engagement that extends beyond the typical 3-5 year window for grazing research projects. My investigation of ranch-SES adaptive processes illustrates diverse decision-making strategies on different ranches. More research is needed on stocking rate decision-making, including around the social and political contexts of stocking rate decisions. This work suggests that a resilience lens can contribute to existing theory on ranch adaptive decision-making. Outreach and education efforts are likely to be more successful if they consider that one size does not fit all for ranch grazing management strategies.</p>