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.

No description available.

International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California / Future U.S. Navy at-sea and littoral battle group training range instrumentation requires a new, secure, high data rate link This link must be capable of providing the ranges with the capacity to increase the number of players, increase the amount of threat simulation, and allow an improved Global Positioning System (GPS) based position tracking system to be implemented This paper describes a Dual Function Transponder (DFT) capable of operating on any R-CUBED (Relay, Reporter, Responder) based range as well as any TACTS/ACMI range without modification of either range type. In addition, the DFT provides a new increased data rate capability for use by planned future ranges, enabling a dramatic increase in the number of participants as well as significantly increasing the quantity of data that can be communicated by each player. Miniaturization and programmability are the keys to this development and many of the methods used are described.

International Telemetering Conference Proceedings / October 26-29, 1992 / Town and Country Hotel and Convention Center, San Diego, California / An improved ionospheric delay correction model for a transionospheric electromagnetic pulse (EMP) is used for estimating the total-electron-content (TEC) profile of the path and accurate ranging of the EMP source. For a known pair of time of arrival (TOA) measurements at two frequency channels, the ionospheric TEC information is estimated using a simple numerical technique. This TEC information is then used for computing ionospheric group delay and pulse broadening effect correction to determine the free space range. The model prediction is compared with the experimental test results. The study results show that the model predictions are in good agreement with the test results.

<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>

Global temperature changes are predicted to influence the distributions of plants and can have significant consequences for population genetic structure. Both the nature of these consequences and the processes that shape them are of interest for both conservation genetics and the development of realistic management programs. Rapid range expansion occurs on short temporal scales not conducive to conventional phylogeographical analyses. This paper presents the findings from a population genetic study of the invasive grass Microstegium vimineum Trin. A. Camus throughout the James River Basin of Virginia. Genotypic analysis using Amplified Fragment Length Polymorphism (AFLP) molecular markers were used to test for evidence of rapid range expansion and the effects associated with colonization and spread of Microstegium vimineum. Within the James River Basin three genetically distinct clusters were identified that were not clearly associated with natural geographic boundaries and recent founder events were also inferred. The James River Basin also appears to act as a corridor for long-distance dispersal events. These findings contribute to our knowledge of the genetic consequences of rapid range expansion for invasive species, and more importantly, native species. Contrary to several studies, the present research also indicates that long-distance dispersal is not rare and can be a major contributor to the genetic structure following range expansion.