共查询到20条相似文献，搜索用时 15 毫秒
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J.y.e. Belnap John A. Ludwig Bradford P. Wilcox Julio L. Betancourt W. Richard J. Dean Benjamin D. Hoffmann Sue J. Milton 《Strength and Conditioning Journal》2012,65(6):569-578
Globally, new combinations of introduced and native plant and animal species have changed rangelands into novel ecosystems. Whereas many rangeland stakeholders (people who use or have an interest in rangelands) view intentional species introductions to improve forage and control erosion as beneficial, others focus on unintended costs, such as increased fire risk, loss of rangeland biodiversity, and threats to conservation efforts, specifically in nature reserves and parks. These conflicting views challenge all rangeland stakeholders, especially those making decisions on how best to manage novel ecosystems. To formulate a conceptual framework for decision making, we examined a wide range of novel ecosystems, created by intentional and unintentional introductions of nonnative species and land-use–facilitated spread of native ones. This framework simply divides decision making into two types: 1) straightforward–certain, and 2) complex–uncertain. We argue that management decisions to retain novel ecosystems are certain when goods and services provided by the system far outweigh the costs of restoration, for example in the case of intensively managed Cenchrus pastures. Decisions to return novel ecosystems to natural systems are also certain when the value of the system is low and restoration is easy and inexpensive as in the case of biocontrol of Opuntia infestations. In contrast, decisions whether to retain or restore novel ecosystems become complex and uncertain in cases where benefits are low and costs of control are high as, for example, in the case of stopping the expansion of Prosopis and Juniperus into semiarid rangelands. Decisions to retain or restore novel ecosystems are also complex and uncertain when, for example, nonnative Eucalyptus trees expand along natural streams, negatively affecting biodiversity, but also providing timber and honey. When decision making is complex and uncertain, we suggest that rangeland managers utilize cost–benefit analyses and hold stakeholder workshops to resolve conflicts. 相似文献
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A comparison of animal gains and vegetation trends was made from 2002–2008 between a continuous season-long stocking (SLS) system and a modified intensive–early stocking system (IES) with late-season grazing (IES 1.6× + 1; 1.6 times the number of animals of the SLS system from May 1 to July 15, and 1 times the number of animals of SLS from July 15 to October 1) on shortgrass native rangeland of western Kansas. The continuous season-long stocked system placed animals at a density of 1.37 ha · steer?1 from May through October, or 2.63 animal unit months (AUM) · ha?1, whereas the intensive–early stocked system with late-season grazing (3.33 AUM · ha?1) stocked pastures at 0.85 ha · steer?1 from May through the middle of July, and then stocked pastures at 1.37 ha · steer?1 for the remainder of the grazing season by removing the heaviest animals mid-July each yr. Average daily gains (0.78 vs. 0.70 kg · d?1, P = 0.039) and total animal gain (58 vs. 52 kg, P = 0.042) were different between the continuous season-long stocked and the intensive–early stocked animals during the first half of the grazing season. No difference was found between average daily gain (0.61 vs. 0.62 kg · d?1, P = 0.726) and total animal gain (48 vs. 49 kg, P = 0.711) for the continuous season-long stocked and intensive–early stocked with late-season grazing animals during the last half of the season. Total individual animal gain (106 vs. 101 kg, P = 0.154) and average daily gain (0.70 vs. 0.66 kg · d?1, P = 0.152) was not different between the continuous season-long stocked and the intensive–early stocked system animals that were on pasture the entire grazing season. Total beef gain on a land-area basis (96 vs. 77 kg · ha?1, P = 0.008) was greater for the modified intensive–early stocked system with late-season grazing with greater animal densities. Changes in residual biomass and most key vegetation components at the end of the grazing season were not different between the two systems. 相似文献
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《Strength and Conditioning Journal》2014,67(1):88-98
Large-scale loss and degradation of North American native prairie coupled with sharp declines in grassland bird populations call for a clear understanding of the effects of livestock production on bird habitat selection. Grassland birds typically select breeding habitat based on a suite of structural and community vegetation features shaped by grazing. Rangeland health indices are a tool for assessing grassland structure and community composition that may offer biologists and range managers common language to achieve grassland bird recovery goals. We used point-count surveys, vegetation measures, and indices of rangeland health to examine bird-habitat relationships on native grassland in southwestern Saskatchewan for 10 grassland bird species. We used an information theoretic approach to compare the support of three hypotheses explaining variation in bird abundance as a function of local vegetation characteristics: bird abundance is best explained by 1) vegetation structure, 2) vegetation structure heterogeneity, or 3) plant community. Vegetation structure variables were present in top-ranking models (i.e., models within four Akaike information criterion units of top model) for eight species and solely comprised top-ranking models for Baird’s sparrow (Ammodramus bairdii), chestnut-collared longspur (Calcarius ornatus), horned lark (Eremophila alpestris), McCown’s longspur (Rhynchophanes mccownii), and savannah sparrow (Passerculus sandwichensis). Structural heterogeneity variables were present in top-ranked models for grasshopper sparrow (Ammodramus savannarum), horned lark (Eremophila alpestris), and western meadowlark (Sturnella neglecta). Plant composition variables solely comprised top-ranking models for clay-colored sparrow (Spizella pallida) and were present in top-ranked models for grasshopper sparrow and vesper sparrow (Pooecetes gramineus). Our results indicate that vegetation structure variables, namely litter mass, vegetation volume, and bare ground cover, best explain variation in bird abundance. Although the rangeland health index received little support as a predictor of bird abundance, vegetation structure components of the index could be used to communicate grazing management guidelines that maintain grassland bird habitat. 相似文献
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《Strength and Conditioning Journal》2014,67(6):650-656
It has recently been proposed that the cost of rehabilitating medusahead (Taeniatherum caput-medusae [L.] Nevski)–invaded rangelands may be reduced by concurrently seeding desired vegetation and applying the preemergent herbicide imazapic. However, the efficacy of this “single-entry” approach has been inconsistent, and it has not been compared to the multiple-entry approach where seeding is delayed 1 yr to decrease herbicide damage to nontarget seeded species. We evaluated single- and multiple-entry approaches in medusahead-invaded rangelands in southeastern Oregon with seeding for both approaches occurring in October 2011. Before seeding and applying herbicide, all plots were burned to improve medusahead control with imazapic and prepare the seedbed for drill seeding–introduced perennial bunchgrasses. Both approaches effectively controlled medusahead during the 2 yr postseeding. However, almost no seeded bunchgrasses established with the single-entry treatment (< 0.5 individals · m-2), probably as a result of nontarget herbicide mortality. Perennial grass cover and density in the single-entry treatment did not differ from the untreated control. In contrast, the multiple-entry treatment had on average 6.5 seeded bunchgrasses · m-2 in the second year postseeding. Perennial grass (seeded and nonseed species) cover was eight times greater in the multiple-entry compared to the single-entry treatment by the second year postseeding. These results suggest that the multiple-entry approach has altered the community from annual-dominated to perennial grass–dominated, but the single-entry approach will likely be reinvaded and dominated medusahead without additional treatments because of a lack of perennial vegetation. 相似文献
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Rachel D. Mealor Paul J. Meiman Ann L. Hild David T. Taylor Jennifer S. Thompson 《Strength and Conditioning Journal》2011,64(5):479-487
Rapid conversion of rural land to exurban development and the ensuing impacts on natural resources have been well-documented, but information about exurban landowners is lacking. To address this knowledge gap, we surveyed exurban landowners in six Wyoming counties and documented demographic characteristics, motivations, knowledge, and attitudes about natural resources and land management. The overall response rate was 55.6%. Generally, respondents were of retirement age, had lived in Wyoming for about 13 yr, and were raised in areas with a population < 10 000. Wyoming respondents lived in exurbia for the lifestyle and aesthetic values and did not expect economic gains from their property. Most respondents had knowledge about, and interest in, invasive species, water quality, landscaping, and gardening. More than half of respondents (54%) had never looked for information regarding land management. Information from this study can be used to strengthen the development and delivery of educational programs. Programs that focus on water quality or weed control likely will appeal to more exurban landowners than those that focus solely on grazing management. Our findings provide an accurate characterization of this audience and their motivations and attitudes regarding land management, and suggest that using a multipronged approach for outreach efforts, which includes both cost- and time-efficient ways to conduct important land management practices, might increase participation in educational programs. 相似文献
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《Strength and Conditioning Journal》2005,58(1):89-98
We evaluated Arizona Cooperative Extension’s Rangeland Monitoring Program with the use of focus groups and a self-administered mail survey of grazing permittees and natural resource agency employees. Our primary objectives were to 1) determine whether Extension is reaching its target audience, 2) describe the monitoring practices and attitudes of permittees and agency staff, 3) determine whether there is a relationship between permittees’ exposure to Cooperative Extension and their monitoring and management practices, and 4) identify the monitoring information needs and preferences of permittees and natural resource agency staff. We found that Arizona’s rangeland monitoring Extension program has been effective in reaching a large part of its target audience, and a significant proportion of Arizona permittees monitor on public, private, and state-owned rangelands. However, overall monitoring adoption rates remain low. Extension contact is associated with use of monitoring and other beneficial management practices, and permittees and agency employees report that monitoring increased their knowledge and led to changes in management. Monitoring by permittees improves agency–permittee relationships in many cases. Most permittees and agency employees believe that their respective peers are the most reliable source of monitoring information and prefer to receive information from Extension through face-to-face contact at workshops or personalized on-site assistance. The evaluation revealed important social dimensions of rangeland monitoring. Extension agents play a key role in facilitating the social process of monitoring, as well as providing technical training in monitoring skills. Further study is needed to investigate whether permittee monitoring actually leads to better management, improved economic returns, or increased tenure security. 相似文献
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Debra P.C. Peters J.y.e. Belnap John A. Ludwig Scott L. Collins José Paruelo M. Timm Hoffman Kris M. Havstad 《Strength and Conditioning Journal》2012,65(6):613-622
A critical challenge for range scientists is to provide input to management decisions for land units where little or no data exist. The disciplines of range science, basic ecology, and global ecology use different perspectives and approaches with different levels of detail to extrapolate information and understanding from well-studied locations to other land units. However, these traditional approaches are expected to be insufficient in the future as both human and climatic drivers change in magnitude and direction, spatial heterogeneity in land cover and its use increases, and rangelands become increasingly connected at local to global scales by flows of materials, people, and information. Here we argue that to overcome limitations of each individual discipline, and to address future rangeland problems effectively, scientists will need to integrate these disciplines successfully and in novel ways. The objectives of this article are 1) to describe the background, historical development, and limitations of current approaches employed by these disciplines; 2) to describe an integrated approach that takes advantage of the strengths and minimizes the weaknesses of these individual approaches; and 3) to discuss the challenges and implications of this integrated approach to the future of range science when climate and human drivers are nonstationary. This integration will be critical for applying range science to the management of specific land units; will contribute to and benefit from the development of general ecological principles; and will assist in addressing problems facing society at regional, continental, and global scales. 相似文献
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Temuulen Ts. Sankey Jackson M. Leonard Margaret M. Moore 《Strength and Conditioning Journal》2019,72(5):858-863
Rangelands comprise a large component of the terrestrial land surface and provide critical ecosystem services, but they are degrading rapidly. Long-term rangeland monitoring with detailed, nonsubjective, quantitative observations can be expensive and difficult to maintain over time. Unmanned aerial vehicles (UAVs) provide an alternative means to gather unbiased and consistent datasets with similar details to field-based monitoring data. Comparing summer 2017 UAV images with long-term plot measurements, we demonstrate that rangeland vegetation cover changes can be accurately quantified and estimate an increase in total absolute shrub/subshrub cover from 34% in 1935 to > 80% in 2017 in central Arizona. We recommend UAV image-based rangeland monitoring for land managers interested in a few specific and dominant species, such as the foundation species, indicator species, or invasive species that require targeted monitoring. Land managers can identify and continuously monitor trends in rangeland condition, health, and degradation related to specific land use policies and management strategies. 相似文献
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《Strength and Conditioning Journal》2020,73(1):84-92
We compared movement patterns of nursing versus non-nursing cows and characterized cow-calf proximity patterns over 2 years in two herds of Raramuri Criollo (RC) cattle that grazed either desert rangeland of southern New Mexico, United States, or woodlands of west-central Chihuahua, Mexico. At each site, 9−14 randomly selected mature cows were fitted with Global Positioning System (GPS) collars configured to record animal position at 5-min intervals. Four to five GPS-collared nursing cows and their calves were also fitted with proximity loggers that recorded initiation time and duration of dam-calf contact events (< 1 m logger-to-logger distance). All calves were < 2 wk old at the onset of the study. Collared animals grazed with a herd of 30 and 35 cows at the NM site and with 68 and 87 cows at the Chihuahua site in 2015 and 2016, respectively. Non-nursing RC cows exhibited straighter travel paths and explored larger daily areas than their nursing counterparts. However, nursing and non-nursing RC cows in this study traveled similar distances each day, moved at comparable velocities, spent similar amounts of time close to drinkers, and did not differ in daily time spent grazing, resting, or traveling. A higher number of cow-calf contact events occurred during day versus nighttime hours, but total day versus night contact time was similar. As calves became older, the number of both day and nighttime contact events, as well as dam-offspring contact time, decreased significantly. Relative to their calves, dams explored larger areas of the pasture each day; however, cow-calf contact events occurred throughout the entire area grazed by the dams including areas surrounding the drinkers. Cow-calf interactions of RC cows resembled those of a strong follower regardless of the grazing environment and differed from previously reported mother-offspring relations in mainstream British beef cattle breeds. 相似文献
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The highly centralized management of rangelands in northwest Iran has caused their degradation. Rangeland Management Cooperatives (RMCs) have been taken into account by the Iranian researchers and practitioners as the best mode of managing and tackling these resources. In this regard, stakeholders’ participation (i.e., the rangers) in such institutions is a substantial issue because without their close collaboration, any management scheme is likely to fail or succeed partially. Therefore, this study investigates the rangers’ participation in RMCs using the theory-triangulation method. We developed the main research question: how the explanatory variables, extracted from the social-psychological models, influence rangers’ participation in RMCs. A sample of 200 rangers participated in the survey method, of which we received 179 completed self-reported questionnaires. The reliability of the questionnaire was calculated using the Confirmatory Factor Analysis and Kuder-Richardson 21, the metrics that measure the consistency of items in indicator variables with the interval and binary scales, respectively. The results of path analysis unveil that job satisfaction and progressivism have a direct effect on participation, and the improved economic conditions of industries developed by the RMCs, good intrarelation, fatalism, progressivism, optimism, and cost-benefit indirectly influence participation via job satisfaction. On the basis of these results, it is concluded that to increase rangers’ participation in RMCs, which is a key factor in preventing the degradation of rangelands, RMCs’ officials need to improve the local industries benefiting from the rangelands and upgrade intracommunication skills via training. It is also suggested that all rangers, even those with fatalistic beliefs, need to be included in RMCs’ participatory activities. Finally, it is needed to assess progressivist rangers’ needs, promote optimism, and visualize the economic, social, and conservation benefits of the participation in RMCs. 相似文献
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The changing concentrations and temporal relationships among a PGF2α metabolite (PGFM), progesterone (P4), LH, and estradiol-17β (E2) before, during, and after luteolysis were studied in 10 mares. Blood samples were collected every hour for ≥4 d beginning on day 12 after ovulation. The luteolytic period extended from a decrease in P4 at a common transitional hour (Hour 0) at the end of preluteolysis and beginning of luteolysis to a defined ending when P4 reached 1 ng/mL. The length of luteolysis was 22.9 ± 0.9 h, contrasting with 2 d in published P4 profiles from sampling every 6 to 24 h. In mares with complete data for Hours −40 to −2 (n = 6), PGFM concentrations remained below assay sensitivity (n = 2) or two or three small pulses (peak, 29 ± 4 pg/mL) occurred. During luteolysis, the pulses became more prominent (peak, 193 ± 36 pg/mL). Rhythmicity of PGFM pulses was not detected by a pulsatility program during preluteolysis but was detected in seven of nine mares during luteolysis and postluteolysis combined. The nadir-to-nadir interval for LH pulses and the peak-to-peak interval between adjacent pulses were longer (P < 0.05) during preluteolysis than during luteolysis (nadir to nadir, 5.2 ± 0.3 h vs 3.6 ± 0.4 h; peak to peak, 9.4 ± 1.0 h vs 4.7 ± 0.5 h). Unlike reported findings in cattle, concentrations of P4 decreased linearly within the hours of each PGFM pulse during luteolysis, and a positive effect of an LH pulse on P4 and E2 concentration was not detected. The reported balancing of P4 concentrations between a negative effect of PGF2α and a positive effect of LH in heifers was not detected in mares. 相似文献
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Heidrun Gehlen Sophie Twickel Sabita Stöckle Corinna Weber Claus P. Bartmann 《Journal of animal physiology and animal nutrition》2020,104(2):679-689
Pituitary pars intermedia dysfunction is the most prevalent endocrine disease in horses. Although donkeys and mules may also be affected, only a few data have been published. Reference values for diagnostic parameters, such as adrenocorticotropic hormone (ACTH), are especially scarce or even lacking. Therefore, in the present study, available data from the literature have been verified and completed to facilitate a reliable diagnosis. Clinical inspections and haematological and biochemical examinations were carried out four times in a three-month interval (February to November) in 44 donkeys and 31 mules. Data from clinically healthy animals were used as an orientation. Plasma ACTH concentrations showed seasonal changes in both animal groups. However, it was generally higher in donkeys than mules. Although blood glucose (EDTA plasma) showed no difference between groups, serum insulin concentrations were consistently higher in donkeys. Serum fructosamine levels were slightly higher in mules, whereas, in some cases, serum triglyceride levels were considerably higher in donkeys. Serum gamma-glutamyltransferase showed a striking peak in mules in August, whereas the remaining gamma-glutamyltransferase values were lower compared to donkeys. By comparing donkeys and mules, the present work reveals differences in various blood parameters which should be considered for diagnoses and future studies. 相似文献