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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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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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This paper gives a brief introduction of Kate Chopin and his famous work The Story of an Hour [1].By analyzing the psychological change of the protagonist Mrs. Mallard and her reactions to her husband'...  相似文献   

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Tropical Animal Health and Production - Johne’s disease (JD) is an economically important infectious disease of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). This...  相似文献   

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To better understand the mechanisms involved in the dynamics of Johne’s disease in dairy cattle, this paper illustrates a novel way to link a within-host model for Mycobacterium avium ssp. paratuberculosis with an epidemiological model. The underlying variable in the within-host model is the time since infection. Two compartments, infected macrophages and T cells, of the within-host model feed into the epidemiological model through the direct transmission rate, disease-induced mortality rate, the vertical transmission rate, and the shedding of MAP into the environment. The epidemiological reproduction number depends on the within-host bacteria load in a complex way, exhibiting multiple peaks. A possible mechanism to account for the switch in shedding patterns of the bacteria in this disease is included in the within-host model, and its effect can be seen in the epidemiological reproduction model.  相似文献   

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Long-term effects of two mechanical interventions, shallow plowing and harrowing, on degraded Leymus chinensis (Trin.) Tzvel. grassland were studied. Species composition and standing biomass of the grassland were monitored at peak biomass each year for 24 yr after application of these two measures, together with grassland in natural recovery and that under public grazing. Results showed a high resilience of degraded grassland, which recovered naturally after excluding grazing animals to a structure similar to the intact L. chinensis community. In comparison with natural recovery, harrowing facilitated restoration of L. chinensis population and community structure and improved grassland production. Shallow plowing accelerated recovery of L. chinensis population to a larger extent than harrowing and led to a flourish of annual species and improvement of herbage production in the years following its application. But the production improvement was unsustainable and was associated with a decrease in grassland species richness and community complexity. We conclude that the best measure for restoring degraded grassland depends on the restoration objectives and severity of grassland degradation. Harrowing is a feasible technique to assist restoration of the degraded grassland. In contrast, shallow plowing is not appropriate for ecological restoration, but may be applied for quick restoration of herbage production.  相似文献   

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A 4.75-year old Simmental cow was presented with symptoms of colic and ileus. The clinical signs and blood analysis resulted in the diagnosis of suspected primary hypoadrenocorticism (Addison’s disease). Although Addison’s disease has been frequently described in other domestic mammals, to our knowledge, this disease has not previously been reported in cattle.  相似文献   

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