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1.
We mapped yearly (2000–2016) estimates of annual grass percent cover for much of the sagebrush ecosystem of the western United States using remotely sensed, climate, and geophysical data in regression-tree models. Annual grasses senesce and cure by early summer and then become beds of fine fuel that easily ignite and spread fire through rangeland systems. Our annual maps estimate the extent of these fuels and can serve as a tool to assist land managers and scientists in understanding the ecosystem’s response to weather variations, disturbances, and management. Validating the time series of annual maps is important for determining the usefulness of the data. To validate these maps, we compare Bureau of Land Management Assessment Inventory and Monitoring (AIM) data to mapped estimates and use a leave-one-out spatial assessment technique that is effective for validating maps that cover broad geographical extents. We hypothesize that the time series of annual maps exhibits high spatiotemporal variability because precipitation is highly variable in arid and semiarid environments where sagebrush is native, and invasive annual grasses respond to precipitation. The remotely sensed data that help drive our regression-tree model effectively measures annual grasses’ response to precipitation. The mean absolute error (MAE) rate varied depending on the validation data and technique used for comparison. The AIM plot data and our maps had substantial spatial incongruence, but despite this, the MAE rate for the assessment equaled 12.62%. The leave-one-out accuracy assessment had an MAE of 8.43%. We quantified bias, and bias was more substantial at higher percent cover. These annual maps can help management identify actions that may alleviate the current cycle of invasive grasses because it enables the assessment of the variability of annual grass ? percent cover distribution through space and time, as part of dynamic systems rather than static systems.  相似文献   
2.
生态系统服务权衡最新研究进展   总被引:1,自引:0,他引:1  
生态系统服务权衡研究对协调生态环境保护和社会经济发展至关重要。为推动生态系统服务管理和提升人类福祉,本文以Web of Science核心合集(WOS)和中国科学引文数据库(CSCD)为数据源,运用文献计量分析法,系统梳理和总结生态系统服务权衡研究的学科知识基础、科学领域结构和热点变化等发展现状以及最新研究进展。研究表明:1)不同研究层面上,生态系统服务间的权衡关系受外部风险和人类需求、参数选取和服务提供者及区域差异性和不均衡性的影响。2)研究方法主要有基于关系识别和具体表征的权衡分析、权衡模拟和预测的模型量化分析和生态系统服务权衡管理优化的多准则分析3类。3)生态系统服务权衡关键驱动因子为城市化、生态工程和气候变化。基于此,我们认为把握生态系统服务权衡不同研究层面的关联特征、创新和优化生态系统服务权衡研究方法、准确甄别生态系统服务权衡关键驱动因子以及充分整合多维生态系统服务权衡资源搭建数据共享平台是未来研究的重点。  相似文献   
3.
Aquaponics is generally regarded as a sustainable practice, but its environmental burdens were not yet deeply investigated. In this study, Life Cycle Assessment (LCA) was used to assess the environmental impacts of two hypothetical coupled aquaponics systems (CAPS): Raft System (RAFT) and Media-Filled Beds System (MFBS). Rainbow trout (Oncorhynchus mykiss) and lettuce (Lactuca sativa) were considered as cultivated species in both systems. The Simapro© software V.8.0 was used for calculation. The comparison between the two virtual systems indicated the floating technique as the less impacting one. Even though energy consumption appears to be higher in the floating system, LCA results were markedly influenced by the extensive use of inert materials in MFSB. In both systems, contribution analyses underlined that the main environmental impacts are related to infrastructures, electricity and fish feed. The LCA analyses carried out in this study highlights that the choice of less impacting materials, and the optimization of management practices, should be taken as priorities in order to reduce environmental impacts of this activity.  相似文献   
4.
以养蚕与缫丝课程模块为例,对其课程内容安排、教学特点、考核方法进行分析,并对其所面临的问题展开探讨,旨在为进一步提高相关实践教学效果提供借鉴。  相似文献   
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This paper presents the development of a simple and generally applicable hydrodynamic method for the estimation of production carrying capacity (PCC) of coastal finfish cage aquaculture. Dimensional analysis was used to find significant and general interdependencies between the hydrodynamics at fish farm locations and particulate wastes deposited on the seafloor by fish farms. Modeled ratios of deposition to emission of particulate wastes underneath fish farms were found to be primarily a function of the flow Reynolds numbers at the farming locations and the non-dimensional settling velocity of emitted wastes. In the non-dimensional model, farming conditions include daily feed rate, proportion of unconsumed feed, and carbon content in feed and fish feces. The relationship can be used to estimate the PCC of floating net cages imposing a threshold value for deposition. Results of in-situ assessments of the benthic impacts of several fish farms in an aquaculture site in the northwest of Bali, Indonesia were used to validate and demonstrate the effectiveness of the method. Predicted results were able to clearly identify fish farms operating beyond ecologically sustainable carrying capacity. The proposed method has broad applicability and could help make decisions regarding the estimation of production potential of individual farms in pristine areas, for providing first estimates in sites that have scarce data, and for assessment, expansion, and optimization of the currently operating aquaculture sites in Southeast Asia, China and potentially other data-poor island nations. As the method relies on dynamic models, it enables straightforward assessments over the entire aquaculture region.  相似文献   
8.
通过借鉴国外森林火灾损失评估方法和评估系统,重点剖析了现阶段我国森林火灾损失评估工作中存在的问题,并针对制定适用于我国的森林火灾损失评估体系,探讨了构建我国森林火灾损失评估体系关键技术问题,提出了未来森林火灾损失评估研究需加强的研究方向。  相似文献   
9.
在我国,资源危机、生态环境危机已成为制约农业可持续性的主要因素,因此需要基于农业生态与产业系统的共生关系视角研究农业可持续性问题.该研究界定了基于农业生态-产业共生关系的农业可持续性的内涵,构建了农业生态-产业复合系统动态共生模型,创新性地运用该模型中农业生态-产业的竞争系数的关系来评价农业的可持续性.  相似文献   
10.
Reactivity in horses, defined as a state of high arousal, has an impact on the daily handling and welfare of horses and can have an impact on the risk of causing human injuries. Behavior tests have been developed to assess reactivity, but these tests are difficult to apply in practice. The objectives of this study were to investigate how reactivity measured in a practical situation associates with rideability and performance and to explore the association between the measured reactivity and reactivity assessed by the horse's owner. A total of 234 Danish Warmblood females, 3 years of age, were videotaped and scored for reactivity during the evaluation of their conformation, and a questionnaire was completed by the owners. Associations between reactivity and performance traits were investigated by computing partial correlations (Pearson, rp). A low negative correlation was found between rideability and reactivity (rp = −0.16, P = .02) and between reactivity and free jumping (rp = −0.14, P = .03). These results suggest that highly reactive horses received lower grades in rideability and free jumping. However, no association with performance traits in dressage was found. Likewise, low but significant association was found between reactivity and ratings from owners (rp = 0.15, P = .02), indicating that horses considered to be nervous by their owners also were scored as reactive. In conclusion, it appears possible to measure reactivity in a practical situation. This study also concluded low negative associations between reactivity and the two performance traits rideability and free jumping.  相似文献   
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