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41.
42.
Natural vegetation enhances the value of agricultural landscapes for people and wildlife. However, the role of anthropogenic versus topographic factors in driving the extent of natural vegetation cover within agricultural lands at large spatial scales remains unexplored. I assessed the influence of anthropogenic and topographic variables on the extent of agricultural mosaics with high natural vegetation cover in the country of Turkey where a large extent of natural and semi-natural vegetation is maintained by traditional agriculture. GIS layers depicting human land use, elevation, slope, roads and population data were obtained and summarized at two spatial scales, within provinces and for 100 km2 grid cells covering the country’s entire agricultural land area. Average farm size was also obtained at province level. Hierarchical Partitioning was conducted to determine the independent effect of anthropogenic and topographic variables on the variation in agriculture with high natural vegetation. Slope had the largest independent effect on the variation in the proportion of agricultural mosaic with high natural vegetation cover. The extent of agricultural and settlement area also explained much of the variation in natural vegetation across both grid cells and provinces. The proportion of natural vegetation increased as human population and road density decreased across grid cells and as average farm size decreased across provinces. These results suggest that while topography is the primary driver of natural vegetation cover within agricultural mosaics in Turkey, the pressures associated with urban development and agricultural industrialization may also influence the cultural and wildlife value of agricultural landscapes. 相似文献
43.
Desertification and land degradation are worldwide problems affecting soil, vegetation and the livelihoods of rural populations. Bowal (plural bowé) is a particular form of degraded land that occurs in tropical regions and leads to the exposure of ferricretes, which are unsuitable for farming. Bowé are more common on farmland and degraded savanna. Changes in land use/land cover were used to map a region of 6.7 million ha in northern Benin, West Africa in 1975, 1990 and 2010. The changes observed during these periods (1975–1990, 1990–2010 and 1975–2010) were used to predict the occurrence of bowé in the period up to 2050 using Markovian chain analysis. The results showed a considerable change in land use/land cover during the three periods. The types of land on which bowé occur (farmland and degraded savanna) increased in northern Benin by 5.4% per year during the period 1975–1990 and 9.5% per year during the periods 1990–2010, while the natural vegetation (forest, woodland and tree savanna) decreased by the same amount. The future scenarios also predicted the same trend. In the period 1975–1990, 1.28 million ha (26%) of natural vegetation was converted to degraded savanna and farmland while 2.23 million ha (53%) of natural vegetation was converted to degraded savanna and farmland in the period 1990–2010. Based on the dynamics recorded during the period 1975–1990 and 1990–2010 respectively, a total of 1.28 million ha (26% of the natural vegetation that was present in 1975) and 1.29 million ha (31% of the natural vegetation that was present in 1990) will be converted to farmland and degraded savanna in the study area by 2050.Thus bowalization will persist and increase in the period up to 2050. The natural vegetation could disappear if protection and restoration measures are not taken. It is thus important to take measures to stop the degradation and to implement programs to restore soils on bowé based on the soil and water conservation techniques used on highly degraded West African soils, such as zaï pit and stone rows with grass strips. Some native plants species adapted to bowalization and resistant to climate change in northern Benin (e.g. Asparagus africanus, Andropogon pseudapricus and Combretum nigricans) should be used in association with soil and water conservation techniques on bowé. 相似文献
44.
Warm or cool ambient temperatures during winter generate plasticity in the within‐year timing of oviposition or breeding phenology shifts through the use of a reaction norm in many riverine ectotherms, but within‐year timing of oviposition in Hynobius kimurae (Caudata: Hynobiidae) is predicted to be constant at different water temperatures of a mountain stream. To clarify this difference, by experimentally controlling water temperatures from fall to spring and thus changing durations of aquatic hibernation and dates of oviposition, we determined whether oviposition is more advanced when water temperatures increase earlier than usual or is more delayed when water temperatures increase later than usual. Oviposition was more delayed than usual with earlier exposure to high water temperatures during spring and was earlier than usual with exposing to higher water temperatures during hibernation. Days from submergence to oviposition were responsive to cumulative daily water temperatures from submergence to oviposition within a population. A rate of increase in days from submergence to oviposition was different between populations but was constant within a population even if minimal water temperatures varied each year. When running a program of a Markov chain Monte Carlo generalized linear mixed model for Bayesian computation to interpret confounding effects, neither different treatments nor different years statistically affected days from submergence to oviposition. These results suggest that a biological clock exits for days from submergence to oviposition in H. kimurae, which could allow survival in situations with either warmer or cooler environments. 相似文献
45.
Increased academic attention on the gendering of leisure pastimes in recent years has highlighted the centrality of the gendered body in influencing how leisure is accessed, experienced and transformed. To date, however, little attention has been paid to how women experience aquatic leisure activity, the second most popular form of leisure activity in the UK, and where female participation predominates. This paper presents results from research investigating the aquatic leisure experiences of 22 women, with children aged under 3, in the North-East of England. A number of key themes emerged from the data, which highlighted the centrality of the gendered, lived body as a key social construct contouring participant perceptions in the swimming pool environment. Women reflected upon their self-perceived physical deficiencies when wearing revealing swimming costumes, particularly under the critical gaze of ‘other’ bodies, whether present or imagined. The co-presence of other bodies was also central in shaping lived experiences, and the presence of ‘dependent’ children’s bodies shifted bodily intentionality away from the self towards perceived maternal responsibilities and the management of perceived risks, including ‘dirt’ and ‘germs’ and the negotiation of the tacit rules of the swimming pool. Results also suggest that the emphasis on maternal responsibility in aquatic leisure activity and timing of parent-toddler sessions could lead to reproduction of gender inequalities and the exclusion of some fathers from participation. 相似文献
46.
影响水产品供应链中企业合作的因素是多方面的,其中合作效率是最为重要的影响因素,主要受到合作能力和合作意向的影响.应利用利益杠杆调动水产品供应链内部诸方面的积极性,使各主体在各个经营环节来实现利益平衡,建立科学、合理的利益分配机制;通过市场约束、交易成本内部化、合同约束等,完善水产品供应链的约束机制;建立违约风险基金,完善水产品供应链风险化解机制. 相似文献
47.
基于GIS技术的人居环境自然适宜性评价研究——以遵义市为例 总被引:5,自引:1,他引:4
以公里格网为基本单元,基于GIS技术,建立包括地形起伏度、温湿指数、水文指数和地被指数的人居环境自然适宜性评价模型,系统评价遵义市不同地区的人居环境自然适宜性与限制性。研究表明,遵义市人居环境以适宜性为主要特征,自然适宜程度整体呈现出由西北向东南递增的趋势,其中44.41%为一般适宜区、54.13%为比较适宜区以及极小比例为临界适宜区;遵义市人居环境自然条件较好,地形、地被、水文和气候对人口分布的限制性不明显,其中地形条件对人口分布的限制性最强,其次是地被条件。 相似文献
48.
水产品加工业供应链风险及其控制策略 总被引:1,自引:0,他引:1
根据对文献的研究成果,结合对水产品加工业的深入调研分析,本文着重从供应、物流、财务、信息、需求、环境等方面对水产品加工业供应链风险进行剖析。供应链中各种风险因素之间并非独立存在,而是相互影响、互为因果。因此,在明确水产业供应链每种风险产生根源及其变动规律的基础上,提出适宜的风险控制策略,以期规避风险,确保水产业供应链整体安全高效运行。 相似文献
49.
采用实地调查和实验分析,结合遥感和地理信息系统技术,研究南四湖湿地在1983-2006年浮游植物和水生维管束植物的种类、分布和生物量变化.结果表明,1983-2006年,南四湖湿地植被生物量整体呈下降趋势,反映了人类的围垦、养殖等活动造成湿地初级生产力的降低,并且这种影响由湖泊外围向湖心弱化,对外围湿地的影响最大. 相似文献
50.