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71.
72.
John Connell 《Asia Pacific viewpoint》2006,47(3):342-350
Abstract: Effective global competitiveness is rare in the Pacific islands, yet FIJI Water has been a major success story since 1997, exporting bottled water to the USA and elsewhere. A bland commodity has been linked to an ‘exotic’ place, and sold to elite consumers, as a form of cultural capital. The company website and newspaper extol the virtues of a ‘pristine’ product, produced in a natural context, in an environmentally sensitive manner. Marketing these themes and product placement have enabled success in a highly competitive market. Place has been used as a means of marketing perceived taste, distinctiveness and quality. 相似文献
73.
小麦/蚕豆间作体系中的氮节约效应及产量优势 总被引:11,自引:2,他引:11
通过田间小区试验,研究了小麦/蚕豆间作条件下作物的产量优势及不同施氮水平和种植方式中土壤硝酸盐累积。研究表明,间作可以提高作物单位面积复合产量,增产幅度在6%3~3%之间,不施氮处理间作小麦产量比单作增加达84%;间作和施氮对蚕豆产量没有显著影响。不同种植方式下土壤剖面中硝酸盐累积量趋势表现为蚕豆单作>小麦、蚕豆间作>小麦单作。不施氮、施氮量为20、406、0.kg/hm2条件下,种蚕豆的土壤硝酸盐累积量分别比种小麦的土壤增加了25.4、63.5、50.9、93.4.kg/hm2,间作降低了土壤中硝酸盐累积。小麦、蚕豆间作体系中的产量优势主要是种间氮营养生态位发生了分化,蚕豆通过固定空气氮而减少对土壤有效氮的吸收,把土壤中的有效氮节约供给与之相伴的作物小麦利用。 相似文献
74.
Víctor Sánchez-Cordero Patricia Illoldi-Rangel Sahotra Sarkar 《Biological conservation》2005,126(4):465-473
Deforestation threatens biodiversity conservation worldwide, but little quantitative information is available on how it affects individual species’ distributions. We modeled potential distributions of 85 continental endemic Mexican mammal species using ecological niche modeling, and produced testable predictions of species’ extant distributions by limiting ecological niches to remnant untransformed habitat based on the Inventario Nacional Forestal 2000. We included point occurrence data for all endemics only from collecting localities prior to 1970, before wide areas of habitat transformation occurred nationwide. Most endemics (61 of 85, 72%) showed a high proportion of transformed habitat (34.5%) at the national level. More than one-fourth of the endemics (23 out of 85, 27%) lost more than 50% of untransformed habitat within their potential distributions; two showed drastic areal loss of more than 90%; another two showed a loss of more than 80%. Only 34 of the endemics are listed as endangered or threatened in the Mexican Norma Oficial Mexicana (NOM). No significant association existed between proportional loss and conservation status as assigned in the NOM, nor are correlations significant between original distributional area and area of remnant untransformed habitat. Both findings suggest that geographic location determines extinction risks rather than area per se. Endemics in the state of Veracruz and in the Transvolcanic Belt suffered the most drastic niche reductions and thus appear to be at high extinction risk from further deforestation. 相似文献
75.
用于水果实时分级系统的同步跟踪自动控制装置 总被引:3,自引:0,他引:3
研究了一种用于计算机视觉水果自动分级系统的同步跟踪自动控制装置。图像处理结果从计算机并行口输出到移位寄存器,利用接近开关产生的脉冲作为寄存器的移位信号,将处理结果在移位寄存器输出端口的位置与水果的实时位置保持一致,实现对水果的同步跟踪,并利用硬件操作步进电机的脉冲分配和相关动作,从而完成对分级执行机构的正确控制。 相似文献
76.
Habitat associations of saplings and adults in an old-growth temperate forest in the Changbai mountains,northeastern China 总被引:2,自引:0,他引:2
Species-habitat association analysis is useful to detect spatial arrangement of individual plants, to discover rules about the distribution of species and to generate hypotheses about the possible underlying process controlling observed structures. Quantifying methods were used to classify habitats in terms of topographical variables in a mixed temperate broad-leaved Korean pine forest of the Changbai mountains in northeastern China. All of the 625 20 m × 20 m quadrats of the plot could be unambiguously assigned to one of three habitat categories (low-plateau, high-plateau and slope). Torus-translation tests were used to estimate species-habitat associations. Many species are clearly distributed in a biased fashion with respect to habitats. Fifteen (55.6%) out of 27 species showed strong positive or negative association with specific habitats. We compared species-habitat associations at the sapling and adult stages. Adjusted density values indicated few species exhibit extremely strong habitat associations. Only 9 out of 26 species had adjusted densities > 3 in the habitat for which they had strong positive affinity. Few species show the same associations at the small tree and large tree stages. Only 3 out of 22 occurring associations with a specific habitat appeared to have a consistent habitat association at the two stages. These results suggest that species-habitat associations exist in the 25-ha plot of the temperate forest of the Chang- bai mountains. Owing to limitations in our statistical methodology, we partly underestimated associations by ignoring rare species. Regeneration niches can contribute to co-existence, but regeneration niches due to habitat associations play a limited role in species co-existence, since most species show a similar trend in habitat associations at the sapling and adult stages. We should pay more attention to shifts in habitat associations, i.e. niche shifts at different stages of existence. 相似文献
77.
78.
以黄土塬区农林复合系统为对象,通过调查研究林带(杨树为主)与农作物界面附近土壤中树木和小麦根系的空间分布,利用树木吸收根和小麦根系生物量计算生态位宽度、生态重叠指数和生态位相似性比例,并据此分析林木和农作物种群在水分和养分资源轴的生态位特征。小麦在40cm以上具有较大的生态位宽度,而林木在距林带1H处20cm以上土层到0.5H处60cm以上土层至林下100cm以上土层内具有较大的生态宽度,但林木在1H以内100cm土层其他空间土壤中也具有一定的生态位宽度。树木具有较大的生态位宽度,虽可利用深层土壤中的水分和养分资源,在一定程度上有助于缓解农林间作对水分和养分资源的利用性竞争,但树木居于竞争的优势者地位,形成对农作物的胁地负效应,距林带1H内林木对农作物生态位重叠,且在0.5H以内重叠较大,竞争剧烈,在此集流补水增肥有利于缓解林木胁地。 相似文献
79.
半干旱地区植被恢复过程中林下植被生态位特征的研究 总被引:9,自引:0,他引:9
应用生态位理论,以黄土半干旱区6个不同密度林分林下草本层植被为研究对象,以林分密度作为资源轴,以物种重要值为生态位计测的状态指标,对林下植被进行生态位计测和分析,揭示林内资源环境利用状况。结果表明:林下植被的生态位宽度值普遍较小,其中阿尔泰紫婉、铁杆蒿等生态位宽度较大,这与无林地相似,同时物种间生态位重叠并不普遍,重叠度普遍不大,各种对间对资源的共享趋势不明显,生态位发生分离,显示了林下植被状况差。 相似文献
80.
土壤腐殖物质的组成和结构复杂,其中含有多种官能团,是土壤碳库中的重要组成部分.固态13C NMR是研究有机化合物结构的有效手段,特别对于不溶性HM,已成为其研究的重要技术方法.本文主要介绍了固体13C NMR在土壤腐殖物质中的应用概况,总结、归纳了土壤腐殖物质中不同官能团所对应的信号区间,对比分析了腐殖物质中不同组分的结构区别,讨论分析了固体13C NMR在土壤腐殖物质结构与形态研究中的应用,以期借助固体13C NMR更加深入地对腐殖物质整体结构进行研究,推进对腐殖物质形成、转化的探讨. 相似文献