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1.
Abstract: Broadly conceived and considered in its many usages, sustainability has grave defects as a planning goal, particularly when used by conservationists: it confuses means and ends; it is vague about what is being sustained and who or what is doing the sustaining; it is uninspiring; it is little more than Pinchot-era conservation (and thus ignores the many lessons learned since then); it need not be linked to land, to the land's functioning, or to any ecological science; it need not include a moral component; it is consistent with the view of humans as all-powerful manipulators of the planet; and, in general, it is such a malleable term that its popularity provides only a facade of consensus. When sustainability is defined broadly to include the full range of economic and social aspirations, it poses the particular risk that ecological and biodiversity concerns will be cast aside in favor of more pressing human wants. Given these many defects, the conservation movement should discard the term in favor of a more alluring goal, attentive to nature and its ecological functioning. A sound goal would incorporate and distill the considerable ecological and moral wisdom accumulated since Pinchot's day while giving conservationists the rhetorical tools needed to defend the land against competing pressures. In our view, conservation would be well served by an updated variant of "land health," Aldo Leopold's ecologically grounded goal from the 1940s. Land health as an independent understanding should set the essential terms of how we live and enjoy the earth, providing the framework within which we pursue our many social and economic aims. 相似文献
2.
Iigo Loureiro M. Concepcin Escorial Jos María García-Baudin M. Cristina Chueca 《Agriculture, ecosystems & environment》2007,120(2-4):384-390
Hybridization between Aegilops geniculata, A. biuncialis and bread wheat Triticum aestivum has been evaluated during two seasons under simulated field conditions to estimate the field hybridization rate under Central Spain conditions. The mean frequencies of hybridization between A. biuncialis and A. geniculata with wheat were 0.34% and 0.31%, respectively. Data from 10 hybrid plants for each combination showed that hybrids can be partially fertile by backcrossing with wheat parent, with percent averages of 3.17 grains/spikelets for A. biuncialis × wheat hybrids and 2.87 grains/spikelets for A. geniculata × wheat hybrids. Self-pollination, although at very low rates, was also possible in hybrids. The potential risks associated with natural hybridization in the context of transgenic wheat cultivation are discussed. 相似文献
3.
影响杉木人工林可持续经营因素探讨 总被引:12,自引:0,他引:12
杉木人工林土壤肥力和林分生产力逐代下降,直接影响杉木林地可持续经营。影响杉木人工林可持续经营的因素是多方面的,主要和杉木人工林所处亚热带红壤区生态系统的脆弱性和杉木人工林群落的单一性及杉木生物学特性等有关,而传统杉木人工林培育过程中采取一系列传统的营林措施则加剧了林地地力衰退。根据目前杉木人工林经营现状,建议在杉木人工林经营过程中应尽量降低营林措施干扰强度,特别是炼山措施的采取;同时开展有关林地可持续模式试验及评价指标体系的研究,以寻找适合不同地区的杉木人工林可持续经营模式。在此基础上,搞好杉木人工林规划和发展,这对南方杉木产区林地可持续经营实践具有较大的指导意义 相似文献
4.
黄土高原砖窑沟试验区土壤资源与改良利用途径 总被引:2,自引:0,他引:2
本文以田间试验、定位观测和野外调查为依据,系统地研究了位于晋西北黄土丘陵区的砖窑沟试验区土壤资源特点及采用改良利用措施后的效果。结果表明,试验区土壤类型多,肥力低。低产原因主要是:土质过砂,有机质含量低,气候多灾,侵蚀严重,经济贫困。通过修建水平梯田,实施快速培肥技术;实行以有机肥与氮肥为主的优化施肥方案;蓄水保水,合理用水,提高水分生产效率等一系列措施,有效地提高了土壤肥力,改善了环境条件。根据科学试验和生产实践,提出了在该地区具有普遍意义的改土培肥途径。 相似文献
5.
文中介绍了一种用于厚壁管双向扩口镦粗成形的工艺及模具。它由两道工序完成 ,即先将管坯两端同时扩口 ,再将两端台阶同时镦粗成形。模具结构采用了带外锥的分瓣式凹模及带内锥的浮动凹模套 ,解决了工件上、下两台阶同时扩口或镦粗成形及卸料问题 ,并提高了零件的尺寸精度和同轴度 相似文献
6.
矿区植被恢复方式对土壤微生物和酶活性的影响 总被引:8,自引:6,他引:2
矿区废弃地生态退化形势严峻,生态修复已成为矿区可持续发展的主要措施,土壤微生物和酶活性可作为评价土壤恢复质量的敏感因子.本研究将以山西省安太堡煤矿复垦区作为对象,分析植被恢复方式对土壤微生物和酶活的影响.结果表明,不同植被方式对土壤理化特征、参与氮代谢的3类菌群(固氮菌、硝化细菌和反硝化细菌)和4种酶活性(蔗糖酶、过氧化氢酶、脲酶和多酚氧化酶活)均有显著影响.土壤总氮含量与固氮菌和硝化细菌数量均显著相关,而与反硝化细菌不相关.多酚氧化酶活性与有机碳和总氮含量之间为负相关,而其它3种酶与有机碳和总氮之间呈正相关.通过主成分分析计算综合肥力指标,刺槐-油松混交林土壤综合肥力指标最高,而未复垦综合肥力指标最低.可见,刺槐-油松混交林是晋西北干旱区矿区复垦较为适宜的植被恢复模式. 相似文献
7.
Variation of soil fertility and carbon sequestration by planting Hevea brasiliensis in Hainan Island, China 总被引:5,自引:0,他引:5
The development of rubber industry depends on the sustainable management of rubber plantation. To evaluate the environmental effects of planting Hevea brasiliensis on a subsystem of tropical forest ecosystem, the variation of soil fertility and carbon sequestration under rubber plantation within 30-year life period were investigated in Hainan Island. Results showed that (1) with the increase of stand age of rubber plantation, soil fertility decreased all along. From 1954 to 1995, soil organic matter, total N, available K and available P decreased by 48.2%, 54.1%, 56.7% and 64.1%, respectively. (2) If the complete return of litters was considered without additional fertilizer application to the soil of the rubber plantations, the consumption periods for P, N, K, Mg were only 825 years, 329 years, 94 years and 65 years, respectively~ To improve soil fertility is essential for rubber plantation development. (3) The C sequestration of rubber trees per hectare accounts for 272.08 t within 30-year life period and 57.91% of them was fixed in litters. In comparison with C sequestration by rain forest (234.305 t/hm^2) and by secondary rain forest (150.203 t/hm^2), rubber forest has more potentials for C fixation. On the base of above results, the following measures would benefit the maintenance of soil fertility and the development of rubber industry, including applying fertilizer to maintain the balance of soil nutrients, intercropping leguminous plant to improve soil fertility, reducing the collection of litters, optimizing soil properties to improve element P availability such as applying CaCO3. The information gathered from the study can be used as baseline data for the sustainable management of rubber plantation elsewhere. 相似文献
8.
F.J. Díaz M. TejedorC. Jiménez R.A. Dahlgren 《Agriculture, ecosystems & environment》2011,144(1):253-261
In the extremely arid (∼150 mm yr−1) eastern Canary Islands of Lanzarote, Fuerteventura and La Graciosa, agriculture has been sustained for decades by a traditional runoff-capture (RC) farming system known as “gavias”. Although the main goal of these systems is to increase water supply for crops, making unnecessary conventional irrigation, a secondary and equally important factor is that this system allows for sustainable agricultural production without addition of chemical or organic fertilizers. A field study was conducted to assess the impact of long-term agriculture (>50 yr) on soil fertility and to evaluate key factors affecting the nutrient sustainability of RC agricultural production. Soil fertility and nutrient dynamics were studied through chemical characterization of the arable layer (0-25 cm) of RC agricultural plots, adjacent natural soils (control) not affected by runoff and cultivation, and sediments contributed by a series of RC events. Results showed that RC soils have enhanced fertility status, particularly because they are less affected by salinity and sodicity (mean electrical conductivity = 1.8 dS m−1 vs. 51.0 dS m−1 in control soils; mean exchangeable sodium percentage = 11.1% vs. 30.6% in control soils), and have higher water and nutrient holding capacities (mean clay plus silt contents ≈87% vs. 69% in control soils). In general, sediments transported with the runoff and deposited in RC plots (average sediment yield ≈ 46 ton ha−1 yr−1), contain sufficient nutrients to prevent a progressive reduction of essential plant nutrients below natural levels in spite of nutrient uptake and removal by the harvested crop. Average additions of nitrogen, phosphorus and potassium with the runoff sediments were 33.6, 35.3 and 48.8 kg ha−1 yr−1, respectively. Results of this study show how a crop production system can be sustained in the long term by natural hydrological and biogeochemical catchment processes. This system maintains a nutrient balance that is not based on energy-intensive inputs of fertilizers, but is integrated in natural nutrient cycling processes, unlike other tropical farming agroecosystems. 相似文献
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