首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   135篇
  免费   22篇
  国内免费   53篇
  2023年   4篇
  2022年   4篇
  2021年   10篇
  2020年   6篇
  2019年   15篇
  2018年   15篇
  2017年   10篇
  2016年   12篇
  2015年   11篇
  2014年   7篇
  2013年   4篇
  2012年   7篇
  2011年   13篇
  2010年   4篇
  2009年   5篇
  2008年   8篇
  2007年   4篇
  2006年   5篇
  2005年   10篇
  2004年   3篇
  2003年   3篇
  2002年   7篇
  2001年   4篇
  2000年   4篇
  1999年   6篇
  1998年   3篇
  1997年   4篇
  1996年   1篇
  1995年   4篇
  1994年   1篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1990年   4篇
  1988年   1篇
  1987年   2篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
排序方式: 共有210条查询结果,搜索用时 15 毫秒
1.
Restoring the flooding‐related disturbance regime by removing and setting back flood defenses (channel widening) is the most efficient strategy for recovering riparian plant communities in floodplains formerly impacted by human activities such as agriculture, mining, and forestry. Removing flood defenses is generally not socially accepted, and alternative recovery strategies must be explored. We assessed vegetation establishment on 33 sites in the floodplains of the Middle Ebro River and three of its tributaries (NE Spain) where restoration approaches applied in the last 20 years include channel widening, floodplain excavation, and abandonment of agriculture, gravel extraction, and hybrid poplar plantations, with and without plantation of native species. Using analysis of similarity and ordinations, we found that channel widening led to plant communities closely resembling those found on natural gravel bars, including new recruits of keystone tree species. Excavation of the floodplain as the restoration approach resulted in pioneer, non‐strictly riparian communities. Abandonment of agricultural land or clearing of poplar plantations resulted in alternative stable states predominating, regardless of time elapsed since restoration and whether poles of native species were planted. However, forest‐like communities relatively similar to mature, natural riparian references were attainable when hybrid poplars were allowed to resprout after clear‐cutting, or after the human activities were abandoned and trees were not cut. Combining channel widening and assisted revegetation where flood defenses cannot be altered may partially reproduce a mosaic of habitats typical of natural floodplains.  相似文献   
2.
肖甜甜  李杨帆  向枝远 《生态学报》2019,39(11):3850-3860
以围填海活动为代表的高强度的人类开发利用方式从根本上改变了海岸带地区的自然属性,区域生态环境发生了深刻变化。定位于我国大陆沿海的围填海区域,通过人机交互目视解译的方法获取我国大陆沿海围填海区域的矢量数据,基于围填海活动影响下海岸带区域的景观类型和生态系统服务变化的评估结果,识别我国海岸带的生态脆弱区和重点保护区,提出围填海区域景观生态红线的划分方法。通过分析可知:(1)围填海区域景观生态红线区呈现出"总体分散、局部集中"的的分布特点;(2)景观生态红线区主要分布在人工湿地和残存自然湿地中。围填海区域是进行海陆统筹研究的关键区域,而景观生态红线作为识别其重要生态功能区,并进行二次保护和抢救性保护的有效手段,将为我国海岸带生态管理提供新思路和新方法。  相似文献   
3.
生态建设的理论分析   总被引:4,自引:2,他引:2  
吕一河  傅伯杰  陈利顶 《生态学报》2006,26(11):3891-3897
20世纪80年代以来,生态恢复逐渐成为生态学和环境科学研究的热点领域。总结了近年来有关生态恢复的众多研究成果,认为生态建设是人类理性行为参与下积极的生态恢复与重建过程,它具有复杂性、针对性、动态性和不确定性特征,受地理环境地域分异的影响,其类型多种多样。从方案运筹的角度,提出了生态建设的共性原则,包括面向区域的问题导向原则、目标的科学性原则、参与的广泛性原则和科学监测与评价原则。生态建设是一个不断试验、学习和优化的过程。具体包括问题识别、方案设计、决策、实施、监测与评价以及方案调整等重要环节。公众参与对于生态建设是一种很好的知识、信息和资源输入渠道,对活化生态建设的管理运行机制,提高生态建设决策的科学性和有效性能够发挥重要作用。以这些理论分析为依据,对中国生态建设中存在的主要问题展开深入剖析,并提出建立科学评价机制是提高生态建设有效性的核心方略。  相似文献   
4.
Question: How does one best choose native vegetation types and site them in reclamation of disturbed sites ranging from cropland and strip mines? Application: World‐wide, demonstrated in SE Montana. Methods: We assumed that pre‐disturbance native communities are the best targets for revegetation, and that the environmental facet each occupies naturally provides its optimal habitat. Given this assumption, we used pre‐strip‐mine data (800 points from a 88 km2 site) to demonstrate statistical methods for identifying native communities, describing them, and determining their environments. Results and conclusions: Classification and pruning analysis provided an objective method for choosing the number of target community types to be used in reclamation. The composition of eight target types, identified with these analyses, was described with a relevé table to provide a species list, target cover levels and support the choice of species to be seeded. As a basis for siting communities, we modeled community presence as a function of topography, slope/aspect, and substrate. Logistic GLMs identified the optimal environment for each community. Classification and Regression Tree (CART) analysis identified the most probable community in each environmental facet. Topography and slope were generally the best predictors in these models. Because our analyses relate native vegetation to undisturbed environments, our results may apply best to sites with minimal substrate disturbance (i.e. better to abandoned cropland than to strip‐mined sites).  相似文献   
5.
Abstract A comparison of a composted organic amendment, a controlled‐release fertilizer, and induced mycorrhizal inoculation as affecting the establishment and nutrition of bareroot Jeffrey pine (Pinus jeffreyi Grev. & Balf.) was conducted on a Sierra Nevada surface mine. The soil amendments were applied at outplanting to the backfill of augered planting holes, with a low rate of 8 g and a high rate of 16 g per seedling for the fertilizer, Gromax 21‐6‐2 + Minors, whereas a single rate of 2.0 L was used for organic matter. Colonization by Pisolithus tinctorius (Pers.) Coker & Couch was induced by coating the root systems with basidiospores suspended in a gel carrier. The organic amendment especially, but also mycorrhizal inoculation, caused substantial seedling mortality, whereas survival was unaffected by controlled‐release fertilization. Gromax applied at the high rate produced a 74% increase in shoot volume after three growing seasons, whereas the organic amendment reduced volume by 28%. Growth was unaffected by mycorrhizal treatment. The growth response to the 16‐g Gromax application probably reflected enhanced N, P, and K nutrition and decreased concentrations of potentially toxic metallic elements, including Mn and Al among others, as revealed through foliar analysis. Because they were accompanied by growth reduction, nutritional responses to the organic amendment, which involved both macronutrients and trace elements, were of little consequence. Impaired water relations may account for the poor response to this amendment. Likewise, nutritional responses to mycorrhizal inoculation produced no discernible benefit in terms of seedling performance. An inoculation procedure that failed to induce substantially greater P. tinctorius colonization in inoculated than uninoculated seedlings, and that may have also impaired water relations, likely explains this result. Overall, these findings indicate that further research is needed before either the organic amendment or the mycorrhizal inoculation procedure used here can be used in forest restoration efforts on dry sites.  相似文献   
6.
The quantitative composition of the rotifer fauna of seven interconnected lakes located in southern California was studied in a preliminary investigation. The lakes are fed by reclaimed sewage, and the water quality increases rapidly from the first lake, barely able to support life, to a series of lovely lakes stocked with fish and utilized for recreation. The Shannon index of rotifer population diversity showed an appropriate increase. Up to 24 – 28 different rotifer taxa in each lake provided a rich community dominated by Brachionids, Keratella and Trichocerca. The diversity and quantity of the rotifer association then declined again in the last lake. Comparison of the lakes using the Bray and Curtis index of similarity and cluster analysis supported the picture of a lake-chain evolution, a biotic development showing a maximum curve.  相似文献   
7.
8.
Algal communities were investigated in two contrasting chronosequences established on reclaimed spoils in the west Bohemian brown coal mining district near Sokolov (Czech Republic) and in the Lusatian lignite mining district near Cottbus (Germany). The Sokolov chronosequence was characterized by tertiary cypric clay substrate, afforestation with Alnus glutinosa (L.) Gaertn., and high pH of deposited spoil material, Cottbus chronosequence by tertiary carboniferous and pyritic sand of extremely low pH ameliorated by fly ash, and afforestation with Pinus sylvestris L. and P. nigra Arnold. A total of 122 species of algae was found in both areas. Although the same species number (80) was identified from Sokolov and Cottbus, both proportion of individual algal groups and species composition were different. Green algae prevailed in both areas, but in Sokolov cyanobacteria and diatoms were also quite diverse, and in younger sites they were also abundant. Total abundance of algae ranged mostly between 104–107 cells/g dry soil, and was one order higher in Cottbus than in Sokolov. Species number was high in young sites, decreased with increasing age, and was the lowest in control forests. In Sokolov, the highest abundance was recorded in the youngest alder plantation. In Cottbus, sludge and compost fertilization used in the youngest pine plantations resulted in rapid formation of visible algal crusts dominated by Klebsormidium crenulatum (Kütz) Lokhorst.  相似文献   
9.
Stockpiling of cover soil can influence vegetation development following reclamation. Cover soil, comprising the upper 15–30 cm of the surface material on sites scheduled for mining, is commonly salvaged prior to mining and used directly or stockpiled for various lengths of time until it is needed. Salvaging and stockpiling causes physical, chemical, and biological changes in cover soils. In particular, stockpiling reduces the availability and vigor of vegetative propagules and seed, and can lead to increases in the abundance of some weedy species. This study uses data from monitoring plots to assess how stockpiling of cover soil impacts plant community development on reclaimed oil sands mine sites in northern Alberta. Development of plant communities differed distinctly between directly placed and stockpiled cover soil treatments even 18 years after reclamation. Direct placement of cover soil resulted in higher percent cover, species richness, and diversity. Nonmetric multidimensional scaling and multiresponse permutation procedure revealed compositional differentiation between the treatments. Indicator species analysis showed that direct placement treatment was dominated by perennial species while grasses and annual forb species dominated sites where stockpiled soil was used. Results indicate that stockpiling leads to slower vegetation recovery while direct placement of cover soil supports more rapid succession (from ruderal and annual communities to perennial communities). In addition, direct placement may be less costly than stockpiling. However, scheduling of salvage and placement remains a challenge.  相似文献   
10.
Unsanctioned travel routes through alpine ecosystems can influence water drainage patterns, cause sedimentation of streams, and erode soils. These disturbed areas can take decades to revegetate. In 2012, a volunteer‐driven project restored a 854‐m section of unsanctioned road along the Continental Divide in Colorado, United States. The restored area was seeded with three native grass species and then treated by installing erosion matting or adding supplemental rock cover. Four years later, results suggest that the seeding along with the use of erosion matting or supplemental rock can enhance revegetation. Matting appeared to accumulate litter, and this effect might have contributed to enhanced moisture retention. Treated areas contained 40% of the vegetation cover found on adjacent controls, which averaged 69% vascular plant absolute cover. Recovery on both treatments was markedly higher than published estimates of passive revegetation of disturbed areas measured elsewhere suggesting seeding with added cover or protection led to substantial vegetative cover after 4 years. Two of the 3 seeded grass species, Trisetum spicatum and Poa alpina, dominated the restored plots, composing 81.7% of relative vegetation cover on matting sites and 73.4% of relative cover on rock‐supplemented areas. Presumably due to its preference for moister sites, Deschampsia cespitosa had low establishment rates. Volunteer species, that is species that appeared on their own, contributed 6.3% to the absolute vegetation cover of matting and rock sites, and species such as Minuartia biflora, Minuartia obtusiloba, Poa glauca, and Festuca brachyphylla should be considered for use in future restorations.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号