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1.
李国强  马克明  傅伯杰 《生态学报》2006,26(12):4127-4134
退化生态系统恢复是保障区域生态安全的重要途径之一。在生态系统结构功能严重受损,威胁到区域生态安全时,通过引入物种进行主动的植被恢复可以有效地加速生态系统恢复进程,维护区域生态安全。但是区域尺度的植被恢复是一项规模浩大的工程,其效果和影响难以立即显现。为了评估区域植被恢复的生态风险,根据岷江上游干旱河谷区域植被恢复格局的设计结果,预测了区域植被恢复对生态安全的影响。通过对比分析现状植被盖度及生物多样性与植被恢复格局预测结果的差异,对区域植被恢复的效果进行评价,认为尽管植被恢复格局设计使部分区域生物多样性下降,但它整体提高了地表植被覆盖度,增强了抵御土壤侵蚀的能力。对保障区域生态安全具有积极的效果。  相似文献   

2.
西北干旱区山地-绿洲-荒漠系统生态恢复综合效益评估   总被引:4,自引:2,他引:4  
康婷婷  李增  高彦春 《生态学报》2019,39(20):7418-7431
西北干旱区目前已实施众多生态恢复举措试图修复和重建受损的生态系统,截至目前恢复效果如何我们不得而知,但生态恢复效益评估却能够检测其结果,并为未来的生态工程提供参考。在前人研究的基础上,以地面观测的气象资料、土壤调查数据、多源遥感数据和陆面模型模拟数据作为输入,对基于像元二分法的植被覆盖度估算方法、修正的风力土壤侵蚀模型、修正的通用土壤流失方程和基于光能利用率的净初级生产力模型中的参数进行本地化,更为准确的估算了西北干旱区生态恢复效益评价体系中的关键指标,并集成生态恢复效益指标,评估了1990—2015年西北干旱区14个山地-绿洲-荒漠子系统的生态恢复效益。研究发现:(1)山地-绿洲-荒漠子系统的生态系统结构、生态系统质量和生态系统功能时空分异明显:全区山地系统的生态系统结构有所改善,北疆和伊犁地区的山地-绿洲-荒漠子系统生态系统质量上升,荒漠生态系统的生态系统功能下降;(2)1990—2015年西北干旱区的荒漠子系统生态恢复效益在下降,而绿洲和山地的生态恢复效益在上升。基于多指标的生态恢复效益定量评估有助于客观认识西北干旱区的生态恢复现状和动态,评估结果可为未来生态工程提供具体的空间位置,也为我国其他生态脆弱区的生态恢复效益评价提供参考。  相似文献   

3.
许积层  唐斌  卢涛 《生态学报》2013,33(16):4966-4974
基于混合像元分解方法,利用Landsat TM卫星遥感数据监测了岷江上游干旱河谷区映秀\汶川段河岸带植被在汶川地震前后的植被覆盖动态变化,并结合高程、坡度及坡向数据,分析了植被受损及地震3a后植被恢复的空间分布特征。结果表明,地震造成研究区河岸带植被的受损总面积为2736.61hm2,且集中分布在海拔1100-1700m,坡度25-55°之间以及东、东南和西坡;地震3年后,受损植被与震前相比,共恢复了56.20%。  相似文献   

4.
干旱河谷-山地森林交错带土壤水分与养分特征   总被引:2,自引:0,他引:2  
干旱河谷-山地森林交错带(EDM)在延伸亚高山森林生态功能,抑制干旱河谷上延等发挥着重要且不可替代的作用。研究了交错带邻近生态系统干旱河谷(DV)、亚高山森林(SF)以及交错带内(EDMⅠ、EDMⅡ、EDM) 3个土层(L1、L2、L3)土壤水分及养分特征,结果表明,(1) 相比于DV,EDM具有更好的土壤水环境,并为植物生长提供更多的可吸收磷,但未表现出更好的土壤氮素环境;SF则是山地垂直带谱中土壤水环境和养分环境最好的区域。(2) 交错带内由于主要植物种类及其群落结构组成不同,土壤水、肥环境仍存显著差异。(3)海拔梯度上,L1中土壤水分与氨态氮相关性不显著,与其它养分均极显著相关(P<0.01)。L3中,速效养分均与土壤水分相关性不显著;剖面层次上,EDM和EDMⅠ不同层次的土壤养分与土壤水均未表现出显著相关性,而在EDMⅡ和SF却表现出显著相关。  相似文献   

5.
2006-2016年岷江上游植被覆盖度时空变化及驱动力   总被引:9,自引:0,他引:9  
基于MODIS NDVI遥感数据,采用像元二分模型估算岷江上游植被覆盖度,运用一元线性回归分析和稳定性分析方法,研究2006-2016年岷江上游植被覆盖度时空变化格局及稳定性,并分段讨论2008年"5.12汶川地震"对岷江上游植被的破坏程度以及震后植被恢复情况,利用地理探测器模型对岷江上游植被覆盖度影响因子及影响力进行探测,分析岷江上游植被覆盖度变化驱动力。结果表明:(1)2006-2016年岷江上游植被覆盖整体状况良好,植被覆盖总体情况较为稳定,多年平均植被覆盖度为0.79,植被覆盖度大于0.8的区域占整个岷江上游地区面积的69%。(2)2008年"5.12汶川地震"给整个岷江上游植被造成了严重的破坏,植被覆盖度退化区域面积为14013.41 km2,占整个岷江上游面积的57%,2008-2016年岷江上游植被恢复状况良好,植被覆盖度改善区域面积为17390.69 km2,占整个岷江上游面积的71%,岷江上游植被覆盖度已经超过震前水平。(3)岷江上游植被覆盖度主要受海拔、气温、土壤类型、降水4个因子的影响,其解释力均在40%以上;地貌类型、植被类型的解释力在20%-40%之间;坡度、坡向的解释力均小于1%。  相似文献   

6.
汶川大地震对生态系统的影响   总被引:24,自引:0,他引:24  
汶川大地震的主要影响区位于四川盆地西缘,是四川盆地向青藏高原的过渡地带,地质构造复杂,山高谷深坡陡,是我国生态环境十分脆弱的地区,同时该地区还是具有重要生态服务功能,是长江上游生态安全的重要屏障。汶川大地震不仅造成巨大人员伤亡和财产损失,也对生态系统造成了严重破坏,对区域生态安全带来巨大威胁。研究运用遥感数据和实地调查,评估了地震对生态系统的影响,研究结果表明:(1)汶川大地震造成严重的生态破坏,导致生态系统丧失面积为122136hm^2,并形成了包括汶川县、彭州市、绵竹市等10县市的地震生态破坏重灾区。(2)地震导致65,584hm^2大熊猫生境丧失,损失比例5.92%。(3)94.64%的受损生态系统分布在地震烈度Ⅸ以上区域,53.82%的受损生态系统分布在海拔2000m以下的区域,66.09%的受损生态系统分布在坡度30~50&#176;之间。地震导致的生态破坏将影响区域生态安全,在恢复重建中要加强生态保护和生态系统的恢复重建。  相似文献   

7.
岷江干旱河谷灌丛土壤种子库及其自然更新潜力评估   总被引:3,自引:0,他引:3  
为了解岷江干旱河谷区灌丛植被土壤种子库的特征及预测灌丛植被自然更新的潜力,利用土壤种子库"萌发法"(每个地段15个2m×2m样方内分土表层、0-5cm土层和5-10cm土层采集土样)及野外植被调查方法(每个地段15个1m×1m的调查样方),研究了岷江干旱河谷3个地段(河谷下游边缘汶川地段、核心茂县地段以及上游边缘松潘地段)阳坡灌丛植被土壤种子库及其与地上植物群落的关系。发现:土壤种子库发芽试验共观察到4274株幼苗,分属于113个物种。土壤种子库密度在102—103ind./m2,物种数在12—23种/0.06m2,边缘地段的土壤种子库平均种子密度(ind./m2)和平均物种数(种/0.06m2)均比中心地段(茂县)高。3个地段土壤种子库和地上植被的组成物种均多为多年生植物,地上灌丛与其土壤种子库的密度及物种数均呈不显著相关性;物种组成的Sorensen相似性指数较低,不足30%,但土壤种子库均比地上植被具有更高的物种丰富度。综合分析表明,岷江干旱河谷灌丛具有依靠土壤种子库实现自然更新的潜力,但由于物种组成相似性较低,现存灌丛植被一旦遭到破坏后,单依靠土壤种子库自然恢复到现存植被是困难的,需要在自然恢复潜力评估基础上积极充分采取人工促进自然恢复的策略,同时也应充分考虑干旱河谷植被及其自然更新潜力的空间异质性。探明岷江干旱河谷区灌丛植被的土壤种子库特征,是认识灌丛植被自然更新潜力的基础,是合理制订该区植被恢复与管理措施的重要依据。  相似文献   

8.
基于NDVI监测5.12震后岷江河谷映秀汶川段滑坡体植被恢复   总被引:1,自引:0,他引:1  
汶川5.12地震造成岷江流域生态环境严重受损,评估地震后自然植被恢复过程,对生态环境恢复和重建有着重要的意义。本研究以5.12地震前后(2007、2008及2011年)空间分辨率为30 m×30 m的TM遥感影像的NDVI指标为数据源,监测了岷江上游干旱河谷(映秀—汶川段)植被在地震前后的动态变化,并结合地形因子,分析了植被受损及地震3年后植被恢复的空间分布特征。结果表明:(1)地震造成的研究区滑坡体面积约5 413.95 hm2,占总面积的34.74%;(2)滑坡体发育总体上与海拔呈负相关,与坡度呈正相关,与坡向无显着相关;(3)地震3年后,受损植被的平均恢复率达66.71%,其中中等及良好恢复的面积为3 942.54 hm2,占滑坡总面积的72.82%。研究结果也显示植被恢复与坡度、海拔有很高的一致性,及植被恢复的复杂性。  相似文献   

9.
汶川地震重灾区恢复期生态系统健康评价   总被引:3,自引:1,他引:2  
朱捷缘  卢慧婷  王慧芳  严岩  唐立娜 《生态学报》2018,38(24):9001-9011
2008年的汶川地震对区域生态系统造成了显著破坏。为了解震后区域生态系统恢复情况,从而为震区生态恢复策略提供科学依据,利用遥感数据研究了四川省汶川地震重灾区39区县2010—2015年的生态系统类型及活力变化,并运用In VEST模型评估了震区土壤保持、水源涵养、生境质量等生态系统服务能力,最后基于VOR模型并耦合关键生态系统服务定量评估了震区生态系统健康状况。结果表明:2010—2015年间震区湿地和城镇面积有所增加,植被和农田有不同程度的减少,但是Ⅹ—Ⅺ地震烈度等级区域内森林面积增加1309.77 hm2;震区生态系统活力均值明显上升,Ⅹ—Ⅺ地震烈度级别区生态系统活力增幅最明显,分别为14.84%、12.47%;水源涵养能力稍有降低,减幅0.46%,土壤保持服务增幅1.26%,生境质量指数无明显变化;生态系统健康指数(EHI)均值有小幅度提升,从0.6761上升到0.6853,增幅1.36%,Ⅹ—Ⅺ地震烈度级别区EHI增幅比其他地区明显,增幅分别为4.01%、3.48%,表明受灾最严重的地区生态恢复比较显著。但是,由于震区重建开发导致局部区域如宝兴、汉源、石棉、涪城、广汉、汶川西北部和震区北部部分区域EHI下降。未来应继续保持Ⅹ—Ⅺ地震烈度级别区良好的生态恢复趋势,同时也要重视震区中部平原地区的基本农田保护和南部、北部地区的自然生态空间保护工作,维持震区生态系统健康和区域可持续发展。  相似文献   

10.
中国科学院成都生物研究所长江上游岷江段干燥河谷山地生态系统定位研究站,位于四川省茂县静州村附近,因此简称“茂县生态站”。站址中心位置为东经103°53′,北纬31°40′,海拔1820米,地处岷江上游左岸一级支流——大沟流域。这里是岷江上游山地生态系统的典型代表地段,属青藏高原东缘高山峡谷区,是较为典型的生态环境脆弱带,立体气候显著,生物多样性丰富。但由于人类活动,过伐森林破坏植被严重,环境严重退化,是典型的退化生态系统。因此,这里是研究生物多样性、退化生态系统和少数民族地区持续发展对策的理想之地。  相似文献   

11.
12.
Ectogenesis, or the use of an artificial womb to allow a foetus to develop, will likely become a reality within a few decades, and could significantly affect the abortion debate. We first examine the implications for Judith Jarvis Thomson’s violinist analogy, which argues for a woman’s right to withdraw life support from the foetus and so terminate her pregnancy, even if the foetus is granted full moral status. We show that on Thomson’s reasoning, there is no right to the death of the foetus, and abortion is not permissible if ectogenesis is available, provided it is safe and inexpensive. This raises the question of whether there are persuasive reasons for the right to the death of the foetus that could be exercised in the context of ectogenesis. Eric Mathison and Jeremy Davis have examined several arguments for this right, doubting that it exists, while Joona Räsänen has recently criticized their reasoning. We respond to Räsänen’s analysis, concluding that his arguments are unsuccessful, and that there is no right to the death of the foetus in these circumstances.  相似文献   

13.
On the diversity of the Cladocera in the tropics   总被引:20,自引:13,他引:7  
The mythical concept of an impoverished tropical cladoceran fauna is refuted. On a planetary scale, around half of the cladoceran species presently known occur exclusively in the tropics-subtropics, often with considerable restriction to particular geographical subzones. On a regional (political) scale, the situation is often unclear because of the continued fragmentary nature of studies, and because political units are not a good basis for biogeographical comparisons. At the finest level of resolution (lake-perlake comparisons), there appears to be an upper limit of c. 50 cladoceran species per individual lake. No significant difference between lakes in the temperate zone and in the tropics could be established here. Daphnia is largely absent from the tropics, but is replaced by more Sidids, Moinids, and Bosminids, such that the average cladoceran community in the limnetic zone of a tropical lake is not characterized by less species but rather by lower population densities. This, in turn, is considered a consequence of higher prevalent predation levels in the tropics.  相似文献   

14.
We discuss the possible links between the fossil record of marine biodiversity, nutrient availability and primary productivity. The parallelism of the fossil records of marine phytoplankton and faunal biodiversity implicates the quantity (primary productivity) and quality (stoichiometry) of phytoplankton as being critical to the diversification of the marine biosphere through the Phanerozoic. The relatively subdued marine biodiversity of the Palaeozoic corresponds to a time of relatively low macronutrient availability and poor food quality of the phytoplankton as opposed to the diversification of the Modern Fauna through the Mesozoic–Cenozoic. Increasing nutrient runoff to the oceans through the Phanerozoic resulted from orogeny, the emplacement of Large Igneous Provinces (LIPs), the evolution of deep-rooting forests and the appearance of more easily decomposable terrestrial organic matter that enhanced weathering. Positive feedback by bioturbation of an expanding benthos played a critical role in evolving biogeochemical cycles by linking the oxidation of dead organic matter and the recycling of nutrients back to the water column where they could be re-utilized. We assess our conclusions against a recently published biogeochemical model for geological time-scales. Major peaks of marine diversity often occur near rising or peak fluxes of silica, phosphorus and dissolved reactive oceanic phosphorus; either major or minor 87Sr/86Sr peaks; and frequently in the vicinity of major (Circum-Atlantic Magmatic Province) and minor volcanic events, some of which are associated with Oceanic Anoxic Events. These processes appear to be scale-dependent in that they lie on a continuum between biodiversification on macroevolutionary scales of geological time and mass extinction.  相似文献   

15.
Summary A tubular network was found in the terminal endings of the visual receptor cells in the human, the monkey (Macaca mulatta), the cat and the dog. These tubules are arranged in close groups in the vicinity of the synaptic lamellae and the invaginated dendrites. According to the form, diameter, density of the tubules and to the consistence of the network formed by them one can distinguish at these places an initial type (type I), a transitory (type II) and a vesicular one (type III). In the the type III branching, bizarre forms are frequent. The diameter of all the tubules reaches 500–600 Å, their density and walls being the same as in the synaptic vesicles.Similar networks also occur in the axons of the visual receptor cells of the monkey.
Zusammenfassung In den Endigungen der Photorezeptorzellen von Mensch, Affe (Macaca mulatta), Katze und Hund kommen aus Tubuli bestehende Komplexe vor. Organellenartig in geschlossenen Gruppen angeordnet, liegen sie in Nähe der synaptischen Lamellen und der invaginierten Dendriten. An diesen Stellen kann man nach Form, Durchmesser, Dichte und Konsistenz der von den Tubuli gebildeten Komplexe drei Typen unterscheiden: 1. einen initialen (Typus I), 2. einen Übergangstypus (Typus II) und 3. einen vesiculären Typus (Typus III). In letzterem kommen häufig verzweigte, bizarre Formen vor. Der Durchmesser sämtlicher Tubuli erreicht 500–600 Å. Ihre Dichte und ihre Wand gleicht denen der synaptischen Vesikel.Ähnliche Komplexe fanden wir auch in den Axonen der Photorezeptorzellen vom Affen.
  相似文献   

16.
17.
Methods of amperometry and potentiometric titration were used to follow dark respiration (DR) and apparent photosynthesis (AP) in the fucoids Ascophyllum nodosum (L.) Le Jol, Fucus vesiculosus L., and F. serratus L. from the Barents Sea littoral by the end of the 40-day-long polar night. The macroalgae were shown to manifest species-specific low rates of photosynthesis and respiration. However, in spite of their low photosynthetic status due to the effects of subzero temperature and prolonged low or zero illumination, the macroalgae have been able to restore DR and AP to the initial level already by the day 9; the ability to restore AP depended on the level of illumination. The study of the changes in the carbonate–bicarbonate system in the light and darkness demonstrated that the macroalgae grown in darkness, in contrast to those grown in twilight, could absorb bicarbonate in darkness; however, they lost this capacity after two-day-long illumination at an irradiance of 7 mol/(m2 s). Bicarbonate uptake in darkness and the capacity to restore the systems of photosynthesis and respiration in fucoid cells are discussed in the context of algal energy metabolism under the polar night conditions.  相似文献   

18.
The voltage-gated potassium channel is currently one of the few membrane proteins where functional roles have been mapped onto specific segments of sequence. Although high-resolution structures of the transmembrane portions of three bacterial potassium channels, the tetramerization domain and the cytoplasmic ball are available, their relative spatial arrangement in mammalian channels remains a matter of ongoing debate. Cryo-electron microscopic images of the six transmembrane voltage-gated Kv channel have been reconstructed at up to 18 Å resolution, revealing that the T1 domain tetramerizes and is suspended below the transmembrane segments. However, the resolution of these images is insufficient to reveal the location of the third piece of the puzzle, the inactivating ball domain. We have used the aberrant interactions observed in a series of chimæric channels to establish that an assembled T1 domain restricts access to the cytoplasmic face of the channel, suggesting that the N-terminal ball and chain may be confined in the space between the T1 domain and the transmembrane portion of the channel.  相似文献   

19.
Summary The choriocapillaris is a fenestrated capillary bed located posterior to the retinal pigment epithelium. It serves as the main source of supply to the photoreceptors, retinal pigment epithelium, and other cells of the outer retina. The permeability of these capillaries to intravenously injected ferritin (MW — approx. 480,000; mol. diam. 11 nm) was examined in the mouse, rabbit, and guinea pig, each of which is characterized by a different type of retinal vascularization. In all three species, the bulk of the ferritin remained in the capillary lumina, where it appeared to be blocked at the level of the diaphragmed fenestrae. Some ferritin was present in endothelial cell vacuoles. The results confirm previous work on the rat choriocapillaris and indicate that the barrier function of the choriocapillary endothelium is present even among species in which the retinal circulation differs significantly.Supported by NIH grant EY03418  相似文献   

20.
Summary According to light- and electron-microscopic observations the pineal organ of the 3-day-old chicken consists of a prominent end vesicle and a tapering parenchymal stalk. During this stage the pineal lumen is in open communication with the third ventricle. However, in the 40-day-old chicken, which still possesses a well-developed end vesicle, the proximal portion of the pineal stalk displays regressive changes leading to local fragmentation. At this stage the pineal stalk is reduced, and the pineal lumen is missing. In 1-year-old chickens the parenchyma of the proximal portion of the stalk is further diminished, and in 3-year-old domestic fowl is completely displaced by bundles of collagenous fibers, only some nerve fibers being present. This post-hatching pineal development may reflect the sequence of changes leading from pineal sense organs to pineal glands.This work was supported by a grant-in-aid for Scientific Research from the Ministry of Education, Science and Culture of Japan  相似文献   

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