275 resultados para Clipping


Relevância:

10.00% 10.00%

Publicador:

Resumo:

O presente estudo busca descrever e analisar a experiência de Ouvidoria da Educação construída na Secretaria Municipal de Educação de Nova Iguaçu durante a gestão iniciada em outubro de 2008 e encerrada em maio de 2010. Nele, é contextualizado o processo de construção da experiência das Ouvidorias no Brasil, as características urbanas, econômicas, políticas e sociais da cidade utilizada como recorte empírico da pesquisa, assim como o Programa Bairro Escola. Esta foi a denominação da política central de desenvolvimento de gestão pública do, então, prefeito Lindberg Farias. O tema se expressa no campo da Educação e o subtema é a Gestão Democrática, apresentando como questão central as condições e os limites de viabilização de um projeto de Ouvidoria na rede pública municipal comprometida com essa referência de gestão. Para efetivação da análise investigativa, a dissertação foi desenvolvida como um caso particular do possível um estudo de caso com a pesquisadora na condição de sujeito/objeto do estudo frente à ação real e utópica de humanização e sustentabilidade do projeto educativo. As interlocuções teóricas adotadas visaram uma abordagem microssociológica com: Pierre Bourdieu na apreensão da prática através do habitus, campo, interesse e espaço social; Foucault, desvelando as relações de poder; Gramsci com a identificação da hegemonia e ideologia; e Boaventura Santos na concepção do contra hegemônico e na fronteira das linhas abissais. A hipótese de trabalho é que a implantação da Ouvidoria da Educação, em um quadro global de um projeto de Educação Integral, tinha como base uma ação inovadora de democracia da gestão e na busca de construir uma governança da polis com um presente e futuro sustentável. Nesse âmbito, a Ouvidoria da Educação atuava como um possível canal de comunicação e instrumento estimulador da mobilização social dos sujeitos-cidadãos da Rede Municipal da Educação da cidade de Nova Iguaçu e disseminador de práticas sustentadas nos Direitos Humanos. Como conclusão, evidencia-se que uma política pública de Educação Integral só se efetiva concretamente no campo educacional quando, substancialmente, se desenvolve uma gestão democrática e propositiva de uma agenda da garantia dos direitos sociais aos diferentes atores escolares, de forma a ressignificar as relações de poder estabelecidas.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Essa dissertação tem por objeto de estudo a política de saúde em geral, recortada a partir do desenvolvimento das conferências internacionais de promoção da saúde. Observando a inflexão ideológica que os próprios conceitos de saúde e promoção sofrem. Há uma ação operada pelo capital através dos organismos internacionais de esvaziamento do conteúdo progressista para que se agregue valores de mercado à esse setor, e sua virtual transformação em mercadoria promotora de lucros em substituição a sua concretização como direito inalienável do ser humano. Com recorte no município de Niterói, município que fora berço do movimento e de experiências da Reforma Sanitário, foi possível observar a repercussão desse processo de inflexão ideológica operada pelo capital no campo da saúde.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

过度放牧是导致浑善达克沙地荒漠化发展的重要原因之一。在该地区占据优势的根茎型克隆草本植物不仅被牲畜频繁地采食,而且也面临着频繁的沙埋和养分胁迫的干扰。通过克隆生长,这些根茎型植物的单个基株能够跨越异质性的资源斑块,同时也可能遭受局部的、非均匀性的采食或沙埋。克隆整合可能会作为一种补偿性机制促进被采食克隆部分或分株的恢复和生长,因而,能够缓解采食及其与环境因素(沙埋/养分胁迫)交互作用对克隆植物的影响。本文以浑善达克沙地草地典型的根茎型沙生植物种和草地植物种为实验材料,应用(野外和温室)实验生态学方法检验了克隆整合的这种效果。 在一个野外实验中,通过对共存在沙丘上的两种根茎型克隆植物沙地雀麦(Bromus ircutensis Kom.)和沙鞭(Psammochloa villosa (Trin.) Bor.),及两种非克隆植物褐沙蒿(Artemisia intramongolica H.C.Fu)和草木樨状黄芪(Astragalus melilotoides Pall.)的个体植株进行不同强度(0、50、90%)的枝叶去除处理,我们发现:50%和90%的枝叶去除增加了沙地雀麦和沙鞭的相对生长率(RGR);而90%的枝叶去除显著减小了褐沙蒿和草木樨状黄芪的RGR。经两个多月处理后,与对照相比,去除枝叶的非克隆植物的地上生物量恢复的远不及克隆植物完全。这些结果表明克隆植物比共存的非克隆植物更能忍耐采食。在分株种群水平上开展的另外一个野外实验表明,在50%的去除强度下,根茎连接明显改善了沙鞭分株种群的表现,但对沙地雀麦分株种群没有显著影响。然而,在90%的去除强度下,根茎连接显著的改善了两种植物分株种群的表现,显示出克隆整合的重要作用。而且,与未剪除的分株种群相比,两种植物当遭受90%的去除强度后,其根茎保持连接的分株种群产生了更多而小的分株个体。 以羊草(Leymus chinensis (Trin.) Tzevl.)和赖草(Leymus secalinus (Georgi) Tzvel)的克隆片断为材料,通过两个温室实验研究了克隆整合对克隆植物忍受采食与沙埋/养分胁迫交互作用的影响。每个克隆片断由一个近端(发育上较老)分株和一个远端(发育上较年轻)分株组成。近端分株不进行胁迫处理,而远端分株进行重复去除 枝叶沙埋/养分胁迫处理;同时,切断或保持克隆片断的根茎连接。结果表明,单因素的干扰对两个种远端分株的影响较小。当遭受剪除处理后,低养供应的赖草远端分株显示出比高养条件下更强的生物量补偿能力。当两个种的远 端分株处于单因素胁迫时,根茎切断很少影响其生物量生产和新分株的形成;而当远端分株同时处于枝叶去除和沙 埋/养分胁迫下时,切断根茎对两个种远端分株的生物量和分株的产生造成了明显的负效果,表明克隆整合发挥了重 要的作用。但克隆整合并没有导致近端分株的显著损耗。 基于以上实验结果,我们得出:克隆整合可以明显提高浑善达克沙地根茎克隆植物应对枝叶去除,及其和沙埋/养分胁迫交互影响的能力,是克隆植物适应频繁干扰的沙地草地环境的重要对策之一。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

放牧是草地最主要的利用方式,草地植物被家畜采食而部分或全部去叶是一个普遍存在的现象。内蒙古草原是我国北方地区最大的干旱半干旱草原,长期以来,过度放牧使草地的植被、土壤状况不断趋于恶化。由于过度放牧,草地植物正常的生理生态特性受到影响,光合作用能力、生长能力和繁殖更新能力等出现不同程度的降低。本文从动物-植物-土壤相互联系的角度出发,着重研究了过度放牧和刈割对内蒙古草原的一种典型植物—羊草(Leymus chinensis (Trin.) Tzevel.)形态、生长和生理的影响,以及羊草对放牧和刈割的生理生态响应,并得出以下主要结论: 1.过度放牧使土壤表层含水量、有机质含量和氮含量显著下降;羊草的叶量减少,比叶面积增大,节间缩短,分蘖减少;羊草的生物量根部分配比例增大,生殖器官则分配很少;羊草种群高度、盖度、密度和相对生物量均比对照显著降低。试验结果说明,过度放牧从短期可以影响到羊草种群和部分形态特征,长期则影响羊草的生物量分配模式,最终还使羊草的生境趋于恶化,不利于羊草的生长。同时,羊草对放牧也形成了一定的适应性。例如,比叶面积增大,增加了更多的光合叶面积;节间缩短可以躲避家畜啃食;生物量向根部集中,增大了对水分和养分的吸收面积等。 2.过度放牧使羊草的净光合速率显著降低;光合作用补偿点增大,光合作用饱和点却降低;蒸腾速率、气孔导度下降,暗呼吸速率增大;光系统Ⅱ的光化学效率、实际量子产量和光化学粹灭值均显著低于围封样地;瞬时和长期的水分利用效率也有不同程度的降低。试验结果表明,过度放牧强烈制约了羊草的光合作用能力和水分利用效率。而植物的光合作用是物质生产的基础,羊草光合能力的降低必然导致其生物产量的降低,从而也改变了羊草种群在整个生物群落中的作用和地位。 3.羊草在轻度(地上20%)和中度(地上40%)刈割条件下可以获得更大的地上累积生物量,表现为超补偿生长,并且地下生物量降低较少,相对生长速率较高,分蘖较多。而重度(地上80%)刈割可收获的地上累积生物量远少于对照,表现为欠补偿生长,且地下生物量大量减少,分蘖较少。在轻度或中度刈割条件下,施氮肥可以起到稳定维持植物生物产量的作用,但是重度刈割条件下,即使施加再多的氮肥也不能补偿植物生物量的损失。施磷肥对羊草的补偿性生长特性没有明显影响。而干旱加刈割处理的羊草不管是哪个刈割水平,均为欠补偿生长,地下生物量低,相对生长速率较低。 4.轻度刈割后羊草剩余叶片经过3天左右的生理恢复期后,表现出了明显的补偿性光合作用。中度和重度刈割羊草的生理恢复时间较长,没有表现出补偿性光合作用。刈割和施氮处理羊草剩余叶片的净光合速率变化和仅刈割处理(对照)基本上相同。刈割和干旱处理羊草剩余叶片的光合速率始终处于一个较低的水平,各刈割水平均没有表现出补偿性光合作用,主要是干旱导致气孔关闭,限制了叶片的气体交换。刈割后叶片气孔导度的增加可能是补偿性光合作用发生的重要原因。但叶片受到强烈伤害后,气孔导度虽然增加,其呼吸作用也增大,所以净光合速率还是较低。重度刈割叶片的叶绿素含量升高可以增加其光合作用潜力,为恢复正常生长作了生理上的准备,这可能是植物对刈割或放牧的一种生理适应性。 研究放牧条件下植物对动物采食的反应不仅具有重要的理论生态学意义,而且对提高植物的净生长量,维持草地持续的生产能力,实现草地的可持续利用具有重要的意义。研究草地主要植物对牲畜采食的补偿性生长效应及其条件,对合理利用草地可再生资源,确定合理的放牧强度有重要意义。应充分利用植物的超补偿效应,适时放牧,控制放牧强度,实现草地植物可食部分的超补偿生长,实现草地的最优化利用和生产力的最大化。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

随着温室气体的大量排放、土地利用方式的改变以及气温的逐步升高,全球变化对自然生态系统的影响也日益加强,全球变化背景下植物群落物种组成的改变能够引起整个生态系统功能的变化。本论文的研究以内蒙古多伦县十三里滩全球变化多因子实验基地为依托,研究割草、施肥、増雨以及红外加热对内蒙古温带典型草原群落物种组成的影响。本研究采用传统的植物调查方法,比较样方中所有物种和功能型的变化,最终揭示植物群落结构对上述四个处理的响应状况。 研究结果表明:氮素作为中国北方典型草原生产力的重要限制因子,增加了禾草优势物种克氏针茅和冰草的盖度,提高了禾草植物盖度和群落总盖度。施磷提高了群落中豆科植物的盖度。 种群水平上,割草提高了乳白花黄芪、苔草和冷蒿等矮小植物盖度;群落水平上,提高了群落总盖度,增加了群落的物种数。但是仅仅在施氮处理下,割草显著地影响了种群和群落水平的指标。 除了氮以外,土壤水分含量也是草原生态系统的限制因素之一。虽然不同增雨方式之间对群落的影响无显著差异,但是增雨都显著地增加了群落中禾草植物和群落的总盖度。在氮肥处理样地,增雨对禾草植物的正效应更加显著。增雨单独对群落的物种丰富度没有显著的影响。 加热减少了土壤水分含量,降低了群落物种数和群落的总盖度。加热提高了群落中非禾草杂类草的比例,降低了群落中禾草植物的比例。 总之,土壤水分和活性氮含量左右了草原植物群落的物种组成。全球变化的四个主要驱动因子正是通过影响生态系统中水分和氮的有效含量来影响群落结构。施氮和增雨降低了土壤水分和氮含量的限制,割草、加热增强了土壤水分和氮的限制。基于四个驱动因子对草原生态系统相反的作用和影响,有必要进行长期的控制实验,充分了解全球变化下,内蒙古典型草原群落物种组成的变化规律。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

自然界中资源的异质性是普遍存在的,既有自然因素导致的,也有人类干扰导致的。在内蒙古草原,植物经常处在地上部异质性的干扰生境和地下异质性的养分生境中。植物的生物量生产反映了植物对不同生境的适应能力,而资源的分配策略是链接进化生态学和功能生态学的纽带。在变化的生境中植物可以通过改变资源分配的格局而适应环境的变化,获得较高的生物产量。但是,关于草原植物在生物量生产和资源分配上如何对异质性的生境做出响应迄今研究尚少。为此在中国科学院内蒙古草原生态系统定位研究站的长期围封样地(1983年围封),设计了氮素添加和刈割处理的小区实验,使植物处于不同的养分和干扰生境中。我们选择羊草(Leymus chinensis ,根茎禾草,群落优势种)、大针茅(Stipa grandis ,丛生禾草,群落优势种)、糙隐子草(Cleistogenes squarrosa , C4 植物,群落常见伴生种)、木地肤(Kochia prostrate ,藜科半灌木,群落常见伴生种)、猪毛菜(Salsola collina,藜科一年生植物,群落常见伴生种)为对象对这一问题进行了研究。同时,以1979 年围封的羊草样地为对照,选择了比邻的刈割草场,就草原植物对长期刈割干扰的响应策略进行了研究。结果显示: 1. 氮素添加使植物群落生物量显著提高,而且高氮生境下群落生物量增加的幅度最大。从季节动态看,植物群落生物量对氮素添加的响应存在滞后现象,在植物进入快速生长期后,氮素添加的效应日趋明显。 2. 不同植物种群对氮素添加的响应不同,按照植物种群生物量的变化可以分为三种类型:极其敏感型 、敏感型和不敏感型。极其敏感型代表植物是羊草,氮素添加后其种群生物量显著增加。敏感型代表植物是糙隐子草和猪毛菜,前者种群生物量在中氮生境下显著增加,后者种群生物量在低氮生境下显著增加。不敏感型代表植物是大针茅和木地肤,氮素添加后,二者的种群生物量均无显著变化。 3.从生物量向地上和地下器官的分配来看,添加氮素后,一年生植物猪毛菜向地上器官分配的生物量的比例均显著增加;多年生草本植物羊草、大针茅和糙隐子草向地上器官分配的比例均没有发生变化;多年生灌木木地肤在中氮生境下向地上器官的分配比例增加。从生殖分配来看,多年生的C3植物羊草和大针茅和一年生的C4植物猪毛菜的生殖分配格局相对稳定,均未因氮素的添加而发生显著改变。多年生C4植物糙隐子草和木地肤在低氮生境中生殖分配比例显著增加。 4. 不同时间刈割对草原群落生物量影响不同。在牧草快速生长期刈割,群落生物量显著降低,当季能恢复,但影响翌年群落水平的生物量生产;而在牧草生物量最大期刈割,当季难恢复,但对第二年的植物的生长影响较小。 5. 刈割对不同植物的影响存在显著差异:C4植物<C3植物,一年生植物<多年生植物,牧草快速生长期刈割<牧草生物量最大期刈割。 6. 面对不同时间的刈割干扰,草原植物的响应不同。在生物量向地上器官和地下器官分配方面:C3植物大针茅、羊草面对刈割干扰生物量分配分配格局相对稳定,变异较小;而C4植物的资源分配对刈割干扰响应敏感,因不同刈割时间其生物量分配格局不同。在生物量生殖分配方面:多年生植物(如羊草、大针茅、糙隐子草、木地肤)资源分配格局相对稳定,面对刈割干扰其生物量生殖分配格局无显著变化,而一年生植物猪毛菜对刈割干扰敏感,因刈割时间不同其生殖分配格局将随之发生变化。 7.长期刈割干扰下大针茅的种群生物量维持不变;而糙隐子草的种群生物量表现为显著增长的趋势。由于大针茅的株丛生物量显著降低,糙隐子草无显著变化,长期刈割干扰下两种植物种群生物量的维持或增加都是因为密度的显著提高。因此,密度调节是两种植物实现种群调节的重要机制。 8. 长期刈割干扰下大针茅的丛面积和单株分蘖数均无显著变化,表明大针茅非生殖株丛密度的增加不是以降低单个非生殖株丛的大小为代价的,而是通过减少生殖株丛的密度来实现的。而糙隐子草丛面积降低,但是单株分蘖数无显著变化,说明糙隐子草密度增加的过程中,单个株丛占据的营养面积减少了,但株丛的生长状况没有受到显著影响。 9.面对长期刈割干扰,两种植物对无性繁殖和有性繁殖过程采取了截然相反的调整策略。大针茅显著提高了非生殖株丛的密度和相对密度,显著降低了生殖株丛的相对密度,而且降低了对有性生殖过程的生物量分配的比例。糙隐子草显著增加了生殖株丛的密度和相对密度,而且增加了对有性生殖过程的生物量分配的比例。面对刈割干扰两个植物种在繁殖策略上的逆向调节,可能是它们在刈割干扰梯度上能够相互取代的重要原因。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

除植被冠层的光合作用之外,土壤的呼吸作用是陆地生态系统碳收支中最大的通量。土壤呼吸即使发生较小的变化也能显著地减缓或加剧大气中CO2浓度的增加,从而明显影响到全球气候变化。土壤呼吸速率变化与否以及变化的方向可以反映生态系统对环境变化的敏感程度和响应模式。尽管如此,土壤呼吸仍是一个为人们了解不多的生态系统过程。 草地生态系统是陆地生态系统的一个重要组成部分。针对草地土壤呼吸进行野外实验研究和相应方法论的探讨将对区域乃至全球碳源汇性质的准确估算具有重要的科学意义。然而,近几年来关于草地土壤呼吸的主要研究工作都集中在温带草原和部分热带草原,而针对高寒草甸生态系统土壤呼吸的研究报道还很少。 2008年4月至2009年4月期间,我分别在2008年6、8、10、12月和2009年2月和4月分6次对川西北的典型高寒草甸群落的土壤呼吸进行观测,分析了不同类型高寒草甸群落土壤呼吸的季节变化特征以及环境因子和放牧模式对其影响。主要研究结果如下: 1)该地区高寒草甸生态系统在生长季(6月~8月)土壤呼吸速率较大(6.07~9.30μmolCO2¡m-2¡s-1 ) , 在非生长季( 12 月~ 2 月) 较小( 0.16 ~0.49μmolCO2¡m-2¡s-1 ) 。土壤CO2 年累积最大释放量为3963 ~ 5730gCO2¡m-2¡yr-1,其中,生长季土壤CO2的释放量占年总释放量的85%~90%。非生长季占10%~15%。非生长季所占比例略小于冬季积雪覆盖地区的冬季土壤呼吸占年土壤呼吸量的比例(14%~30%)。温度,尤其地温,是影响该地区高寒草甸生态系统土壤呼吸速率的最主要环境因子。土壤呼吸速率与地上生物量和土壤水分之间没有显著相关性,但是土壤含水量过大会导致土壤呼吸速率下降。 2)在观测期内,草丘区的土壤呼吸显著高于对照区的土壤呼吸,其最大土壤呼吸速率为16.77μmolCO2¡m-2¡s-1,土壤CO2 年累积最大释放量为8145gCO2¡m-2¡yr-1,是对照区的近2 倍。由于草丘在高寒草甸中占有较大的面积比例(近30%),因此,它将对高寒草甸生态系统的碳循环起着重要的作用。 3)放牧模式不仅可以影响高寒草甸群落的土壤CO2 排放,而且还可以改变土壤呼吸的温度敏感性(Q10)。本研究表明,在生长季有长期放牧活动干扰时将会增加土壤向大气中释放二氧化碳的速度,促使土壤碳库中碳的流失。禁牧样地的土壤呼吸速率在刚禁牧时先迅速增大,随着禁牧时间的延长土壤呼吸速率将会下降。此外,与其它放牧模式相比,冬季放牧将高寒草甸群落土壤呼吸速率在生长季达到最大值的时间明显向后推迟。不同放牧模式下高寒草甸群落土壤呼吸的Q10 值大小顺序为:禁牧一年群落>冬季放牧群落>禁牧三年群落>夏季放牧群落>自由放牧群落。 4)基于呼吸室技术的观测方法中,测量前的剪草处理可以明显改变该地区高寒草甸群落的土壤温度和土壤呼吸速率。在生长季,剪草处理将使土壤呼吸速率的瞬时响应增加90%左右。由于剪草处理明显增加了剪草样方白天的土壤温度,而土壤温度与土壤呼吸之间存在着极显著的指数相关关系,因而剪草处理导致土壤呼吸速率迅速增加。因此,在高寒地区基于呼吸室技术观测的土壤呼吸应当进行校正。 综上所述,川西北高寒草甸生态系统土壤呼吸速率在生长季较高,而在非生长季较低。土壤温度是影响该地区土壤呼吸的最主要环境因子。在实验观测期,草丘区土壤呼吸速率显著高于对照区的,是对照区土壤呼吸速率的近2倍。由于测量前的剪草处理可以明显改变待测点的土壤呼吸速率,因此,应对在高寒地区基于呼吸室技术观测的土壤呼吸进行校正。 Soil respiration is the second largest component (less than plant phtotosynthesis) of carbon dioxide flux between terrestrial ecosystems and the atmosphere. A minor change in soil respiration rate can significantly slow down or accelerate the increase of atmospheric CO2 concentration that is closely related to global climatic change. In turn, the change in the flux direction and rate of soil respiration may indicate the elasticity and stability of ecosystems to global changes and human disturbance. However, soil respiration is still an ecosystem process that has been poorly understood. Grassland ecosystem is an important component of the terrestrial ecosystem. Accurately estimating the CO2 flux from soil to atmosphere in situ is the key to evaluating the carbon resource and sink regionally or globally. Despite of extensive studies on the temperate and tropic grasslands, the soil respiration of alpine meadows has not substantially been measured. In the current study, soil respiration was measured for an annual cycle from April, 2008 to April, 2009 for the alpine meadow in northwestern Sichuan Province of China to determine the seasonal variation of soil respiration for the typical plant communities. The results are shown as follows: 1) Large seasonal variation of soil respiration was observed in the alpine meadow. The rate of soil respiration was the greatest (6.07~9.30μmolCO2¡m-2¡s-1) in June and the smallest (0.16 ~ 0.49μmolCO2¡m-2¡s-1) occurred from December to February in the non-growing season. The total emission of soil CO2 was estimated as 3963~5730 gCO2¡m-2¡yr-1, 85%~90% of which was released during the growing season, and 10%~15% during the non-growing season which was slightly less than the ratio of winter and annual CO2 flux from soil. Temperature, particularly the soil temperature, was the major environmental factor regulating the soil respiration. Significant and positive relationships were not found between soil respiration and soil moisture and between soil respiration and plant above-ground biomass, but excessive soil water content would decrease in the rate of soil respiration. 2) The rate of soil respiration in grass hummock communities was up to 16.77μmolCO2¡m-2¡s-1, which was about twice as great as in the controls (communities located in low and even sites). Considering the large proportion (about 30% on average) of hummock area in the meadow, it can be concluded that the hummocks played an important role in the carbon cycling of the study ecosystem. 3) Grazing patterns affected the flux of CO2 emission and the temperature sensitivity of soil respiration (Q10) in the alpine meadow. Grazing during growing season increased the rate of soil respiration. The rate of soil respiration increased significantly immediately after the alpine meadow being fenced, but thereafter decreased. In addition, grazing in winter delayed the peak respiration rate relative to the non-grazing mode. The Q10 value was the largest in the non-grazed area for one year, and next came the area with grazing in winter, followed by the non-grazed area for three years, the area with grazing in summer, and the non-limited grazed area. 4) In the chamber-based techniques, clipping manipulation before each measurement increased the transient rate of soil respiration by about 90% in the summer of the alpine meadow. As increase in soil temperature at daytime in the clipped plots by clipping and the exponential relationship between soil respiration and temperature, clipping manipulation led to increase in the rate of soil respiration. This suggested that a correction should be done for the techniques if employed in alpine and cold regions. In summary, the rate of soil respiration in the alpine meadow was the greatest in June and the smallest occurred from ecember to February in the non-growing season. Soil temperature was the major environmental factor regulating the soil respiration. The rate of soil respiration in grass hummock communities was up to 16.77μmolCO2¡m-2¡s-1, which was about twice as great as in the controls. A correction should be done for the techniques if employed in alpine and cold regions, because of the effect of clipping manipulation on soil temperature and respiration.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

通过趾骨切片可以准确鉴定年龄,了解一个物种的最长寿命,也为我们研究确定一个物种的生长特点、性成熟期,以及一个地区一个物种的年龄结构、种群生态(Marnell,1998)和群落生态提供重要信息(Morrison,et a1.,2004)。 本论文使用骨骼鉴龄法对中国浙江省宁波市北仑瑞岩寺林场的镇海棘螈(Echinotriton chinhaiensis)雌性繁群进行了年龄结构研究。结果显示:第一次参加繁殖的年龄为3龄;繁群中数量占优势的是5龄、6龄。而在6龄以后参加繁殖的雌性个体数便开始随着年龄的增大而逐渐减少。参加繁殖的雌性年龄最大个体为8龄。平均年龄为5.13龄。同时对其年龄和头体长、体全长的相关性检验,发现其年龄与头体长和体全长不相关,镇海棘螈雌性的生长方式表现为性成熟后能量主要用于繁殖。 另外,对李子坪大凉疣螈(Tylototriton taliangensis) 雄性繁群进行了年龄结构研究。结果显示:大凉疣螈雄性第一次参加繁殖的年龄为4龄;繁群中数量占优势的是5龄、6龄、7龄。而在7龄以后参加繁殖的雄性个体数便开始随着年龄的增大而逐渐减少。参加繁殖的雄性中年龄最大的个体为10龄。平均年龄为6.7龄。对其年龄和头体长、体全长的相关性检验,发现其年龄与头体长和体全长不相关,大凉疣螈雄性生长特点也表现为性成熟后生长缓慢的特点。 研究材料方面,本文采用野外采样与标本馆标本相结合的方式获得了中国蝾螈科2个重要保护物种繁殖群体的剪(指)趾材料,使得建立于其上的年龄结构工作更加可靠、更加具有代表性。 此外,本论文讨论了镇海棘螈瑞岩寺种群繁殖总量年度间的差异及其产生原因。将1998、1999、2000、2008、2009年镇海棘螈(Echinotriton chinhaiensis) 瑞岩寺种群的繁殖量进行比较,发现虽然雌性平均窝卵数比较稳定,但繁殖总量小于1998、1999、2000年任何一年总产卵量的50%。对2008年镇海棘螈繁殖量大幅下降的原因分析发现, 2007年9、10月影响严重台风的两次强台风、瑞岩寺景区开发等因素可能是造成近年该种群繁殖量大幅下降的原因。而2008年初50年不遇的低温是否影响镇海棘螈的繁殖值得进一步追踪研究。2009年繁殖量较2008年没有明显的增长,可能是由于2007年的台风影响了其繁殖营养的积累。台风的影响可能存在滞后现象,对此有待进一步监测证明。 本研究首次对中国蝾螈科物种进行的年龄结构鉴定,为进一步了解中国蝾螈科动物的种群生态打下了坚实的基础。 Using skeletochronology, we can know the life span of a species, age of reaching sexual mature, and of course age structure, which are vital(Morrison,et a1.,2004). Skeletochronology was performed on Echinotriton chinhaiensis Ruiyansi female population. The result shows that: The oldest individuals were 8 years old and the youngest ones were 3 years old. Individuals of age class 5(39.13%) and 6(21.74%) were most numerous. The number of individuals participated in reproduction decreased with the increase of age after the sixth year. Average age is 5.13 years. There is no correlation between age and body size (SVL and TL). For female chinhai salamander, energy is devoted to reproduction after reaching sexual maturation. While using skeletochronology to study Tylototriton taliangensis Liziping male population, the oldest individuals is 10 years old, and the youngest ones is 4 years old. Individuals of the age class 5, 6, and 7 dominat this population. The number of individuals decrease with the increase of age also after the seventh year. Average age is 6.7 years old in this population. there is also no correlation between age and body size (SVL and TL).It turned out that T. taliangensis tend to grow slowly after reaching sexual maturation. In this thesis, specimens from both wild and museum were used to gain enough toe clipping samples. A big sample size guarantees the reliability of this study. In the meantime, E. chinhaiensis’s annual reproduction of the year 1998, 1999, 2000 ,2008,and 2009 was compared. The result shows there is a huge decline in E. chinhaiensis’s annual reproduction in 2008,even the egg clutch is very stable. After analyzing, it turned out the huge decline in 2008 was probably caused by typhoon in 2007, besides the effect of tourism development and cash crop planting. While the impact of extreme weather of 2008 on reproduction needs further investigation. In the year 2009, there is no obvious increase in annual reproduction. It maybe due to lasting impact of typhoon in 2007. It is the first age-structure study on these two Chinese salamanders. A solid foundation was laid for further population ecology study of these two species.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

genetics, such as: population size, reproduction, mating system, growth, development,genetic structure and systematics status; The main results are presented below: The seasonal variation of the operational sexual ratio of this animal was found in the field and the ration always bias the female in the breeding season. Aiming at this character and considering the distance of time and space of both sexual habitat in breeding season, we census female population first by toe-clipping mark-recapture method, then estimated the population size with the definitive sexual ratio. Up to now, this species was found only at the Beilun district of the Ningbo City. The population size of the Ruiyan Temple Forest Park approximates to 369. The status of this population is extremely endangered, so besides protecting this population at the original locality, we also suggested to breed the salamander in fenced locality and to hatch embryos artificially, and send metamorphosed juveniles back to nature. We can transfer some individuals to other similar habitats or breed them under artificial conditions for saving this species from extinction. The early developmental stage of the Chinhai salamander is the same as its relative species, E. andersoni. Their balanceres are poorly developed and disappear very early. Temperature and moisture significantly influence the embryonic development of the Chinhai salamander. The embryonic stage is approx. 29 days under room temperature. The hatchling grows in a logarithmic curve. The larvae stage in water is approx. 58- 88 days. Many factors influence the nomal development, including two aspects of internal and external. Due to these factors, the effective protected measures were presented in detail. The breeding migration of E. chinhaiensis takes place at late March~late April every year. This salamander's hatching rate is high, but the rate of hatchling migrating into water is low. The average effectiveness of all the nest sites is 36.7%. The maternal self-conservation was contrary to the reproductive success of the egg-laying strategy. In the strategy of egg-laying behavior, the first factor selected by the female was its self-conservation, the second is embryonic survival rate, and the last is rate of hatchling survival rate. The oviposition selection is significant for the survival of the larvae. Based on the analysis of the evolutionary process of reproductive behaviors nad egg-laying site selections of all genera of the family Salamandridae, we deduced that perhaps Echinotriton is a transitional type in the evolutionary process from water to land. Due to its location in the adaptive stage in the terrestrial evolution, Echinotriton chinhaiensis's terrestrial nest may be one of important reason that causes this species to be endangered. The genetic deversity analysis shows that although the population size of the Chinhai salamander is quite small compared to other Chinese salamandrid species, the genetic diversity of this population is not reduce remarkably. We explain this phenomena with the polygamy mating system of this species. The result of 4 families' parenthood determinations shows that the parenhood determination can be taken without any paternal information. The "children" of every female include rich genetic information from at least two "fathers". It implies that female Chinhai salamander mates more than once with different males in a breeding season. The molecular evidence, the behavioral observation evidences and the sperm evidence in the female cloaca proved that this species has a polygamy mating system. The kin recognition in the mating of adult salamander was first discussed. The taxonomic status and phylogenetic relationships of 12 species representing 6 genera in the family Salamandridae were studied using DNA fingerprinting. The results showed that the DNA fingerprinting. The results showed that the DNA fingerprinting patterns demonstrated rich genetic diversity and species diversity, and also revealed the taxonomic status and phylogenetic relationshipes of higher taxa to a certain extent. The results are highly consistent with those obtained from the studies based on the morphology, ecology, cytology and molecular biology. The compreshensive analysis indicate that Tylototrition hainanensis and T. wenxianensis should be valid species; Echinotriton should be a valid genus;Tylotortriton is a natural cluster; Tylotortriton asperrimus should be put in Tylototrition rather than in Echinotriton, Hypselotriton and Allomestriton are synonyms of Cynops and Paramesotriton, respectively. There are three main groups in Chinese salamandride: Cynops, Paramesotriton and Pachytrition from the first group, the species of the Tylototriton from the second, and E. chinhaiensis composes the third.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Although studies show that grazing and browsing by herbivores have marked effects on host plants, the mechanisms remain unclear. The objective of this study is to determine the effects of sheep saliva on host plant growth. Sheep saliva was manually applied to clipped plants of two different life forms, a semi-shrub, Artemisia frigida Willd., and a herbaceous species, Leymus chinensis (Trin.) Tzevel. The results showed that sheep saliva significantly enhanced aboveground net primary productivity (ANPP) and the ratio of ANPP to belowground net primary productivity (BNPP) for both species. This indicated that sheep saliva promotes aboveground compensatory growth and allocation of photosynthate to aboveground for both plant species. Sheep saliva stimulated only tillering of L. chinensis. Regardless of saliva application, clipping significantly decreased BNPP and plant height, but significantly increased the number of branches or tillers for both plant species. The relative growth rates (RGRs) on both species were significantly greater after clipping with saliva compared with control and clipping without saliva treatments. In addition, RGR of the herbaceous species L. chinensis was faster than that of the semi-shrub A. frigida after application of saliva. (c) 2006 Elsevier Ltd. All rights reserved.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

We investigated experimental warming and simulated grazing ( clipping) effects on rangeland quality, as indicated by vegetation production and nutritive quality, in winter-grazed meadows and summer- grazed shrublands on the Tibetan Plateau, a rangeland system experiencing climatic and pastoral land use changes. Warming decreased total aboveground net primary productivity ( ANPP) by 40 g . m(-2) . yr(-1) at the meadow habitats and decreased palatable ANPP ( total ANPP minus non- palatable forb ANPP) by 10 g . m(-2) . yr(-1) at both habitats. The decreased production of the medicinal forb Gentiana straminea and the increased production of the non- palatable forb Stellera chamaejasme with warming also reduced rangeland quality. At the shrubland habitats, warming resulted in less digestible shrubs, whose foliage contains 25% digestible dry matter ( DDM), replacing more digestible graminoids, whose foliage contains 60% DDM. This shift from graminoids to shrubs not only results in lower- quality forage, but could also have important consequences for future domestic herd composition. Although warming extended the growing season in non- clipped plots, the reduced rangeland quality due to decreased vegetative production and nutritive quality will likely overwhelm the improved rangeland quality associated with an extended growing season.Grazing maintained or improved rangeland quality by increasing total ANPP by 20 - 40 g . m(-2) . yr(-1) with no effect on palatable ANPP. Grazing effects on forage nutritive quality, as measured by foliar nitrogen and carbon content and by shifts in plant group ANPP, resulted in improved forage quality. Grazing extended the growing season at both habitats, and it advanced the growing season at the meadows. Synergistic interactions between warming and grazing were present, such that grazing mediated the warming- induced declines in vegetation production and nutritive quality. Moreover, combined treatment effects were nonadditive, suggesting that we cannot predict the combined effect of global changes and human activities from single- factor studies.Our findings suggest that the rangelands on the Tibetan Plateau, and the pastoralists who depend on them, may be vulnerable to future climate changes. Grazing can mitigate the negative warming effects on rangeland quality. For example, grazing management may be an important tool to keep warming- induced shrub expansion in check. Moreover, flexible and opportunistic grazing management will be required in a warmer future.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Synthesis efforts that identify patterns of ecosystem response to a suite of warming manipulations can make important contributions to climate change science. However, cross-study comparisons are impeded by the paucity of detailed analyses of how passive warming and other manipulations affect microclimate. Here we document the independent and combined effects of a common passive warming manipulation, open-top chambers (OTCs), and a simulated widespread land use, clipping, on microclimate on the Tibetan Plateau. OTCs consistently elevated growing season averaged mean daily air temperature by 1.0-2.0 degrees C, maximum daily air temperature by 2.1-7.3 degrees C and the diurnal air temperature range by 1.9-6.5 degrees C, with mixed effects on minimum daily air temperature, and mean daily soil temperature and moisture. These OTC effects on microclimate differ from reported effects of a common active warming method, infrared heating, which has more consistent effects on soil than on air temperature. There were significant interannual and intragrowing season differences in OTC effects on microclimate. For example, while OTCs had mixed effects on growing season averaged soil temperatures, OTCs consistently elevated soil temperature by approximately 1.0 degrees C early in the growing season. Nonadditive interactions between OTCs and clipping were also present: OTCs in clipped plots generally elevated air and soil temperatures more than OTCs in nonclipped plots. Moreover, site factors dynamically interacted with microclimate and with the efficacy of the OTC manipulations.These findings highlight the need to understand differential microclimate effects between warming methods, within warming method across ecosystem sites, within warming method crossed with other treatments, and within sites over various timescales. Methods, sites and scales are potential explanatory variables and covariables in climate warming experiments. Consideration of this variability among and between experimental warming studies will lead to greater understanding and better prediction of ecosystem response to anthropogenic climate warming.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Dissertação para obtenção do grau de Mestre em Engenharia Electrotécnica Ramo de Automação e Electrónica Industrial

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia de Redes de Comunicação e Multimédia

Relevância:

10.00% 10.00%

Publicador:

Resumo:

BACKGROUND AND PURPOSE: Surgical clipping of unruptured intracranial aneurysms (UIAs) has recently been challenged by the emergence of endovascular treatment. We performed an updated systematic review and meta-analysis on the surgical treatment of UIAs, in an attempt to determine the aneurysm occlusion rates and safety of surgery in the modern era. METHODS: A detailed protocol was developed prior to conducting the review according to the Cochrane Collaboration guidelines. Electronic databases spanning January 1990-April 2011 were searched, complemented by hand searching. Heterogeneity was assessed using I(2), and publication bias with funnel plots. Surgical mortality and morbidity were analysed with weighted random effect models. RESULTS: 60 studies with 9845 patients harbouring 10 845 aneurysms were included. Mortality occurred in 157 patients (1.7%; 99% CI 0.9% to 3.0%; I(2)=82%). Unfavourable outcomes, including death, occurred in 692 patients (6.7%; 99% CI 4.9% to 9.0%; I(2)=85%). Morbidity rates were significantly greater in higher quality studies, and with large or posterior circulation aneurysms. Reported morbidity rates decreased over time. Studies were generally of poor quality; funnel plots showed heterogeneous results and publication bias, and data on aneurysm occlusion rates were scant. CONCLUSIONS: In studies published between 1990 and 2011, clipping of UIAs was associated with 1.7% mortality and 6.7% overall morbidity. The reputed durability of clipping has not been rigorously documented. Due to the quality of the included studies, the available literature cannot properly guide clinical decisions.