966 resultados para Hengduan Mountains
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O Vale do Paraíba passou por um conjunto de transformações espaciais guiadas pelo cultivo do café para exportação ao longo do século XIX. A história ambiental sugere que a natureza seja integrada à análise histórica elaborada por estudiosos do passado. Neste sentido, busca-se compreender a dinâmica de interação entre sociedade e ambiente natural através das técnicas utilizadas no cultivo do café no Vale do Paraíba fluminense no século XIX, com o objetivo de analisar os elementos que condicionaram o processo de estruturação desse cultivo no Vale, assim como o impacto dele resultante àquele ambiente natural. Procura-se ainda investigar de que maneira indivíduos daquela sociedade se posicionaram frente às técnicas utilizadas e perceberam as dinâmicas promovidas pela cultura cafeeira ao ambiente natural.
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Coherent ecological networks (EN) composed of core areas linked by ecological corridors are being developed worldwide with the goal of promoting landscape connectivity and biodiversity conservation. However, empirical assessment of the performance of EN designs is critical to evaluate the utility of these networks to mitigate effects of habitat loss and fragmentation. Landscape genetics provides a particularly valuable framework to address the question of functional connectivity by providing a direct means to investigate the effects of landscape structure on gene flow. The goals of this study are (1) to evaluate the landscape features that drive gene flow of an EN target species (European pine marten), and (2) evaluate the optimality of a regional EN design in providing connectivity for this species within the Basque Country (North Spain). Using partial Mantel tests in a reciprocal causal modeling framework we competed 59 alternative models, including isolation by distance and the regional EN. Our analysis indicated that the regional EN was among the most supported resistance models for the pine marten, but was not the best supported model. Gene flow of pine marten in northern Spain is facilitated by natural vegetation, and is resisted by anthropogenic landcover types and roads. Our results suggest that the regional EN design being implemented in the Basque Country will effectively facilitate gene flow of forest dwelling species at regional scale.
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A hipótese de doutoramento aqui proposta consiste na necessidade teórica de repensar o conceito de irresponsabilidade organizada, oriundo da obra do sociólogo alemão Ulrich Beck, a partir da realidade do Município de Teresópolis, localizado na Região Serrana do Estado do Rio de Janeiro, cenário de uma tragédia ocorrida em janeiro de 2011. Serão ainda considerados os debates envolvendo a revogação do segundo Código Florestal pela Lei 12.651/2012, especialmente os relativos às áreas de preservação permanente nos topos de morro, faixas marginais de proteção e encostas com declividade superior a 45 graus. A hipótese da presente tese é que o conceito de irresponsabilidade organizada seja repensado diante da necessidade de explicar a organização jurídica de riscos reconhecidos a partir de processos políticos. Inclui-se na hipótese a análise de situações nas quais, mesmo ante a existência de normas jurídicas validamente editadas e aplicáveis, persiste a omissão na gerência dos riscos por elas disciplinados. A pesquisa trabalhará com a análise crítica da teoria da sociedade de risco e do conceito em questão, considerando estudos, relatórios e demais documentos referentes à tragédia teresopolitana e à edição da atual legislação florestal.
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Background: In the present study we have assessed whether the Carpathian Mountains represent a genetic barrier in East Europe. Therefore, we have analyzed the mtDNA of 128 native individuals of Romania: 62 of them from the North of Romania, and 66 from South Romania. Results: We have analyzed their mtDNA variability in the context of other European and Near Eastern populations through multivariate analyses. The results show that regarding the mtDNA haplogroup and haplotype distributions the Romanian groups living outside the Carpathian range (South Romania) displayed some degree of genetic differentiation compared to those living within the Carpahian range (North Romania). Conclusion: The main differentiation between the mtDNA variability of the groups from North and South Romania can be attributed to the demographic movements from East to West (prehistoric or historic) that differently affected in these regions, suggesting that the Carpathian mountain range represents a weak genetic barrier in South-East Europe.
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[EN] The goal of this contribution is twofold: on the one hand, to review two relatively recent contributions in the field of Eskimo-Aleut historical linguistics in which it is proposed that Eskimo-Aleut languages are related genealogically to Wakashan (Holst 2004) and?/or Nostratic (Krougly-Enke 2008). These contributions can be characterized by saying that their authors have taken little care to be diligent and responsible in the application of the comparative method, and that their familiarity with the languages involved is insufficient. Eskimo-Aleut languages belong to a very exclusive group of language families that have been (and still are) used, sometimes compulsively, in the business of so-called “long-range comparisons”. Those carrying out such studies are very often unaware of the most basic facts regarding the philological and linguistic traditions of those languages, as a result of what mountains of very low quality works with almost no-relevancy for the specialist grow every year to the desperation of the scientific community, whose attitude toward them ranges from the most profound indifference to the toughest (and most explicit) critical tone. Since Basque also belongs to this group of “compare-with-everything-you-come- across” languages, it is my intention to provide the Basque readership with a sort of “pedagogical case” to show that little known languages, far from underrepresented in the field, already have a very long tradition in historical and comparative linguistics, i.e. nobody can approach them without previous acquaintance with the materials. Studies dealing with the methodological inappropriateness of the Moscow School’s Nostratic hypothesis or the incorrectness of many of the proposed new taxonomic Amerindian subfamilies (several of them involving the aforementioned Wakashan languages), that is to say, the frameworks on which Krougly-Enke and Holst work, respectively, are plenty (i.a. Campbell 1997: 260-329, Campbell & Poser 2008: 234-96), therefore there is no reason to insist once more on the very same point. This is the reason why I will not discuss per se Eskimo-Aleut–Wakashan or Eskimo-Aleut–Nostratic. On the contrary, I will focus attention upon very concrete aspects of Krougly-Enke and Holst´s proposals, i.e. when they work on “less ambitious” problems, for example, dealing with the minutiae of internal facts or analyzing certain words from the sole perspective of Eskimo-Aleut materials (in other words, those cases in which even they do not invoke the ad hoc help of Nostratic stuff). I will try to explain why some of their proposals are wrong, demonstrate where the problem lies, and fix it if possible. In doing so, I will propose new etymologies in an attempt at showing how we may proceed. The main difference between this and handbook examples lies in the reality of what we are doing: this is a pure etymological exercise from beginning to end. I will try to throw a bit of light on a couple of problematic questions regarding Aleut historical phonology, demonstrating how much work should be done at the lowest level of the Eskimo-Aleut pyramid; it is technically impossible to reach the peak of the pyramid without having completed the base. As far as Aleut is regarded, I will mainly profit not only from the use of the traditional philological analysis of Aleut (and, eventually, of Eskimo) materials, but also of diachronic typology, bringing into discussion what in my opinion seems useful, and in some cases I think decisive, parallels. It is worth noting that this paper makes up yet another part of a series of exploratory works dealing with etymological aspects of the reconstruction of Proto-Eskimo-Aleut, with special emphasis on Aleut (vid. i.a. Alonso de la Fuente 2006/2007, 2008a, 2008b, 2010a), whose main goal is to become the solid basis for an etymological dictionary of the Aleut language, currently in progress.
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Purpose. To review the proposed pathogenic mechanisms of age macular degeneration (AMD), as well as the role of antioxidants (AOX) and omega-3 fatty acids (omega-3) supplements in AMD prevention. Materials and Methods. Current knowledge on the cellular/molecular mechanisms of AMD and the epidemiologic/experimental studies on the effects of AOX and omega-3 were addressed all together with the scientific evidence and the personal opinion of professionals involved in the Retina Group of the OFTARED (Spain). Results. High dietary intakes of omega-3 and macular pigments lutein/zeaxanthin are associated with lower risk of prevalence and incidence in AMD. The Age-Related Eye Disease study (AREDS) showed a beneficial effect of high doses of vitamins C, E, beta-carotene, and zinc/copper in reducing the rate of progression to advanced AMD in patients with intermediate AMD or with one-sided late AMD. The AREDS-2 study has shown that lutein and zeaxanthin may substitute beta-carotene because of its potential relationship with increased lung cancer incidence. Conclusion. Research has proved that elder people with poor diets, especially with low AOX and omega-3 micronutrients intake and subsequently having low plasmatic levels, are more prone to developing AMD. Micronutrient supplementation enhances antioxidant defense and healthy eyes and might prevent/retard/modify AMD.
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[ES] El género Sabacon (Arachnida: Opiliones) tiene distribución holártica, y en la Península Ibérica se restringe a Pirineos y Cordillera Cantábrica. Se menciona la presencia de S.viscayanus en la Sierra Cebollera, a partir del hallazgo de una hembra, lo que constituye el primer registro al sur del Ebro. En este trabajo se ha determinado la subespecie a la que pertenece esa población gracias a la captura de un macho, que corresponde a Sabacon viscayanus viscayanus. Con los ejemplares de las colecciones (ZUPV y CRBA) se han redescrito las especies ibéricas y se ha descrito por primera vez el macho de S. franzi. A su vez, se han construido mapas de distribución de todas las especies con datos citados y de las colecciones propias.
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A evolução da margem continental do sudeste do Brasil tem sido discutida por diversos autores desde meados do século passado até os dias atuais, especialmente no contexto da origem e evolução dos escarpamentos e das bacias tafrogênicas. Buscou-se contribuir com novos dados sobre a evolução da área a partir da aplicação da termocronologia de baixa temperatura (U-Th)/He em apatita, que oferece uma sensibilidade significativa para registrar movimentações tectônicas na crosta superior. Foi possível obter idades em 107 cristais de apatita de 18 amostras do embasamento coletadas no perfil com orientação NW-SE, numa seção entre a Serra da Mantiqueira e o Gráben da Guanabara. As idades corrigidas variam entre 250,1 8,7 Ma e 43,5 1,9 Ma (2 σ) e as não corrigidas entre 174,13 3,03 Ma e 27,07 0,60 Ma (1 σ). O Neocretáceo, o Eocretáceo e o Paleoceno são os principais registros no conjunto de dados, em ordem de importância. No Neocretáceo, o intervalo entre 83,6 e 72,1 Ma (Campaniano) representa o maior destaque nos registros termocronológicos, embora os outros registros (Maastrichtiano e Santoniano) também estejam presentes e sejam importantes. As idades do Neocretáceo destacam a importância dos eventos tectonomagmáticos e soerguimento regional na história térmica dessa área, inclusive com idades (~86 Ma) atribuídas ao contexto de soerguimento da Serra do Mar. As idades do Eocretáceo indicam o registro de eventos térmicos mais antigos, vinculados à evolução pré-rifte. Já os dados do Paleoceno estariam associados ao evento de reativação responsável pela implantação do sistema de riftes continentais (~65 Ma) e as idades do Eoceno, restritas à borda de falha da bacia de Resende (49,7 Ma e 43,5 Ma), à reativação do sistema de riftes nessa área. A dispersão de idades foi interpretada como efeito dos danos de radiação já que muitos grãos apresentam correlação entre idade e concentração de urânio (eU). Os padrões de tempo-temperatura (t-T), definidos a partir dos modelos HeFTy calibrados para o modelo de difusão que considera os efeitos de danos de radiação nos cristais, registraram eventos de resfriamento rápido, os quais mostram correlação direta com episódios de reativação e soerguimento na margem continental e com registros nas bacias continentais e marginais. O padrão de aumento das idades com a elevação, assim como da costa em direção ao interior é observado, mas mostra-se alterado pela ocorrência de idades mais jovens associadas à complexa evolução dessa margem continental com desnivelamentos de blocos vinculados à tectônica pós-rift, numa situação que ressalta a influência dos episódios de reativação. As estimativas de denudação total variam entre 1,2 e 2,8 km. As taxas de erosão variam entre 15,2 e 35,3 m/Ma. A evolução da área indica não apenas a influência de um evento específico mas, possivelmente, uma combinação de episódios que se alternaram e/ou atuaram em conjunto em determinados períodos. Os eventos de reativação mais antigos, combinados com os mais recentes, exibem os seus remanescentes na paisagem (serras da Mantiqueira e do Mar e os grábens e bacias sedimentares) e assumem papel fundamental na evolução da área. Os registros de tais episódios podem ser observados nas histórias térmicas das rochas e nos depósitos correlativos nas bacias sedimentares marginais e intracontinentais.
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本论文包括两部分的内容,第一部分是秦岭苔类植物的区系研究,第二部分是中国剪叶苔属Herbertus的分类学修订。 秦岭位于我国的中部,东经104º30´~112º52´,北纬32º50´~34º45´N,约76 500 km2。它主要位于陕西省的南部地区,并包括了河南、甘肃和湖北的部分县、市。秦岭的最高峰是太白山,海拔3 767米。秦岭是长江和黄河的分水岭,也是我国温带和亚热带气候的过渡地带。 本研究包含了对自19世纪开始对秦岭苔藓植物的主要采集活动的回顾,和截止2008年以来对秦岭苔类和角苔类植物报道的总结和分析,且首次给出了一份秦岭地区详细的苔类植物的名录,并包括了各个种在秦岭地区的详细分布。根据目前的研究,现已知秦岭的苔类植物有226种(包括种下单位,以下同),其中角苔纲1科3属6种,苔纲30科59属220种;提出了1个新异名:Radula constricta Steph.被处理为Radula lindenbergiana Gottsche var. atypa Massalongo的异名;并提出了1个新组合Metzgeria pubescens var. kinabaluensis (Kuwah) F.X. Li & Y. Jia;发现秦岭新分布的苔类有78种。根据种数,秦岭地区苔类的优势科为光萼苔科(34种),其次为耳叶苔科(23种),裂叶苔科(23种)和羽苔科(19种)。 通过对这些种地理成分的统计,发现秦岭苔类的地理成分以北温带成分为主,占35.05%;其次是东亚成分占到31.78%,这两种地理成分在秦岭占了很大比例,高达66.83%。热带成分相对较少,有22种,占到10.29%。对于苔类来说,中国特有成分在秦岭地区较多,已知有34种,占到15.89%。说明秦岭地区苔类地理成分以温带为主,热带成分占少量比例,且秦岭地区的特有性也比较高。 文章第二部分是对中国剪叶苔属Herbertus S. Gray的分类学修订。剪叶苔属隶属于剪叶苔科,是一个古老而自然的类群,广泛分布于热带和南北温带地区。剪叶苔属植物由于其叶横生或近于横生,侧叶2裂,腹叶2裂或部分不对称3裂,并具假肋,叶细胞具大的三角体而明显区别于苔类的其它属。虽然这个属的概念比较清楚,但在属内种间的划分上存在较大的问题,是苔类中分类较混乱的一个类群。剪叶苔属种的概念多基于叶片形态,包括裂瓣的顶端细胞和假肋的形态及叶基盘边缘附属物的形态。但这些形态特征具很大的可塑性,性状不稳定,造成该属种的概念很模糊。目前全世界剪叶苔属约100余种。中国剪叶苔属的种类尚不确定,《中国苔藓志》中报道了中国有25种l亚种,但Juslen在2006年对亚洲剪叶苔属的修订中,提到中国分布的仅有6种。二者的研究中都存在有一些疏漏和不足之处,对有些种还有争议;且他们的研究中引证的标本都很少,不能全面反映中国剪叶苔属的种类和分布情况。 本研究着手于中国的剪叶苔属,从模式标本入手,从模式标本入手,结合对前人文献中引证标本的查阅,并检视了全国各大标本馆收藏的大量该属的普通标本,对于分类归并上有争议的种,采用扫描电镜和分子生物学的手段进行实验性的研究,对中国的剪叶苔属进行一个全面系统的分类学修订。期望通过本研究,明确中国剪叶苔属的种类和分布情况,为东亚乃至世界剪叶苔属的分类修订提供一份翔实的资料。共查阅了剪叶苔属26个种的模式标本,并检视了中科院北京植物研究所、华南植物园和深圳仙湖植物园馆藏的大量该属植物标本,约600余份。 通过本研究,提出2个新异名:将H. buchii Juslén和H. longispinus var calvs Massalongo处理为H. dicranus (Taylor) Trevis.;将樱井剪叶苔H. sakuraii (Warnst.) S. Hatt.(原并入H. dicranus)和H. minimus Horik.(原并入H. dicranus)重新提出;发现1个中国新分布:H. setigerus (Steph.) H. A. Mill.;确认中国的剪叶苔属17种1亚种:剪叶苔H. aduncus (Dicks.) Gray,剪叶苔纤细亚种H. aduncus subsp. tenuis (A. Evans) H. A. Mill.et E. B. Bohrer,H. armitanus (Steph.) H. A. Mill.,南亚剪叶苔H. ceylanicus (Steph.) Abeyw.,长角剪叶苔H. dicranus (Taylor) Trevis.,高氏剪叶苔H. gaochienii Fu,广东剪叶苔H. guangdongii P.J. Lin & Piippo,卵叶剪叶苔H. herpocladioides Scott. et. Miller,红枝剪叶苔H. huerlimannii Miller,细指剪叶苔H. kurzii (Steph.) H. A. Mill.,长肋剪叶苔H. longifissus Steph.,长刺剪叶苔H. longispinus Jack et Steph.,H. minimus Horik.,长茎剪叶苔H. parisii (Steph.) H. A. Mill.,多枝剪叶苔H. ramosus (Steph.) H. A. Mill.,樱井剪叶苔H. sakuraii (Warnst.) S. Hatt.,短叶剪叶苔H. sendtneri (Nees) Lindb.和H. setigerus (Steph.) H. A. Mill.。本研究还在扫描电镜下观察了H. armitanus、长角剪叶苔H. dicranus和多枝剪叶苔H. ramosus的孢子形态。对于剪叶苔属的修订,还需要更多模式标本的借阅,随着研究深入,剪叶苔属的种类可能会有大量的减少,中国剪叶苔属的种类也将会有一定的减少。
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At decadal period (10-20 years), dynamic linkage was evident between atmospheric low pressure systems over the North Pacific Ocean and circulation in a Pacific Northwest fjord (Puget Sound). As the Aleutian low pressure center shifts, storms arriving from the North Pacific Ocean deposit varying amounts of precipitation in the mountains draining into the estuarine system; in turn, the fluctuating addition of fresh water changes the density distribution near the fjord basin entrance sill, thereby constraining the fjord's vertical velocity structure. This linkage was examined using time series of 21 environmental parameters from 1899 to 1987. Covariation in the time series was evident because of the strong decadal cycles compared with long-term averages, interannual variability, and seasonal cycles.
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东灵山地区年均降水量659.7mm,单次降水以雨量小、雨强低的降水为主。水汽压(年均17.7mb)、相对湿度(年均66%)的季节变化呈现生长季高、冬季低的趋势。年均蒸发量1019.5mm;气温、风速、日照时间和水压与月蒸发量和日蒸量相关显著;气温、日照时间和水压分别在11-6月、7-8月和9-10月为决定蒸发量的首要因子。枯枝落叶层、土壤层湿度主要受前十日降水量和坡向影响。 植物体含水量生长季节较高,冬季较低;含水量随径级的增大而降低。六个灌木树种的平均含水量大小顺序为:毛榛(48.62%)最高荆条(36.32%)最低;七个乔木树种水分含量为油松,56.14%;蒙椴,54.19%;华北落叶松,52.91%;五角枫,43.64%;辽东栎,41.87%;棘皮桦,41.13%;大叶白腊,37.79%。几种植被类型的储水量为:辽东栎林,82.08mm;华北落叶松林,47.35mm;混交林,34.60mm;油松林,31.33mm;灌丛,12.40mm。各树种叶片日最低水势的季节均值为:辽东栎,-16.1bar;五角枫,-15.8bar;大叶白腊,-15.1bar;糠椴,-13.4bar;棘皮桦,-12.3bar;蒙椴,-12.2bar。叶片水势的日间变化均呈一“V”形曲线;光照在叶片水势的日间变化中起着决定性作用。 96年各树种平均单株树干茎流量为辽东栎,30.3mm(4.19%);华北落叶松,16.1mm(2.22%);油松,8.9mm(1.23%);棘皮桦,2.9mm(0.40%)。两个生长季各林分冠层的水量平衡为:辽东栎林,树干流茎量101.87mm(9.18%),穿透降水量823.08mm(74.15%),截留量185.05mm(16.67%);华北落叶松林,树干径流量66.88mm(6.03%),穿透降水量836.92mm(75.40%),截留量206.20mm(18.58);混交林,树干径流量50.13(4.52%),穿透降水量846.78mm(76.29%),截留量212.20mm(19.12%);油松林,树干径流量33.90mm(3.05%),穿透降水量934.88mm(84.22%),截留量141.22mm(12.72%)。多元回归分析表明,树干流茎量S与降水量P和前24小时降水量P_1呈显著正相关关系;穿透降水量T与降水量P和最大雨强M正相关显著。附加截留量与降水时间成正比。 枯枝落叶层的生物量为:油松林,25.56t/hm~2;华北落叶松林20.01t/hm~2;辽东栎林,8.31t/hm~2;混交林,7.98t/hm~2。枯枝落叶层的平均实际持水量和有效持水量均以油松林最大,其次是华北落叶松林,而混交林和辽东栎林较低;枯枝落叶层的实际持水量和有效持水量的季节变化分别与前十日降水量P10成正相关和负相关关系。枯枝落叶层的截留量为油松林>华北落叶松林>辽东栎林>混交林;油松林(145.632mm和90.800mm)混交林(61.816mm和54.504mm)。油松林、辽东栎林、混交林和华北落叶松林去除枯枝落叶层后,土壤入渗量比对照平均降低100mm以上;表层土壤含水量分别比对照土壤下降了6.26、18.26、15.06和15.07个百分点。地表径流量分别增加了,辽东栎林34.299mm(603%)和15.816mm(525%);油松林14.593mm(732%)和10.584mm(1321%);混交林12.004mm(181%)和7.275mm(364%);华北落叶松林3.555mm(118%),3.275mm(229%)。96年生长季,各土壤流失量分别增加了:油松林172.751t/hm~2(124倍);辽东栎林836.500t/hm~2(119倍);混交林172.499t/hm~2(47倍);华北落叶松林11.557t/hm~2(11倍)。表层土壤容重分别增加了:油松林15.0%和20.6%,辽东栎林18.4%和28.2%,混交林11.5%和38.5%,华北落叶松林4.3%和17.1%。 0-60cm深度土壤容重平均值的大小顺序为:草地>灌丛>辽东栎林>油松林>混交林>华北落叶松林;而土壤孔隙度的大小顺序为华北落叶松林>混交林>油松林>辽东栎林>灌丛>草地。两个生长季为土壤实际储水量的均值:油松林,124.45mm,78.62mm;辽东栎林,131.23mm,87.72mm;混交林,180.41mm,113.90mm;华北落叶松林,165.53mm,127.95mm;灌丛,172.50mm,89.81mm;草地,152.92mm,89.59 mm分别比干旱年份97年高出45.83mm、43.51mm、51.63mm、37.58mm、82.69mm和63.33mm。两个生长季的地表径流量为草地,30.930mm(2.79%);灌丛,16.321mm(147%);油松林,2.911mm(0.26%);辽东栎林,8.703mm(0.78%);混交林,8.625mm(0.78%);华北落叶松林,4.447mm(0.40%)。油松林、混交林和华北落叶松林地表径流量与降水量P(mm)和最大雨强(mm/h)正相关显著;而辽东栎林、灌丛和草地的地表径流量则与降水量P(mm)、平均雨强Q(mm/hr)和最大雨强M(mm/hr)三者之间呈显著正相关关系。与草地相比(1220.093kg/hm~2,100%),灌丛、辽东栎林、混交林、油松林和华北落叶松林96年生长季的土壤流失量分别降低了85.05%、94.26%、96.99%、98.86和99.14%。 降水量是影响小流域径流量时间变化的主要因素;南沟和马牙石沟96年的径流量分别是97年的8.19倍和7.87倍,而径流深(46.25mm,52.75mm)分别比97年(5.65mm,6.70mm)高出40.60mm和46.05mm。两个小流域由于面积的差异而使南沟两年的径流量分别比马牙石沟高出2773.136m~3(13.15%)和235.434m~3(8.79%)。96年和97年马牙石沟径流深比南沟高出6.5mm(14.05%)和1.05mm(18.58%)。在地处大陆性季风气候区的东灵山地区,用0.010m~3/min/km~2/hr能较好地分割小流域的洪峰和基流。在五次暴雨水文曲线中,马牙石沟的快速径流量分别比南沟高出25.00%到143.33%。五次洪水水文响应R的平均值南沟为0.218%,马牙石沟为0.404%;与海洋性气候地区相比,东灵山地区小流域的R值要低一到两个数量级。马牙石沟洪峰流量Qp的平均值为418.772L/min要比南沟(281.191L/min)大48.9%。东灵山地区小流域的洪水径流过程可分为三种类型。
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Wintertime precipitation in the mountains of the western United States during a warm or cool period has a pronounced influence on streamflow. During a warm year, streamflow at intermediate elevations responds more immediately to precipitation events; during a cold year, much of the discharge is delayed until the snow melts in spring and summer. Previous efforts at studying these extremes have been hampered by a limited number and length of observational analyses. In this study, we augment this limited observational record by analyzing a simplified general circulation model.
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Seasonal snow cover in the mountains of the Upper Colorado River Basin is a major source of water for a large portion of the southwestern United States. The extent and amount of this snowpack not only reflects changes in weather patterns and climate but also influences the general circulation through modification of the energy exchange between land and atmosphere. ... Satellite observations and remote sensing techniques can enhance the standard snowpack observations to provide the temporal and spatial measurements required for understanding the role of snow in the surface energy balance and improving the management of water resources.
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本文选择东灵山地区具有代表性的11种植物,研究了植物叶片养分元素动态特征以及各个层次物种、生活型和生境等对植物叶片养分元素再吸收的影响。主要结论如下: 1、不同物种间、以及相同物种在不同森林类型内的叶片C素含量变化程度较小;11个物种之间叶片N素养分浓度差很大,但各种植物叶片的N素含量的季节变化比较一致,大多数情况下表现为单峰型或双峰变化曲线;各种森林类型中11种植物叶片P的最高含量都出现在生长初期,以后开始下降。 2、在物种水平、养分再吸收是一种重要的养分保存机制,N素和P素再吸收率大约为50%,对这两种养分元素而言,相同生境下生长的不同植物种的养分再吸收率不同,存在显著差异,而同一植物种不同生境下养分再吸收率之间也存在差异,而S素的差异则不显著。 3、同一生活型在不同的森林类型中养分再吸收率差异不明显,同一森林类型中不同生活型的养分再吸收率差异也不明显;高养分再吸收率不是低养分环境所选择的优势性状,低养分环境中的物种主要通过延长叶片寿命和加强低养分浓度状况下的物质合成来适应低养分环境。 4、除了土壤pH值外,土壤容重、土壤有机质、土壤全氮、土壤阳离子交换量在三种生境下都表现出一定的差异性。华北落叶松林生境下的土壤养分含量较丰富,其次是落叶阔叶混交林,辽东栎林相对前二种生境其土壤养分相对低一些,但在三种生境之间养分元素再吸收率差异不显著,植物养分再吸收没有或微弱地受控于土壤养分获得的能力。