848 resultados para Ecological succession


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Establishment of Pinus kesiya Roy. ex Gord. plantations in Thailand began in the 1960s by the Royal Forest Department. The aim was to reforest abandoned swidden areas and grasslands in order to reduce erosion and to produce timber and fuel wood. Today there are about 150, 000 ha of P. kesiya plantations in northern Thailand. Most of these plantations cannot be harvested due to a national logging ban. Previous studies have suggested that Pinus kesiya plantations posses a capability as a foster environment for native broadleaved tree species, but little is known about the extent of regeneration in these plantations. The general aim of the study was to clarify the extent of forest regeneration and interactions behind it in Pinus kesiya plantations of the Ping River basin, northern Thailand. Based on the results of this study and previous literature, forest management proposals were produced for the area studied. In four different pine plantation areas, a total of seven plantations were assessed using systematic data collection with clustered circular sample plots. Vegetation and environmental data were statistically analysed, so as to recognise the key factors affecting regeneration. Regeneration had occurred in all plantations studied. Regeneration of broadleaved trees was negatively affected by forest fire and canopy coverage. A high basal area of mature broadleaved trees affected the regeneration process positively. Forest fire disturbance had a strong effect also on plantation structure and species composition. Because of an unclear future forest management setting as regards forest laws in Thailand, a management system that enables various future utilisation possibilities and emphasises local participation is recommended for P. kesiya watershed platations of northern Thailand.

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"Literature cited": p. 491.

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In order to imitate the restoration succession process of natural water ecosystem, a laboratory microcosm system of constant-flow-restoration was designed and established. A eutrophycation lake, Lake Donghu, was selected as the subject investigated. Six sampling stations were set on the lake, among which the water of station IV was natural clean water, and others were polluted with different degrees. Polyurethane foam unit microbial communities, which had colonized in the stations for a month, were collected from these stations and placed in their respective microcosms, using clean water of station IV to gradually replace the water of these microcosms. In this process, the healthy community in clean water continuously replaced the damaged communities in polluted water, the restoration succession of the damaged communities was characterized by weekly determination of several functional and structural community parameters, including species number (S), diversity index (DI), community pollution value (CPV), heterotrophy index (HI), and similarity coefficient. Cluster analysis based on similarity coefficient was used to compare the succession discrepancies of these microbial communities from different stations. The ecological succession of microbial communities during restoration was investigated by the variable patterns of these parameters, and based on which, the restoration standards of these polluted stations were suggested in an ecological sense. That was, while being restored, the water of station 0 (supereutrophycation) should be substituted with natural clean water by 95%; station I (eutrophycation), more than 90%; station II (eutrophycation), more than 85%; station III (eutrophycation), about 85%; station V (mesoetitrophycation), less than 50%. The effects of the structural and functional parameters in monitoring and assessing ecological restoration are analyzed and compared. (C) 2007 Elsevier Ltd. All rights reserved.

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Les écosystèmes dunaires remplissent plusieurs fonctions écologiques essentielles comme celle de protéger le littoral grâce à leur capacité d’amortissement face aux vents et vagues des tempêtes. Les dunes jouent aussi un rôle dans la filtration de l’eau, la recharge de la nappe phréatique, le maintien de la biodiversité, en plus de présenter un attrait culturel, récréatif et touristique. Les milieux dunaires sont très dynamiques et incluent plusieurs stades de succession végétale, passant de la plage de sable nu à la dune bordière stabilisée par l’ammophile à ligule courte, laquelle permet aussi l’établissement d’autres herbacées, d’arbustes et, éventuellement, d’arbres. Or, la survie de ces végétaux est intimement liée aux microorganismes du sol. Les champignons du sol interagissent intimement avec les racines des plantes, modifient la structure des sols, et contribuent à la décomposition de la matière organique et à la disponibilité des nutriments. Ils sont donc des acteurs clés de l’écologie des sols et contribuent à la stabilisation des dunes. Malgré cela, la diversité et la structure des communautés fongiques, ainsi que les mécanismes influençant leur dynamique écologique, demeurent relativement méconnus. Le travail présenté dans cette thèse explore la diversité des communautés fongiques à travers le gradient de succession et de conditions édaphiques d’un écosystème dunaire côtier afin d’améliorer la compréhension de la dynamique des sols en milieux dunaires. Une vaste collecte de données sur le terrain a été réalisée sur une plaine de dunes reliques se trouvant aux Îles de la Madeleine, Qc. J’ai échantillonné plus de 80 sites répartis sur l’ensemble de ce système dunaire et caractérisé les champignons du sol grâce au séquençage à haut débit. Dans un premier temps, j’ai dressé un portait d’ensemble des communautés fongiques du sol à travers les différentes zones des dunes. En plus d’une description taxonomique, les modes de vie fongiques ont été prédits afin de mieux comprendre comment les variations au niveau des communautés de champignons du sol peuvent se traduire en changements fonctionnels. J’ai observé un niveau de diversité fongique élevé (plus de 3400 unités taxonomiques opérationnelles au total) et des communautés taxonomiquement et fonctionnellement distinctes à travers un gradient de succession et de conditions édaphiques. Ces résultats ont aussi indiqué que toutes les zones des dunes, incluant la zone pionière, supportent des communautés fongiques diversifiées. Ensuite, le lien entre les communautés végétales et fongiques a été étudié à travers l’ensemble de la séquence dunaire. Ces résultats ont montré une augmentation claire de la richesse spécifique végétale, ainsi qu’une augmentation de la diversité des stratégies d’acquisition de nutriments (traits souterrains lié à la nutrition des plantes, soit mycorhizien à arbuscule, ectomycorhizien, mycorhizien éricoide, fixateur d’azote ou non spécialisé). J’ai aussi pu établir une forte corrélation entre les champignons du sol et la végétation, qui semblent tous deux réagir de façon similaire aux conditions physicochimiques du sol. Le pH du sol influençait fortement les communautés végétales et fongiques. Le lien observé entre les communautés végétales et fongiques met l’emphase sur l’importance des interactions biotiques positives au fil de la succession dans les environnements pauvres en nutriments. Finalement, j’ai comparé les communautés de champignons ectomycorhiziens associées aux principales espèces arborescentes dans les forêts dunaires. J’ai observé une richesse importante, avec un total de 200 unités taxonomiques opérationnelles ectomycorhiziennes, appartenant principalement aux Agaricomycètes. Une analyse de réseaux n’a pas permis de détecter de modules (c'est-à-dire des sous-groupes d’espèces en interaction), ce qui indique un faible niveau de spécificité des associations ectomycorhiziennes. De plus, je n’ai pas observé de différences en termes de richesse ou de structure des communautés entre les quatre espèces hôtes. En conclusion, j’ai pu observer à travers la succession dunaire des communautés diversifiées et des structures distinctes selon la zone de la dune, tant chez les champignons que chez les plantes. La succession semble toutefois moins marquée au niveau des communautés fongiques, par rapport aux patrons observés chez les plantes. Ces résultats ont alimenté une réflexion sur le potentiel et les perspectives, mais aussi sur les limitations des approches reposant sur le séquençage à haut-débit en écologie microbienne.

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Les écosystèmes dunaires remplissent plusieurs fonctions écologiques essentielles comme celle de protéger le littoral grâce à leur capacité d’amortissement face aux vents et vagues des tempêtes. Les dunes jouent aussi un rôle dans la filtration de l’eau, la recharge de la nappe phréatique, le maintien de la biodiversité, en plus de présenter un attrait culturel, récréatif et touristique. Les milieux dunaires sont très dynamiques et incluent plusieurs stades de succession végétale, passant de la plage de sable nu à la dune bordière stabilisée par l’ammophile à ligule courte, laquelle permet aussi l’établissement d’autres herbacées, d’arbustes et, éventuellement, d’arbres. Or, la survie de ces végétaux est intimement liée aux microorganismes du sol. Les champignons du sol interagissent intimement avec les racines des plantes, modifient la structure des sols, et contribuent à la décomposition de la matière organique et à la disponibilité des nutriments. Ils sont donc des acteurs clés de l’écologie des sols et contribuent à la stabilisation des dunes. Malgré cela, la diversité et la structure des communautés fongiques, ainsi que les mécanismes influençant leur dynamique écologique, demeurent relativement méconnus. Le travail présenté dans cette thèse explore la diversité des communautés fongiques à travers le gradient de succession et de conditions édaphiques d’un écosystème dunaire côtier afin d’améliorer la compréhension de la dynamique des sols en milieux dunaires. Une vaste collecte de données sur le terrain a été réalisée sur une plaine de dunes reliques se trouvant aux Îles de la Madeleine, Qc. J’ai échantillonné plus de 80 sites répartis sur l’ensemble de ce système dunaire et caractérisé les champignons du sol grâce au séquençage à haut débit. Dans un premier temps, j’ai dressé un portait d’ensemble des communautés fongiques du sol à travers les différentes zones des dunes. En plus d’une description taxonomique, les modes de vie fongiques ont été prédits afin de mieux comprendre comment les variations au niveau des communautés de champignons du sol peuvent se traduire en changements fonctionnels. J’ai observé un niveau de diversité fongique élevé (plus de 3400 unités taxonomiques opérationnelles au total) et des communautés taxonomiquement et fonctionnellement distinctes à travers un gradient de succession et de conditions édaphiques. Ces résultats ont aussi indiqué que toutes les zones des dunes, incluant la zone pionière, supportent des communautés fongiques diversifiées. Ensuite, le lien entre les communautés végétales et fongiques a été étudié à travers l’ensemble de la séquence dunaire. Ces résultats ont montré une augmentation claire de la richesse spécifique végétale, ainsi qu’une augmentation de la diversité des stratégies d’acquisition de nutriments (traits souterrains lié à la nutrition des plantes, soit mycorhizien à arbuscule, ectomycorhizien, mycorhizien éricoide, fixateur d’azote ou non spécialisé). J’ai aussi pu établir une forte corrélation entre les champignons du sol et la végétation, qui semblent tous deux réagir de façon similaire aux conditions physicochimiques du sol. Le pH du sol influençait fortement les communautés végétales et fongiques. Le lien observé entre les communautés végétales et fongiques met l’emphase sur l’importance des interactions biotiques positives au fil de la succession dans les environnements pauvres en nutriments. Finalement, j’ai comparé les communautés de champignons ectomycorhiziens associées aux principales espèces arborescentes dans les forêts dunaires. J’ai observé une richesse importante, avec un total de 200 unités taxonomiques opérationnelles ectomycorhiziennes, appartenant principalement aux Agaricomycètes. Une analyse de réseaux n’a pas permis de détecter de modules (c'est-à-dire des sous-groupes d’espèces en interaction), ce qui indique un faible niveau de spécificité des associations ectomycorhiziennes. De plus, je n’ai pas observé de différences en termes de richesse ou de structure des communautés entre les quatre espèces hôtes. En conclusion, j’ai pu observer à travers la succession dunaire des communautés diversifiées et des structures distinctes selon la zone de la dune, tant chez les champignons que chez les plantes. La succession semble toutefois moins marquée au niveau des communautés fongiques, par rapport aux patrons observés chez les plantes. Ces résultats ont alimenté une réflexion sur le potentiel et les perspectives, mais aussi sur les limitations des approches reposant sur le séquençage à haut-débit en écologie microbienne.

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A Área de Proteção Ambiental de Massambaba concentra diversas formações vegetais com uma grande riqueza florística e endemismos. Infelizmente esta área está sujeita à ação antrópica tanto que alguns fragmentos se encontram degradados. Para recuperar ecologicamente esta vegetação é importante compreender os mecanismos de sucessão ecológica. Como se sabe pouco sobre interações entre plantas de restinga, e menos ainda sob o prisma da alelopatia (efeito negativo que uma planta exerce em outras, ao liberar metabólitos secundários para o seu entorno),objetivou-se a realização de ensaios biológicos com espécies nativas. Inicialmente determinamos as melhores condições de extração de metabólitos, e por fim realizamos bioensaios com 18 espécies (Allagoptera aenaria, Andira legalis, Byrsonima sericea, Clusia fluminensis, Couepia ovalifolia, Erythroxylum ovalifolium, Eugenia copacabanensis, Eugenia selloi, Garcinia brasiliensis, Guapira opposita, Maytenus obtusifolia, Myrsine parvifolia, Neomitranthes obscura, Ocotea notata, Pouteria caimito, Renvoizea trinii, Tocoyena bullata e Vitex megapotamica). A aplicação dos extratos foi sobrea germinação e ocrescimento inicial de sementes de alface. Para isso, folhas destas espécies foram coletadas sazonalmente na formação arbustiva aberta não inundável (fácies alta) na restinga de Massambaba para o preparo de extratos aquosos. Os extratos foram obtidos a através da secagem das folhas à60C para posterior maceração, aquecimento, diluição e filtração, obtendo-se as concentrações de 5 e 10% de concentração (peso/volume). Os parâmetros para avaliar a fitotoxidez foram:a porcentagem ea velocidade de germinação e o comprimento da raiz após sete dias de crescimento em placas de Petri umedecidas com os extratos. Além desses três parâmetros, foi utilizado o índice de efeito global, que transforma as três variáveis em um índice único e uma analise de agrupamento (distância euclidiana, método de Ward) para classificá-las em espécies de fraca, média ou alta fitotoxidez de acordo com o valor do índice. A inibição do crescimento foi observada em todas as espécies, e verificou-se diferenças sazonais significativas, com destaque no inverno. Isso sugere que as diferenças os entre níveis de fitotoxidez estejam correlacionada são ambiente e à genética. Se a ação inibitória das espécies com maior efeito alelopático for comprovada, novas estratégias podem ser elaboradas para a reintrodução em projetos de conservação ambiental

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Ao longo de quase cinco anos de trabalho, foi desenvolvido o Índice de Qualidade dos Municípios - Verde, pela Fundação CIDE. O trabalho buscou retratar as características da fragmentação florestal fluminense. Como um elemento para apoiar a gestão ambiental do território, o projeto identificou corredores ecológicos prioritários para a interligação de fragmentos florestais. A grande contribuição do trabalho, do ponto de vista conceitual, foi reorientar o debate acerca da fragmentação florestal no Estado do Rio de Janeiro. O projeto IQM - Verde apresentou, exaustivamente, lugares onde ocorreram perdas e ganhos de estoques de vegetação com porte arbóreo, num recorte por municípios, bacias hidrográficas e Unidades de Conservação. Existem importantes questões que foram levantadas e ainda aguardam maiores e melhores respostas. Uma delas é tentar explicar, a partir da ecologia de paisagens, quais são os mecanismos que facilitam ou dificultam o processo natural de sucessão florestal. A situação da sucessão florestal é completamente diferente de uma região para outra do Estado. No Noroeste do Estado existem indícios claros de retração e fragmentação dos remanescentes enquanto na região Serrana do Sul Fluminense aparecem sinais claros de recuperação e recomposição florestal. Novos conceitos de gestão ambiental procuram minimizar os efeitos decorrentes da fragmentação e do isolamento espacial das espécies. O aumento da conectividade através de corredores ecológicos entre unidades de conservação e até mesmo entre os fragmentos mais bem conservados é apontado por muitos pesquisadores como uma das formas mais eficazes de promover a manutenção dos remanescentes florestais - a longo prazo - e até mesmo promover a recuperação funcional de determinadas unidades ecológicas atualmente ilhadas. A atual geração de pesquisadores e gestores públicos está diante do problema do controle dos processos que desencadeiam a fragmentação florestal. Portanto, é urgente a necessidade de entender todas as consequências associadas ao processo de fragmentação florestal e, ao mesmo tempo, descobrir os efeitos inibidores deste complexo fenômeno que possui raízes físicas, naturais e sociais. O objetivo central da tese é, a partir de elementos da História das Mentalidades e da Teoria da Decisão, construir cenários de pressão antrópica sobre os remanescentes florestais e propor um programa possível de intervenção econômica, jurídica e política, denominado no presente estudo como bolsa floresta, capaz de aliviar o atual processo de fragmentação florestal.

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A National Frog Survey of Ireland is planned for spring 2011. We conducted a pilot survey of 25 water bodies in ten 0.25 km2 survey squares in Co. Mayo during spring 2010. Drainage ditches were the most commonly available site for breeding and, generally, two 100 m stretches of ditch were surveyed in each square. The restricted period for peak spawning activity renders any methodology utilizing only one site visit inherently risky. Consequently, each site was visited three times from late March to early April. Occurrence of spawn declined significantly from 72 % to 44 % between the first and third visit whilst the overall occurrence of spawn at all sites was 76 %. As the breeding season advanced, spawn either hatched or was predated and, therefore, disappeared. In those water bodies where spawning was late, however, greater densities of spawn were deposited than in those sites where breeding was early. Consequently, spawn density and estimated frog density did not differ significantly between site visits. Future surveys should nevertheless include multiple site visits to avoid biased estimation of species occurrence and distribution. Ecological succession was identified as the main threat present at 44 % of sites.

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We describe the career of John Birks as a pioneering scientist who has, over a career spanning five decades, transformed palaeoecology from a largely descriptive to a rigorous quantitative science relevant to contemporary questions in ecology and environmental change. We review his influence on students and colleagues not only at Cambridge and Bergen Universities, his places of primary employment, but also on individuals and research groups in Europe and North America. We also introduce the collection of papers that we have assembled in his honour. The papers are written by his former students and close colleagues and span many of the areas of palaeoecology to which John himself has made major contributions. These include the relationship between ecology and palaeoecology, late-glacial and Holocene palaeoecology, ecological succession, climate change and vegetation history, the role of palaeoecological techniques in reconstructing and understanding the impact of human activity on terrestrial and freshwater ecosystems and numerical analysis of multivariate palaeoecological data.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Studying the physical environment of a watershed is the basic condition for a successful planning of the riparian forest preservation, and for water production and conservation. The aims of the present study were to analyze and quantify the spatial and temporal evolution (1984 and 2010) using Landsat-5 satellite images of Cintra Stream sub-watershed, Botucatu, São Paulo State, Brazil, processed by the software IDRISI Andes, as well as to analyze the water quality through the parameters pH, EC, DO and BOD5 at 4 different sites in the years 1999, 2008 and 2009. Considering the 1076.48ha area of the sub-watershed, the pasture class of 1984 was reduced by 25.55% in 2010, resulting in an increase in the remaining classes. The most important class was native forest and reforestation since it had an increase of 5.08%, which indicates recovery of the riparian forest. Degraded areas were identified close to the inferior limit of the sub-watershed (P3 and P4), as well as local contamination (P1 and P2) with worsening of the water quality in the remaining sites in the periods 2008 and 2009. Recovery and management of the ecological succession of degraded areas and water quality monitoring at 1 and 2 sites will be necessary to reestablish the natural condition of the area studied.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Ecological restoration aims to restore the self-sustainability potential of degraded environments. The successional trajectory of areas in restoration may differ from the reference ecosystem on a number of factors, especially the disturbance history of the area and management techniques applied in order to reverse the degradation scenario. In this sense, the objective of this study was to characterize the dynamics of natural regeneration and the structure of the regenerating community in an area of ecological restoration for 25 years on the right bank of the Rio Grande in the Power Station in Camargos that belongs to the Companhia Energetica de Minas Gerais - CEMIG, Nazareno, MG, in order to identify the current state of environmental regeneration. In November 2014, there was the first community inventory of seedlings existing in regeneration subplots (2 x 2 m) within the inclusion criteria (height ≥ 10 cm and DBH <5 cm), divided into 44 subplots (11 plots) in two areas, one area in restoration (REF) and a fragment of native vegetation (FRAG). In October 2015, the second sampling was carried out, in which individuals were resampled and recruits and dead individuals quantified. The parameters abundance, floristic similarity, density, dominance, importance value, equability, richness and diversity were analyzed in both samples. The dynamics was evaluated for the number of individuals and basal area in the period of 2014-2015 and individuals distributed according to height. The history of usage area provoked different behavior between the study environments; the patterns of the FRAG and REF communities along the years allowed the distinction between environments and demonstrated great environmental diversity, with differences in the abundance of species, floristic similarity, richness, diversity, vertical structure and dynamics parameters. In the REF area, there was a considerable increase in the density of individuals along the years and the establishment of different species. In this sense, the evaluation of natural regeneration in REF has shown that resilience is gradually being resumed, a necessary condition to support the potential for environmental self-sustainability. However, given the disturbance history, it can be concluded that the environment moves to an alternative state, which is possibly different from that prior to degradation.