998 resultados para Vegetation succession
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1950s2%1990s50% 1) ;(P<0.05); 2)32;3-5;6 (Agriophyllum squarrosum)+ (Bassia dasyphylla)(Salix gordejevii)+ (Agropyron cristatum)(Artemisia intramongolica) + (Ulmus pumila var. sabulosa)+ 3) 384 > ; > > ; 4) 5) ;
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312,()>>,,362.29%673.33%574.71%930.00%;,,,1.42%5.59%;,,,,>0.5mm
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,,140 a,,(0~20 cm)(20~40 cm),0~20 cm,23.8%~534.9%9.3%~300.0%213.6%~521.5%40.4%~286.5%22.7%~232.2%3.2%~22.4%,,;(0.930/0.918);(0.804);(0.977/0.984);,0.996
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,20,8:,>>;,0-15 cm,8>>>>>>>;,,30~40,20,15~20,10~20,,,;,,3~5,,,,,,,,
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Here we present the first high-resolution multi-proxy analysis of a rich fen in the central-eastern European lowlands. The fen is located in the young glacial landscape of the Sta{ogonek}zki river valley. We investigated the fen's development pathways, asking three main questions: (i) what was the pattern and timing of the peatland's vegetation succession, (ii) how did land use and climate affect the succession in the fen ecosystem, and (iii) to what degree does the reconstructed hydrology for this site correlate with those of other sites in the region in terms of past climate change? Several stages of fen history were determined, beginning with the lake-to-fen transition ca. AD 700. Brown mosses dominated the sampling site from this period to the present. No human impact was found to have occurred until ca. AD 1700, when the first forest cutting began. Around AD 1890 a more significant disturbance took place-this date marks the clear cutting of forests and dramatic landscape openness. Deforestation changed the hydrology and chemistry of the mire, which was revealed by a shift in local plant and testate amoebae communities. We also compared a potential climatic signal recorded in the peat profile before AD 1700 with other sites from the region. 2013 John Wiley & Sons, Ltd.
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A radiocarbon-dated multiproxy palaeoenvironmental record from the Lower Thames Valley at Hornchurch Marshes has provided a reconstruction of the timing and nature of vegetation succession against a background of Holocene climate change, relative sea level movement and human activities. The investigation recorded widespread peat formation between c. 6300 and 3900 cal. yr BP (marine regression), succeeded by evidence for marine incursion. The multiproxy analyses of these sediments, comprising pollen, Coleoptera, diatoms, and plant and wood macrofossils, have indicated significant changes in both the wetland and dryland environment, including the establishment of Alnus (Alder) carr woodland, and the decline of both Ulmus (Elm; c. 5740 cal. yr BP) and Tilia (Lime; c. 5600 cal. yr BP, and 41603710 cal. yr BP). The beetle faunas from the peat also suggest a thermal climate similar to that of the present day. At c. 4900 cal. yr BP, Taxus (L.; Yew) woodland colonised the peatland forming a plant community that has no known modern analogue in the UK. The precise reason, or reasons, for this event remain unclear, although changes in peatland hydrology seem most likely. The growth of Taxus on peatland not only has considerable importance for our knowledge of the vegetation history of southeast England, and NW Europe generally, but also has wider implications for the interpretation of Holocene palaeobotanical records. At c. 3900 cal. yr BP, Taxus declined on the peatland surface during a period of major hydrological change (marine incursion), an event also strongly associated with the decline of dryland woodland taxa, including Tilia and Quercus, and the appearance of anthropogenic indicators.
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The results of an integrated geoarchaeological and palaeoecological pilot study of a prehistoric agricultural terrace and nearby mire basin are presented. They reveal two stages of terrace construction for the cultivation of Zea mays during the Middle Horizon (615695 AD) and late, Late Intermediate Period (12001400 AD). These stages were strongly associated with evidence for vegetation succession, destabilisation and erosion of the surrounding landscape, and changes in mire surface wetness. The reasons for agricultural terrace abandonment and/or reconstruction are uncertain, with only circumstantial evidence for climatically induced agricultural change.
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Radiocarbon-dated palaeoecological records from the upland zone of the northern Apennines spanning the Mid-Late Holocene (last 7000 years) have been evaluated using established criteria for detecting anthropogenic impact on the landscape and environment. The integrated palaeoecological records across the study area collectively indicate human interference with natural vegetation succession and landscape modification from at least the Middle Neolithic. These activities resulted in the progressive decline of Abies, Ulmus, Fraxinus and Tilia, and the spread of Fagus, from 7000 cal BP, accompanied at various times by evidence for biomass burning, soil erosion, the expansion of shrubland and herbaceous taxa, and the possible cultivation of Olea, Juglans and Castanea. Comparison of these data with the archaeological scheme for the region, and the climate history of the central-western Mediterranean, has revealed that the palaeoecological records broadly support the archaeological evidence, but suggest that several key vegetation changes also coincide with important periods of climate change, especially at 78005000 cal BP.
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An enhanced radiocarbon-dated pollen-stratigraphical record from Rovegno (Liguria, 812m asl), northern Apennines (Italy), has provided a history of vegetation succession from before 17,056-16,621 cal yrs BP to the present day. The record indicates the transition from open Pinus woodland to Artemisia dominated grassland, and finally Juniperus shrubland during the late Wrm. This is succeeded by Betula and Pinus woodland, and the expansion of thermophilous taxa, namely Abies, Corylus and Quercus during the Late Wrm Lateglacial Interstadial. The Younger Dryas is possibly represented by an increase in Betula and Artemisia. During the early Holocene, mixed coniferous-deciduous woodland is dominant with Quercus, as well as Abies, Fagus and Corylus. Fagus woodland becomes established sometime before 6488-6318 cal yrs BP, but never becomes a major component of the woodland cover. Throughout the middle Holocene, Abies woodland fl uctuates, with marked declines between 6488-6318 cal yrs BP and 5287-4835 cal yrs BP, although the cause remains uncertain. Finally, the paper evaluates the application of non-pollen palynomorphs, especially coprophilous fungal spores, at Prato Spilla A (Emilia Romagna) and concludes that greater caution must be used when interpreting middle Holocene human activity based upon pollen data alone
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Fire influences the distribution of fauna in terrestrial biomes throughout the world. Use of fire to achieve a mosaic of vegetation in different stages of succession after burning (i.e., patch-mosaic burning) is a dominant conservation practice in many regions. Despite this, knowledge of how the spatial attributes of vegetation mosaics created by fire affect fauna is extremely scarce, and it is unclear what kind of mosaic land managers should aim to achieve. We selected 28 landscapes (each 12.6 km2) that varied in the spatial extent and diversity of vegetation succession after fire in a 104,000 km2 area in the semiarid region of southeastern Australia. We surveyed for reptiles at 280 sites nested within the 28 landscapes. The landscape-level occurrence of 9 of the 22 species modeled was associated with the spatial extent of vegetation age classes created by fire. Biogeographic context and the extent of a vegetation type influenced 7 and 4 species, respectively. No species were associated with the diversity of vegetation ages within a landscape. Negative relations between reptile occurrence and both extent of recently burned vegetation (≤10 years postfire, n = 6) and long unburned vegetation (>35 years postfire, n = 4) suggested that a coarse-grained mosaic of areas (e.g. >1000 ha) of midsuccessional vegetation (11–35 years postfire) may support the fire-sensitive reptile species we modeled. This age class coincides with a peak in spinifex cover, a keystone structure for reptiles in semiarid and arid Australia. Maintaining over the long term a coarse-grained mosaic of large areas of midsuccessional vegetation in mallee ecosystems will need to be balanced against the short-term negative effects of large fires on many reptile species and a documented preference by species from other taxonomic groups, particularly birds, for older vegetation.
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Os quirpteros representam 25 % da mastofauna mundial. So os mamferos neotropicais mais diversificados e abundantes. A Amaznia brasileira apresenta cerca de 128 espcies de morcegos registradas. Eles possuem uma grande variabilidade morfolgica, a qual os permite ocupar diferentes nichos trficos no ecossistema. So muito importantes para a manuteno e regenerao dos ecossistemas em que vivem. So eficientes na disperso de sementes, polinizao e no controle biolgico de insetos e constituem timos bioindicadores do estado e das dinmicas sofridas por esses ecossistemas. O presente estudo objetivou caracterizar a quiropterofauna de uma regio da Floresta Nacional do Tapajs, Par, Brasil, em reas de floresta primria, capoeira e de um experimento de corte seletivo de madeira. O nvel de impacto sobre a comunidade de morcegos desse manejo e da rea de capoeira foi comparado aos testemunhos de mata primria em cada habitat e em seus micro-habitats, ou fisionomias: matrizes de sub-bosques, clareiras e ptios de armazenamento de madeira. A comparao se deu atravs de anlises de distribuio, diversidade, abundncia, nmero de espcies e densidade das guildas. Foram amostradas 55 espcies, a maioria frugvoras, representantes de seis famlias. Ao comparar o nmero de espcies e a diversidade, as reas de explorao exibem algum impacto, mas no to acentuado como as reas de capoeira. As amostras sugerem que a vegetao secundria proporciona uma maior densidade de quirpteros na comparao entre habitats. Mas poucas espcies so favorecidas por esta estrutura de vegetao. As guildas mais favorecidas nesta vegetao so de morcegos frugvoros/onvoros e insetvoros areos. A comparao entre fisionomias sugere que os quirpteros de sub-bosque evitam espaos abertos na vegetao. Os processos de sucesso aqui observados apresentam dinmicas que necessitam de acompanhamento peridico, para a formulao de um modelo mais prximo da realidade.
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Poucos estudos tm considerado a colonizao pela fauna em reas reflorestadas aps minerao. Para determinar os padres de colonizao por anfbios e lagartos de reas de reflorestamento em Porto Trombetas, Par, foram examinadas a composio, riqueza e abundncia de espcies, e as caractersticas biolgicas de anfbios e lagartos que ocupam reas reflorestadas. Tambm foi avaliado o efeito da estrutura da vegetao e da distncia da floresta nativa sobre a comunidade de anfbios dos reflorestamentos. Anfbios e lagartos foram amostrados ao longo de oito campanhas em oito reas de reflorestamento e quatro reas de floresta nativa atravs de procura ativa e com a utilizao de poas artificiais para a reproduo de anfbios. Foram registradas 20 espcies de anfbios e 20 espcies de lagartos, sendo 14 espcies de anfbios e 11 de lagartos em reflorestamentos e 19 espcies de anfbios e 16 de lagartos em floresta nativa. Entre os anfbios, Leptodactylus sp., Osteocephalus oophagus e Allobates femoralis foram as espcies mais abundantes nos dois ambientes e entre os lagartos, Gonatodes humeralis e Leposoma guianense foram as espcies mais abundantes em reflorestamentos e floresta nativa, respectivamente. Espcies de anfbios de reproduo terrestre ou que utilizam pequenos corpos dgua temporrios para a desova e lagartos arborcolas foram os grupos mais abundantes nos reflorestamentos. Espcies fossoriais e semifossoriais de anfbios e lagartos de liteira foram os principais grupos ausentes nos reflorestamentos, sugerindo que o atual estgio da sucesso da vegetao ainda no oferece microhbitats apropriados para algumas espcies. A riqueza de espcies de anfbios foi maior em reas com maior cobertura do dossel. reas com maior cobertura de dossel tiveram maior abundncia de Leptodactylus sp., Osteocephalus oophagus e Allobates femoralis. Apenas quatro espcies de anfbios utilizaram as poas artificiais para desova e no houve relao significativa do nmero de espcies que utilizaram estas poas com a distncia para a floresta nativa ou com a cobertura do dossel. Osteocephalus oophagus desovou em poas a maiores distncias e A. femoralis em poas mais prximas em relao floresta nativa. Os resultados evidenciam que a fauna de anfbios e lagartos nas diferentes reas de reflorestamento um subconjunto da fauna da floresta nativa, e compreendem espcies florestais que indicam a importncia relativa destas reas para a conservao da fauna local.
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Background Meadows are regularly mown in order to provide fodder or litter for livestock and to prevent vegetation succession. However, the time of year at which meadows should be first mown in order to maximize biological diversity remains controversial and may vary with respect to context and focal taxa. We carried out a systematic review and meta-analysis on the effects of delaying the first mowing date upon plants and invertebrates in European meadowlands. Methods Following a CEE protocol, ISI Web of Science, Science Direct, JSTOR, Google and Google Scholar were searched. We recorded all studies that compared the species richness of plants, or the species richness or abundance of invertebrates, between grassland plots mown at a postponed date (treatment) vs plots mown earlier (control). In order to be included in the meta-analysis, compared plots had to be similar in all management respects, except the date of the first cut that was (mostly experimentally) manipulated. They were also to be located in the same meadow type. Meta-analyses applying Hedgesd statistic were performed. Results Plant species richness responded differently to the date to which mowing was postponed. Delaying mowing from spring to summer had a positive effect, while delaying either from spring to fall, or from early summer to later in the season had a negative effect. Invertebrates were expected to show a strong response to delayed mowing due to their dependence on sward structure, but only species richness showed a clearly significant positive response. Invertebrate abundance was positively influenced in only a few studies. Conclusions The present meta-analysis shows that in general delaying the first mowing date in European meadowlands has either positive or neutral effects on plant and invertebrate biodiversity (except for plant species richness when delaying from spring to fall or from early summer to later). Overall, there was also strong between-study heterogeneity, pointing to other major confounding factors, the elucidation of which requires further field experiments with both larger sample sizes and a distinction between taxon-specific and meadow-type-specific responses.
