953 resultados para plant communities
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Soilla on merkittv rooli ilmastonmuutoksen hillitsemisess suuren hiilivarastonsa sek ekosysteemin ja ilmakehn vlisen kaasunvaihdon ansiosta. Ilmastonmuutoksen ennustetaan vaikuttavan suokasvillisuuteen ja suon toimintaan epsuorasti. Vedenpinnan ennustetaan laskevan 1421 cm johtuen kasveista ja avoimilta pinnoilta tapahtuvan haihdunnan lisntymisest lmptilan noustessa, mikli sadanta ei lisnny. Aiemmat vedenpinnan laskun jlkeist kasvillisuutta seuranneet tutkimukset ovat osoittaneet, ett putkilokasvit hytyvt alhaisemmasta vedenpinnan tasosta ja ett kuljuun sopeutuneet rahkasammalet krsivt kuivuneista oloista. Kasvillisuuden runsaussuhteiden muuttumisen lisksi kasviyhteisjen monimuotoisuus vhenee. Erityisen herkki vedenpinnan laskulle ovat olleet vlipinta- ja kuljurahkasammalet ja sarat. Funktionaalisten kasviryhmien vasteiden selvittmiksesi kytettiin BACI (before-after-control-impact) tutkimusotetta. Tutkimuksessa oli kolme verrokkialaa ja kolme ksittelyalaa, joissa vedenpintaa oli laskettu 1421 senttimetriin. Lisksi vertailukohdaksi tutkimuksessa oli mukana kolme alaa, joissa oli tehty metsojitus n. 50 vuotta sitten. Nm toistot sijaitsivat meso-, oligo ombrotrofisilla suotyypeill Oriveden Lakkasuolla. Kasvillisuus kartoitettiin ja vedenpinnat mitattiin aloilta ennen ksittely vuonna 2000 sek vuosina 20012003 ja 2009. Aineisto analysoitiin TWINSPAN- (PC-Ord), PRC ja DCA (CANOCO)-monimuuttujamenetelmill. Tulokset osoittivat, ett verrokki- ja ksittelyalat olivat samanlaisia lhtkohdiltaan, joten niit voitiin ksittelyn jlkeen verrata toisiinsa. Kasvillisuuden rakenne vaihteli vuosien vlill mys verrokkialoilla, mik osoittaa kasvien sopeutumiskyvyn muuttuviin soloihin (lmptila, sademr). Vuosi 2003 erottui tutkimuksessa alhaisella vedenpinnantasolla, mutta toisaalta mys ainavihantien varpujen suuren peittvyyden osalta. Vuoteen 2009 menness kasvillisuuden erityisesti sarojen peittvyys vheni. Ravinteikkaimmilla toistoilla kasvillisuuden vasteet vaikuttivat olevan vahvemmat kuin vhravinteisilla toistoilla. Kasviryhmist kulju- ja vlipintasammalilla oli vahvimmat vasteetvedenpinnan laskuun ja mtslajeilla heikoimmat. Tulosten mukaan kasviryhmien vasteet vaihtelevat riippuen tarkasteltavasta aikajaksosta: ensimmiset kolme vuotta ksittelyn jlkeen suo oli hiritilassa ja vasta sen jlkeen kasvillisuus sopeutui muuttuneisiin oloihin.
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1. Resilience-based approaches are increasingly being called upon to inform ecosystem management, particularly in arid and semi-arid regions. This requires management frameworks that can assess ecosystem dynamics, both within and between alternative states, at relevant time scales. 2. We analysed long-term vegetation records from two representative sites in the North American sagebrush-steppe ecosystem, spanning nine decades, to determine if empirical patterns were consistent with resilience theory, and to determine if cheatgrass Bromus tectorum invasion led to thresholds as currently envisioned by expert-based state-and-transition models (STM). These data span the entire history of cheatgrass invasion at these sites and provide a unique opportunity to assess the impacts of biotic invasion on ecosystem resilience. 3. We used univariate and multivariate statistical tools to identify unique plant communities and document the magnitude, frequency and directionality of community transitions through time. Community transitions were characterized by 37-47% dissimilarity in species composition, they were not evenly distributed through time, their frequency was not correlated with precipitation, and they could not be readily attributed to fire or grazing. Instead, at both sites, the majority of community transitions occurred within an 8-10year period of increasing cheatgrass density, became infrequent after cheatgrass density peaked, and thereafter transition frequency declined. 4. Greater cheatgrass density, replacement of native species and indication of asymmetry in community transitions suggest that thresholds may have been exceeded in response to cheatgrass invasion at one site (more arid), but not at the other site (less arid). Asymmetry in the direction of community transitions also identified communities that were at-risk' of cheatgrass invasion, as well as potential restoration pathways for recovery of pre-invasion states. 5. Synthesis and applications. These results illustrate the complexities associated with threshold identification, and indicate that criteria describing the frequency, magnitude, directionality and temporal scale of community transitions may provide greater insight into resilience theory and its application for ecosystem management. These criteria are likely to vary across biogeographic regions that are susceptible to cheatgrass invasion, and necessitate more in-depth assessments of thresholds and alternative states, than currently available.
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Invasive species, local plant communities and invaded ecosystems change over space and time. Quantifying this change may lead to a better understanding of the ecology and the effective management of invasive species. We used data on density of the highly invasive shrub Lantana camara (lantana) for the period 1990-2008 from a 50 ha permanent plot in a seasonally dry tropical forest of Mudumalai in southern India. We used a cumulative link mixed-effects regression approach to model the transition of lantana from one qualitative density state to another as a function of biotic factors such as indicators of competition from local species (lantana itself, perennial grasses, invasive Chromolaena odorata, the native shrub Helicteres isora and basal area of native trees) and abiotic factors such as fire frequency, inter-annual variability of rainfall and relative soil moisture. The density of lantana increased substantially during the study period. Lantana density was negatively associated with the density of H. isora, positively associated with basal area of native trees, but not affected by the presence of grasses or other invasive species. In the absence of fire, lantana density increased with increasing rainfall. When fires occurred, transitions to higher densities occurred at low rainfall values. In drier regions, lantana changed from low to high density as rainfall increased while in wetter regions of the plot, lantana persisted in the dense category irrespective of rainfall. Lantana seems to effectively utilize resources distributed in space and time to its advantage, thus outcompeting local species and maintaining a population that is not yet self-limiting. High-risk areas and years could potentially be identified based on inferences from this study for facilitating management of lantana in tropical dry forests.
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Long term forest research sites in India, going by different names including Linear Tree Increment Plots, Linear Increment Plots, Linear Sample Plots and Permanent Preservation Plots, cover diverse plant communities and environmental conditions. Presently, some of these long-term observational studies are functional, some are disturbed and others have almost been lost. The accumulated data will become increasingly important in the context of environmental modelling and climate change, especially if the plots and data can be maintained and/or revived. This contribution presents the history and current state of forest research plots in India, including details of locations and re-measurements. We provide a brief introduction of the National Forest Inventory (NFI), Preservation Plots in natural forests, the 50-ha Mudumalai Forest Dynamics Plot as part of the Centre for Tropical Forest Science and Smithsonian Institution Global Earth Observatories network (CTFS-SIGEO), and research plots established in plantations for tree growth studies and modelling. We also present some methodological details including assessment and analysis for two types of observational studies, the Tree Count Plots (TCP) and Tree Re-measurement Plots (TRP). Arguments are presented in favour of enumeration and analysis methods which are consistent with current approaches in forest ecological research. (c) 2013 Elsevier B.V. All rights reserved.
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Termites, herbivores and fire are recognized as major guilds that structure woody plant communities in African savanna and woodland ecosystems. An understanding of their interaction is crucial to design appropriate management regimes. The aim of this study was to evaluate the long-term impacts of herbivore, fire and termite activities on regeneration of trees. Permanent experimental quadrats were established in 1992 in the Sudanian woodland of Burkina Faso subjected to grazing by livestock and annual early fire and the control. Within the treatment quadrats, an inventory of the woody undergrowth community was conducted on termitaria occupied by Macrotermes subhyalinus, extended termitosphere (within 5 m radius from the mound base) and adjacent area (beyond 5 m from the mound base). Hierarchical analysis was performed to determine significant differences in species richness, abundance and diversity indices among vegetation patches within fire and herbivory treatments. Grazed quadrats had significantly (P < 0.001) more species and stem density of woody undergrowth than non-grazed quadrats but maintained similar level of species richness and stem density of woody undergrowth on termitaria. There were not significant differences (P>0.05) in species richness and stem density between burnt and unburnt quadrats. Termitaria supported a highly diverse woody undergrowth with higher stem density than either the extended termitosphere or rest of quadrats. The density of woody undergrowth was significantly related with mature trees of selected species on termitaria (R-2 = 0.593; P<0.001) than that on the extended termitosphere (R-2 = 0.333; P<0.001) and adjacent area (R-2 = 0.197; P<0.001). It can be concluded that termites facilitate the regeneration of woody species while grazing and annual early fire play a minor role in the regeneration of woody species. The current policy that prohibits grazing should be revised to accommodate the interests of livestock herders. (C) 2014 Elsevier GmbH. All rights reserved.
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To assess the potential for monoecious hydrilla ( Hydrilla verticillata (L.f.) Royle) to invade existing aquatic plant communities, monoecious hydrilla was grown in mixtures with American pondweed ( Potamogeton nodosus Poiret). When grown with hydrilla from axillary turions, American pondweed was a stronger competitor. When grown with hydrilla from tubers, American pondweed was equally as strong a competitor as hydrilla.
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Anlisis de los pastos meso-xerfitos del centro norte de Espaa. El objetivo es conocer la posible relacin entre composicin florstica y los atributos de las plantas. Tratamiento de datos y analsis estadsticos que dan como resultado relaciones numricas entre los grupos obtenidos en la clasificacin y los atributos de las especies. El documento est escrito en Castellano
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Os afloramentos rochosos apresentam flora peculiar, sendo constitudos de habitats nicos que podem representar barreira para muitas espcies devido s suas condies ambientais diferenciadas do entorno. O Estudo desse tipo de rea pode fornecer informaes relevantes sobre o processo evolutivo e distribuio das espcies que ali ocorrem. Esta pesquisa teve como objetivos gerar maiores informaes sobre ecologia, florstica e conservao de comunidades de moitas em quatro pes-de-acar do Estado do Rio de Janeiro. So eles o Macio do Itaoca (Campos dos Goytacazes), o Costo de Itacoatiara (Niteri), o Morro dos Cabritos do Parque Natural Municipal da Prainha e o Monumento Natural dos Morros da Urca e Po de Acar (Rio de Janeiro). Os resultados so apresentados em duas sees, a primeiro trata da florstica, estrutura e relaes ambientais desse tipo de vegetao; e a segunda aborda a florstica e estado de conservao da flora rupcola de forma geral das quatro reas de estudo. Para a primeira seo foram distribudas 72 parcelas de 1m x 1m ao longo de trs linhas de 50m em cada rea amostrada e registrados dados da presena de cada espcie por parcela, rea de cobertura e altura dos indivduos. Tambm foi verificado o tipo de substrato e tomadas medidas de declividade e profundidade do solo e serrapilheira. No total foram marcadas 288 parcelas nas quatro reas. Entre as famlias mais importantes para as quatro reas esto Cactaceae, Bromeliaceae, Orchidaceae e Asteraceae. Os resultados mostram que entre as espcies apontadas com maiores valores de importncia esto entre as que exercem maior peso na ordenao dos grupos florsticos evidenciados pela anlise de componentes principais (PCA) para as quatro reas. Uma anlise de redundncia (RDA) foi realizada e mostrou que as variveis que mais parecem influenciar a composio florstica das moitas so as mais sujeitas aos processos biolgicos e dinmica da vegetao como um todo. Dados acerca do espectro biolgico e ndices de diversidade e equabilidade tambm so apresentados nesta seo. Para a 2 seo foram compiladas informaes de herbrios e coletas realizadas em campo, formando uma listagem geral com 193 espcies rupcolas para as quatro reas. So apresentados os dados florsticos da vegetao e sua distribuio geogrfica. No total 28 espcies so restritas ao Estado do Rio de Janeiro e 68 so endmicas da Mata Atlntica. Dentre elas, 26 encontram-se inseridas em alguma categoria de ameaa de extino. As principais ameaas e impactos sobre a vegetao dessas reas foram abordados no contexto da conservao da flora rupcola encontrada, dentre elas, as mais significativas so o fogo, a minerao e a abertura de novos acessos em encostas com vegetao abundante.
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Seagrass ecosystems are protected under the federal "no-net-loss" policy for wetlands and form one of the most productive plant communities on the planet, performing important ecological functions. Seagrass beds have been recognized as a valuable resource critical to the health and function of coastal waters. Greater awareness and public education, however, is essential for conservation of this resource. Tremendous losses of this habitat have occurred as a result of development within the coastal zone. Disturbances usually kill seagrasses rapidly, and recovery is often comparatively slow. Mitigation to compensate for destruction of existing habitat usually follows when the agent of loss and responsible party are known. Compensation assumes that ecosystems can be made to order and, in essence, trades existing functional habitat for the promise of replacement habitat. While ~lant ingse agrass is not technically complex, there is no easy way to meet the goal of maintaining or increasing seagrass acreage. Rather, the entire process of planning, planting and monitoring requires attention to detail and does not lend itself to oversimplification.
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/18 20021816root to shoot ratio1810 (Infra red gas analysis abbreviated as IRGA)Alkali absorption, abbreviated as AA 1680~500 gm-2;16533 gm-22590 gm-21.511.21 5.69 ;; 10 10394~894mg Cm-2d-1313~2043 mg Cm-2d-167.5% R20.8739;
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1 + ; + + ; + 4;;C3C4 4 0~10 cm ;0~30 cm Y = 809 + 774x R2=0.84, P<0.001Yx 2 40%52%54%67% ;;; 420.8~3819.2/m2 107 3 23.3% 1040.1~0.75 4
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Practical testing of the feasibility of cyanobacterial inoculation to speed up the recovery of biological soil crusts in the field was conducted in this experiment. Results showed that cyanobacterial and algal cover climbed up to 48.5% and a total of 14 cyanobacterial and algal species were identified at the termination of inoculation experiment; biological crusts' thickness, compressive and chlorophyll a content increased with inoculation time among 3 years; moss species appeared in the second year; cyanobacterial inoculation increased organic carbon and total nitrogen of the soil; total salt, calcium carbonate and electrical conductivity in the soil also increased after inoculation. Diverse vascular plant communities composed of 10 and 9 species are established by cyanobacterial inoculation on the windward and leeward surface of the dunes, respectively, after 3 years. The Simpson index for the above two communities are 0.842 and 0.852, while the Shannon-Weiner index are 2.097 and 2.053, respectively. In conclusion, we suggest that cyanobacterial inoculation would be a suitable and effective technique to recover biological soil crusts, and may further restore the ecological system. (C) 2008 Published by Elsevier Ltd.
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,Jordan(1971)()Long(1934),2080(,1983;,1986),(,2000)(,2004)(,1999)(,2006)(,2003),,(,2002),,6(Hippophae rhamnoides)(Populus davidiana)(Betula platyphylla)(Pinus tabulaeform...
