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1.
Although coral declines have been reported from major reefs of the world, region-specific trends still remain unclear, particularly in areas with high diversity such as the Philippines. We assessed the temporal patterns of the magnitude and trajectory of coral cover change in the Philippines using survey data collected from 317 sites. We examined the rate of change in coral cover in relation to time, effects of bleaching and protection against fishing and assessed the efficacy of marine protected areas (MPAs) using meta-analysis. Results showed an overall increase in coral cover in the Philippines from 1981 to 2010. Protection from fishing contributed to the overall increase in the mean annual rate of change as the coral cover significantly increased within MPAs than outside. The significant differences in the rate of coral cover change through time were influenced by chronic anthropogenic stresses, coinciding with the timing of thermal stress and the establishment of MPAs. The rate of change in coral cover was independent of the level of protection and the age and size of MPA.  相似文献   

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This study highlights spatial characterization of evergreen forests of the Western Ghats – an ecological hotspot in Tamil Nadu, India – using remote sensing and GIS-based analysis in conjunction with ground-based phytosociological data. The evergreen forests of Tamil Nadu are distributed in four distinct hill ranges, Nilgiri, Anamalai, Palni and Tirunelveli, having different topographic, bioclimatic and disturbance levels. The evergreen forests in these four hill ranges are characterized for their uniqueness in terms of patch characteristics and phytosociology. A vegetation type map was prepared using IRS LISS III satellite data and was used to study the patch characteristics in terms of patch size, number, shape, porosity and landcover diversity (LD). The phytosociological characteristics, namely species richness, diversity, similarity and community assemblages, were studied using ground data collected from 95 sample points of 0.1 ha size. Patch size and number revealed distinct intactness and disturbance levels in these four hill ranges. Evergreen forests in the Tirunelveli hills comprising 216.09 km2 are distributed in 306 patches, and in the Palni hills, with 285 km2, forests are distributed in 1029 patches, indicating a high level of fragmentation. LD, indicating the spatial heterogeneity of landcover, was very high in the Nilgiri hills and low in the Tirunelveli hills. The spatial analysis helped to delineate homogenous large patches of evergreen forest, which can be adopted for appropriate conservation strategies. A total of 342 tree species belonging to 4490 stems were evaluated for phytosociology. Only 15–28% of similarity in terms of species distribution was found across the hill ranges. Conjunctive analysis of patch characteristics and species distribution showed high species richness in less fragmented evergreen forests and vice versa. The study identified the areas of prioritization in terms of ecorestoration and conservation based on patch and phytosociological characteristics.  相似文献   

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In this article, we attempt to estimate the contemporary phytoplankton species pool of a particular lake, by assessing the rate of floral change over a period of 15 years. Phytoplankton time series data from Lake Stechlin, an oligo-mesotrophic lake in the Baltic Lake District (Germany) were used. Of the 254 algal species recorded during the 15-year of studies with roughly biweekly sampling, 212 species were planktonic. In the individual plankton years, the recorded total number of species changed between 97 and 122, of which the number of dominants (>1% contribution to the annual average of total biomass) was only 10–19. The 15-year cumulative number of species exhibited an almost linear increase after an initial saturation phase. This increase was attributed to two reasons: increase of sample size and immigration of species new to the flora. Based on a probabilistic model developed in this study, we estimated the number of co-existing planktonic species of the lake as some 180, and the rate of floral change as 1–2 species per year. Of these co-existing species, only few maintain the matter–energy processing ecosystem functions in any particular plankton year. Selection of these dominants is probably driven by mesoclimatic cycles, coupled with human-induced forcing, like eutrophication. All others are hiding as an ecological memory, in the sense of the capacity or experiences of past states to influence present or future responses of the community. Data analyses suggest that selection of the ‘memory species’ that show temporary abundance increases over shorter (several years) periods are largely dependent upon the dominants. These results show that interspecific interactions and the particular autecological features of the dominants, together with their effects on the whole ecosystem, act as a major organizing force. Some phytoplankton species, like Planktothrix rubescens, are efficient ecosystem engineers with cascading effects of both a top-down and bottom-up nature. Historical scientific data on Planktothrix blooms in Lake Stechlin suggest cyclic patterns in long-term development of phytoplankton which, as the legend of the Red Cock suggests, dates back much further than scientific archives.  相似文献   

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New Caledonia is well known as a hot spot of biodiversity whose origin as a land mass can be traced back to the Gondwanan supercontinent. The local flora and fauna, in addition to being remarkably rich and endemic, comprise many supposedly relictual groups. Does the New Caledonian biota date back to Gondwanan times, building up its richness and endemism over 100 Myr or does it result from recent diversifications after Tertiary geological catastrophic events? Here we use a molecular phylogenetic approach to answer this question with the study of the Neocaledonian cockroach genus Angustonicus belonging to the subfamily Tryonicinae from Australia and New Caledonia. Both geological and molecular dating show that the diversification of this group is less than two million years old, whatever the date of its origin itself. This dating is not consistent with hypotheses of Gondwanan richness and endemism in New Caledonian biota. In other terms, local richness and endemism at the specific level are not necessarily related to an old Gondwanan origin of the Neocaledonian groups. © The Willi Hennig Society 2005.  相似文献   

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With 76% of its 3063 native species of flora endemic, the New Caledonia biodiversity hotspot has long been recognized as having a high potential for conservation. Under the new IUCN Red List categories, 25% of the endemic plants are at risk (Conservation Dependent, Vulnerable, Endangered, Critically Endangered), and five species are already extinct. A review of their distribution demonstrates that 83% of the threatened species do not occur at all in a conservation area, and only 11% have their conservation status improved by a protected area. The protected area network is geographically and floristically very unbalanced, with the rainforest and high altitude maquis in the south concentrating most of the conservation effort. Conversely, the middle and northern segments of the island, as well as all of the dry west coast, are left without adequate conservation area. Two vegetation types, the sclerophyll forest and the unique low/middle altitude maquis, are virtually totally unprotected. We conclude that the current network of protected areas needs to be considerably expanded, in terms of both geographical/floristic subregions within New Caledonia and vegetation type covered. With only 54% of the conservation area covered by strict mining restrictions, existing reserves need to have their conservation efficiency improved by a more vigorous enforcement of their status, and by extending mining bans to all of them.  相似文献   

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Two species of Pancheria (Cunoniaceae) described here, Pancheria minima J.C. Bradford and Pancheria ouaiemensis J.C. Bradford, draw attention to a recently recognized biodiversity pattern in New Caledonia. Montane maquis on acidic substrates, especially on the Roche Ouaïème, harbors numerous endemic species and is a rare and globally unique ecosystem. We cite 12 species, most described in the past several years, known only from the Roche Ouaïème in an area less than 10km2. Overall, 27 species are known only from montane maquis and currently not found in a well-protected area. The major local threat to montane maquis habitat is anthropogenic fire, with climate change a possible long-term problem. Those montane maquis species known from one or two localities, occupying very small areas, and with declining habitat quality are critically endangered or endangered based on IUCN Red List criteria. Adding the Roche Ouaïème to the reserve system of New Caledonia is recommended to protect and manage a representative area of montane maquis on acidic substrates. A research strategy is proposed to identify species most at risk, locate possible unknown areas of montane maquis, and update taxonomic knowledge. A review of characters that vary among Pancheria species is provided, and the inflorescence architecture is described and diagramed. Both new Pancheria species occur at upper elevations in shrubby habitats. P. minima is remarkable in that the size of plants, leaves and reproductive parts is highly reduced compared to other known species.  相似文献   

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We investigated the spatial structures of soil properties and snow-bed vegetation, and their relationships, in southern Italy. We analyzed data on 26 plant species and 10 soil traits from adjacent 1 × 1 m plots in two snow-bed patches. Measures of spatial autocorrelation revealed striking spatial structures for plant cover and soil properties at both sites. Bivariate statistics and Mantel tests highlighted a significant correlation between spatial patterns of plants and soil in the study sites. Canonical correspondence analysis related such relationships to an ecological gradient connecting soil properties and plant assemblages in this unusual ecological context. Among the variables significantly related to plant patterns is the soil organic matter, which is recognized as being sensitive to global warming. Our analyses suggest that soil dynamics due to increasing temperature may promote the replacement of species typical of southern snow-bed ecosystems by more mesophilous plants.  相似文献   

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Based on an updated census for the endangered Dupont’s lark (Chersophilus duponti), we conducted a phytosociological survey of 167 sites representative of the distribution area of the species in Europe. Results were used as a starting point for conservation assessment. According to our observations, the bird selects flat deforested areas colonized by small shrubs corresponding to successional, subclimax stages that are either naturally or artificially exploited. Four groups of scrubs were occupied by the bird: (1) supramediterranean dwarf cushion scrubs dominated by Genista pumila ssp. rigidissima or Erinacea anthyllis; (2) gypicolous shrublands and grasslands associated with Lygeum spartum; (3) shrubs dominated by chamaephytes producing allelopathic substances (Thymus, Lavandula, Salvia) and showing different facies according to the level of disturbance; and (4) supramediterranean acidophilous scrubs dominated by Cistus, Erica or Cytisus species. As management measures, we propose reducing tree density in flat areas, promoting the growth of chamaephytes by clearing phanerophytes, and encouraging traditional low-level transhumance grazing. These measures will provide high-quality habitats and help preserve, or even expand, habitable patches to ensure the viability of the European metapopulation of this rare and sensitive songbird.  相似文献   

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To address potential causes of disturbances in recent New Zealand vegetation a sediment core from Tiniroto Lakes near Gisborne was used to reconstruct the local history of ecological disturbance and vegetation dynamics. Our approach was to examine the pattern and rate of vegetation change, against known disturbances, in order to identify different causes of disturbance. Despite intermittent disturbances, a steady transformation of vegetation dominates the period from c. 4,900 to c. 2,300 cal. yrs b.p. This is a time of climatic amelioration, with increasing precipitation suggested by the decline of light-adapted taxa, together with the establishment of forest. After c. 2,300 cal. yrs b.p., vegetation change becomes much more irregular, and apparently driven by disturbances, including unusual ones, such as earthquakes. In contrast to earlier disturbances, later vegetation responses are typified by a reduction of forest species and the establishment of semi-open vegetation, which persists for decades. This dichotomy suggests that a change in disturbance regime, especially in terms of fire, characterises the period after c. 2,300 cal. yrs b.p. The rises of fire frequency and of intensity at that time could be a result of severe droughts under climate extremes associated with intensified ENSO frequencies.  相似文献   

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Stable forested environments can be converted to savanna in response to changes in environmental disturbances. New Caledonia is a biodiversity hotspot; significant ecological and economic resources would be lost if forests were turned into savanna by anthropogenic environmental changes. On the landscape scale, systems that have undergone shifts of this kind are characterized by sharp forest–savanna boundaries and mosaic‐like distributions of savanna and forest. Understanding the locations and the dynamics of such boundaries is a challenge for ecologists and is critical for landscape management and biodiversity conservation. Using a time series of aerial photographs (1955–2000) and a forest habitat suitability map, we tested the hypothesis that topography and spatial processes, especially those relating to fire spread and seed dispersal, are the main determinants of the spatial distribution of rainforest and savanna in a New Caledonian landscape covering 24 km2. Within the studied landscape, the overall forest coverage decreased by 24% between 1976 and 2000. This was primarily due to the contraction of forests on west‐facing slopes, which accounted for about 90% of the total loss. Conversely, the east‐facing forests seemed to have contracted extensively prior to the studied period, and were confined to refuges. A habitat suitability index calculated from the landscape's topographical features using generalized additive models accurately predicted both the presence of forests and the probability of forest expansion/contraction. We also provide evidence that spatial processes such as fire spread and seed dispersal limit the expansion and contraction of forests. Our results suggest that rainforests on west‐facing slopes in New Caledonia will be progressively destroyed by fire until they are restricted to refuges along thalwegs and creeks, as appears to have already happened for their east‐facing counterparts.  相似文献   

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A 17-month study was made of the primates using a 9-ha “island” of forest, surrounded by savanna, in the northern part of the Lopé Reserve, Gabon. One group ofCercopithecus cephus (plus a young maleCercopithecus nictitans who was in permanent association with them) were resident in the fragment and groups of five other species of primates made visits during 127 days of observation:Pan troglodytes, 15 visits;Cercocebus albigena, 10;Colobus satanas, 3;Cercopithecus nictitans, 2;C. pogonias, 1. Visits were also made by lone males of three species,C. nictitans, Cercocebus albigena, andMandrillus sphinx. The eighth species of diurnal primate present at Lopé,Gorilla g. gorilla, did not visit the fragment during the study. Compared to conspecific groups in neighbouring continuous forest, primates in the fragment ate less fruit, seeds and flowers and more insects and leaves. The local population density of primates resident in the fragment was equivalent to that of the neighbouring continuous forest where all eight species occur, despite the diversity and abundance of fruit being less in the fragment. The costs imposed on the resident group by the reduced diversity and availability of preferred fruit foods appeared to be offset by a number of benefits that increased individual feeding efficiency for monkeys residing within a single fragment. These included lower travel costs, reduced feeding competition between individuals through group fission, and excellent knowledge of the location and quality of food resources in the small home range. It is also possible that the overall negative impact of inter-specific feeding competition was lower in fragments than in continuous forest and that micro-habitat differences resulted in an increased availability of palatable insect and leaf fallback foods in the fragment.  相似文献   

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Landscape and Ecological Engineering - Urban residents need to live in an ecologically sustainable way to mitigate and adapt to climate change. To discuss the model of urban ecological life, this...  相似文献   

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Shrub encroachment and declining grass production are widespread throughout the grasslands and savannas of the Mexico–US borderlands, with negative consequences for ecosystem services, livestock production, and native biodiversity. The problem suggests a complex interaction of social and ecological drivers that are not well understood. Using the Chihuahuan Desert grasslands of the Janos Biosphere Reserve of northern Mexico as a case study, we sought to understand the social–ecological context that shaped landscape change. Our approach included a synthesis of the historical literature and interviews with local residents, with the goal of facilitating long-term grassland restoration. Findings indicate that recent changes in Chihuahuan Desert grasslands are likely related to the co-occurrence of heavy grazing, fire suppression, and the elimination of key species, including prairie dogs and native ungulates. Local residents widely perceive both fire and prairie dogs to be destructive to grasslands and livelihoods. Over the last 50 years, evolving land tenure policies have fragmented the landscape into smaller parcels which typically produce an insufficient livelihood from cattle despite high stocking rates. Declining cattle profitability has motivated the sale and conversion of rangelands to more profitable croplands irrigated with groundwater. Since the founding of the Janos Biosphere Reserve in 2009, universities, local cattle operators, conservation organizations, and federal agencies have begun collaborating on restoration activities. While complete restoration of grasslands is unlikely, progress appears possible largely because of the willingness of local residents to try new management practices that may improve their ability to benefit from the land.  相似文献   

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Cylindrospermopsis raciborskii is a diazotrophic and potentially toxic cyanobacterium that was initially thought to be confined to tropical freshwaters. Recently it appears to have expanded its range to more temperate regions of the globe. There are contrasting hypotheses to explain this spread including; dispersal of highly adapted strains or localised spread from warm refuges as climatic or environmental conditions change. C. raciborskii was first detected in the isolated island nation of New Zealand in 2003, providing a unique opportunity to explore whether this recent identification is due to a new incursion or resultant from climatic or environmental change. Phylogenetic analysis (nifH, ITS1-L, ITS1-S, and rpoC1) of six strains isolated from two New Zealand lakes showed they were most closely related to those from South America, and suggest that the recent detection of this species was not due to a new incursion. Ten years of environmental data from three lakes (Waaki, Waikare and Whangape) experiencing blooms were analysed to identify potential reasons for recent C. raciborskii blooms. This analysis showed that the relatively recent (within the last 20–30 years) collapses of extensive macrophyte stands in lakes Waaki, Waikare and Whangape have resulted in increased turbidity’, low water column dissolved reactive phosphorus and seasonal shifts in the dissolved inorganic nitrogen availability, all conditions known to facilitate C. raciborskii dominance. Collectively these data indicate that C. raciborskii has always been present in New Zealand, and that recent changes in environmental conditions in these lakes are now facilitating bloom events.  相似文献   

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