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1.
Question: Species diversity is commonly expressed as the number of species present in an area, but this unique value assumes that all species contribute equally to the area's biodiversity. Can taxonomic diversity be used as a complementary measure for species richness in order to assess plant biodiversity in remnants of primary forest and patches of secondary vegetation? Location: Veracruz, Mexico. Methods: Using data from six sampling transects of each vegetation type in an elevation gradient (400‐900 m a.s.l.), we compare the point, mean and cumulative floristic diversity of primary forest and secondary vegetation in a tropical deciduous landscape, using species richness and two measures of taxonomic diversity: average taxonomic distinctness (Δ+) and variation in taxonomic distinctness (Λ+). We performed a randomization test to detect differences in the observed taxonomic diversity, from the expected values derived from the species pool of each vegetation type. Results: We found that the species of secondary vegetation are more closely related at low taxonomic levels (lower Δ+ value) than the species of primary forest remnants. Also, in secondary vegetation the distribution of species is uneven among the taxonomic levels and units (high Λ+ value). These patterns are consistent for point, mean and cumulative taxonomic diversity. Families Asteraceae, Euphorbiaceae, Fabaceae and Poaceae are over‐represented, while families Bromeliaceae, Cactaceae, Orchidaceae and Pteridaceae are under‐represented in secondary vegetation. Conclusions: Although in a previous paper we concluded that secondary vegetation is more alpha‐diverse than primary forest (in terms of both cumulative and mean species richness), and beta‐diversity between vegetation types is notoriously high, we now provide a wider view by highlighting the importance of taxonomic diversity in primary forest remnants. Our data indicate that to measure biodiversity accurately, we should seek to capture its different facets. This will allow us to make conservation recommendations based on a broader view, and not on a single dimension.  相似文献   

2.
The associations between floristic and palynological richness and landscape structure were studied based on modern pollen?Cvegetation data from a patchy cultural landscape in southern Estonia (northern temperate vegetation zone). Nine study sites (small lakes and their surrounding vegetation) represent land cover gradient from closed forest to semi-open vegetation. Floristic richness (number of species) and floristic richness of pollen types (number of pollen-equivalent taxa) were used to describe the vegetation within the radius of 250?m from the pollen sampling sites. Palynological richness was calculated to describe the modern pollen samples diversity. Landscape structure was estimated on the basis of landscape openness and three landscape diversity measures: richness of community patches, Simpson evenness of community patches and Simpson diversity of community patches. To study the effect of the spatial scale of landscapes on the vegetation?Clandscape and pollen?Clandscape associations, landscape structure was estimated within eight radii (250?C2,000?m) around each lake. The results showed that landscape openness was the most important determinant of both floristic richness and palynological richness in southern Estonia and that landscape diversity estimated by Simpson diversity index was also significantly associated with the richness estimates. Floristic and palynological richness were significantly positively correlated with landscape structure within the radii greater than 1,000?m from the pollen sampling sites, which is similar to the estimated Relevant Source Area of Pollen in southern Estonia. We conclude that within one floristic or climatic region, palynological richness gives reliable estimates about the variation in floristic richness and landscape structure; however, caution must be taken when comparing pollen-inferred vegetation diversities from different regions or when interpreting fossil pollen records from times with highly different vegetation associations.  相似文献   

3.
Aim Most of the Atlantic Forest in Brazil occurs in fragments of various sizes. Previous studies indicate that forest fragmentation affects fruit‐feeding butterflies. Conservation strategies that seek to preserve organisms that are distributed in high‐fragmented biomes need to understand the spatial distribution of these organisms across the landscape. In view of the importance of understanding the fauna of these forest remnants, the objective of the present work is to investigate the extent to which the diversity of this group varies across spatial scales ranging from within‐forest patches to between landscapes. Location South America, south‐eastern Brazil, São Paulo State. Methods We used bait traps to sample fruit feeding butterflies at 50 points in 10 fragments in two different landscapes during a period of 12 months. Total species richness and Shannon index were partitioned additively in diversity at trap level, and beta diversity was calculated among traps, among forest patches, and between landscapes. We used permutation tests to compare these values to the expected ones under the null hypothesis that beta diversity is only a random sampling effect. Results There was significant beta diversity at the smallest scale examined; however, the significance at higher scales depends on the diversity measurement used. Beta diversity with Shannon index was smaller than expected by chance among fragments, whereas species richness was not. Among landscapes, only beta diversity in richness was higher than expected by chance. Main conclusions The results observed occur because there is great variability in species composition among forest patches in the same landscape, changing this diversity even though the communities are formed from the same pool of species. At the largest scale evaluated (between landscapes), these pattern changes and differences in beta diversity in richness were detectable. This difference is probably caused by the presence of rare species. Thus, a conservation strategy that seeks to preserve as many species as possible per unit of area in high‐fragmented biomes should give priority to protecting fragments in different landscapes, rather than more fragments in the same landscape.  相似文献   

4.
Collective properties of biodiversity, such as beta diversity, are suggested as complementary measures of species richness to guide the prioritisation and selection of important biodiversity areas in regional conservation planning. We assessed variation in the rate of plant species turnover along and between environmental gradients in KwaZulu-Natal, South Africa using generalised dissimilarity modelling, in order to map landscape levels of floristic beta diversity. Our dataset consisted of 434 plots (1000 m2) containing 997 grassland and savanna matrix species. Our model explained 79 % of the null deviance observed in floristic dissimilarities. Variable rates of turnover existed along the major environmental gradients of mean annual temperature, median rainfall in February, and soil cation exchange capacity, as well as along gradients of geographical distance. Beta diversity was highest in relatively warm, drier summer regions and on dystrophic soils. Areas of high beta diversity identify areas that should be included in conservation plans to maximise representation of diversity and highlight areas best suited to protected area expansion. Biome transition areas in high beta diversity areas may be susceptible to climate variability. Including beta diversity turnover rates in regional conservation plans will help to preserve evolutionary and ecological processes that create and maintain diversity.  相似文献   

5.
6.
Intensive deforestation is reducing dry tropical forest areas worldwide and increasing its fragmentation. Forest remnants can be the basis for the future recovery of this forest type if appropriate management practices are applied. This requires a better knowledge of their conservation status and the assessment of their perceived value by land users. In this study we compare the structure, species richness and diversity of different types of tropical dry forest remnants in Nicaragua and we assess their conservation status based on a new index: Social simplified Importance Value Index (SsIVI). This index summarizes both ecological indicators and the perception by local stakeholders of the conservation status of the tree species present. Results show that gallery and hillslope forest remnants have higher species richness and diversity than isolated vestigial patches. In all remnants, species richness and diversity is higher in the tree layer than in the regeneration layer. No differences are observed in valorisation among different types of remnants either for the tree layer or for the regeneration layer. In the hillslope forests, where several degrees of disturbance are present, the valorisation decreases with increasing degradation. Results of species composition and forest structure indicate a strong degradation of dry tropical forest remnants in Nicaragua. However, the similar social valorisation of the three types of remnants suggests that they face similar threats but also similar opportunities to be preserved. A decrease in valorisation with increasing degradation warns about the potential loss of the most degraded areas, unless forest restoration is applied.  相似文献   

7.
The diversity, composition and structure of vegetation in a cattle landscape in Matiguás, Nicaragua was characterized, and the floristic and structural differences of six types of habitats (secondary forests, riparian forests, charrales, live fences and pastures with high and low tree cover) were compared. A total of 3 949 trees of 180 species and 52 families were recorded. Forty six percent of the total trees reported for the landscape were represented by Guazuma ulmifolia (18.5%), Bursera simaruha (13.2%), Tabebuia rosea (6.3%), Enterolobium cyclocarpum (4.2%) and Albizia saman (3.4%). Many of the dominant species in the landscape were typical of open and disturbed areas. There were significant differences between the different habitats in the patterns of tree species richness, abundance, diversity, structure and floristic composition. The riparian forests had greater tree richness (p=0.0001) and diversity (p=0.0009) than other habitats. The floristic composition varied across habitats. with pairs of habitats sharing between 18.4 and 51.6% of the same tree species, and with clear differences in composition between the forested (riparian and secondary forests) and agricultural habitats. Of the habitats studied, the riparian forests and secondary forests seem to have greatest value for the conservation of the flora in the agropaisaje because they have the greatest species richness, and maintain small populations of endangered species. On the basis of the study, we recommend including agricultural landscapes in strategies to conserve tree diversity and suggest measures to ensure the maintenance of tree diversity in the Matiguas landscape.  相似文献   

8.
Land-use systems (LUS), placed in originally forested areas, represent different degrees of opportunity for species conservation. In this study, we examined the dung beetle communities in order to identify the conservation value of different LUS: primary forest, old secondary forest, young secondary forest, agroforestry, agriculture and pasture in Western Amazon. The LUS were sampled in two campaigns during the highest precipitation period and dryest period. The primary forest has a high number of total and exclusive species. Large beetles show a continuous decreasing in richness and abundance from primary forest to pastures, while small ones are not sensible to intermediate systems (secondary forest to agriculture) in terms of species richness and exhibit a increase in abundance at agroforest and agriculture when contrasted to secondary forest and pasture The beetle community composition was not sensible to secondary forest recovering time. Secondary forests and agroforestry stood out as harboring many species shared with primary forests. Cloud-point dispersion (average dissimilarity) increased from primary forest towards LUS’s submitted to more intense use. The higher sampling points similarity observed in primary forest might be the result of the relative stability of this system, given that environmental impacts might increase variability in community structure and beta diversity. Increase in beta diversity as expressed by greater dispersion of sites in multivariate space suggests that these areas are dependent on nearby species pools, possibly primary forests, and harbor a higher spatial heterogeneity in species composition. This high variability can overestimate the importance of occasional species, thus biasing the actual value of alternative LUS for biodiversity conservation.  相似文献   

9.
Aim The purpose of the study was to assess the degree of floristic differentiation between tropical dry forest (TDF) and savanna occurring in a single landscape. This comparison provides information on the responses of vegetation to the prevailing environmental conditions, while it also allows us to make inferences about large‐scale events and processes, both biogeographical and evolutionary. Our approach included three levels of analysis: (1) taxonomic, (2) morphological and (3) vegetational. Location The seasonal dry tropical landscape in the Nizanda region, Oaxaca State, southern Mexico. The landscape comprises a complex vegetation mosaic in which tropical dry forest and savannas are the most conspicuous components. Methods Comparisons between TDF and savanna were based on inventories for these communities produced after 8 years of botanical survey. At the taxonomic level, the relative representation of taxa of different hierarchical levels in each community was examined. Morphological analyses required the classification of species on each of three criteria: (1) growth form, (2) life form and (3) growth habit. Vegetation level analysis was based on the frequencies of taxa in one hundred 100‐m2 composition plots with which matrices of binary data were constructed for species, genera and families. These were subjected to classification analysis with Ward's method and using Euclidean distances as the dissimilarity algorithm. Results The combined flora for both communities comprised 600 species, 375 genera and 94 families; between them they shared 31, 40 and 34 taxa, respectively. The corresponding Sørensen similarity values were 10%, 21% and 72%, respectively. Ranking genera and families according to their species richness displayed large differences between savanna and TDF. Large differences between these communities were observed for Acanthaceae, Cactaceae, Euphorbiaceae and Mimosaceae, whereas Fabaceae and Asteraceae had similar high ranks according to the species richness in the two systems. The growth form spectrum diverged between the two communities, with TDF having more trees, shrubs and climbers. Savanna was characterised by forbs and graminoid herbs. Growth habit spectra revealed a clear dominance of herbaceous and suffruticose plants in savanna, and of woody elements and epiphytes in TDF. Regarding Raunkiaer's life forms, savanna had relatively more hemicryptophytes, and TDF more phanerophytes. Classification analyses showed that savanna and TDF forest samples kept their identities, regardless of taxonomic level (species, genera and families) at which the analyses were performed. Main conclusions The TDF and savanna of Nizanda represent two floristic systems with a large degree of differentiation at all taxonomic levels and patterns of morphological attributes. This suggest that the two floristic sets have evolved independently for extended periods of time, despite their close proximity. One important implication of this floristic differentiation is the large joint contribution made by these communities to the regional flora.  相似文献   

10.
Agricultural intensification typically leads to changes in bird diversity and community composition, with fewer species and foraging guilds present in more intensively managed parts of the landscape. In this study, we compare bird communities in small (2–32 ha) brigalow (Acacia harpophylla) remnants with those in adjacent uncultivated grassland, previously cultivated grassland and current cropland, to determine the contribution of different land uses to bird diversity in the agricultural landscape. Twenty remnant brigalow patches and adjacent agricultural (‘matrix’) areas in southern inland Queensland, Australia were sampled for bird composition and habitat characteristics. The richness, abundance and diversity of birds were all significantly higher in brigalow remnants than in the adjacent matrix of cropping and grassland. Within the matrix, species richness and diversity were higher in uncultivated grasslands than in current cultivation or previously cultivated grasslands. Forty-four percent of bird species were recorded only in brigalow remnants and 78% of species were recorded in brigalow and at least one other land management category. Despite high levels of landscape fragmentation and modification, small patches of remnant brigalow vegetation provide important habitat for a unique and diverse assemblage of native birds. The less intensively managed components of the agricultural matrix also support diverse bird assemblages and thus, may be important for local and regional biodiversity conservation.  相似文献   

11.
The traditional shade cacao plantations (cabrucas) of southern Bahia, Brazil, are biologically rich habitats, encompassing many forest-dwelling species. However, a critical question for the conservation management of this specific region, and the highly fragmented Atlantic forest in general, is to what extent the conservation value of cabrucas relies on the presence of primary forest habitat in the landscape. We investigated the relative importance of cabrucas and forests for the conservation of five diverse biological groups (ferns, frogs, lizards, birds and bats) in two contrasting landscapes in southern Bahia, one dominated by forest with some interspersed cabrucas, and one dominated by cabrucas with interspersed forest fragments. The community structure (richness, abundance and diversity) of all biological groups differed between cabrucas and forests, although these differences varied among groups. A high number of forest species was found in the cabrucas. However, there were pronounced differences between the two landscapes with regard to the ability of cabrucas to maintain species richness. Irrespective of the biological group considered, cabrucas located in the landscape with few and small forest fragments supported impoverished assemblages compared to cabrucas located in the landscape with high forest cover. This suggests that a greater extent of native forest in the landscape positively influences the species richness of cabrucas. In the landscape with few small forest fragments interspersed into extensive areas of shade cacao plantations, the beta diversity of birds was higher than in the more forested landscape, suggesting that forest specialist species that rarely ventured into cabrucas were randomly lost from the fragments. These results stress both the importance and the vulnerability of the small forest patches remaining in landscapes dominated by shade plantations. They also point to the need to preserve sufficient areas of primary habitat even in landscapes where land use practices are generally favorable to the conservation of biodiversity.  相似文献   

12.
Aim To analyse how the dung beetles (Scarabaeinae) respond to a modified, variegated landscape, taking into account the biogeographical peculiarities of the Mexican Transition Zone. Location This study covers cloud forest (CF) of the Sierra Norte de Puebla mountain range and part of the Sierra Madre Oriental mountain range (Mexico). Methods We applied proportional sampling based on the landscape variegation model with Scarabaeinae as the indicator group, and using two approaches: structural units (vegetation type) and spatial units (windows). We used two measures – richness and Shannon diversity – and applied multiplicative diversity partitioning to obtain independent alpha and beta diversities for the landscape, windows and vegetation types. We grouped species by biogeographical distribution pattern for the biogeographical analysis and by whether they were originally from CF. Results The transformation of CF into secondary forest, pastures and other types of vegetation increases the Scarabaeinae diversity of the landscape, in vegetation types and windows. This increase is the result of species arriving from the tropical lowlands. However, the original dung beetle community of the CF dominates at different scales in the number of species, abundance and biomass. With increasing habitat modification, beta diversity increases in the windows, and species with the Tropical Palaeoamerican distribution pattern increase in abundance in vegetation types and windows. Main conclusions The variegated character of the landscape explains well the distribution and diversity of this dung beetle community. The peculiar characteristics of the Mexican Transition Zone have an effect owing to the overlap of fauna with different biogeographical origins. The conversion of fragmented landscapes to variegated landscapes could be a conservation goal in human‐modified mountain landscapes. Sampling proportional to the area of different types of vegetation and the use of windows offer an alternative experimental design in variegated landscapes.  相似文献   

13.
Abstract. Soil seed bank and floristic diversity were studied in a forest of Quercus suber, a forest of Quercus canariensis and a grassland, forming a vegetation mosaic in Los Alcornocales Natural Park, southern Spain. The soil seed bank was estimated by the germination technique. In each community patch, diversity, woody species cover and herbaceous species frequency was measured. Three biodiversity components – species richness, endemism and taxonomic singularity – were considered in the vegetation and the seed bank. Forest patches had a soil seed bank of ca. 11 200–14 100 seed.m?2 and their composition had low resemblance to (epigeal) vegetation. The grassland patch had a more dense seed bank (ca. 31 800 seed.m?2) and a higher index of similarity with vegetation, compared with the forests nearby. The complete forest diversity was 71–78 species on 0.1 ha, including 12–15 species found only in the seed bank; the grassland species richness was higher (113 species on 0.1 ha). We discuss the role of soil seed banks in the vegetation dynamics and in the complete plant biodiversity of the mosaic landscape studied.  相似文献   

14.
Understanding the responses of insects to ecological variables provides information that is fundamental for their conservation. The present study took place in three different landscapes (three plots of 10 × 10 km each) in a typical Mediterranean ecosystem of a Spanish national park. Each landscape included three vegetation types, grasslands, scrublands, and woodlands, and was characterised by a dominant vegetation type. Our objectives were: (1) to assess how important the influence of the dominant vegetation type and the vegetation type of sites are on hoverfly (Diptera: Syrphidae) diversity at landscape scale; (2) to assess whether scrublands are contributing to the loss of hoverfly diversity in an ecosystem with a long history of human use. In order to achieve these goals, we compared hoverfly diversity among sampling sites by prospecting all three diversity levels, alpha, beta and gamma, at each landscape. We sampled adult hoverflies at 18 sites located in different vegetation types within the three landscapes. No evidence was found that demonstrated an effect of the dominant vegetation type on alpha or beta diversity of sites, but the vegetation type of sites did have an affect. The highest species richness was found in woodland sites, particularly in the grassland-dominated landscape. At each landscape, beta diversity among sampling sites contributed more to gamma diversity than alpha diversity did. Our results highlight the need to focus on the conservation of woodland remnants of grassland-dominated landscape and scrubland-dominated landscape in order to preserve a large proportion of the biodiversity of Cabañeros hoverflies, as well as on the maintenance of the mosaic landscape, which is linked to high beta diversity, typical in many Mediterranean ecosystems. We emphasise the importance of open clearings in the vast mass of scrubland in the scrubland-dominated landscape in order to provide extra resources for the hoverflies.  相似文献   

15.
There are thousands of protected forest areas existing on earth, yet the deforestation rate continues unabated both inside and outside the protected areas especially in the tropical forests. It identifies the less effectiveness of the current conservation strategies, which is normally oriented around the forest area cover rather than the quality of the protected areas. This calls for realistic and effective management strategies for forests. Based on the drawbacks the present study aims at identifying conservation priority sites within the protected areas (Reserved Forests) of Shervarayan hills, Eastern Ghats of Tamil Nadu, India. The remnant forest patches having less effective management/protection is identified and analysed for its qualitative contribution to the ecosystem. Quadrats of 20 × 20 m were laid in different vegetation based on the percentage of forest cover and assess the species diversity pertaining the richness, Endemism and Red list categories. Thematic layers (maps) such as vegetation type, floristic species richness, floristic endemism, and red list flora are created and categorized according to their weightage classes and overlaid in GIS domain to demarcate the Conservation Priority Zones (CPZ). The CPZ are classified according to the priority status i.e., high, moderate and low based on the contributing species richness, levels of endemism and concentration of Red listed plants.  相似文献   

16.
Vandvik  V.  Birks  H.J.B. 《Plant Ecology》2004,170(2):203-222
This paper discusses vegetation types and diversity patterns in relation to environment and land-use at summer farms, a characteristic cultural landscape in the Norwegian mountains. Floristic data (189 taxa) were collected in 130 4-m2 sample plots within 12 summer farms in Røldal, western Norway. The study was designed to sample as fully as possible the range of floristic, environmental, and land-use conditions. Vegetation types delimited by two-way indicator species analysis were consistent with results from earlier phytosociological studies. Detrended correspondence analysis and canonical correspondence analysis show that rather than being distinct vegetation types, the major floristic variation is structured along a spatial gradient from summer farm to the surrounding heathland vegetation. Species richness (alpha diversity) was modelled against environmental variables by generalized linear modelling and compositional turnover (beta diversity) by canonical correspondence analysis. Most environmental factors made significant contributions, but the spatial distance-to-farm gradient was the best predictor of both species richness and turnover. While summer farms reduce mean species richness at the plot scale, the compositional heterogeneity of the upland landscapes is increased, thereby creating ‘ecological room’ for additional vegetation types and species. Within an overall similarity across scales, soil variables (pH, base saturation, LOI, phosphate and nitrogen) differed considerably in their explanatory power for richness and turnover. A difference between ‘productivity limiting’ factors and ‘environmental sieves’ is proposed as an explanation. Species turnover with altitude is relatively low in grasslands as compared to heaths.  相似文献   

17.
We explore the effect of land‐use change from extensively used grasslands to intensified silvi‐ and agricultural monocultures on metacommunity structure of native forests in Uruguay. We integrated methods from metacommunity studies, remote sensing, and landscape ecology to explore how woody species distribution was influenced by land‐use change from local to regional scale. We recorded richness and composition of adult and juvenile woody species from 32 native forests, created land‐use maps from satellite image to calculate spatial metrics at landscape, class, and patch levels. We also analyzed the influence of land use pattern, climate, topography, and geographic distance between sites (d) on metacommunity, and created maps to visualize species richness and (dis)similarity between communities across the country. Woody species communities were distributed in a discrete pattern across Uruguay. Precipitation and temperature seasonality shaped species distribution pattern. Species richness and community dissimilarity increased from West to East. Latitude did not influence these patterns. Number of patches, landscape complexity, and interspersion and juxtaposition indexes determine woody species distribution at landscape level. Increasing areas covered by crops and timber plantation reduced species richness and increased community dissimilarity. The spatial metrics of native forest fragments at patch level did not influence metacommunity structure, species richness, and community dissimilarity. In conclusion, Uruguayan native forests display a high range of dissimilarity. Pressure of neighborhood land uses was the predominant factor for species assemblages. Conserving landscape structures that assure connectivity within and among native forest patches is crucial. On sites with rare target species, the creation of alliances between governmental institution and landowner complemented by incentives for biodiversity conservation provides opportunities to advance in species protection focused on those less tolerant to land‐use change.  相似文献   

18.
Uncontrolled urban development is threatening the survival of many terrestrial species worldwide, especially those with limited dispersal capabilities. Soil invertebrates account for a high proportion of the global biodiversity but there are few studies on how soil biodiversity varies with different parameters of landscape structure, especially in fragmented tropical habitats. Millipedes are among the most abundant detritivore invertebrates in the soil-litter macrofauna. We examined the relationships between soil millipede diversity and landscape structure in 12 forest patches of approximately 30 years of age, in northeastern Puerto Rico. Spatial characteristics of the landscape were determined from aerial color photographs and were digitized into a GIS package for analysis. Millipede species diversity and composition in these forest patches showed correlations with their surroundings (e.g. amount of forest in the matrix) and with the presence of vegetation corridors that connected to other forest patches, rather than forest patch attributes such as patch area and shape. Millipede species richness correlated negatively with the degree of isolation of forest patch (within 600 m radius), while species evenness correlated positively to the amount of forest within a 50 m buffer. Millipede species composition was related with the presence of vegetation corridors and the distance to the Luquillo Experimental Forest reserve. These findings show that a low degree of patch isolation, forested buffers, and presence of vegetation corridors need to be considered for the conservation and management of forest patches surrounded by urban developments, especially to protect terrestrial invertebrate species that require forested habitats for their dispersal.  相似文献   

19.
Tropical plantations are rapidly expanding as a source of industrial wood. In Indonesia, such large-scale industrial plantations are generally made of large mono-specific blocks interspersed with natural forest remnants. The extent and biodiversity value of these remnants vary as laws and regulations on their design and management are either unclear, without solid scientific basis or left to the interpretation of private companies responsible for the plantations. Our study area comprises of three Acacia mangium plantations, which have on average 18% of their total area set aside from production and conserved as natural forests. These remnant natural forests may, if appropriately designed and managed, be used to mitigate the negative impact of plantations on biodiversity by providing some degree of connectivity with and between remaining natural forest patches (such as the Tesso Nilo conservation area). We sampled natural vegetation in one and primate diversity in all three plantation sector and examined patterns of primate species richness and abundance with relation to spatial arrangement and dimensions of conservation area, which has been set aside from plantation production. We demonstrate unambiguously the critical importance of a well-connected network of natural forest corridors in the plantation landscape to maintain primates and discuss the potential biodiversity value of natural forest remnants in broad-scale industrial landscapes.  相似文献   

20.
In the Taita Hills in southern Kenya, remnants of the original Afromontane forest vegetation are restricted to isolated mountain peaks. To assess the level of degradation and the need for forest restoration, we examined how forest plant communities and their indicator species vary between and within remnant patches of cloud forest. We used ordinal abundance data to compare plant communities in eight forest fragments. We also analyzed data on the diversity and abundance of trees in 57 0.1 ha plots to compare tree communities within and between the largest two of these fragments, Ngangao (120 ha) and Mbololo (220 ha). The extant vegetation of the Taita Hills at landscape scale consists of secondary moist montane to intermediate montane forest. There was a high species dissimilarity between fragments (69%). Variation in species composition coincided with an abiotic gradient related to elevation. At plot level, secondary successional species and species of forest edges were most abundant and most frequent. Inferred clusters of plots almost entirely coincided with the two forest fragments. Indicator species associated with forest margins and gaps were more frequent in the smaller of the two forest fragments, while indicators for the larger fragment were more typical for less disturbed moist forest. Abiotic site variability but also different levels of disturbance determine site-specific variants of the montane forest. Conservation efforts should not only focus on maintaining forest quantity (size), but also on forest quality (species composition). Late-successional rainforest species are underrepresented in the woody plant communities of the Taita Hills and assisting restoration of viable populations of cloud forest climax tree species is urgently needed.  相似文献   

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