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1.
The majority of forests in urban areas are small and isolated. Improving habitat quality of small forests instead of increasing
habitat size and connectivity could be an effective means of conserving the biodiversity of such highly fragmented landscapes.
In this study, we investigated the relative importance of habitat quantity, quality and isolation on butterfly assemblages
in urban fragmented forests in Tokyo, Japan. We used four habitat geographic parameters: (1) fragment size, (2) shape index,
(3) isolation (distance to the mainland), and (4) connectivity; and three habitat quality parameters: (1) herbaceous nectar
plant abundance, (2) herbaceous nectar plant diversity, and (3) larval host plant diversity. We surveyed butterfly assemblages
along transects in 20 forest fragments that ranged in size from 1 to 122 ha. We used generalized linear models to relate the
number of species in a fragment to four habitat geographic parameters and three habitat quality parameters. The averaged models
based on AICc showed that fragment size had a strong positive effect on butterfly species richness. There was also a positive effect of
herbaceous nectar plant abundance on species diversity. These findings suggest that improving the habitat quality of small
and isolated forests in highly fragmented landscapes may be capable of maintaining levels of butterfly diversity comparable
to those of large fragments. 相似文献
2.
Roland Horváth Tibor Magura Csaba Szinetár János Eichardt Béla Tóthmérész 《Biodiversity and Conservation》2013,22(10):2139-2150
The role of fragment size, isolation and habitat diversity in the conservation of spider assemblages living in fragmented landscape were studied in dry sandy grasslands (East Hungary, Nyírség). Spiders were collected using pitfall traps at eight dry grassland fragments from 2001 to 2009 from March to October fortnightly. We tested the rules of island biogeography, which suggest that the species richness increases with the size and decreases with the isolation of fragments. The habitat diversity is an important factor for species richness, since large areas usually have more habitats; therefore, the number of species may be higher in these areas. During the 9-year study period, altogether 10,544 individuals belonging to 106 species were collected. Contradicting the classical theory, we found a significant negative relationship between the total number of spider species and the grassland size, while the ratio of sandy grassland specialist spider species increased with fragment size. The relationship between the ratio of generalist species and the fragment size was not significant. The overall species richness and the isolation of studied grasslands did not show a significant relationship. The ratio of sandy grassland specialist species decreased, while the ratio of generalist species increased with the increasing of isolation. The habitat diversity did not show any effect on spider species richness. We concluded that to conserve the habitat specialist species it is recommended to preserve the large and least isolated grassland fragments, furthermore to increase the size of small fragments with the restoration of the adjacent croplands. 相似文献
3.
Question: Is plant diversity in fragmented semi‐natural grasslands related to present and historical landscape context? Location: Southern Sweden. Methods: Plant diversity was described at 30 semi‐natural grassland sites in terms of total and specialist plant species richness at the site and species density at different scales (0.5–10 m2). These measures are commonly used to assess conservation value of semi‐natural grasslands. Landscape context was measured as contemporary connectivity to other semi‐natural grasslands, historical connectivity 50 years ago, amount of linear elements potentially suitable for dispersal (road verges, power line clearings), and amount of forest (inverse of the openness of the landscape). Results: The diversity measures were generally correlated with each other, implying that species richness in a subset of the grassland can predict the total richness. Plant species density at three scales (0.5 m2, 10 m2 and total) was related to the landscape context using an information theoretic approach. Results showed that total species richness increased with increased size of grasslands, contrary to earlier diversity studies in semi‐natural grasslands. Larger grasslands were more heterogeneous than smaller grasslands, and this is a likely reason for the species‐area relationship. Heterogeneity was also of high importance at the smaller scales (0.5 m2, 10 m2). With increased amount of forest, total species richness increased but species density on 10 m2 decreased. There was no influence of connectivity in either the contemporary or the historical landscape, contrary to previous studies. Conclusions: Grassland size and heterogeneity are of greater importance for plant diversity in semi‐natural grassland, than grassland connectivity in the landscape. 相似文献
4.
The Importance of Tropical Rain Forest Fragments to the Conservation of Plant Species Diversity in Los Tuxtlas, Mexico 总被引:1,自引:0,他引:1
Of what value are forest fragments to the conservation of the tropical rain forest diversity for a landscape? We compared the changes in composition, diversity, and plant structure of 15 small (1–76 ha) relatively unprotected forest fragments with those of a large (700 ha) well protected fragment (LWPF) in Los Tuxtlas, Mexico. The trees, shrubs, lianas, palms, and herbs with dbh?≥?2.5 cm were sampled in 1000 m2 at each site. For each ecological group (based on light requirements for germination: primary, secondary, and non-secondary light demanding, NSLD, species) and life form, estimates of species diversity, density, and basal area were analyzed using a stepwise multiple regression to determine whether there were any relationships between these variables and fragment characteristics (size, shape index, and isolation). The composition and plant structure of LWPF were different from those of the small fragments and large trees are absent from the canopy of the latter. Fragment size best explained the differences in composition and plant structure. Species composition in the largest fragments was similar to that of LWPF, but there was no significant difference in total richness between LWPF and the fragments, even though both the richness and abundance of secondary and NSLD species did differ. LWPF had more large primary trees in the canopy, and a greater abundance and basal area of palms and herbs. For tropical rain forest conservation, it is important to maintain the greatest possible number of large fragments and establish policies that prevent forest remnants from being further reduced in size and increasingly isolated from each other. 相似文献
5.
Laura Meneses Calvillo Virginia Meléndez Ramírez Víctor Parra-Tabla Jorge Navarro 《Journal of Insect Conservation》2010,14(4):323-334
The effects of fragmentation on tropical bee communities are not well understood. The present study investigated these effects
on wild bee species richness and diversity in fragments of tropical forest in the Yucatan Estate (Mexico). We present an analysis
of bee community structure based on fragment size, connectivity, and bee life form, and include an analysis of m-dominance to evaluate if large fragments sustain greater species diversity compared to small fragments. Results indicated
that the bee community within each fragment was composed of different bee species, and that species richness and diversity
increased with fragment size, although this relationship varied between the life forms. Results suggest a high degree of isolation
between fragments and greater differences in species composition. The m-dominance analysis indicated that 37% of the species recorded were restricted to medium and large-size fragments, while all
other species were randomly distributed across fragments of different size in general; ours results indicate that not only
do large fragments support greater species diversity than small fragments, but they are also essential for the conservation
of wild bee species. 相似文献
6.
Question: We asked how landscape configuration and present management influence plant species richness and abundance of habitat specialists in grasslands in a ‘modern’(much exploited and transformed) agricultural Swedish landscape. Location: Selaön, south‐eastern Sweden (59°24’ N, 17°10’ E). Methods: Present and past (150 and 50 years ago) landscape pattern was analysed in a 25 km2 area. Species richness was investigated in 63 different grassland patches; grazed and abandoned semi‐natural grasslands, and grazed ex‐arable fields. Influence of landscape variables; area, past and present grassland connectivity, present management on total species richness, density and abundance of 25 grassland specialists was analysed. Results: Semi‐natural grasslands (permanent unfertilised pastures or meadows formed by traditional agricultural methods) had declined from 60% 150 years ago to 5% today. There was a significant decline in species richness and density in abandoned semi‐natural grasslands. Total species richness was influenced by present management, size and connectivity to present and past grassland pattern. Landscape variables did not influence species density in grazed semi‐natural grassland suggesting that maintained grazing management makes grassland patches independent of landscape context. The abundance of 16 grassland specialists was mainly influenced by management and to some extent also by landscape variables. Conclusion: Although species richness pattern reflect management and to some extent landscape variables, the response of individual species may be idiosyncratic. The historical signal from past landscapes is weak on present‐day species richness in highly transformed, agricultural landscapes. Generalizations of historical legacies on species diversity in grasslands should consider also highly transformed landscapes and not only landscapes with a high amount of diversity hotspots left. 相似文献
7.
European calcareous grasslands have decreased dramatically in area and number during the last two centuries. As a result,
many populations of calcareous grassland species are confined to small and isolated fragments, where their long-term survival
is to some extent uncertain. Recently, several restoration projects have been initiated to enlarge the current grassland area
in order to maintain the exceptionally high species richness. However, from a genetic point of view, the success of these
restoration measures is not necessarily guaranteed, as strong historical decreases in population size and limited gene flow
may have led to low genetic diversity through genetic bottlenecks and drift. In this study, we investigated genetic diversity
and structure of 16 populations of the calcareous grassland specialist Cirsium acaule in a severely fragmented landscape in south-western Belgium. The overall distribution of this species in the study area was
significantly and positively related to patch area, suggesting that small patches do not allow survival of this species. Both
allelic richness and genetic diversity were significantly and positively related to population size. Estimation of observed
and expected gene diversity provided evidence for population bottlenecks in the history of not less than 31% of all sampled
populations. Reconstruction of the historical land use showed that patch area decline in populations that went through a recent
bottleneck was significantly larger than that in populations that showed no evidence of a bottleneck. Assignment analyses
showed low migration rates, suggesting that replenishment of lost alleles through gene flow is highly unlikely. Overall, our
results indicate that in the absence of gene flow strong decreases in calcareous grassland area may have long-lasting effects
on genetic diversity of plant populations and may hamper the success of restoration projects that simply aim at restoring
initial habitat conditions or enlarging population fragments, as indicated by the fact that none of the recently restored
areas has been occupied by C. acaule. 相似文献
8.
Landscape and area effects on beetle assemblages in Ontario 总被引:5,自引:0,他引:5
We compared beetles collected from eight forest fragments in a suburban-agricultural setting and one contiguous forest in south-central Ontario. Samples were collected by pan traps from the interior of continuous forest and upland deciduous forest fragments ranging in size from 43 to 2350 ha. The pooled sample was composed of 4561 individuals from 117 species. Differences in beetle assemblages was primarily due to variation in patch isolation, although actual fragment size had a significant effect on the abundance of native and forest specializing carabid species, and the amount of forest interior habitat had a significant effect on the total number of beetle species and ground beetle species richness (family Carabidae). Fragments which were less isolated on a local scale (within a 2 km radius) had a species composition most similar to that found in continuous forest, regardless of whether the actual forest area was small or large. Marked differences in abundance and biomass were also attributed to variation in the amount of local forest cover. We suggest that a reduction in patch isolation may be an appropriate conservation strategy to improve beetle diversity and abundance in fragmented landscapes. 相似文献
9.
Scott M. Reid Nicholas E. Mandrak Leon M. Carl Chris C. Wilson 《Environmental Biology of Fishes》2008,81(1):111-125
Redhorse, Moxostoma spp., are considered to be negatively affected by dams although this assertion is untested for Canadian populations. One
hundred and fifty-one sites in the Grand River watershed were sampled to identify factors influencing the distribution of
redhorse species. Individual species of redhorse were captured from 3 to 32% of sites. The most widespread species were golden
redhorse, M. erythrurum (30%) and greater redhorse, M. valenciennesi (32%), while river redhorse, M. carinatum, was only found along the lower Grand River. Redhorse were absent from the highly fragmented Speed River sub-watershed and
upper reaches of the Conestogo River and the Grand River. Redhorse species richness was positively correlated to river fragment
size and upstream drainage area. Generalized additive models (GAMs) were applied to evaluate the influence of river fragment
length, connectivity and habitat on species distribution. Principal component analysis reduced habitat data to three axes
representing: channel structure, substrate, and pool, riffle and run habitats (PC1); gradient and drainage area (PC2); and
cover (PC3). GAMs indicate that PC2 was important for predicting black redhorse and greater redhorse site occupancy and PC1
was important for golden redhorse. River fragment length was important for predicting site occupancy for shorthead redhorse,
but not other species. 相似文献
10.
As a consequence of agricultural intensification and habitat fragmentation since the mid-20th century, biological diversity has declined considerably throughout the world, particularly in Europe. We assessed how habitat and landscape-scale heterogeneity, such as variation in fragment size (small vs. large) and landscape configuration (measured as connectivity index), affect plant and arthropod diversity. We focused on arthropods with different feeding behaviour and mobility, spiders (predators, moderate dispersal), true bugs (mainly herbivores and omnivores with moderate dispersal), wild bees (pollinators with good dispersal abilities), and wasps (pollinators, omnivores with good dispersal abilities). We studied 60 dry grassland fragments in the same region (Hungarian Great Plain); 30 fragments were represented by the grassland component of forest-steppe stands, and 30 were situated on burial mounds (kurgans). Forest-steppes are mosaics of dry grasslands with small forests in a matrix of plantation forests. Kurgans are ancient burial mounds with moderately disturbed grasslands surrounded by agricultural fields. The size of fragments ranged between 0.16–6.88 ha (small: 0.16–0.48 ha, large: 0.93–6.88 ha) for forest-steppes and 0.01–0.44 ha (small: 0.01–0.10 ha and large: 0.20–0.44 ha) for kurgans. Fragments also represented an isolation gradient from almost cleared and homogenous landscapes, to landscapes with relatively high compositional heterogeneity. Fragment size, connectivity, and their interaction affected specialist and generalist species abundances of forest-steppes and kurgans. Large fragments had higher species richness of ground-dwelling spiders, and the effect of connectivity was more strongly positive for specialist arthropods and more strongly negative for generalists in large than in small fragments. However, we also found a strong positive impact of connectivity for generalist plants in small kurgans in contrast to larger ones. We conclude that besides the well-known effect of enhancing habitat quality, increasing connectivity between fragments by restoring natural and semi-natural habitat patches would help to maintain grassland biodiversity. 相似文献
11.
Habitat fragmentation reduces the available habitat area and increases both the distance between fragments and the amount of fragment edges. Therefore, there are more probabilities of plant population size reduction and species extinction. In the same way, biotic and abiotic changes associated with forest fragmentation can dramatically alter plant growth and phenological patterns. We conducted a 3-year study to analyze effects of habitat fragmentation and seasonal variation on host plant quality (quantity of leaves, diameter at breast height, tree height), gall abundance and species richness in a temperate oak forest. Our results show that host plant quality was significantly higher in isolated oaks and small fragments, increasing the abundance and species richness of oak gall wasp species in most fragmented habitats. Oak canopy cover is altered by forest fragmentation, there being higher production of leaves on trees that are more exposed to fragmentation, and can provide important resources for maintaining gall wasp species diversity in a fragmented landscape. We found higher gall wasp richness and abundance in autumn than in the spring, which matches with the higher quantity of leaves in this season. 相似文献
12.
Noé U. de la Sancha José F. González-Maya Sarah A. Boyle Pastor E. Pérez-Estigarribia J. Nicolas Urbina-Cardona Nancy E. McIntyre 《Diversity & distributions》2023,29(3):349-363
Aim
Deforestation of the Atlantic Forest of eastern Paraguay has been recent but extensive, resulting in a fragmented landscape highly influenced by forest edges. We examined edge effects on multiple dimensions of small mammalian diversity.Location
Forest fragments of eastern Paraguayan Atlantic Forest.Methods
We trapped small mammal species at different distances from the forest edge (DTE) in reserves and estimated multiple dimensions of diversity per site. Similarity analysis identified species clusters that best described the patterns of diversity across reserves. Multivariate ordination and linear mixed models were used to determine the influence of DTE on various dimensions of small mammal diversity.Results
There was an increase in richness and abundance along a DTE gradient, and remnants with higher edge:area ratios showed higher richness and abundance, independent of remnant size. Species at edges were generalists, open-habitat species or exotic species (spillover effect). We found higher phylogenetic diversity and functional richness and divergence towards forest edges. Spillover of non-forest and invasive species best explained richness, generalist forest species best explained total abundance, abundance of Hylaeamys megacephalus best explained diversity and evenness metrics and the presence of Marmosa paraguayana best explained various phylogenetic diversity models. None of the models that included megafauna or social factors were shown to be important in explaining patterns as a function of DTE.Main Conclusions
We found strong support for a spillover effect and mixed support for complementary resource use and enhanced habitat resources associated with ecotones. Generalists characterized edge assemblages but not all generalists were equivalent. Edges showed more phylogenetically and functionally distinct assemblages than the interior of remnants. There was a conservation of functional diversity; however, open-habitat species, habitat generalists and exotic species boosted diversity near forest edges. Mechanisms governing diversity along forest edges are complex; disentangling those mechanisms necessitates the use of multiple dimensions of diversity. 相似文献13.
Landscape‐level tree cover predicts species richness of large‐bodied frugivorous birds in forest fragments
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Scott T. Walter Luke Browne Juan Freile Jorge Olivo Mónica González Jordan Karubian 《Biotropica》2017,49(6):838-847
Large‐bodied frugivorous birds play an important role in dispersing large‐sized seeds in Neotropical rain forests, thereby maintaining tree species richness and diversity. Conversion of contiguous forest land to forest fragments is thought to be driving population declines in large‐bodied frugivores, but the mechanistic drivers of this decline remain poorly understood. To assess the importance of fragment‐level versus local landscape attributes in influencing the species richness of large‐bodied (>100 g) frugivorous birds, we surveyed 15 focal species in 22 forest fragments (2.7 to 33.6 ha, avg. = 16.0 ha) in northwest Ecuador in 2014. Fragment habitat variables included density of large trees, canopy openness and height, and fragment size; landscape variables included elevation and the proportion of tree cover within a 1 km radius of each fragment. At both the individual species level, and across the community of 12 species of avian frugivore we detected, there was higher richness and probability of presence in fragments with more tree cover on surrounding land. This tendency was particularly pronounced among some endangered species. These findings corroborate the idea that partially forested land surrounding fragments may effectively increase the suitable habitat for forest‐dwelling frugivorous birds in fragmented landscapes. These results can help guide conservation priorities within fragmented landscapes, with particular reference to retaining trees and reforesting to attain high levels of tree cover in areas between forest patches. 相似文献
14.
Loss and fragmentation of natural ecosystems are widely recognized as the most important threats to biodiversity conservation, with Neotropical dry forests among the most endangered ecosystems. Area and edge effects are major factors in fragmented landscapes. Here, we examine area and edge effects and their interaction, on ensembles of arthropods associated to native vegetation in a fragmented Chaco Serrano forest. We analyzed family richness and community composition of herbivores, predators, and parasitoids on three native plant species in 12 fragments of varying size and at edge/interior positions. We also looked for indicator families by using Indicator Species Analysis. Loss of family richness with the reduction of forest fragment area was observed for the three functional groups, with similar magnitude. Herbivores were richer at the edges without interaction between edge and area effects, whereas predators were not affected by edge/interior position and parasitoid richness showed an interaction between area and position, with a steeper area slope at the edges. Family composition of herbivore, predator, and parasitoid assemblages was also affected by forest area and/or edge/interior situation. We found three indicator families for large remnants and five for edges. Our results support the key role of forest area for conservation of arthropods taxonomic and functional diversity in a highly threatened region, and emphasize the need to understand the interactions between area and edge effects on such diversity. 相似文献
15.
Manoel Santos-Filho Carlos A. Peres Dionei J. da Silva Tânia M. Sanaiotti 《Biodiversity and Conservation》2012,21(4):1127-1147
Tropical forest mammal assemblages are widely affected by the twin effects of habitat loss and habitat fragmentation. We evaluated
the effects of forest patch metrics, habitat structure, age of patch isolation, and landscape metrics on the species richness,
abundance and composition of small mammals at 23 forest fragments (ranging in size from 43 to 7,035 ha) in a highly deforested
3,609-km2 landscape of southwestern Brazilian Amazonia. Using pitfall traps and both terrestrial and arboreal traplines of Sherman, Tomahawk and snap traps, we captured a total of 844 individuals over 34,900 trap-nights representing 26 species and 20 genera of small-mammals,
including 13 rodent and 13 marsupial species. We also consider the effects of distance from forest edges on species occupancy
and abundance. Overall small mammal abundance, species richness and species composition were primarily affected by the quality
of the open-habitat matrix of cattle pastures, rather than by patch metrics such as fragment size. Ultimately, small mammal
community structure was determined by a combination of both landscape- and patch-scale variables. Knowledge of the anthropogenic
factors that govern small mammal community structure is of critical importance for managing the persistence of forest vertebrates
in increasingly fragmented neotropical forest landscapes. 相似文献
16.
Scale-specific correlations between habitat heterogeneity and soil fauna diversity along a landscape structure gradient 总被引:1,自引:0,他引:1
Vanbergen AJ Watt AD Mitchell R Truscott AM Palmer SC Ivits E Eggleton P Jones TH Sousa JP 《Oecologia》2007,153(3):713-725
Habitat heterogeneity contributes to the maintenance of diversity, but the extent that landscape-scale rather than local-scale
heterogeneity influences the diversity of soil invertebrates—species with small range sizes—is less clear. Using a Scottish
habitat heterogeneity gradient we correlated Collembola and lumbricid worm species richness and abundance with different elements
(forest cover, habitat richness and patchiness) and qualities (plant species richness, soil variables) of habitat heterogeneity,
at landscape (1 km2) and local (up to 200 m2) scales. Soil fauna assemblages showed considerable turnover in species composition along this habitat heterogeneity gradient.
Soil fauna species richness and turnover was greatest in landscapes that were a mosaic of habitats. Soil fauna diversity was
hump-shaped along a gradient of forest cover, peaking where there was a mixture of forest and open habitats in the landscape.
Landscape-scale habitat richness was positively correlated with lumbricid diversity, while Collembola and lumbricid abundances
were negatively and positively related to landscape spatial patchiness. Furthermore, soil fauna diversity was positively correlated
with plant diversity, which in turn peaked in the sites that were a mosaic of forest and open habitat patches. There was less
evidence that local-scale habitat variables (habitat richness, tree cover, plant species richness, litter cover, soil pH,
depth of organic horizon) affected soil fauna diversity: Collembola diversity was independent of all these measures, while
lumbricid diversity positively and negatively correlated with vascular plant species richness and tree canopy density. Landscape-scale
habitat heterogeneity affects soil diversity regardless of taxon, while the influence of habitat heterogeneity at local scales
is dependent on taxon identity, and hence ecological traits, e.g. body size. Landscape-scale habitat heterogeneity by providing
different niches and refuges, together with passive dispersal and population patch dynamics, positively contributes to soil
faunal diversity.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
17.
《Plant Ecology & Diversity》2013,6(4):483-492
Background: Habitat loss and fragmentation have been argued to drastically alter the composition of tree assemblages inhabiting small forest fragments but the successional trajectory experienced by such edge-affected habitats remains controversial.Aims: Here we examine whether small fragments (3.4–91.2 ha) support seedling assemblages more similar to those in 10–70-year-old secondary forests than to those in mature forests, in order to infer to what extent fragments move toward early successional systems.Methods: Using 59 0.1-ha plots distributed in a fragmented landscape of Brazilian Atlantic forest, we evaluated species richness and functional and taxonomic composition of seedling assemblages in 20 small forest fragments, 19 stands of secondary forest and 20 stands of mature forests in the interior of an exceptionally large fragment (ca. 3500 ha).Results: Small fragments presented the least species-rich seedling assemblages (17.2 ± 5.7 species), followed by secondary (22.5 ± 5.3), and mature forest (28.4 ± 5.3). Small fragments had seedling assemblages with functional and taxonomic composition more similar to those in secondary than in mature forest. Small fragments had a greater relative richness and abundance of pioneer trees (ca. 40% more), vertebrate-dispersed (6–25%), and those bearing medium-sized seeds (30–70%), while large-seeded species and individuals were reduced (>50% decrement) in comparison to seedling assemblages in mature forest.Conclusions: By comparing seedlings across a wide range of successional habitats we offer evidence that small forest fragments are experiencing an alternative successional pathway towards an early-successional system with reduced plant diversity. 相似文献
18.
Seth B. Magle Kristin A. Salamack Kevin R. Crooks Richard P. Reading 《Biodiversity and Conservation》2012,21(11):2803-2821
Urbanization and habitat fragmentation have the potential to influence bird communities. In addition, these phenomena, as well as ongoing lethal control measures, have also greatly reduced the range of the black-tailed prairie dog (Cynomys ludovicianus) since the beginning of the 20th century. Although prairie dogs are highly interactive species that can influence avian communities, few studies have investigated whether these interactions persist in urban settings. Our goal was to investigate the relative impacts of habitat fragmentation and prairie dogs on bird communities within an urban matrix. We performed bird surveys on 20 habitat fragments (10 colonized by prairie dogs, 10 uncolonized by prairie dogs) distributed throughout the Denver metropolitan area, and calculated Shannon–Weiner diversity and richness of all birds and native species, as well as total counts of grassland birds and raptors. Diversity, richness, and counts of many species increased with increasing fragment connectivity, and decreased on fragments isolated for longer periods of time. Avian diversity and richness did not differ between fragments with and without prairie dogs, suggesting that this element of the ecological role of prairie dogs is not fully retained in urban habitat. Future studies of the role of prairie dogs as keystone species in urban systems should include other taxa as well as consider the influence of the urban matrix surrounding prairie dog habitat. Our results emphasize that conservation of urban avian diversity should focus on landscape connectivity as well as local habitat features. 相似文献
19.
Effects of Habitat Structure and Adjacent Habitats on Birds in Tropical Rainforest Fragments and Shaded Plantations in the Western Ghats, India 总被引:4,自引:4,他引:0
T. R. Shankar Raman 《Biodiversity and Conservation》2006,15(4):1577-1607
As large nature reserves occupy only a fraction of the earth’s land surface, conservation biologists are critically examining
the role of private lands, habitat fragments, and plantations for conservation. This study in a biodiversity hotspot and endemic
bird area, the Western Ghats mountains of India, examined the effects of habitat structure, floristics, and adjacent habitats
on bird communities in shade-coffee and cardamom plantations and tropical rainforest fragments. Habitat and birds were sampled
in 13 sites: six fragments (three relatively isolated and three with canopy connectivity with adjoining shade-coffee plantations
and forests), six plantations differing in canopy tree species composition (five coffee and one cardamom), and one undisturbed
primary rainforest control site in the Anamalai hills. Around 3300 detections of 6000 individual birds belonging to 106 species
were obtained. The coffee plantations were poorer than rainforest in rainforest bird species, particularly endemic species,
but the rustic cardamom plantation with diverse, native rainforest shade trees, had bird species richness and abundance comparable
to primary rainforest. Plantations and fragments that adjoined habitats providing greater tree canopy connectivity supported
more rainforest and fewer open-forest bird species and individuals than sites that lacked such connectivity. These effects
were mediated by strong positive effects of vegetation structure, particularly woody plant variables, cane, and bamboo, on
bird community structure. Bird community composition was however positively correlated only to floristic (tree species) composition
of sites. The maintenance or restoration of habitat structure and (shade) tree species composition in shade-coffee and cardamom
plantations and rainforest fragments can aid in rainforest bird conservation in the regional landscape. 相似文献
20.
Question: Does increasing Festuca canopy cover reduce plant species richness and, therefore, alter plant community composition and the relationship of litter to species richness in old‐field grassland? Location: Southeastern Oklahoma, USA. Methods: Canopy cover by species, species richness, and litter mass were collected within an old‐field grassland site on 16, 40 m × 40 m plots. Our study was conducted during the first three years of a long‐term study that investigated the effects of low‐level nitrogen enrichment and small mammal herbivory manipulations. Results: Succession was altered by an increase in abundance of Festuca over the 3‐yr study period. Species richness did not decline with litter accumulation. Instead, Festuca increased most on species‐poor plots, and Festuca abundance remained low on species‐rich plots. Conclusions: Festuca may act as an invasive transformer‐species in warm‐season dominated old‐field grasslands, a phenomenon associated more with invasions of cool‐season grasses at higher latitudes in North America. 相似文献