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1.
Intensification of food production in tropical landscapes in the absence of land‐use planning can pose a major threat to biological diversity. Decisions on whether to spatially integrate or segregate lands for production and conservation depend in part on the functional relations between biological diversity and agricultural productivity. We measured diversity, density, and species composition of birds along a gradient of production intensification on an agricultural frontier of the Argentine Chaco, where dry tropical forests are cleared for cattle production. Bird species diversity in intact forests was higher than in any type of cattle‐production system. Bird species richness decreased nonlinearly as cattle yield increased. Intermediate‐intensity silvopastoral systems, those in which forest understory is selectively cleared to grow pastures of non‐native plants beneath the tree canopy, produced 80% of the mean cattle yield obtained in pastures on cleared areas and were occupied by 70–90% of the number of bird species present in the nearest forest fragments. Densities of >50% of bird species were significantly lower in open pastures than in silvopastoral systems. Therefore, intermediate‐intensity silvopastoral systems may have the greatest potential to sustain cattle yield and conserve a large percentage of bird species. However, compared with low‐intensity production systems, in which forest structure and extent were intact, intermediate‐intensity silvopastoral systems supported significantly fewer forest‐restricted bird species and fewer frugivorous birds. These data suggest that the integration of production and conservation through intermediate‐intensity silvopastoral systems combined with the protection of forest fragments may be required to maintain cattle yield, bird diversity, and conservation of forest‐restricted species in this agricultural frontier. Compromisos entre la Producción de Ganado y la Conservación de Aves en una Frontera Agrícola del Gran Chaco de Argentina  相似文献   

2.
To meet the growing demand for chocolate, cocoa (Theobroma cacao) agriculture is expanding and intensifying. Although this threatens tropical forests, cocoa sustainability initiatives largely overlook biodiversity conservation. To inform these initiatives, we analyzed how cocoa agriculture affects bird diversity at farm and landscape scales with a meta-analysis of 23 studies. We extracted 214 Hedges' g* comparisons of bird diversity and 14 comparisons of community similarity between a forest baseline and 4 farming systems that cover an intensification gradient in landscapes with high and low forest cover, and we summarized 119 correlations between cocoa farm features and bird diversity. Bird diversity declined sharply in low shade cocoa. Cocoa with >30% canopy cover from diverse trees retained bird diversity similar to nearby primary or mature secondary forest but held a different community of birds. Diversity of endemic species, frugivores, and insectivores (agriculture avoiders) declined, whereas diversity of habitat generalists, migrants, nectarivores, and granivores (agriculture associates) increased. As forest decreased on the landscape, the difference in bird community composition between forest and cocoa also decreased, indicating agriculture associates replaced agriculture avoiders in forest patches. Our results emphasize the need to conserve forested landscapes (land sparing) and invest in mixed-shade agroforestry (land sharing) because each strategy benefits a diverse and distinct biological community.  相似文献   

3.
As tropical regions are converted to agriculture, conservation of biodiversity will depend not only on the maintenance of protected forest areas, but also on the scope for conservation within the agricultural matrix in which they are embedded. Tree cover typically retained in agricultural landscapes in the neotropics may provide resources and habitats for animals, but little is known about the extent to which it contributes to conservation of animal species. Here, we explore the animal diversity associated with different forms of tree cover for birds, bats, butterflies, and dung beetles in a pastoral landscape in Nicaragua. We measured species richness and abundance of these four animal taxa in riparian and secondary forest, forest fallows, live fences, and pastures with high and low tree cover. We recorded over 20,000 individuals of 189 species including 14 endangered bird species. Mean abundance and species richness of birds and bats, but not dung beetles or butterflies, were significantly different among forms of tree cover. Species richness of bats and birds was positively correlated with tree species richness. While the greatest numbers of bird species were associated with riparian and secondary forest, forest fallows, and pastures with >15% tree cover, the greatest numbers of bat species were found in live fences and riparian forest. Species assemblages of all animal taxa were different among tree cover types, so that maintaining a diversity of forms of tree cover led to conservation of more animal species in the landscape as a whole. Overall, the findings indicate that retaining tree cover within agricultural landscapes can help conserve animal diversity, but that conservation efforts need to target forms of tree cover that conserve the taxa that are of interest locally. Preventing the degradation of remaining forest fragments is a priority, but encouraging farmers to maintain tree cover in pastures and along boundaries may also make an important contribution to animal conservation.  相似文献   

4.
Spatial and Seasonal Patterns of Bird Communities in Italian Agroecosystems   总被引:2,自引:0,他引:2  
Abstract:  Despite agricultural landscapes covering almost 60% of the total land area of Italy, knowledge of the effects of agriculture and its intensification on bird communities is still scarce. I analyzed the effects of land uses on bird diversity and community structure in different farmland habitats of lowland northwestern Italy. I surveyed breeding and overwintering birds with a hierarchically nested sampling design and used generalized linear and mixed models to investigate the relationships between the diversity and abundance of birds and habitat or landscapes attributes. The effects of agriculture on α avian diversity varied with season and spatial scale, whereas nonagricultural habitats (long-term fallows or woodlands) had a generally positive effect that was constant throughout time and space. As the amount of woodland habitat increased, spatial turnover (β diversity) of breeding birds decreased. Arable landscapes supported low levels of avian diversity throughout the year but were favored by emblematic farmland birds that have declined severely in Europe and in the study area. Farmland birds (40% of which are experiencing population declines) were more abundant or foraged more frequently in the less-disturbed habitat types such as fallows, grasslands, and winter stubbles and tended to avoid the prevailing cultivations (maize, vineyard, and wheat). Landscape simplification, the expansion of maize cultivation, winter plowing practices, and the conversion of highly diverse grasslands to tilled lands are likely to be responsible for the local decline of most farmland species (Skylark [Alauda arvensis ], Starling [Sturnus vulgaris ], buntings [Emberiza spp.], and wagtails [Motacilla spp.]) and for the increase of birds that are turning into agricultural pests (Hooded Crow [Corvus corone cornix ]).  相似文献   

5.
Agroforests can play an important role in biodiversity conservation in complex landscapes. A key factor distinguishing among agroforests is land-use history – whether agroforests are established inside forests or on historically forested but currently open lands. The disparity between land-use histories means the appropriate biodiversity baselines may differ, which should be accounted for when assessing the conservation value of agroforests. Specifically, comparisons between multiple baselines in forest and open land could enrich understanding of species’ responses by contextualizing them. We made such comparisons based on data from a recently published meta-analysis of the effects of cocoa (Theobroma cacao) agroforestry on bird diversity. We regrouped rustic, mixed shade cocoa, and low shade cocoa agroforests, based on land-use history, into forest-derived and open-land-derived agroforests and compared bird species diversity (species richness, abundance, and Shannon's index values) between forest and open land, which represented the 2 alternative baselines. Bird diversity was similar in forest-derived agroforests and forests (Hedges’ g* estimate [SE] = -0.3144 [0.3416], p = 0.36). Open-land-derived agroforests were significantly less diverse than forests (g* = 1.4312 [0.6308], p = 0.023) and comparable to open lands (g* = -0.1529 [0.5035], p = 0.76). Our results highlight how land-use history determined the conservation value of cocoa agroforests. Forest-derived cocoa agroforests were comparable to the available – usually already degraded – forest baselines, but entail future degradation risks. In contrast, open-land-derived cocoa agroforestry may offer restoration opportunities. Our results showed that comparisons among multiple baselines may inform relative contributions of agroforestry systems to bird conservation on a landscape scale.  相似文献   

6.
Abstract: Studies have documented biodiversity losses due to intensification of coffee management (reduction in canopy richness and complexity). Nevertheless, questions remain regarding relative sensitivity of different taxa, habitat specialists, and functional groups, and whether implications for biodiversity conservation vary across regions. We quantitatively reviewed data from ant, bird, and tree biodiversity studies in coffee agroecosystems to address the following questions: Does species richness decline with intensification or with individual vegetation characteristics? Are there significant losses of species richness in coffee‐management systems compared with forests? Is species loss greater for forest species or for particular functional groups? and Are ants or birds more strongly affected by intensification? Across studies, ant and bird richness declined with management intensification and with changes in vegetation. Species richness of all ants and birds and of forest ant and bird species was lower in most coffee agroecosystems than in forests, but rustic coffee (grown under native forest canopies) had equal or greater ant and bird richness than nearby forests. Sun coffee (grown without canopy trees) sustained the highest species losses, and species loss of forest ant, bird, and tree species increased with management intensity. Losses of ant and bird species were similar, although losses of forest ants were more drastic in rustic coffee. Richness of migratory birds and of birds that forage across vegetation strata was less affected by intensification than richness of resident, canopy, and understory bird species. Rustic farms protected more species than other coffee systems, and loss of species depended greatly on habitat specialization and functional traits. We recommend that forest be protected, rustic coffee be promoted, and intensive coffee farms be restored by augmenting native tree density and richness and allowing growth of epiphytes. We also recommend that future research focus on potential trade‐offs between biodiversity conservation and farmer livelihoods stemming from coffee production.  相似文献   

7.
The South American dry Chaco is a mosaic of woody vegetation and grasslands with high deforestation rates in recent decades. Considering forests and grasslands as the main natural habitats, we assessed the trade-offs between bird populations and agricultural production to compare the potential consequences of different land use strategies (‘sharing’, ‘sparing’, and intermediate) for populations of bird species sensitive to agriculture, while attaining a regional production target. We evaluated how populations responded to scenarios with different proportions of forest and grasslands, considering three reference states (100% forest, 80:20% and 50:50% forest and grasslands, respectively); and scenarios capable of meeting three after-farming scenarios, with land destined to reach a regional production target with three variations of forest:grasslands within spared land. We fitted curves to relate bird abundance to agricultural yield along a gradient of meat production intensity; and we classified bird species as ‘losers’ (if their populations were lower than the baseline population in the reference state, at any level of production) and ‘winners’ (if their current populations were higher than the baseline population). At the ‘current’ (c. 2010) level of regional agricultural production, we found a similar number of loser species maximized by land-sparing and land-sharing strategies; while intermediate strategies were the least favourable to balance production and bird populations. Under the most probable scenarios of increases in regional meat production, most loser bird species populations were maximized by a land-sparing strategy, suggesting that if meat production targets are going to increase in the region, this can be more efficiently achieved by combining well-protected forests and grasslands, and high-yielding mechanized agriculture (e.g. soybean). Our results highlight the importance of assessing all the important natural habitats (e.g. forests and grasslands) of a region to explore conservation strategies at a regional scale.  相似文献   

8.
Abstract: Changes in land use and land cover have affected and will continue to affect biological diversity worldwide. Yet, understanding the spatially extensive effects of land‐cover change has been challenging because data that are consistent over space and time are lacking. We used the U.S. National Land Cover Dataset Land Cover Change Retrofit Product and North American Breeding Bird Survey data to examine land‐cover change and its associations with diversity of birds with principally terrestrial life cycles (landbirds) in the conterminous United States. We used mixed‐effects models and model selection to rank associations by ecoregion. Land cover in 3.22% of the area considered in our analyses changed from 1992 to 2001, and changes in species richness and abundance of birds were strongly associated with land‐cover changes. Changes in species richness and abundance were primarily associated with changes in nondominant types of land cover, yet in many ecoregions different types of land cover were associated with species richness than were associated with abundance. Conversion of natural land cover to anthropogenic land cover was more strongly associated with changes in bird species richness and abundance than persistence of natural land cover in nearly all ecoregions and different covariates were most strongly associated with species richness than with abundance in 11 of 17 ecoregions. Loss of grassland and shrubland affected bird species richness and abundance in forested ecoregions. Loss of wetland was associated with bird abundance in forested ecoregions. Our findings highlight the value of understanding changes in nondominant land cover types and their association with bird diversity in the United States.  相似文献   

9.
Although agricultural intensification is thought to pose a significant threat to species, little is known about its role in driving biodiversity loss at regional scales. I assessed the effects of a major component of agricultural intensification, agricultural chemical use, and land‐cover and climatic variables on butterfly diversity across 81 provinces in Turkey, where agriculture is practiced extensively but with varying degrees of intensity. I determined butterfly species presence in each province from data on known butterfly distributions and calculated agricultural chemical use as the proportion of agricultural households that use chemical fertilizers and pesticides. I used constrained correspondence analyses and regression‐based multimodel inference to determine the effect of environmental variables on species composition and richness, respectively. The variation in butterfly species composition across the provinces was largely explained (78%) by the combination of agricultural chemical use, particularly pesticides, and climatic and land‐cover variables. Although overall butterfly richness was primarily explained by climatic and land‐cover variables, such as the area of natural vegetation cover, threatened butterfly richness and the relative number of threatened butterfly species decreased substantially as the proportion of agricultural households using pesticides increased. These findings suggest that widespread use of agricultural chemicals, or other components of agricultural intensification that may be collinear with pesticide use, pose an imminent threat to the biodiversity of Turkey. Accordingly, policies that mitigate agricultural intensification and promote low‐input farming practices are crucial for protecting threatened species from extinction in rapidly industrializing nations such as Turkey. Efectos del Uso Extensivo de Agroquímicos sobre la Diversidad de Mariposas en Provincias Turcas  相似文献   

10.
Conversion of agricultural land to forest plantations is a major driver of global change. Studies on the impact of forest plantations on biodiversity in plantations and in the surrounding native vegetation have been inconclusive. Consequently, it is not known how to best manage the extensive areas of the planet currently covered by plantations. We used a novel, long‐term (16 years) and large‐scale (30,000 ha) landscape transformation natural experiment (the Nanangroe experiment, Australia) to test the effects of land conversion on population dynamics of 64 bird species associated with woodland and forest. A unique aspect of our study is that we focused on the effects of plantations on birds in habitat patches within plantations. Our study design included 56 treatment sites (Eucalyptus patches where the surrounding matrix was converted from grazed land to pine plantations), 55 control sites (Eucalyptus patches surrounded by grazed land), and 20 matrix sites (sites within the pine plantations and grazed land). Bird populations were studied through point counts, and colonization and extinction patterns were inferred through multiple season occupancy models. Large‐scale pine plantation establishment affected the colonization or extinction patterns of 89% of studied species and thus led to a comprehensive turnover in bird communities inhabiting Eucalyptus patches embedded within the maturing plantations. Smaller bodied species appeared to respond positively to plantations (i.e., colonization increased and extirpation of these species decreased in patches surrounded by plantations) because they were able to use the newly created surrounding matrix. We found that the effects of forest plantations affected the majority of the bird community, and we believe these effects could lead to the artificial selection of one group of species at the expense of another.  相似文献   

11.
Importance of Reserve Size and Landscape Context to Urban Bird Conservation   总被引:15,自引:1,他引:15  
Abstract:  We tested whether reserve size, landscape surrounding the reserve, and their interaction affect forest songbirds in the metropolitan area of Seattle, Washington (U.S.A.), by studying 29 reserves of varying size (small, medium, large) and surrounding urbanization intensity (urban, suburban, exurban). Larger reserves contained richer and less even bird communities than smaller reserves. These size effects disappeared when we removed the positive correlation of shrub diversity with reserve size, suggesting that greater habitat diversity in large reserves supported additional species, some of which were rare. Standardizing the number of individuals detected among all reserve size classes reversed the effect of size on richness in exurban landscapes and reduced the magnitude of the effect in suburban or urban landscapes. The latter change suggested that richness increased with reserve size in most landscapes because larger areas also supported larger samples from the regional bird species pool. Most bird species associated with native forest habitat (native forest species) and with human activity (synanthropic species) were present in reserves larger than 42 ha and surrounded by >40% urban land cover, respectively. Thus, we recommend these thresholds as means for conserving the composition of native bird communities in this mostly forested region. Native forest species were least abundant and synanthropic species most abundant in urban landscapes, where exotic ground and shrub vegetation was most common. Therefore, control of exotic vegetation may benefit native songbird populations. Bird nests in shrubs were most dense in medium (suburban) and large reserves (urban) and tended to be most successful in medium (suburban) and large reserves (exurban), potentially supplying another mechanism by which reserve size increased retention of native forest species.  相似文献   

12.
Abstract:  As primary forest is cleared, pastures and secondary forest occupy an increasing space in the Amazonian landscape. We evaluated the effect of forest clearing on a soil macrofauna (invertebrate) community in a smallholder farming system of southeastern Amazonia. We sampled the soil macrofauna in 22 plots of forest, upland rice fields, pastures, and fallows of different ages. In total, we collected 10,728 invertebrates. In cleared plots the species richness per plot of the soil macrofauna fell from 76 to 30 species per plot immediately after forest clearance, and the composition of the new community was different. Ants, termites, and spiders were most affected by the disturbance. In plots deforested several years before, the effect of forest clearance was highly dependent on the type of land use (pasture or fallow). In fallows, the community was similar to the initial state. The species richness per plot in old fallows rose to 66, and the composition was closer to the primary forests than to the other types of land use. On the contrary, in the pastures the species richness per plot remained low at 47. In fallows, all the groups showed a richness close to that in primary forest, whereas in the forest only the richness of earthworms and Coleoptera recovered. Our results show that forest clearing constitutes a major disturbance for the soil macrofauna and that the recovery potential of the soil macrofauna after 6 or 7 years is much higher in fallows than in pastures. Thus, fallows may play a crucial role in the conservation of soil macrofauna.  相似文献   

13.
Abstract: We explored the impact of forest conversion to agricultural mosaic on anuran, lizard, snake, and turtle assemblages of Neotropical dry forests. Over 2 years, we sampled 6 small watersheds on the west coast of Mexico, 3 conserved and 3 disturbed. The disturbed watersheds were characterized by a mosaic of pastures and cultivated fields (corn, beans, squash) intermingled with patches of different successional stages of dry forest. In each watershed, we conducted 11 diurnal and nocturnal time‐constrained searches in 10 randomly established plots. We considered vulnerability traits of species in relation to habitat modification. Eighteen anuran, 18 lizard, 23 snake, and 3 turtle species were recorded. Thirty‐six species (58%) occurred in both forest conditions, and 14 (22%) and 12 species (19%) occurred only in the conserved and disturbed sites, respectively. Assemblages responded differently to disturbance. Species richness, diversity, and abundance of lizards were higher in disturbed forests. Anuran diversity and species richness were lower in disturbed forest but abundance was similar in both forest conditions. Diversity, richness, and abundance of turtles were lower in disturbed forest. The structure and composition of snake assemblages did not differ between forest conditions. We considered species disturbance sensitive if their abundance was significantly less in disturbed areas. Four anuran (22%), 2 lizard (11%), and 3 turtle (100%) species were sensitive to disturbance. No snake species was sensitive. The decline in abundance of disturbance‐sensitive species was associated with the reduction of forest canopy cover, woody stem cover, roots, and litter‐layer ground cover. Anuran species with small body size and direct embryonic development were especially sensitive to forest disturbance. An important goal for the conservation of herpetofauna should be the determination of species traits associated with extinction or persistence in agricultural mosaics.  相似文献   

14.
In the United States, housing density has substantially increased in and adjacent to forests. Our goal in this study was to identify how housing density and human populations are associated with avian diversity. We compared these associations to those between landscape pattern and avian diversity, and we examined how these associations vary across the conterminous forested United States. Using data from the North American Breeding Bird Survey, the U.S. Census, and the National Land Cover Database, we focused on forest and woodland bird communities and conducted our analysis at multiple levels of model specificity, first using a coarse-thematic resolution (basic models), then using a larger number of fine-thematic resolution variables (refined models). We found that housing development was associated with forest bird species richness in all forested ecoregions of the conterminous United States. However, there were important differences among ecoregions. In the basic models, housing density accounted for < 5% of variance in avian species richness. In refined models, 85% of models included housing density and/or residential land cover as significant variables. The strongest guild response was demonstrated in the Adirondack-New England ecoregion, where 29% of variation in richness of the permanent resident guild was associated with housing density. Model improvements due to regional stratification were most pronounced for cavity nesters and short-distance migrants, suggesting that these guilds may be especially sensitive to regional processes. The varying patterns of association between avian richness and attributes associated with landscape structure suggested that landscape context was an important mediating factor affecting how biodiversity responds to landscape changes. Our analysis suggested that simple, broadly applicable, land use recommendations cannot be derived from our results. Rather, anticipating future avian response to land use intensification (or reversion to native vegetation) has to be conditioned on the current landscape context and the species group of interest. Our results show that housing density and residential land cover were significant predictors of forest bird species richness, and their prediction strengths are likely to increase as development continues.  相似文献   

15.
Primary tropical forests are renowned for their high biodiversity and carbon storage, and considerable research has documented both species and carbon losses with deforestation and agricultural land uses. Economic drivers are now leading to the abandonment of agricultural lands, and the area in secondary forests is increasing. We know little about how long it takes for these ecosystems to achieve the structural and compositional characteristics of primary forests. In this study, we examine changes in plant species composition and aboveground biomass during eight decades of tropical secondary succession in Puerto Rico, and compare these patterns with primary forests. Using a well-replicated chronosequence approach, we sampled primary forests and secondary forests established 10, 20, 30, 60, and 80 years ago on abandoned pastures. Tree species composition in all secondary forests was different from that of primary forests and could be divided into early (10-, 20-, and 30-year) vs. late (60- and 80-year) successional phases. The highest rates of aboveground biomass accumulation occurred in the first 20 years, with rates of C sequestration peaking at 6.7 +/- 0.5 Mg C x ha(-1) x yr(-1). Reforestation of pastures resulted in an accumulation of 125 Mg C/ha in aboveground standing live biomass over 80 years. The 80 year-old secondary forests had greater biomass than the primary forests, due to the replacement of woody species by palms in the primary forests. Our results show that these new ecosystems have different species composition, but similar species richness, and significant potential for carbon sequestration, compared to remnant primary forests.  相似文献   

16.
Abstract: Quality of the agricultural matrix profoundly affects biodiversity and dispersal in agricultural areas. Vegetatively complex coffee agroecosystems maintain species richness at larger distances from the forest. Epiphytes colonize canopy trees and provide resources for birds and insects and thus effects of agricultural production on epiphytes may affect other species. We compared diversity, composition, and vertical stratification of epiphytes in a forest fragment and in two coffee farms differing in management intensity in southern Mexico. We also examined spatial distribution of epiphytes with respect to the forest fragment to examine quality of the two agricultural matrix types for epiphyte conservation. We sampled vascular epiphytes in a forest fragment, a shade polyculture farm, and a shade monoculture farm at 100 m, 200 m, and 400 m from the forest. Epiphyte and orchid richness was greater in the forest than in the monoculture but richness was similar in the forest and polyculture farm. Epiphyte species composition differed with habitat type, but not with distance from the forest. In the forest, epiphytes were distributed throughout tree canopies, but in the farms, epiphytes were primarily found on trunks and larger branches. Epiphyte richness and species similarity to forest species declined with distance from the forest fragment in the monoculture, but richness and similarity to forest species did not decline with distance from forest in the polyculture. This suggests polyculture coffee has greater conservation value. In contrast, monoculture coffee is likely a sink habitat for epiphytes dispersing from forests into coffee. Coffee farms differ from forests in terms of the habitat they provide and species composition, thus protecting forest fragments is essential for epiphyte conservation. Nonetheless, in agricultural landscapes, vegetatively complex coffee farms may contribute to conservation of epiphytes more than other agricultural land uses.  相似文献   

17.
Abstract: Extensive habitat loss and changing agricultural practices have caused widespread declines in grassland birds throughout North America. The Flint Hills of Kansas and Oklahoma—the largest remaining tallgrass prairie—is important for grassland bird conservation despite supporting a major cattle industry. In 2004 and 2005, we assessed the community, population, and demographic responses of grassland birds to the predominant management practices (grazing, burning, and haying) of the region, including grasslands restored under the Conservation Reserve Program (CRP). We targeted 3 species at the core of this avian community: the Dickcissel (Spiza americana), Grasshopper Sparrow (Ammodramus savannarum), and Eastern Meadowlark (Sturnella magna). Bird diversity was higher in native prairie hayfields and grazed pastures than CRP fields, which were dominated by Dickcissels. Although Dickcissel density was highest in CRP, their nest success was highest and nest parasitism by Brown‐headed Cowbirds (Moluthrus ater) lowest in unburned hayfields (in 2004). Conversely, Grasshopper Sparrow density was highest in grazed pastures, but their nest success was lowest in these pastures and highest in burned hayfields, where cowbird parasitism was also lowest (in 2004). Management did not influence density and nest survival of Eastern Meadowlarks, which were uniformly low across the region. Nest success was extremely low (5–12%) for all 3 species in 2005, perhaps because of a record spring drought. Although the CRP has benefited grassland birds in agricultural landscapes, these areas may have lower habitat value in the context of native prairie. Hayfields may provide beneficial habitat for some grassland birds in the Flint Hills because they are mowed later in the breeding season than elsewhere in the Midwest. Widespread grazing and annual burning have homogenized habitat—and thus grassland‐bird responses—across the Flint Hills. Diversification of management practices could increase habitat heterogeneity and enhance the conservation potential of the Flint Hills for grassland birds.  相似文献   

18.
Abstract: Little is known about the effects of anthropogenic land‐use change on the amphibians and reptiles of the biodiverse tropical forests of Southeast Asia. We studied a land‐use modification gradient stretching from primary forest, secondary forest, natural‐shade cacao agroforest, planted‐shade cacao agroforest to open areas in central Sulawesi, Indonesia. We determined species richness, abundance, turnover, and community composition in all habitat types and related these to environmental correlates, such as canopy heterogeneity and thickness of leaf litter. Amphibian species richness decreased systematically along the land‐use modification gradient, but reptile richness and abundance peaked in natural‐shade cacao agroforests. Species richness and abundance patterns across the disturbance gradient were best explained by canopy cover and leaf‐litter thickness in amphibians and by canopy heterogeneity and cover in reptiles. Amphibians were more severely affected by forest disturbance in Sulawesi than reptiles. Heterogeneous canopy cover and thick leaf litter should be maintained in cacao plantations to facilitate the conservation value for both groups. For long‐term and sustainable use of plantations, pruned shade trees should be permanently kept to allow rejuvenation of cacao and, thus, to prevent repeated forest encroachment.  相似文献   

19.
Widespread loss of primary habitat in the tropics has led to increased interest in production landscapes for biodiversity conservation. In the Western Ghats biodiversity hotspot in India, shade coffee plantations are located in close proximity to sites of high conservation value: protected and unprotected forests. Coffee is grown here under a tree canopy that may be dominated by native tree species or by nonnative species, particularly silver oak (Grevillea robusta). We investigated the influence of properties at the local scale and the landscape scale in determining bird communities in coffee plantations, with particular emphasis on species of conservation priority. We used systematic point counts in 11 coffee plantation sites and analyzed data in a randomized linear modeling framework that addressed spatial autocorrelation. Greater proportion of silver oak at the local scale and distance to contiguous forests at the landscape scale were implicated as factors most strongly driving declines in bird species richness and abundance, while increased basal area of native tree species, a local-scale variable, was frequently related to increased bird species richness and abundance. The influence of local-scale variables increased at greater distances from the forest. Distance to forests emerged as the strongest predictor of declines in restricted-range species, with 92% reduction in the abundance of two commonly encountered restricted-range species (Pompadour Green Pigeon and Yellow-browed Bulbul) and a 43% reduction in richness of bird species restricted to Indian hill forests within 8 km of forests. Increase in proportion of silver oak from 33% to 55% was associated with 91% reduction in the abundance of one commonly encountered restricted-range species (Crimson-fronted Barbet). One conservation strategy is providing incentives to grow coffee in a biodiversity-friendly manner. One implication of our study is that plantations located at varying distances to the forest cannot be compared fairly for biodiversity friendliness by existing certification methodology. Another is that conservation of existing forests at the landscape scale is essential for maintaining higher biodiversity in coffee plantations. Incentive schemes that promote conservation of remnant forests at the landscape scale and biodiversity-friendly practices locally and that relate to coffee communities as a whole rather than individual planters are likely to be more effective.  相似文献   

20.
Increasing the density of natural reserves in the forest landscape may provide conservation benefits for biodiversity within and beyond reserve borders. We used 2 French data sets on saproxylic beetles and landscape cover of forest reserves (LCFR) to test this hypothesis: national standardized data derived from 252 assessment plots in managed and reserve stands in 9 lowland and 5 highland forests and data from the lowland Rambouillet forest, a forested landscape where a pioneer conservation policy led to creation of a dense network of reserves. Abundance of rare and common saproxylic species and total saproxylic species richness were higher in forest reserves than in adjacent managed stands only in highland forests. In the lowland regional case study, as LCFR increased total species richness and common species abundance in reserves increased. In this case study, when there were two or more reserve patches, rare species abundance inside reserves was higher and common species richness in managed stands was higher than when there was a single large reserve. Spillover and habitat amount affected ecological processes underlying these landscape reserve effects. When LCFR positively affected species richness and abundance in reserves or managed stands, >12‐20% reserve cover led to the highest species diversity and abundance. This result is consistent with the target of 17% forested land area in reserves set at the Nagoya biodiversity summit in 2010. Therefore, to preserve biodiversity we recommend at least doubling the current proportion of forest reserves in European forested landscapes.  相似文献   

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