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1.
Anecdotal observations suggest that some vertebrates follow plantation rows when crossing between habitat patches in fragmented landscapes, but the frequency of such behavior was never formally tested despite its potential implications for landscape management. We experimentally tested if the didelphid marsupials Didelphis aurita and Philander frenatus use plantation rows as guidelines when searching for habitat patches in a landscape of fragmented Atlantic Forest in Brazil. Thirty-seven individuals of P. frenatus and 24 of D. aurita were captured in forest fragments and released carrying spool-and-line tracking devices at four distances (30-200 m) from a forest fragment, in a matrix of manioc plantations. Animals of both species used plantation rows to orient their initial movements and used rows as guidelines along their paths for navigating in the matrix. By moving predominantly parallel to the plantation rows animals reduced the tortuosity of their paths and obtained an unobstructed view of the landscape ahead. These results demonstrate that the orientation of linear plantations can strongly influence functional connectivity between habitat fragments. Plantation rows should be oriented to maximize connection between nearby fragments, enhancing dispersal success of these species and probably many other terrestrial vertebrates in agricultural landscapes.  相似文献   

2.
Forest fragmentation leads to the creation of isolated forest patches and habitat edges with subsequent impact on forest-interior bird species. Although the effects of fragmentation and edge on avian nesting success are well documented for open cup-nesting species in eastern deciduous forests in North America, it is unclear whether these effects are common for all birds nesting in predominantly forested landscapes. In particular, edge effects on nesting success of cavity-nesting birds are poorly understood. Using natural cavity nests, we examined nesting success of four species of cavity-nesting birds (two nonexcavators and two excavators), the yellow-rumped flycatcher (Ficedula zanthopygia), the great tit (Parus major), the great spotted woodpecker (Picoides major), and the grey-faced woodpecker (Picus canus) in relation to forest edges in Zuojia Nature Reserve, Jilin province, northeastern China. Our primary objective was to assess whether distance to the edge of agricultural lands was related to nesting success for cavity-nesting birds in fragmented forests. A total of 439 natural cavity nests of the four species were located and monitored during four breeding seasons. Probability of nest success was influenced by distance to forest edge for nonexcavators, but not for excavators. The rate of nesting success of the two nonexcavators, yellow-rumped flycatcher and the great tit, increased with distance from the edges. For all cavity nests, nesting success was 0.43 at 0-100 m, 0.56 at 101-200 m, 0.68 at 201-300 m, 0.61 at 301-400 m, 0.77 at 401-500 m from the edges. Nesting success ranged from 0.57 for the yellow-rumped flycatcher to 0.89 for the Grey-faced Woodpecker. Failed nests were often occupied by nest-site competitors (accounting for 68%). However, predation only accounted for 20% of all nest failures. Our results suggest that negative edge effects do exist for some cavity-nesting birds, especially for nonexcavator species.  相似文献   

3.
The loss, fragmentation and degradation of native vegetation are major causes of loss of biodiversity globally. Extinction debt is the term used to describe the ongoing loss of species from fragmented landscapes long after the original loss and fragmentation of habitat. However, losses may also result from habitat changes that are unrelated to fragmentation, which reduce breeding success and recruitment. Many woodland birds have declined in fragmented landscapes in Australia, probably due to loss of small, isolated populations, though the ecological processes are poorly understood. We record the progressive regional loss of two ground-foraging, woodland birds, the Brown Treecreeper Climacteris picumnus and Hooded Robin Melanodryas cucullata, in northern New South Wales, over 30 years. This has happened despite most habitat loss occurring over 100 years ago, suggesting the payment of an extinction debt. Our observations suggest that several ecological processes, caused by habitat loss, fragmentation or degradation, and operating over different time scales, have led to both species’ declines. Female Brown Treecreepers disperse poorly among vegetation remnants, leaving only males in isolated populations, which then go extinct. In contrast, Hooded Robins suffer high nest predation in fragmented landscapes, producing too few recruits to replace adult mortality. Foraging by both species may also be affected by regrowth of ground vegetation and shrubs. We found little support for a major role played by drought, climate change or aggressive Noisy Miners Manorina melanocephala. We propose that both extinction debt in the classical sense and ongoing habitat change frequently contribute to species’ decline in modified landscapes. Management to arrest and reverse such declines needs to consider these multiple causes of decline. For instance, reconnecting isolated populations may be inadequate alone, and activities such as appropriate grazing, fires and the addition of woody debris may also be required.  相似文献   

4.
Fragmented and degraded vegetation characterises agricultural landscapes across southern Australian. Remnant vegetation within these regions performs a number of vital ecological and hydrological roles, but little is known about whether or how fragmentation is affecting the long-term persistence of these critical landscape elements. Acacias are a significant component of many remnant vegetation communities across Australia, forming numerous integral faunal and floral relationships. Here, reproductive output of 11 fragmented Acacia dealbata (Mimosaceae) populations from across the southern tablelands of New South Wales was assessed over 2 years to identify reproductive constraints associated with increasing vegetation fragmentation. Fertilization success is the major reproductive constraint, particularly in small populations, and probably reflects a self-incompatible reproductive strategy. During 2002 larger and more dense populations produced more legumes (p = 0.014 and <0.001, respectively) while in 2003 these two variables were associated with increased fertilization success (p = 0.004 and 0.017, respectively). There was also some suggestion that populations with fewer exotic species also experienced increased fertilization success (p = 0.055). Assessment of plant performance within populations suggests that consistent reproductive output of particular individuals within small populations may limit reproductive compatibility within these populations over time. The long-term persistence of many small A. dealbata populations may be jeopardised by low seed set, and limited recruitment and aging stands. Immediate steps are now required to ensure that these populations continue contributing to landscape function by augmenting populations, improving connectivity, and allowing disturbance events that will stimulate recruitment.  相似文献   

5.
The persistence of amphibian populations in fragmented landscapes requires dispersal and recolonization of habitat patches after local extinction. These processes entail individuals crossing habitat edges. Edge permeability integrates the behavior of individuals with the vegetative structure of the habitat edge and may influence the dispersal rates between habitat patches. We used drift fences, radio telemetry, and an experimental displacement to examine the movement behavior of juvenile and adult spotted salamanders (Ambystoma maculatum) at a pond located in continuous forest and a pond located on a distinct forest-grassland edge. At the pond on the habitat edge, adult salamanders migrated to and from the forested side of the pond. Resident adults with transmitters migrated to forested habitat without approaching the habitat edge. Displaced adults with transmitters halted emigration movements when they approached the habitat edge. None of the radio-tagged adults were observed more than a few meters into the grassland. Recently metamorphosed juveniles exiting the grassland side of the pond changed their direction of movement and migrated into the forested habitat. We conclude that salamanders oriented movements with respect to features in the terrestrial habitat, detected the habitat edge, and behaviorally avoided the grassland. Exploring the permeability of habitat edges will improve our understanding of dispersal within fragmented landscapes and enhance efforts to conserve regional populations of amphibians.  相似文献   

6.
Across the deforestation frontier in eastern Amazonia, we examined the relationship between edge-related forest desiccation and deforestation patterns using remote-sensing techniques. Canopy-moisture levels were estimated over an eight-year period in three study sites that encompassed ∼100,000 km2 in area. We found four main effects of deforestation on dry-season canopy desiccation. First, intact forests showed no detectable change in canopy water content whereas forests adjacent to clearings showed significant water loss. Second, the distance to which edge-related desiccation penetrated into forest interiors varied among landscapes with differing forest loss and fragmentation. In moderately fragmented landscapes (with 65% and 51% remaining forest cover), canopy desiccation extended 1-1.5 km into forest interiors, whereas in heavily fragmented landscapes (20% forest cover) desiccation penetrated up to 2.7 km into forests. Third, the magnitude of edge-related desiccation varied among landscapes with differing fragmentation. Moderately fragmented landscapes exhibited a greater magnitude of change in canopy-water loss over the first 1 km from an edge than did heavily fragmented landscapes. Finally, forest desiccation penetrated further into forests over time in the moderately fragmented landscapes, but not in the heavily fragmented landscape, where edge-related desiccation had evidently ‘saturated’ remaining forests. We conclude that protracted dry seasons will have far more serious effects on fragmented than intact rainforests, with the former becoming highly vulnerable to destructive fires. With ∼30,000 km of new forest edge being created annually in Brazilian Amazonia, these finding have serious implications for forest conservation.  相似文献   

7.
Remnant forest strips are frequently proposed as valuable conservation tools in fragmented tropical landscapes, yet we currently lack evidence to evaluate their potential conservation value for native biota. We examined the potential value for understorey forest birds of 30-year-old riparian and terra firme (unflooded) primary forest strips within a large silvicultural landscape in the north-east Brazilian Amazon, where the matrix is dominated by Eucalyptus plantations. We conducted mist-netting in eight forest strips connected to continuous forest (four of each forest type), with a total of 24 replicate sampling sites located near to (<1 km), far from (2.5-9 km), and within undisturbed forest controls (i.e. 16 samples within the strips, and 8 in controls). Bird communities in both strip types changed with increasing distance along forest remnants into the plantation matrix. Matrix-embedded samples were characterised by a higher representation of birds typical of secondary growth forest but not those typical of the Eucalyptus-dominated matrix. While the long-term viability of the bird populations in these remnants remains unclear, our data demonstrate that forest strips can provide important habitat for many bird species that are otherwise rarely found outside primary forest. Forest strips therefore provide an important tool to enhance biodiversity conservation in plantation landscapes. The relative practical ease with which these areas can be selected and maintained means that the protection of forest strips as part of a wider conservation strategy is likely to have particular appeal to policy makers and landscape managers working in the human-dominated tropics.  相似文献   

8.
Forest clearcutting is a form of habitat alteration that drastically alters the landscape and may contribute to declines in amphibian populations. Indeed, many studies have documented decreases in amphibian abundances and species richness in clearcuts. The development of effective conservation strategies to reduce the effects of timber harvesting has been hindered by lack of knowledge of the mechanisms underlying these changes in abundance. To better understand the potentially negative consequences of forest clearcutting, we used field enclosures in forested and clearcut habitats to examine changes in the survival and growth of juvenile southern toads (Bufo terrestris) over a two-month period. We also conducted a comparative monitoring study using drift fences and pitfall traps in forests and clearcuts to determine the effect of clearcutting on the abundance of juvenile southern toads. We found no significant effect of habitat on the number of juvenile southern toads captured in forests or clearcuts. In contrast, the average survival of toads in clearcut enclosures was significantly reduced compared to that of toads in forested enclosures (17 ± 5% versus 61 ± 3%). Toads surviving in clearcuts were also significantly smaller than those surviving in forested enclosures (27.9 ± 0.1 mm versus 30.3 ± 0.8 mm SVL). Our results highlight the difficulty in interpreting abundance patterns as a sole metric for habitat comparison. Because there is much interest in studying the effects of habitat alteration on amphibian populations, we recommend that future studies place more emphasis on determining changes in vital rates of populations following habitat alteration.  相似文献   

9.
Geographically-based threat assessments are important for identifying natural resources at risk, yet have rarely been applied to identify habitat conservation priorities for imperiled organisms at a local scale. Pool-breeding amphibians have complex life cycles that place them at risk from habitat loss and fragmentation both in wetlands and in adjacent uplands. Because the most rapidly growing cause of habitat degradation in North America has been urbanization, a threat analysis of pool-breeding amphibian habitat should both be dynamic, i.e., sensitive to land-use change, and comprehensive, recognizing traditional protected area networks as well as less formal conservation assets (e.g., land-use regulations). To assess threats to wood frogs (Rana sylvatica) and spotted salamanders (Ambystoma maculatum) in a rapidly urbanizing, forested region of New England (USA) we examined gaps in the current protection network, as well as changing human settlement patterns. We found that greater than 50% of 542 potential breeding pools delineated using low-level infra-red aerial photography (median area 379.5 m2) were not represented on National Wetland Inventory (U.S.FWS) maps, and thus de facto at risk. Most importantly, conservation lands and regulatory protections failed to protect 46% of potential breeding pools and 80% of adjacent non-breeding habitat. While an assessment of human settlement patterns projected that only 5% of the region contained high quality amphibian habitat under acute development pressure, nearly half of the region (44.7%) had attained a moderate threat level, highlighting the importance of conservation planning during early stages of urbanization. We conclude by illustrating the role for multiple conservation strategies when protecting functional landscapes for pool-breeding amphibians.  相似文献   

10.
Many studies have reported increased numbers of certain synanthropic species in urbanizing landscapes, but few have evaluated if urban habitats constitute ecological traps for these species. The Northern cardinal (Cardinalis cardinalis) was used as a model species to evaluate if urban riparian forests might act as ecological traps for understory-nesting birds. Cardinals were surveyed within 2-ha riparian forest plots within rural (n = 6) and urban (n = 6) landscapes in Ohio USA during breeding and non-breeding seasons 2003-2005. Cues used by cardinals to select habitats were identified based on measurements surrounding 219 nests and in 106 randomly-located plots and 96 systematically-located plots. Productivity of 161 cardinal pairs and survival of 180 adults were monitored from late March-September, 2003-2005. Cardinals were 1.7× (in the breeding season) to nearly 4× (in non-breeding season) more abundant in urban than rural forests, and the results suggest that these differences in abundance stemmed from urban-associated changes in habitat and microclimate features used by cardinals to select habitats. Most notably, cardinals were strongly associated with dense understory vegetation and warmer minimum January temperatures, both of which were promoted as urban development increased within the landscapes surrounding riparian forests. Although other studies suggest mismatches between the habitat cues used by cardinals and how those features affect nesting success (e.g., higher nest predation in exotic shrubs), these results provide no evidence that urban forests were acting as ecological traps for cardinals. Instead, cardinals in urban and rural forests had similar numbers of nesting attempts, young fledged over the breeding season, and apparent annual survival rates. Thus, these findings do not support for the idea that urban forests in central Ohio represent ecological traps for synanthropic understory birds.  相似文献   

11.
The little tern (Sterna albifrons) is a species of shorebird that nests in colonies on sandy beaches and riverbanks with little vegetation cover. In Japan, the natural breeding habitats of the terns have decreased drastically, and the species is listed under the category “vulnerable” in the Red List of the Government of Japan. To reduce the effects of habitat loss on the terns, conservationists are attempting to create and manage artificial colony sites in highly developed landscapes, such as reclaimed lands located in Tokyo Bay, central Japan. We present the factors that contribute to breeding success for this species and the habitat characteristics related to nest-site selection in the artificial colony sites along Tokyo Bay. Our data show that around 3 ha of a building rooftop without vegetation cover could sustain more than 2000 little tern nests. We found a strong positive relationship between colony size and hatching success, observing that a colony size of more than 100 lowered predation rates of eggs. On sites built upon white crushed-concrete, nest densities were high and predation rates of eggs were low. We also found that feeding rates were affected by foraging habitats, of which the best types were the shoreline of sandy beaches and mud flats. The 40 km dispersal range of the breeding terns, inferred from distribution data, should be considered when establishing a network of the multiple colony sites.  相似文献   

12.
Many threatened primates now exist in fragmented forest habitats. The survival of these populations may depend on their ability to utilise agricultural or other matrix habitats between forest fragments, but this is poorly known. Here, we systematically investigate an arboreal primate’s use of a heterogeneous matrix in a fragmented forest landscape: the Angola black-and-white colobus (Colobus angolensis palliatus) in southern Kenya. We used a novel technique, based on semi-structured interviews with local informants, to address the difficulty of sampling relatively rare but important events, such as dispersal between fragments. We found that colobus frequently travelled and foraged in indigenous matrix vegetation (such as mangrove, wooded shrubland and shrubland) up to 4 km from the nearest forest fragments. Agricultural habitats, such as perennial plantation (coconut, mango and cashew nut) were also used by colobus for travelling and foraging (in remnant indigenous trees). The probability of sighting colobus in the matrix increased with the proportion of both tall (>6 m) vegetation cover and food tree cover, but declined with distance from forest habitat. Our findings suggest that certain matrix habitats are important for C. a. palliatus, and that future primate conservation initiatives might benefit from adopting a ‘landscape-level’ approach to habitat management, particularly in fragmented forest systems.  相似文献   

13.
The global trend toward more intensive forms of agriculture is changing the nature of matrix habitat in agricultural areas. Removal of components of matrix habitat can affect native biota at the paddock and the landscape scale, particularly where intensification occurs over large areas. We identify the loss of paddock trees due to the proliferation of centre pivot irrigation in dryland farming areas as a potentially serious threat to the remnant biota of these areas. We used a region of south-eastern Australia as a case study to quantify land use change from grazing and dryland cropping to centre pivot irrigation over a 23-year period. We also estimated rates of paddock tree loss in 5 representative landscapes within the region over the same period. The total area affected by centre pivots increased from 0 ha in 1980 to nearly 9000 ha by 2005. Pivots were more likely to be established in areas which had originally been plains savannah and woodlands containing buloke (Allocasuarina luehmannii), a food source for an endangered bird. On average, 42% of paddock buloke trees present in 1982 were lost by 2005. In the two landscapes containing several centre pivots, the loss was 54% and 70%. This accelerated loss of important components of matrix habitat is likely to result in species declines and local extinctions. We recommend that measures to alleviate the likely negative impacts of matrix habitat loss on native biota be considered as part of regional planning strategies.  相似文献   

14.
The rufous treecreeper (Climacteris rufa) has declined in abundance in the agricultural regions of southwestern Australia. The patterns of decline are well documented, but the processes that threaten population persistence are poorly understood. I compared the reproductive success and survival of the treecreeper between three sites in an unfragmented landscape and four remnant categories (large, small, grazed and ungrazed) in a fragmented, agricultural landscape. Nest success and annual productivity were significantly higher in the unfragmented landscape, but varied between sites and remnant categories within landscapes. Nest success was lowest in grazed remnants and annual productivity was positively associated with territory size in the fragmented landscape. Fledgling survival rates did not differ between landscapes, but there was a trend for juvenile survival rates to be higher in the unfragmented landscape. I used artificial nests to compare relative predation rates between landscapes, and provisioning rates and prey biomass brought to nestlings to assess differences in food availability. There were no landscape differences in predation rates, but provisioning rates to nestlings and total prey biomass were significantly lower in the fragmented landscape. Mean habitat quality was also lower in the fragmented landscape, although it differed between remnant categories. Reduced reproductive success, juvenile survival, food availability and habitat quality may threaten the viability of the rufous treecreeper population living in the fragmented landscape. Limiting the modification of remaining habitat (e.g. removing stock grazing) and improving habitat quality are required to assist in the conservation of this species.  相似文献   

15.
The effects of habitat fragmentation on the Australian avifauna have been widespread with species richness and abundance declining with reduced remnant size and habitat quality and increased habitat isolation. The speckled warbler, Chthonicola sagittata is one species from the highly fragmented temperate woodlands of eastern Australia that has declined across its range and populations that remain appear to be patchily distributed in habitat remnants. Specific causes of decline are unknown but several aspects of its biology make the species particularly vulnerable to decline in fragmented landscapes. Here, we analyse survey data (presence/absence) of speckled warblers in a large sample of habitat remnants from three regions to identify patterns of occupancy. We explore the effects of patch size on extinction risk using population viability analyses (PVA) and detailed demographic data from a behavioural study of individuals in the Australian Capital Territory, south-eastern Australia. Patch size was a strong predictor of the persistence of speckled warblers in habitat remnants. High density populations had higher probabilities of persisting, and inclusion of an Allee effect during drought decreased the probability of persistence. In the absence of an Allee effect, only high density populations in patches greater than 300 ha and low density populations in patches greater than700 ha had more than an 80% probability of persisting over 100 years. The accelerating decrease in population persistence below approximately 200-400 ha suggests that small populations were particularly vulnerable to stochastic demographic and environmental events. Adult female mortality was the single most important factor in driving population extinction. Our PVA model predictions matched the survey data for the Australian Capital Territory region remarkably well, but failed to predict occupancy rates in remnants in other regions. Differences in occupancy patterns between regions may, however, have resulted from inbreeding depression. This study demonstrates both the strengths and limitations of PVA analysis. PVA can predict occupancy patterns with reasonable accuracy, given good demographic data, but data for one region cannot be used universally for all regions. We highlight the need for studies of demography in different regions to interpret regional patterns of occupancy and to identify mechanisms of decline in remnant habitat.  相似文献   

16.
The Grass skipper subfamily (Hesperiinae) includes many at risk species across the globe. Conservation efforts for these skippers are hindered by insufficient information about their basic biology. Mardon skipper (Polites mardon) is declining throughout its range. We surveyed mardon oviposition across nine study meadows in the Gifford Pinchot National Forest of Washington State. We conducted habitat surveys with respect to oviposition (n = 269) and random (n = 270) locations, recording data on over 50 variables. Mardon oviposited on 23 different graminoid species, yet are selective for specific graminoids within meadows. Most frequent ovipositions across meadows occurred on Festuca idahoensis and Poa pratensis (accounting for 112 of 269 total oviposition observations). Discriminant Function Analyses revealed that mardon habitat was too variable to detect oviposition selection across study meadows, yet there was strong selection occurring within meadows (r2 ranging from 0.82 to 0.99). Variables important to within meadow selection were graminoid cover, height, and community; oviposition plant structure (leaf density, height, area); insolation factors (tree abundance and canopy shading); and litter layer factors (cover and depth). With few exceptions the primary variables discriminating between oviposition and random locations were significantly different (p < 0.001). Conservation implications include maintaining native meadow ecosystems with sensitivity to local habitat preferences.  相似文献   

17.
We examined the influence of habitat characteristics at the microhabitat, macrohabitat, and landscape spatial scales on small mammals occurring in 12 forest patches within four agricultural landscapes of Prince Edward Island (Canada). Landscape features were important determinants of small mammal variables at all levels, but especially at the community level, whereas microhabitat characteristics tended to influence small mammals at the population level. Macrohabitat characteristics had only minor effects on small mammals occurring in our study sites. Species richness was most strongly influenced by patch area, reaching a threshold at forest patches of roughly 8-10 ha. The proportions of both forest and hedgerow cover within 400 m from the study site were also significant determinants of small mammals species diversity, possibly reflecting their ability to perceive suitable habitats, forage in areas outside the forest patches, and/or disperse in agricultural landscapes. At least one small mammal species (Napaeozapus insignis) benefitted from the presence of agricultural fields at distances up to 1000 m. Tamias striatus benefitted from the presence of hedgerow cover within 400 m from forest patches, possibly allowing them to move between forest patches. Clearly, the maintenance of forest patches of 8-10 ha and of forest cover within 400 m from them is fundamental for the conservation of small mammals inhabiting agricultural landscapes on the Island. Conservation strategies should also consider the establishment of more effective regulations to prevent and/or reduce hedgerow removal on Prince Edward Island.  相似文献   

18.
In the grassland/forest ecotone of North America, many areas are experiencing afforestation and subsequent shifts in ecosystem carbon (C) stocks. Ecosystem scientists commonly employ a suite of techniques to examine how such land use changes can impact soil organic matter (SOM) forms and dynamics. This study employs four such techniques to compare SOM in grassland (Bromus inermis) and recently forested (∼35 year, Ulmus spp. and Quercus spp.) sites with similar soil types and long-term histories in Kansas, USA. The work examines C and nitrogen (N) parameters in labile and recalcitrant SOM fractions isolated via size and density fractionation, acid hydrolysis, and long-term incubations. Size fractionation highlighted differences between grassland and forested areas. N concentration of forested soils’ 63-212 μm fraction was higher than corresponding grassland soils’ values (3.0±0.3 vs. 2.3±0.3 mg gfraction−1, P<0.05), and N concentration of grassland soils’ 212-2000 μm fraction was higher than forested soils (3.0±0.4 vs. 2.3±0.2 mg gfraction−1, P<0.05). Similar trends were observed for these same fractions for C concentration; forested soils exhibited 1.3 times the C concentration in the 63-212 μm fraction compared to this fraction in grassland soils. Fractions separated via density separation and acid hydrolysis exhibited no differences in [C], [N], δ15N, or δ13C when compared across land use types. Plant litterfall from forested sites possessed significantly greater N concentrations than that from grassland sites (12.41±0.10 vs. 11.62±0.19 mg glitter−1). Long-term incubations revealed no differences in C or N dynamics between grassland and forested soils. δ13C and δ15N values of the smallest size and the heavier density fractions, likely representing older and more recalcitrant SOM, were enriched compared to younger and more labile SOM fractions; δ15N of forested soils’ 212-2000 μm fraction were higher than corresponding grassland soils (1.7±0.3‰ vs. 0.5±0.4‰). δ13C values of acid hydrolysis fractions likely reflect preferential losses of 13C-depleted compounds during hydrolysis. Though C and N data from size fractions were most effective at exhibiting differences between grassland and forested soils, no technique conclusively indicates consistent changes in SOM dynamics with forest growth on these soils. The study also highlights some of the challenges associated with describing SOM parameters, particularly δ13C, in SOM fractions isolated by acid hydrolysis.  相似文献   

19.
The Hainan gibbon (Nomascus hainanus) is one of the most endangered primates in the world, confined to mature natural forest in Hainan Island, China. We assessed changes in habitat condition on the island between 1991 and 2008, using vegetation maps generated by remote-sensing images. We defined forest suitable for gibbons based on composition, tree size and canopy cover. During the 17-year period, the area of suitable gibbon forest decreased by 540 km2 (35%) across the whole island, and by 6.3 km2 (7%) in the locality of the sole remaining gibbon population at Bawangling National Nature Reserve. The forest patches large enough (>1 km2) to support a gibbon group decreased from 754 km2 to 316 km2 in total area, and from 92 to 64 in number. Suitable natural forest was mainly replaced by plantations below 760 m, or degraded by logging, grazing and planting of pines above 760 m. Meanwhile, forests in former confirmed gibbon areas became more fragmented: mean area of patches decreased by 53%. We mapped the patches of natural forest in good condition which could potentially support gibbons. We recommend a freeze on further expansion of plantations between core patches at Bawangling, Jiaxi-Houmiling and Yinggeling Nature Reserves in accordance with forest protection regulations; establishment of nature reserves in currently unprotected natural forest patches elsewhere in line with the local government’s nature reserve expansion policy; and active natural-forest restoration between remaining fragments at Bawangling.  相似文献   

20.
In previous centuries human activities had a profound effect on the distribution of Eurasian lynx (Lynx lynx) in Europe. The species has since been reintroduced to several areas but still much former range remains unoccupied. A relatively poor coloniser, it is likely that further reintroductions will be required to restore the species to potentially suitable areas. However, in the human-modified landscapes of Europe, where extensive wooded habitats are often fragmented, it is important to assess the potential lynx population size that could be supported in the available habitat. A previous study identified two networks of potential lynx habitat in Scotland. The present study further explores the feasibility of reintroducing lynx to Scotland by estimating the potential population size for the identified habitat by considering the availability of prey. An examination of lynx and wild ungulate densities from four areas in Europe, revealed a highly significant relationship between lynx density and the density of ungulate biomass. Based on the biomass represented by the densities of roe, red, sika and fallow deer occurring in two potential lynx habitat networks in Scotland, it was predicted that habitat in the Highlands could support 2.63 lynx 100 km−2, while the Southern Uplands could support 0.83 lynx 100 km−2. Applied to the amount of identified habitat, it is estimated that a Highlands habitat network could support around 400 lynx, and a Southern Uplands network, around 50. Scotland could support a large population of Eurasian lynx, which at current estimates, would be the fourth largest in Europe.  相似文献   

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