Effects Of Forest Fragmentation Research Articles

Assessing anthropogenic disturbance on forest health based on fragment grading in Durgapur Forest Range, West Bengal, India

With the increasing degradation and encroachment of natural landscape environmentalists are now highly concerned with declining forest cover as well as increasing forest fragmentation at different scales across the world for last several decades. Considering the major fourfold effect of forest fragmentation i.e., reduction in habitat area, increased number of fragmented habitats, decrease in area coverage of habitat patch and increased number of isolated patches forest fragmentation is recognized as a major threat to forest ecosystems. Indicators of forest fragmentation are thereby gaining gradual importance at national and international environmental programs. But Spatio-temporal change of forest cover using forest fragmentation along with incorporation of population growth and associated anthropogenic intervention, at a micro-spatial scale has become the major thrust area in the present study. Kanksa is one of the few forest dominated block in Barddhaman District mostly affected by the rapid population growth, land use change in terms of increase in irrigated area as well as agricultural land, rapid urbanization in the last three decades. Present study focuses on forest fragmentation and spatio-temporal dynamics of forest cover from the beginning of 1990s up to present using geospatial techniques.

Forest fragmentation reduced carbon storage in a moist tropical forest in Bangladesh: Implications for policy development

Forest fragmentation is continued to be widespread in the tropics resulting in reduced ecosystem services including carbon storage. However, the effect of forest fragmentation is not considered in the current carbon policy. We investigated the effect of forest fragmentation on tree biomass carbon and soil organic carbon (SOC) storage in a moist tropical forest in Bangladesh. Above and below-ground tree biomass carbon were calculated by using widely accepted allometric equations and SOC was measured by sampling soils up to 10cm depth and analyzing them in a soil laboratory. Results showed that carbon storage in tree biomass was significantly lower in fragmented forests (16.3±1.37tCha−1) than in contiguous forests (31.21±2.75tCha−1) (p<0.001). Likewise, a significantly lower SOC was contained in the soils of fragmented forests (17.26±0.83tCha−1) than in contiguous forests (21.62±0.78tCha−1) (p<0.001). Thus a total of 36% less carbon retained in tree biomass and soils in fragmented forests than in contiguous forests. Backward multiple linear regression analysis revealed tree density, tree height, tree DBH, height-diameter ratio (H/D) and tree species richness as influential factors of carbon variation in fragmented forests. All these structural parameters except tree species richness were significantly lower in fragmented forests, were positively associated with carbon storage and explained together 69% of the carbon storage variation. These findings suggest that the altered stand structure and tree allometry likely caused reduced carbon storage in fragmented forests and highlight the importance of landscape scale management intervention in the tropics. Here, we provided with the evidence of strong negative impact of forest fragmentation on carbon storage and argue that this effect should be in consideration which is currently overlooked in existing carbon accounting systems for tropical forests.

The effect of forest fragmentation on the soil seed bank of Central Amazonia

Deforestation of tropical forests has contributed to the formation of fragmented landscapes, surrounded mainly by a matrix of secondary forests, pastures and agriculture. In this study we evaluated the fragment-area effects on the density, diversity and composition of the soil seed bank. Fragments of primary forest of different sizes (1, 10 and 100ha) and continuous primary forests were sampled in a region of terra firme forest in Central Amazonia. We collected 180 soil samples (45 samples per treatment), and monitored seedling emergence from the soil seed bank in a greenhouse for seven months. Density of emerged seedlings, floristic composition, richness and diversity of species were compared among treatments with Kruskal-Wallis non-parametric test, Mann-Whitney test, Fisher's Alpha diversity index and Non-metric multidimensional scaling (NMDS). Seedling density was inversely proportional to the size of the fragment, being higher in fragments of 1ha, 10ha, and lower in the primary forest and fragments of 100ha. Diversity was higher in the fragments when compared to the primary forests. Melastomataceae was the most abundant family in all treatments. Species composition changed along the disturbance gradient, and is dominated, in the smaller fragments by species that are indicators of degraded environments. Results suggested that the area of the forest fragments affects the size and composition of the soil seed bank, and can significantly influence the potential resilience and regeneration of these sites in the event of natural or anthropic disturbance.

THE RAPID CHANGES OF THE LANDSCAPE STRUCTURE OF THE MERANTI-DANGKU TROPICAL LOWLAND FOREST IN THE SOUTH SUMATRA PROVINCE, INDONESIA

The fragmentation of forest vegetation cover can be measured quantitatively, using tools that can characterize the geometry and spatial properties of the patch or patches of mosaic, which depicts the forest loss and the changes in the temporal pattern. The aims of this paper are to observe the process of the forest fragmentation, to find out the changes of spatial patterns of habitat continuum by applying the spatial dynamics change analysis of the forest fragmentation phases, and to provide the comprehensive approach in determining the rapid change of the forest landscape structure in the spatial transformation process, based on the decision tree models. We find three phases of the forest fragmentation were identified, namely dissection, dissipation, and attrition. This study shows that the production forest area and a wildlife conservation area that contiguous or borders, has the same phases in the process of fragmentation of the forest, but both have a difference of the magnitude of forest loss. We find there are at least five effects of forest fragmentation to the landscape structure, those are increasing in a number of habitat patches, decreasing in a size of habitat patches, reduction in a habitat amount, increasing in a dispersion and interspersion of patch types, and reduction in a size of spatial connectedness between patches. Keywords: fragmentation, landscape metrics, spatial transformation.

Pollen movement by the bat Artibeus jamaicensis (Chiroptera) in an agricultural landscape in the Yucatan Peninsula, Mexico

Artibeus jamaicensis is a medium-sized frugivorous microchiropteran bat that complements its diet with nectar and pollen during the dry season. We investigated which species of pollen are carried by A. jamaicensis in order to determine its potential role as a plant pollinator in the northern Yucatan Peninsula. We collected pollen from the fur of 192 individuals throughout the year from April 2004 to March 2005. We recorded pollen from nine plant species of eight families and found five unidentified pollen types, with the highest pollen species richness recorded in June. A. jamaicensis moved pollen of Erythrina standleyana and Mimosa bahamensis, which have not hitherto been reported as visited by this species. The most abundant pollen in the samples was found to be that of three tree species: Ceiba pentandra, C. aesculifolia and Lysiloma latisiliquum. Very few samples contained pollen in the rainy season, when the bats fed mainly on fruits. A. jamaicensis can fly several kilometres among foraging locations and dispersed large amounts of pollen from tree species growing near cenotes as well as those not present at cenotes but occurring in other forest fragments, highlighting its importance as a pollen vector among forest fragments in the largely deforested landscape of the Yucatan Peninsula, helping to reduce the negative effects of forest fragmentation. Ceiba appears to benefit from the role of A. jamaicensis as a pollen vector, and the species play an important ecological role in the Yucatan landscape, supplying shade, nectar and fruit for wildlife.

Effects of forest fragmentation on the morphological and genetic structure of a dispersal-limited, endangered bird species

Effects of forest fragmentation on the morphological and genetic structure of a dispersal-limited, endangered bird species

Historical environmental change in Africa drives divergence and admixture of Aedes aegypti mosquitoes: a precursor to successful worldwide colonization?

Increasing globalization has promoted the spread of exotic species, including disease vectors. Understanding the evolutionary processes involved in such colonizations is both of intrinsic biological interest and important to predict and mitigate future disease risks. The Aedes aegypti mosquito is a major vector of dengue, chikungunya and Zika, the worldwide spread of which has been facilitated by Ae.aegypti's adaption to human-modified environments. Understanding the evolutionary processes involved in this invasion requires characterization of the genetic make-up of the source population(s). The application of approximate Bayesian computation (ABC) to sequence data from four nuclear and one mitochondrial marker revealed that African populations of Ae.aegypti best fit a demographic model of lineage diversification, historical admixture and recent population structuring. As ancestral Ae.aegypti were dependent on forests, this population history is consistent with the effects of forest fragmentation and expansion driven by Pleistocene climatic change. Alternatively, or additionally, historical human movement across the continent may have facilitated their recent spread and mixing. ABC analysis and haplotype networks support earlier inferences of a single out-of-Africa colonization event, while a cline of decreasing genetic diversity indicates that Ae.aegypti moved first from Africa to the Americas and then to Asia. ABC analysis was unable to verify this colonization route, possibly because the genetic signal of admixture obscures the true colonization pathway. By increasing genetic diversity and forming novel allelic combinations, divergence and historical admixture within Africa could have provided the adaptive potential needed for the successful worldwide spread of Ae.aegypti.

Dung beetle (Coleoptera: Scarabaeinae) persistence in Amazonian forest fragments and adjacent pastures: biogeographic implications for alpha and beta diversity

The aim of this study is to analyze the effects of habitat loss and forest replacement by cattle pasture on the alpha and beta diversity, abundance, biomass and species composition of dung beetles with different dispersal ability. Dung beetles were captured in 19 forest fragments and neighbouring pastures. Forest fragment area ranged from 3.7 to 4825 ha and in this study were grouped into four categories: small, medium, large and control forest. A total of 35,048 dung beetles representing 101 species were collected. Forest fragments had the highest richness with 81 species, followed by pasture with 58 species. Replacement of forest by pasture reduced species richness; however, due to the proximity and connectivity of these areas with Cerrado patches, pastures also had high species richness, but species composition was independent of adjacent fragments. Small fragments had lower abundance and species richness than our other habitat categories, even pastures. Our results highlight that proximity and connectivity with Cerrado areas influenced the patterns of alpha and beta diversity of dung beetles in fragments and pastures. We highlight that the ability to cross the pasture matrix is a strong adaptive trait for species living in human-modified landscapes. Consequently, species with these abilities are less susceptible to the effects of forest fragmentation and local extinction. Our results reinforce the importance of considering the biogeographic location and distribution pattern of species in forest fragmentation studies.

Forest specialist and generalist small mammals in forest edges and hedges

Agricultural intensification often leads to fragmentation of natural habitats, such as forests, and thereby negatively affects forest specialist species. However, human introduced habitats, such as hedges, may counteract negative effects of forest fragmentation and increase dispersal, particularly of forest specialists. We studied effects of habitat type (forest edge versus hedge) and hedge isolation from forests (connected versus isolated hedge) in agricultural landscapes on abundance, species richness and community composition of mice, voles and shrews in forest edges and hedges. Simultaneously to these effects of forest edge/hedge type we analysed impacts of habitat structure, namely percentage of bare ground and forest edge/hedge width, on abundance, species richness and community composition of small mammals. Total abundance and forest specialist abundance (both driven by the most abundant species Myodes glareolus, bank vole) were higher in forest edges than in hedges, while hedge isolation had no effect. In contrast, abundance of habitat generalists was higher in isolated compared to connected hedges, with no effect of habitat type (forest edge versus hedge). Species richness as well as abundance of the most abundant habitat generalist Sorex araneus (common shrew), were not affected by habitat type or hedge isolation. Decreasing percentage of bare ground and increasing forest edge/hedge width was associated with increased abundance of forest specialists, while habitat structure was unrelated to species richness or abundance of any other group. Community composition was driven by forest specialists, which exceeded habitat generalist abundance in forest edges and connected hedges, while abundances were similar to each other in isolated hedges. Our results show that small mammal forest specialists prefer forest edges as habitats over hedges, while habitat generalists are able to use unoccupied ecological niches in isolated hedges. Consequently even isolated hedges can be marginal habitats for forest specialists and habitat generalists and thereby may increase regional farmland biodiversity.

Spatial metrics effect of forest fragmentation on forest bird abundance and site occupancy probability: the influence of patch size and isolation

The persistence of species taxa within fragmented habitats is dependent on the source–sink metapopulation processes, and forest patch size and isolation are key factors. Unveiling species–patch area and/or species–patch isolation relationships may help provide crucial information for species and landscape management. In this study, relationship between forest patch size and isolation with abundance and occupancy probability of forest-dependent birds was investigated. This study was based within a coastal landscape that faces deleterious human activities such as clearing for agriculture. The study aimed to answer the question of whether the size and extent of isolation of forest patches influence abundance and/or occupancy probability of forest-specialist and generalist birds. Two bird species, namely Tiny Greenbul Phyllastrephus debilis subsp. rabai and Yellow-bellied Greenbul Chlorocichla flaviventris, were used as models. Birds were surveyed using distance sampling methods, and spatial metrics were measured from satellite imagery. Focal forest size and distance between forest patches were the most influential metrics whereby abundance and occupancy probabilities increased with increasing patch size, but were negatively influenced by increasing gaps between patches. These findings provide evidence of the existence of patch size/ isolation–occupancy relationships characterised by higher occupancy rate of large patches and distance-dependent dispersal, which decreased with increasing gaps between patches. Controlling deleterious human activities that reduce forest size should be a priority for the long-term conservation of forest-dependent birds.

Foliar diseases in a seasonal tropical dry forest: Impacts of habitat fragmentation

The effects of forest fragmentation on fungal pathogens causing leaf damage to the shrub and tree community were investigated in a seasonal tropical dry forest. The study was carried out in 4 forest fragments, and 2 continuous forest sites located in the Chamela-Cuixmala Biosphere Reserve and surrounding areas (Jalisco, Mexico), along three years. Results showed that fungi were the pathogenic agents causing foliar damage in plants from both, fragments and continuous forest. Disease incidence was higher in 2004 due to a relatively high annual precipitation. The occurrence of leaf fungal pathogens was lower in fragments, than in continuous forest. Plant species diversity was significantly lower in fragments than in continuous forest, and was positively correlated to the number of diseased plant species, and to the proportion of diseased leaves and the leaf area damaged per plant. In addition, disease occurrence was negatively correlated with canopy openness. In conclusion, our results highlight the consequences of environmental changes associated to fragmentation on foliar fungal plant pathogens, a particular group of organisms that until recently has been mostly overlooked in tropical natural systems.

Recent literature on lichens—240

Recent literature on lichens—240

Does tropical forest fragmentation affect plant anti-herbivore defensive and nutritional traits?

Abstract:Leaf traits of tropical tree species are known to operate as intrinsic determinants of insect herbivory. However, we know little about how habitat fragmentation affects these traits and what, if any, are the consequences of this process on herbivory. We tested the effects of forest fragmentation on the leaf traits of sapling of four light-demanding species: Acalypha diversifolia, Hampea nutricia, Myriocarpa longipes, Siparuna thecaphora, and two shade-tolerant species: Pseudolmedia glabrata and Garcinia intermedia, in Los Tuxtlas, Mexico. We also conducted an acceptability assay with a generalist herbivore Spodoptera frugiperda. Plant traits did not change with forest fragmentation, but did with plant regeneration mode and species identity. Light-demanding species had significantly higher water content, nitrogen concentration and specific leaf area than shade-tolerant species. The latter had significantly higher leaf strength, carbon concentration and carbon:nitrogen ratio. Acceptability was affected by fragmentation but only in P. glabrata; plant tissue from forest fragments was consumed 2.6 times more than that from continuous forest. We conclude that forest fragmentation did not affect leaf traits in this site.

完达山东部林区生境特征对东北林蛙产卵的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 完达山东部林区生境特征对东北林蛙产卵的影响 DOI: 10.5846/stxb201411232318 作者: 作者单位: 黑龙江省野生动物研究所,东北大学,黑龙江省野生动物研究所,黑龙江省野生动物研究所,黑龙江省野生动物研究所,黑龙江省野生动物研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 黑龙江省财政厅资助项目(2011-10) Effect of habitat characteristics on the reproductive effort of dybowsky's frogs (Rana Dybowskii) in eastern Wanda Mountains, Heilongjiang Province Author: Affiliation: Heilongjiang Research Institute of Wildlife,College of Information Science and Engineering,Northeastern University,Shenyang,,Heilongjiang Research Institute of Wildlife Harbin,Heilongjiang Research Institute of Wildlife Harbin;China;College of Information Science and Engineering,Northeastern University,Shenyang,;China,Heilongjiang Research Institute of Wildlife Harbin;China;College of Information Science and Engineering,Northeastern University,Shenyang,;China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:在研究人员逐渐将研究的焦点集中在栖息生境破碎化和生境丧失对在池塘繁育的两栖动物的影响方面。至今,许多研究已经评估了在多个空间尺度下生境因子对两栖类动物繁育池选择的影响。由于在1个繁育池内1只林蛙只产1团卵,因此利用繁育池内蛙卵团数与生境因子之间存在的内在联系建立生境选择函数模型,探究林蛙繁育期不同生境因子对东北林蛙种群大小的影响。从2012年到2014年5月初至7月末的东北林蛙繁育期,在完达山东部五泡林场,共调查了105个水池,93.33%的池塘中发现了林蛙卵团。在繁育池微生境尺度水平,广义可加模型分析表明,繁育池面积对东北林蛙卵团数产生积极影响,对林蛙卵团数的贡献为0.17;但林木郁闭度和繁育池水表面杂物盖度对林蛙卵团数产生负面影响,对林蛙卵团数贡献分别为-0.30和-0.43。在繁育池周围5km景观尺度水平,森林面积对蛙卵数产生积极影响,对GAM预测模型的贡献为17.99;公路干扰对蛙卵团数产生负面影响,随着距公路距离增加,林蛙卵团数增加,对GAM预测模型的贡献为1.40。研究结果表明,虽然在繁育池微生境尺度水平预测模型包含的变量较景观尺度水平预测模型包含的变量多,但两个模型对于预测林蛙个体产卵团数均有效。因此,可以认为,保护林蛙种群生存和繁育,需要优先保护面积为4-150m2,池内水表面有一定杂物覆盖(0-14%),林木郁闭度较小(约10%),森林覆盖率高,距公路较远的区域。 Abstract:Wildlife biologists and conservationists are concerned about the effects of forest fragmentation and habitat loss on pond-breeding frog populations. Most studies have assessed the effects of habitat characteristics on the presence or absence of frogs bred in water ponds at multiple spatial scales. In this study, we focused on the effects of habitat composition on Dybowsky's frog population size. We used Dybowsky's frog egg-mass counts as a dependent variable and other habitat factors as independent variables to construct a generalized additive model (GAM), in order to describe the relationship between the frog population size and habitat factors. During the breeding periods of 2012 and 2014, we collected data from 105 water ponds in the forested landscapes of the Wupao Forest Farm, Eastern Wanda Mountains, Heilongjiang Province. Egg masses were detected at 98 breeding ponds (93.33%), 3 breeding ponds were dry during the breeding season of 2012, and egg mass counts were less than 29 at 67 breeding ponds. The size of breeding ponds ranged from 4 to 300 m2 with an average size of 55.88 m2. GAM response curves showed that the egg mass counts were positively associated with the size of breeding ponds from 0 to 150 m2, but the egg mass counts declined with increasing breeding pond size beyond 150 m2. The relationship between the egg mass counts and the pond size showed a contribution factor to GAM of 0.15. The egg mass counts were negatively associated with two habitat factors, namely forest canopy and sundries coverage ratio over the surface of pond water. The forest canopy and sundries coverage ratio contribution factors to GAM were -0.30 and -0.43, respectively. This study assumed that female frogs preferred ponds with higher water temperature. Water temperature was negatively correlated with forest canopy, and it changed from 7.5℃ to 13℃ with the change of forest canopy from 0% to 100%. We also assumed that shade over water surface was very useful for frog breeding. During breeding process, drainage area can be used to avoid predators; however, excess drainage may negatively affect spawning activity of frogs. Egg mass counts at landscape level were positively associated with forest area and the contribution factor to GAM was 17.99. Our results showed that the effect of forest size to egg mass counts was in accordance with many previous studies, since the forest around the breeding ponds was considered as the core habitat for frog living. Roads were another key habitat factor that was negatively associated with egg mass counts at landscape level. The egg mass counts declined near the roads and the contribution factor to GAM was 1.40. Multivariate models developed using within-pond variables explained more variation in egg mass counts than those developed using landscape-level factors; however, we suggested that both models were useful for predicting the breeding effort of frogs at individual sites. Since urbanization of eastern Wanda Mountains continues, forest regulations should effectively protect terrestrial habitats around the seasonal ponds and proactive techniques are required to assure the maintenance of pond-breeding forest populations. 参考文献 相似文献 引证文献

Genetic variation at microsatellite loci in the tropical herb Aphelandra aurantiaca (Acanthaceae).

Premise of the study:To assess the effect of forest fragmentation on genetic variation and population structure of Aphelandra aurantiaca (Acanthaceae), a tropical and ornamental herbaceous perennial plant, we developed the first microsatellite primers for the species.Methods and Results:Fourteen microsatellite markers were isolated and characterized from A. aurantiaca genomic libraries enriched for di-, tri-, and tetranucleotide repeat motifs. Polymorphism was evaluated in 107 individuals from four natural populations. Twelve out of 14 genetic markers were polymorphic. The number of alleles per locus ranged from two to 12, and the observed and expected heterozygosities ranged from 0.22 to 0.96 and from 0.20 to 0.87, respectively. Fixation indices ranged from −0.41 to 0.44.Conclusions:These newly developed microsatellite markers for A. aurantiaca will be useful for future population genetic studies, specifically to detect the possible loss of genetic diversity due to habitat fragmentation.

Agricultural matrix affects differently the alpha and beta structural and functional diversity of soil microbial communities in a fragmented Mediterranean holm oak forest

Given the increase in habitat fragmentation in the Mediterranean forests, understanding its impacts over the ecology of soil microbial communities, responsible for many ecosystem functions, and their capacity to metabolize different substrates from soil organic matter, is of upmost importance. We evaluated how the influence of the agricultural matrix, as one of the main consequences of forest fragmentation, may affect both the composition and the functioning of soil microbial communities in Mediterranean holm oak forests. We determined structural and functional alpha and beta-diversity of microbial communities, as well as microbial assemblages and metabolic profiles, by using a commonly used fingerprinting technique (Denaturing Gel Gradient Electrophoresis) and a community level physiological profiles (CLPP) technique (EcoPlate). Key drivers of soil microbial structure and metabolism were evaluated by using structural equation models (SEM) and multivariate ordination (envfit) approaches. Our results pointed out that forest fragmentation affects microbial community structure and functioning through a complex cascade of causal-effect interactions with the plant–soil system, which ultimately affects the nutrient cycling and functioning of forest soils. We also found a strong scale-dependency effect of forest fragmentation over the ecology of microbial communities: fragmentation increases the local (alpha) diversity, but affected negatively microbial diversity at the landscape scale (beta diversity). This homogenization of the microbial communities and their metabolism at landscape scale resulting from habitat fragmentation may have unknown potential consequences on the capacity of these communities, and hence these ecosystems, to respond to the climate change. Finally, we found a consistent relation between the structure and functional diversity of bacterial community, which further showed the important role that the assemblage of microbial communities might have over their functioning.

Woodland habitat quality prevails over fragmentation for shaping butterfly diversity in deciduous forest remnants

The effects of forest fragmentation on biodiversity can be partitioned into habitat loss and increased isolation of habitat fragments. Habitat quality may however prevail over the effects of fragment area and isolation, especially for mobile animals such as butterflies. To test this hypothesis we surveyed butterfly communities in 36 deciduous forest fragments embedded in a conifer plantation matrix, along two orthogonal gradients of fragment area and isolation. We also sampled eight deciduous riparian forests to compare the complete pool of forest butterflies, expected to be found in riparian forests, to the composition of deciduous fragments. We quantified the effects of deciduous woodland area, isolation and quality on total and forest butterfly richness, community composition and several Community-Weighted Mean traits known to mediate butterfly responses to habitat fragmentation. For the 36 fragments, forest butterfly richness and community composition were not affected by fragment area or isolation but by habitat quality, especially host-plant composition. Riparian forests had higher forest butterfly richness and hosted more habitat specialists, with higher sensitivity to temperature extremes, than deciduous forest remnants. We thus provide new evidence that habitat quality can prevail over fragment area and isolation in shaping the composition of butterfly communities in mosaic landscapes.

Markedly Divergent Tree Assemblage Responses to Tropical Forest Loss and Fragmentation across a Strong Seasonality Gradient.

We examine the effects of forest fragmentation on the structure and composition of tree assemblages within three seasonal and aseasonal forest types of southern Brazil, including evergreen, Araucaria, and deciduous forests. We sampled three southernmost Atlantic Forest landscapes, including the largest continuous forest protected areas within each forest type. Tree assemblages in each forest type were sampled within 10 plots of 0.1 ha in both continuous forests and 10 adjacent forest fragments. All trees within each plot were assigned to trait categories describing their regeneration strategy, vertical stratification, seed-dispersal mode, seed size, and wood density. We detected differences among both forest types and landscape contexts in terms of overall tree species richness, and the density and species richness of different functional groups in terms of regeneration strategy, seed dispersal mode and woody density. Overall, evergreen forest fragments exhibited the largest deviations from continuous forest plots in assemblage structure. Evergreen, Araucaria and deciduous forests diverge in the functional composition of tree floras, particularly in relation to regeneration strategy and stress tolerance. By supporting a more diversified light-demanding and stress-tolerant flora with reduced richness and abundance of shade-tolerant, old-growth species, both deciduous and Araucaria forest tree assemblages are more intrinsically resilient to contemporary human-disturbances, including fragmentation-induced edge effects, in terms of species erosion and functional shifts. We suggest that these intrinsic differences in the direction and magnitude of responses to changes in landscape structure between forest types should guide a wide range of conservation strategies in restoring fragmented tropical forest landscapes worldwide.

Terrestrial mammal diversity in forests close to pineapple crops, Cutris San Carlos, Costa Rica.

Pineapple crops reduce the size of forest fragments and generate pressure on biodiversity in the remnants. To determine potential negative effects of forest fragmentation we assessed diversity and composition of terrestrial mammals in forest patches on three farms under pineapple crops. We placedSherman and Tomahawk traps, footprints traps near water bodies, and made daily tracks to obtain traces and direct observation of mammals. We identified seven species of wild mammals, mostly omnivorous and under a least concern conservation status. The effect of cover type generated by the pineapple crops is consistent with mammal composition. Pineapple crops could enhance the most common wildlife problems, such as predator-prey relationships. Therefore, pineapple plantations, by causing fragmentation and lack of connectivity among forest patches, threaten extinction of mammals in some of their original range.

Tropical Forest Fragmentation Affects Floral Visitors but Not the Structure of Individual-Based Palm-Pollinator Networks

Despite increasing knowledge about the effects of habitat loss on pollinators in natural landscapes, information is very limited regarding the underlying mechanisms of forest fragmentation affecting plant-pollinator interactions in such landscapes. Here, we used a network approach to describe the effects of forest fragmentation on the patterns of interactions involving the understory dominant palm Astrocaryum mexicanum (Arecaceae) and its floral visitors (including both effective and non-effective pollinators) at the individual level in a Mexican tropical rainforest landscape. Specifically, we asked: (i) Does fragment size affect the structure of individual-based plant-pollinator networks? (ii) Does the core of highly interacting visitor species change along the fragmentation size gradient? (iii) Does forest fragment size influence the abundance of effective pollinators of A. mexicanum? We found that fragment size did not affect the topological structure of the individual-based palm-pollinator network. Furthermore, while the composition of peripheral non-effective pollinators changed depending on fragment size, effective core generalist species of pollinators remained stable. We also observed that both abundance and variance of effective pollinators of male and female flowers of A. mexicanum increased with forest fragment size. These findings indicate that the presence of effective pollinators in the core of all forest fragments could keep the network structure stable along the gradient of forest fragmentation. In addition, pollination of A. mexicanum could be more effective in larger fragments, since the greater abundance of pollinators in these fragments may increase the amount of pollen and diversity of pollen donors between flowers of individual plants. Given the prevalence of fragmentation in tropical ecosystems, our results indicate that the current patterns of land use will have consequences on the underlying mechanisms of pollination in remnant forests.