Landscape-scale habitat loss can change the floristic composition of forest fragments, affecting the survival of specific groups of plants, as shade-tolerant and emergent trees. This increasing in tree mortality creates forest canopy gaps of different sizes that ultimately determine the solar radiation available in the forest understorey. We conducted a study aiming to assess how the loss of forest cover at landscape level (i.e. deforestation) affects the sunfleck dynamics, a proxy of light regime in forest understorey. We expected that fragments located in landscapes with less forest cover have a high number of larger canopy gaps and, consequently, long-lasting sunflecks. In each forest fragment, a 100 per 50 m plot was established, and in each plot, we took 10 hemispherical photographs. The images were analysed using the Gap Light Analyzer software. The sunflecks were divided into six temporal classes. We evidenced that landscape-scale deforestation increased the frequency of all sunfleck intervals >8 min, particularly the long-lasting (> 32 min) sunflecks. We propose that the increasing frequency of long-lasting sunflecks reduces suitability of microhabitat to some shade-tolerant species in local fragments, a potential proximal mechanism contributing to compositional shifts of tree assemblages observed in forest fragments within deforested landscapes.
The expansion of human activities has led to drastic changes in the original landscapes in which tropical forests stand, causing the loss and fragmentation of natural habitats. Both processes induce changes in forest structure and local microclimatic conditions that are important modulators of the survival and demographic structure of plant species. The Neotropical palm Euterpe edulis Mart. (Arecaceae) is a keystone species largely consumed by several animals. Nevertheless, such emblematic species has also been over-harvested for palm-heart extraction, which led it to be currently classified as vulnerable to extinction. Understanding the main predictors affecting its persistence in forest remnants is essential for proposing strategies to modify this current scenario. In this context, we aimed to investigate how processes occurring in two different spatial scales (i.e. forest cover at the landscape scale and local microclimatic conditions) affect the demographic structure of E. edulis. We selected 20 forest fragments along the Brazilian Atlantic Forest in southern Bahia, embedded within landscapes ranging from 10 to 98% of forest cover amount. In each fragment, a plot of 100 × 50 m was established and all individuals of E. edulis were counted. A datalogger was also deployed in the center of the fragment to collect data of air temperature and relative local humidity. We used a zero-altered negative binomial regression (ZANB) to investigate the influence of forest cover and microclimate variables on the demographic structure of E. edulis. A total of 6528 individuals distributed in the five ontogenetic stages was recorded, with Juveniles presenting the highest number of individuals. Forest cover, not microclimate, was the best predictor of the demographic structure for all ontogenetic stages. We suggest that deforested areas are also more prone to palm harvest, which might explain the pervasive effects on the species persistence. We strongly recommend the maintenance and restoration of forest areas to ensure the maintenance of current populations of this endangered palm species. Yet due to the species overexploitation, reintroducing the species to already depleted fragments is urgently required along the Atlantic coast, combined with an increase in surveillance and environmental education programs to curb illegal extraction in highly deforested areas.
Global biodiversity is threatened by land-use changes through human activities. This is mainly due to the conversion of continuous forests into forest fragments surrounded by anthropogenic matrices. In general, sensitive species are lost while species adapted to disturbances succeed in altered environments. However, whether the interactions performed by the persisting species are also modified, and how it scales up to the network level throughout the landscape are virtually unknown in most tropical hotspots of biodiversity. Here we evaluated how landscape predictors (forest cover, total core area, edge density, inter-patch isolation) and local characteristics (fruit availability, vegetation complexity) affected understory birds seed-dispersal networks in 19 forest fragments along the hyperdiverse but highly depauperate northeast distribution of the Brazilian Atlantic Forest. Also, our sampled sites were distributed in two regions with contrasting land cover changes. We used mist nets to obtain samples of understory bird food contents to identify the plant species consumed and dispersed by them. We estimated network complexity on the basis of the number of interactions, links per species, interaction evenness, and modularity. Our findings showed that the number of interactions increased with the amount of forest cover, and it was significantly lower in the more deforested region. None of the other evaluated parameters were affected by any other landscape or local predictors. We also observed a lack of significant network structure compared to null models, which we attribute to a pervasive impoverishment of bird and plant communities in these highly modified landscapes. Our results demonstrate the importance of forest cover not only to maintain species diversity but also their respective mutualistic relationships, which are the bases for ecosystem functionality, forest regeneration and the provision of ecological services.
Seed removal is a key component of seed dispersal and may be influenced by both landscape-scale and local attributes, and it has been used as an indicator of the intensity of interactions between ecosystem components. We examined how the seed removal rates, which integrate the activity of seed dispersers and seed predators, vary with landscape-scale forest cover. We collected data under 34 trees belonging to two zoochoric species (Helicostylis tomentosa (Poepp. and Endl.) J. F. Macbr. and Inga vera Willd.) in 17 remnants in the Brazilian Atlantic forest, with different percentages of forest cover. The seed removal rate was estimated using a fast method based on the abundance of intact fruits and fruit scraps on the ground. The amount of forest cover affected the rate of seed removal in a humpbacked shape, with a maximum seed removal rate at intermediate forest cover. Seed removal rates must be related to the amount of food resources offered and diversity of dispersers and predators in the region. In landscapes with intermediate forest amount, there is a better balance between supply and demand for fruits, leading to a higher seed removal rate than more deforested or forested landscape. Our results also show that local factors, such as crop size and canopy surface, together with forest cover amount, are also important to the removal rate, depending on the species. In addition, our results showed that plant–animal interactions are occurring in all fragments, but the health status of these forests is similar to disturbed forests, even in sites immersed in forested landscapes.
Agriculture and development transform forest ecosystems to human-modified landscapes. Decades of research in ecology have generated myriad concepts for the appropriate management of these landscapes. Yet, these concepts are often contradictory and apply at different spatial scales, making the design of biodiversity-friendly landscapes challenging. Here, we combine concepts with empirical support to design optimal landscape scenarios for forest-dwelling species. The supported concepts indicate that appropriately sized landscapes should contain ≥40% forest cover, although higher percentages are likely needed in the tropics. Forest cover should be configured with ~10% in a very large forest patch, and the remaining 30% in many evenly-dispersed smaller patches and semi-natural treed elements (e.g. vegetation corridors). Importantly, the patches should be embedded in a high-quality matrix. The proposed landscape scenarios represent an optimal compromise between delivery of goods and services to humans and preserving most forest wildlife, and can therefore guide forest preservation and restoration strategies.
Biodiversity-friendly agricultural systems allow the maintenance of native species even in highly fragmented landscapes by providing corridors to species dispersion and offering supplementary resources for animal populations. In the tropical region, cocoa agroforestry systems are of great importance for biodiversity conservation as they maintain part of the native vegetation, and therefore can be used by the local fauna. In this system, understory of native forests is replaced by cocoa trees, which are shaded by large old-growth trees. However, the persistence of native species in cocoa agroforests depends on local vegetation characteristics but also the landscape structure in which these systems are located. Here, we investigated the influence of landscape composition (i.e. amount of forest cover, cocoa agroforestry and cattle pasture) and local vegetation structure (i.e. number of native and cocoa trees, basal area of native trees and canopy closure) on understory birds in 18 cocoa agroforestry systems located in three regions in the Brazilian Atlantic forest, presenting distinct land use contexts. Specifically, we assessed the effects of these landscape and local features in predicting richness and abundance patterns of the entire community, and also in distinct ecological groups, such as forest-dependent and non-forest-dependent birds, and insectivores, frugivores, and omnivores. Using generalized linear models and Akaike information criterion, we observed lower species richness of complete community, non-forest and omnivorous birds in the most deforested region. Also, our findings demonstrated that cocoa agroforests integrated in more forested landscapes harbor greater richness and abundance of frugivorous birds. Conversely, the increase in cattle pasture amount at the landscape had a harsh effect on all bird groups evaluated. Regarding local vegetation, we observed that the increase of canopy closure leads to greater abundance of insectivorous birds in cocoa agroforestry systems. Similarly, abundance of non-forest species increased in agroforests with higher number of cocoa trees. Our study demonstrated that cocoa agroforestry systems can provide complementary habitats for many species, including forest birds, and therefore can mitigate the effects of habitat loss. However, this key benefit for bird conservation will be more effective when these agroforestry systems are located in more forested landscapes, with low amount of cattle pastures. Our findings therefore reinforce the alarming need to maintain and recover landscape-scale forest amount to ensure species persistence of birds in anthropogenic landscapes, even in those comprising biodiversity-friendly land uses such as cocoa agroforestry systems.
Context. Biodiversity in tropical region has declined in the last decades, mainly due to forest conversion into agricultural areas. Consequently, species occupancy in these landscapes is strongly governed by environmental changes acting at multiple spatial scales. Objectives. We investigated which environmental predictors best determines the occupancy probability of 68 bird species exhibiting different ecological traits in forest patches. Methods. We conducted point-count bird surveys in 40 forest sites of the Brazilian Atlantic forest. Using six variables related to landscape composition and configuration and local vegetation structure, we predicted the occupancy probability of each species accounting for imperfect detections. Results. Landscape composition, especially forest cover, best predicted bird occupancy probability. Specifically, most bird species showed greater occupancy probability in sites inserted in more forested landscapes, while some species presented higher occurrence in patches surrounded by low-quality matrices. Conversely, only three species showed greater occupancy in landscapes with higher number of patches and dominated by forest edges. Also, several species exhibited greater occupancy in sites harbouring either larger trees or lower number of understory plants. Of uttermost importance, our study revealed that a minimum of 54% of forest cover is required to ensure high (>60%) occupancy probability of forest species. Conclusions. We highlighted that maintaining only 20% of native vegetation in private property according to Brazilian environmental law is insufficient to guarantee a greater occupancy for most bird species. We recommend that policy actions should safeguard existing forest remnants, expand restoration projects, and curb human-induced disturbances to minimise degradation within forest patches.
Habitat loss is the main driver of the current high rate of species extinction, particularly in tropical forests. Understanding the factors associated with biodiversity loss, such as the extinction of species interactions and ecological functions, is an urgent priority. Here, our aim was to evaluate how landscape-scale forest cover influences fruit biomass comparing different tree functional groups. We sampled 20 forest fragments located within landscapes with forest cover ranging from 2 to 93 percent in the Atlantic forest of southern Bahia, Brazil. In each fragment, we established five plots of 25 9 4 m and carried out phenological observations on fleshy fruit throughout 1 year on all trees ≥5 cm dbh. We estimated fruit availability by direct counting of all fruits and derived fruit biomass from this count. We used spatial mixed linear models to evaluate the effects of forest cover on species richness, abundance, and fruit biomass. Our results indicated that forest cover was the main explanatory variable and negatively influenced the total richness and abundance of zoo-choric and shade-tolerant but not shade-intolerant species. A linear model best explained variations in richness and abundance of total and shade-tolerant species. We also found that forest cover was positively correlated with the fruit biomass produced by all species and by the shade-tolerant assemblages, with linear models best explaining both relationships. The loss of shade-tolerant species and the lower fruit production in fragments with lower landscape-scale forest cover may have implications for the maintenance of frugivore, seed dispersal service, and plant recruitment. Abstract in Portuguese is available with online material.
Forest loss and fragmentation change the dynamics and structure of remnant populations, ultimately affecting key processes with implications for ecosystem functioning. Fruit consumption has important consequences for seed dispersal, maintaining the plant demography, which is also critical to the populations of animals that utilize them for resources. Therefore, understanding how forest cover reduction affects fruit consumption and, consequently, seed dispersal is essential to informing conservation policy for the remaining forest patches. This study was conducted in 20 forest sites with varying amounts of forest cover (from 6% - 85%) located in the Atlantic forest of southern Bahia, Brazil. We investigated whether forest loss and local bird diversity affected fruit consumption rates in the forest edge and interior. We used artificial fruit to estimate fruit consumption by birds. At each site, we set up 14 experimental stations, one located on the forest edge (~ 3m) and the others in the forest interior (75 m), each one composed of 15 artificial fruits fixed to a plant. Our results showed that forest loss and the reduction of bird abundance led to a decrease in fruit consumption in the forest interiors, but not on the forest edges. This verifies that forest cover loss results in changes in fruit consumption, and has important consequences for seed dispersal by birds in forest remnants.
Anthropogenic disturbances represent the main threat to biodiversity around the globe, yet effects are not restricted to species loss. Assessing the functional diversity, which measures the range and value of ecological traits of organisms, can provide a more direct link between biodiversity and ecosystem functioning. Therefore, as species’ responses to disturbances depend on their ecological traits, ecosystem functions are likely to be also imperiled by human perturbations. Although the literature on the effects of disturbances on functional diversity has been increasing, results are highly varied. Here, we provided the first comprehensive global meta-analysis on the effects of human disturbances on functional diversity of birds. We also performed subgroup analyses by region, habitat specialization, functional trait, functional diversity index and disturbance type. Our results indicate a consistent negative effect of disturbances on bird functional diversity, regardless of the variability caused by the different predictor variables considered. Specifically, we revealed that studies that were conducted in the tropics, focused on feeding traits and calculated functional diversity and richness indices presented negative responses to disturbances. Additionally, the functional diversity of birds, regardless of habitat specialization, was also negatively affected by anthropogenic disturbances. Lastly, habitat isolation, logging and urbanization exhibited a consistent negative effect on the functional diversity of birds, whereas agriculture, habitat loss and multiple disturbances had no detectable influence. These results indicate that anthropogenic disturbances can be detrimental to birds, possibly jeopardizing their ecological functions and threatening ecosystem resilience. We therefore suggest that conservation efforts should particularly focus on reducing or mitigating the effects of these three disturbances to at least diminish their effects on avian functional diversity. Additionally, we highlight the need for novel studies to simultaneously investigate the direct relationship between disturbance, functional diversity and especially ecosystem function, through the employment of multiple complementary indices, in order to effectively assist conservation decisions.
en Tropical forests have been facing high rates of deforestation driven by multiple anthropogenic disturbances, with severe consequences for biodiversity. However, the understanding of such effects on functional diversity is still limited in tropical regions, especially considering different ecological groups responses. Here, we evaluated the functional responses of birds to forest loss at the threatened Brazilian Atlantic forest, considering the complete assemblage, and both forest‐dependent and non‐forest‐dependent species. Birds were surveyed in 40 forest sites with a forest cover gradient, located in two regions showing different land use types. We tested different models to assess the responses of functional diversity indices to forest loss in these sites. Although functional diversity did not differ between regions, forest and non‐forest birds showed divergent responses to forest loss. Deforested landscapes presented an increase in functional richness (SESFRic) and evenness for forest species and an increase of functional dispersion for non‐forest birds. Additionally, forested landscapes harbor birds presenting lower body mass and wing length, and non‐forest species with lower tarsus length. The maintenance of some functional metrics through forest loss resulted from a compensatory dynamic between forest and non‐forest birds, indicating that only evaluating the complete assemblage may mask important idiosyncratic patterns of different ecological groups. Although non‐forest species are relatively capable to maintain bird functional diversity in deforested landscapes, forest birds are facing a drastic ongoing collapse in these sites, representing an alarming signal for the maintenance of forest ecosystem function. Abstract in Portuguese is available with online material. RESUMO pt Florestas tropicais têm apresentando altas taxas de desmatamento causadas por múltiplas perturbações antrópicas, com severas consequências para a biodiversidade. Porém, o entendimento dos efeitos na diversidade funcional ainda é limitado em regiões tropicais, especialmente considerando as respostas de diferentes grupos ecológicos. Nós avaliamos as respostas funcionais de aves à perda de floresta na ameaçada Mata Atlântica brasileira, considerando a assembleia completa e espécies florestais e não‐florestais. As aves foram amostradas em 40 sítios florestais dentro de um gradiente de cobertura florestal, em duas regiões com diferentes usos de solo. Nós testamos diferentes modelos para avaliar as respostas de índices de diversidade funcional à perda de floresta nesses locais. Apesar da diversidade funcional não diferir entre as regiões, aves florestais e não‐florestais mostraram respostas divergentes à perda de floresta. Paisagens desmatadas apresentaram aumento na riqueza (SESFRic) e uniformidade funcionais para espécies florestais e aumento na dispersão funcional para não‐florestais. Adicionalmente, paisagens florestadas abrigam aves com menor massa corporal e comprimento de asa, e espécies não‐florestais com menor comprimento de tarso. A manutenção de algumas métricas com a perda de floresta resultou de uma dinâmica compensatória entre aves florestais e não‐florestais, indicando que avaliar apenas a assembleia completa pode mascarar importantes padrões idiossincráticos dos grupos ecológicos. Apesar das espécies não‐florestais serem relativamente capazes de manter a diversidade funcional de aves em paisagens desmatadas, as aves florestais estão enfrentando um drástico colapso nesses locais, representando um sinal de alerta para a manutenção do funcionamento da floresta.
Habitat loss is the primary driver of biodiversity decline worldwide, but the effects of fragmentation (the spatial arrangement of remaining habitat) are debated. We tested the hypothesis that forest fragmentation sensitivity-affected by avoidance of habitat edges-should be driven by historical exposure to, and therefore species' evolutionary responses to disturbance. Using a database containing 73 datasets collected worldwide (encompassing 4489 animal species), we found that the proportion of fragmentation-sensitive species was nearly three times as high in regions with low rates of historical disturbance compared with regions with high rates of disturbance (i.e., fires, glaciation, hurricanes, and deforestation). These disturbances coincide with a latitudinal gradient in which sensitivity increases sixfold at low versus high latitudes. We conclude that conservation efforts to limit edges created by fragmentation will be most important in the world's tropical forests.
Although Miconia mirabilis is a very common species in disturbed forest areas and is known for providing food resources for the local fauna, little is known about its reproductive phenology and other ecological aspects. The present study compares intra- and inter-annual patterns in the reproductive phenophases of that species in three distinct physiognomies of Atlantic Forest in Southeastern Bahia based on semi-quantitative observations conducted over a period of three years. We searched for possible relationships with climatic variables, differences among sites and synchrony. Both the flowering and fruiting strategies of M. mirabilis were classified as annual extended in all three study sites. We found no significant differences among years. Despite low seasonality of the regional climate, intensities of the different phenophases were negatively correlated with day length and temperature. In general, inter- and intra-population synchrony for flowering and fruiting was high (between 0.65 and 0.78), except for inundated forest, probably due to the stress caused by flooding. Given that Miconia mirabilis has the potential to be an important food resource for the local fauna due to the large quantities of flowers and fruits produced and their almost year-round availability, and its capacity for occupying impoverished areas, the species may be considered in restoration programs as a potentially interesting species capable of attracting frugivores to disturbed areas.
1.Agricultural activities such as crop production and cattle ranching are rapidly replacing forests worldwide, especially in the tropics. Resulting forest loss can adversely affect biodiversity in many ways, including trajectories of community reassembly, community composition, forest structural profiles, and taxonomic diversity. Yet, effects of forest loss on specific ecosystem functions remain limited. Processes closely linked with tree reproduction, such as pollination and seed dispersal are of paramount importance for many ecological functions in tropical forests. Disruption in these processes is known to delay or change forest regeneration, diversity, and structural dynamics. 2.To explore how reproductive and dispersal traits are being altered by landscape‐scale deforestation, we surveyed and compiled trait data for tree communities in 20 tropical Atlantic rainforest remnants in northeastern Brazil, across a gradient of deforested landscapes, each retaining 3 to 93% forest cover. 3.The functional richness of reproductive plant attributes decreased as the amount of forest cover decreased, while divergence increased along the same gradient. Loss of forest cover disproportionately affected certain dispersal and reproductive attributes, with most heavily impacted functional attributes including: brief flowering duration, hermaphrodite sexual system, and zoochoric dispersal mode. We identified a clear threshold at 25‐30% of forest cover, below which, reproductive attributes disappeared more quickly than expect from forest remnants. 4.Synthesis. Deforestation may impair tree community functional diversity, particularly by decreasing the number of functions. Under scenarios of extensive deforestation, changes to reproductive and dispersal trait profile of forest communities suggest that profound modifications in the availability of floral and seed resources are likely to be substantial. Such extensive changes to food supply of pollinating and dispersing animals suggest carry‐over effects to the fauna of these important forest systems. This article is protected by copyright. All rights reserved.
It is generally assumed that deforestation affects a species consistently across space, however populations near their geographic range edge may exist at their niche limits and therefore be more sensitive to disturbance. We found that both within and across Atlantic Forest bird species, populations are more sensitive to deforestation when near their range edge. In fact, the negative effects of deforestation on bird occurrences switched to positive in the range core (>829 km), in line with Ellenberg’s rule. We show that the proportion of populations at their range core and edge varies across Brazil, suggesting deforestation effects on communities, and hence the most appropriate conservation action, also vary geographically.
Study Description In a recently accepted article for publication in Ecological Applications, we observed that habitat simplification and fruit scarcity in highly deforested landscapes of Brazilian Atlantic forest limits the maintenance of forest-dependent frugivorous birds. Conversely, landscapes with higher forest edge amount showed higher diversity of non-forest frugivorous birds, probably because the increasing length of ecotones in these landscapes can increase resource availability and foraging efficiency of this bird group. As the seed dispersal services offered by forest-dependent species cannot be ecologically compensated for by the proliferation of non-forest-dependent species, preventing forest loss is imperative to maintain forest-dependent birds and forest regeneration in this vanishing biodiversity hotspot.
Habitat loss is one of the primary drivers of change in forest biodiversity and ecosystem function worldwide. The synergetic effects of habitat loss and fragmentation might lead to profound impacts on forest structure and composition, conducting forest fragments towards early successional stages (retrogressive succession). In this study, we tested this hypothesis by evaluating how landscape-scale forest loss affects the forest structure. We sampled forest structure descriptors in 40 forest sites in landscapes ranging from 3 to 100% forest cover. Forest cover was negatively related to most of the structural variables, generally in a non-linear manner. In contrast, dead trees and logging were ubiquitous and not related to forest cover. The forest remnants in more deforested landscapes retain early successional forest attributes, with tree assemblages that are less dense, shorter, thinner, with an overall basal area loss, and with increasing canopy openness. This structural degradation indicates that landscape scale forest loss strongly determines the trajectory of the local forest structure, pushing forests to a retrogressive succession process, which is more likely to occur in deforested landscapes and can lead to functional forest erosion. Our findings indicate that remnants within deforested landscapes may suffer recruitment limitation, primarily of large trees. Additionally, the forest structure characteristics were more severely degraded in landscapes with less than 40% forest cover. In the face of these results, the recommendation is to avoid the reduction of forest cover belowthis threshold, atwhich point structural erosion becomesmore severe,with predictable negative consequences on biodiversity and ecosystem service maintenance.
Global biodiversity is increasingly threatened by land-use change, but the direct and indirect drivers of species diversity in human-modified tropical landscapes are poorly known. Forest-dependent species are expected to be particularly sensitive to changes in landscape composition (e.g., forest loss) and configuration (e.g., increase of forest edges), both directly and indirectly through cascading landscape effects on local patterns of forest structure and resource availability. In contrast, non-forest dependent species are probably more strongly related to landscape changes than to local forest patterns, as these species are able to use resources not only from the forest, but also from other landscape elements over larger spatial scales. We tested these hypotheses using structural equation modeling. In particular, we sampled 20 landscapes (115 ha each) from the Brazilian Atlantic rainforest to assess the effect of landscape-scale forest cover and amount of forest edges on the diversity of frugivorous birds, both directly and indirectly through the effect that these landscape variables may have on vegetation complexity and fruit biomass. We separately assessed the response of forest-dependent and non-forest dependent frugivores to infer potential mechanisms underlying bird assemblages in fragmented landscapes. The diversity of forest-dependent birds mainly decreased with the simplification of vegetation complexity in more deforested landscapes, but increased with increasing fruit biomass in more forested landscapes (indirect effects). Both patterns were significant, thus supporting a strong bottom-up control, i.e., local habitat simplification and resource scarcity in highly deforested landscapes limits the maintenance of forest-dependent birds. Conversely, but as expected, non-forest dependent birds were more strongly and directly related to landscape-scale patterns. In particular, landscapes with higher forest edge amount showed higher bird species diversity, probably because the increasing length of ecotones and interspersion/juxtaposition of different habitat types in landscapes with more forest edges can increase resource availability and foraging efficiency of non-forest dependent birds. As the seed dispersal services offered by forest-dependent species cannot be ecologically compensated for by the proliferation of non-forest dependent species, preventing forest loss is imperative to maintain forest-dependent birds and forest regeneration in this vanishing biodiversity hotspot.
O Programa de Pós-graduação em Ecologia e Conservação da Biodiversidade (PPGECB) da Universidade Estadual de Santa Cruz (UESC), Ilhéus-BA, oferece uma vaga de pós-doutorado PNPD (Programa Nacional de Pós-Doutorado – CAPES), para realizar pesquisa em ecologia da conservação em paisagens antrópicas no sul da Bahia, em um dos trechos mais ricos em biodiversidade da costa Atlântica. Maiores informações em: http://www.ecologiauesc.com.br/page.php?l=br&p=306
Unveiling the minimum amount of habitat required for different taxa represents a great contribution of ecologists to conservation management actions at the landscape-scale. However, groups from different life-stages are likely to exhibit divergent shifts in species diversity and community composition, yet greatly neglected in ecological studies. We sampled adult and juvenile tree assemblages at twenty sites of Brazilian Atlantic Forest surrounded by different percentages of forest cover remaining at the landscape-level (3–93%) to compare patterns of species richness and community composition between both life-stages in response to habitat amount. We also investigated distinct functional guild responses (proportion of species and stems of shade-intolerant, biotically-dispersed and large-seeded species) among adult and juvenile trees to forest cover reduction. We hypothesize that juveniles will exhibit dissimilar community composition, faster responses, and higher vulnerability of functional guilds to forest loss than adults. Our results indicate that community composition was markedly different among life-stages and strongly correlated with forest cover. Additionally, the number of species of both life-stages was negatively affected by landscape-scale forest loss, exhibiting a greater decline of species richness when forest cover was reduced to < 19.5% and 34.6% of forest cover, for adults and juveniles, respectively. Forest loss might led to non-random floristic shifts, characterized by an increased proportional representation of shade-intolerant species and stems from both life-stages, a severe decline of biotically-dispersed adult species, and reduction in large-seeded juvenile species in severely deforested landscapes. Of uppermost importance, our results show that young assemblages are not mirroring the preceding generation, indicating that future woody plant communities are likely to exhibit an impoverished sample of the original biota with subsequent loss of functionality in deforested landscapes. Given that 20% of native vegetation at the property-scale is the legal minimum amount required by the current Brazilian Forest Code in the Atlantic Forest, we reveal that this amount is not enough to safeguard diverse plant communities e particularly juveniles, an essential group of population dynamics, which require greater forest cover amount at the landscape-scale. We strongly recommend the implementation of restoration projects within severely fragmented landscapes.
Forest edges influence more than half of the world's forests and contribute to worldwide declines in biodiversity and ecosystem functions. However, predicting these declines is challenging in heterogeneous fragmented landscapes. Here we assembled a global dataset on species responses to fragmentation and developed a statistical approach for quantifying edge impacts in heterogeneous landscapes to quantify edge-determined changes in abundance of 1,673 vertebrate species. We show that the abundances of 85% of species are affected, either positively or negatively, by forest edges. Species that live in the centre of the forest (forest core), that were more likely to be listed as threatened by the International Union for Conservation of Nature (IUCN), reached peak abundances only at sites farther than 200-400 m from sharp high-contrast forest edges. Smaller-bodied amphibians, larger reptiles and medium-sized non-volant mammals experienced a larger reduction in suitable habitat than other forest-core species. Our results highlight the pervasive ability of forest edges to restructure ecological communities on a global scale.
Functional traits associated with plant-animal interactions are essential for forest functionality, given that a higher diversity of fruit traits is likely to maintain a more diverse assemblage of frugivores and consequently promote the seed dispersal function. Yet, shade-intolerant species tend to persist in human-modified landscapes in the long term, which in turn is expect to reduce fruit trait diversity. Here we evaluate how forest cover at the landscape-scale influences the functional diversity of fruit traits, considering the zoochoric tree community and two regeneration strategies separately (shade-tolerant and shade-intolerant species). We sampled 20 forest remnants in the Brazilian Atlantic Forest, located in landscapes with forest cover ranging from 2 to 93 %. In each remnant, we established five plots of 25 x 4 m and marked all trees ≥ 5 cm diameter at breast height (DBH). We compared morphological and chemical attributes of fleshy fruits directly related to the attraction of frugivores, and evaluated the similarity of the zoochoric tree assemblage composition along the forest cover gradient, taking into account the two regeneration strategies. We calculated four functional indices (richness, evenness, divergence, and community-level weighted means of trait values) and used either linear models or spatial mixed linear models to evaluate the effects of forest cover on functional diversity. Our main results revealed that forest cover loss has negatively affected fruit functional diversity for the overall zoochoric community. Forest cover loss also affected functional richness and functional eveness for total and shade-tolerant species, and was positively correlated with the content of protein and lipid in fruits of shade-intolerant species. Additionally, sites exhibiting a lower amount of forest cover showed greater compositional similarity among shade-intolerant species but reduced similarity among shade-tolerant species. We conclude that patterns of species reassembly triggered by landscape-scale deforestation decreases the capacity of the remaining forest for provisioning food resources for frugivore assemblages. The maintenance of shade-tolerant species is pivotal in deforested areas, since their fruit quality is not offset by shade-intolerant species. This is particularly important, mainly because shade-intolerant species are those still persisting in disturbed forests; however, their presence will not provide the same food quality supplied by those species lost.
Birds perform several ecological roles for ecosystem functioning and generate great benefits for human population in some circumstances. However, environmental disturbances, mostly due to anthropogenic actions, have caused a decrease of bird diversity and can lead to the loss of their functions in the remaining habitats. Here, we conducted a scientific literature review to understand the general trends on the ecosystem functions executed by birds and the possible effects of environmental disturbances on them. Our research was conducted in September 2016 in Google Scholar, Scopus and Web of Science databases, which returned 154 papers that targeted the importance of birds to the ecosystems’ maintenance. Among the studies (n = 99) that effectively assessed the ecological role of bird species, most were conducted in natural habitats (n = 63), and the most evaluated function was invertebrate population control (n = 70). About 58% of the publications related some environmental characteristic to the ecological function, but patch and landscape-scaled factors were poorly investigated. Furthermore, 52% of the papers showed that the ecological function of birds can arise from a cascade effect on other trophic levels, though this may depend on the environmental characteristics. Despite the numerous studies in the ornithology field, the ecological roles of birds in several ecosystems are still poorly understood. Future research should consider others ecological functions mediated by birds, such as disease control, and must take different spatial scales and human modification of habitats into consideration, enabling generalizations based on ecosystem type and landscape composition variation.
1. Tropical forest loss can drive the extinction of forest-dependent species. Yet, non-forest species can proliferate in deforested landscapes, thus enabling community-level attributes (e.g., total abundance and richness) to be maintained in the remaining forest patches. Such compensatory dynamics have been, however, poorly investigated regarding the phylogenetic dimension of species diversity. Here, we assessed whether compensatory dynamics can stabilize the phylogenetic richness, divergence and structure of bird communities in response to forest loss in two regions in the Brazilian Atlantic forest, each under with different levels of land use intensification. 2. We surveyed birds in 40 forest sites, and assessed the response of five phylogenetic metrics to forest cover measured in local (600-m radius) landscapes. We separately assessed the entire community, forest-dependent and non-forest-dependent species and used information-theoretic criteria to assess the effect of forest cover on each response variable. In particular, we evaluated the plausibility of four models: a null model (no effect of forest cover), a linear model, a power law model (nonlinear effect), and an analysis of covariance model (to assess whether the effect of forest cover differed between regions). 3. Forest cover varied from 7% to 98%, and was positively related to the phylogenetic richness of forest-dependent species, but negatively related to the phylogenetic richness and divergence of non-forest birds, particularly in the more disturbed region. As consequence, the phylogenetic richness and divergence of the entire community were weakly related to forest cover. 4. Forest birds were less phylogenetically clustered in sites surrounded by lower forest cover, but the phylogenetic structure of non-forest birds was independent of forest cover. 5. Synthesis and applications. The phylogenetic impoverishment of forest-dependent birds is offset by the phylogenetic enrichment and divergence of non-forest-dependent birds in severely tropical deforested landscapes. These compensatory dynamics suggest that both bird groups are important for safeguarding bird evolutionary diversity in human-modified landscapes. Although deforested landscapes are reservoirs of bird phylogenetic diversity, suggesting that ecosystem functioning may be maintained in these sites, preventing further deforestation is urgently needed to preserve forest birds and their key ecological roles in the ecosystem.