Influence of the landscape matrix on the abundance of arboreal primates in fragmented landscapes

Composition of the landscape matrix of surrounding forest fragments is thought to be critically important to the survival of arboreal primates because it offers structures that help the animals move between fragments and other foraging sites. However, little is known about the composition of the matrix used by these animals. The aim of this study was to quantitatively assess the importance of the landscape matrix and its effects on primate abundance, using black howler monkeys (Alouatta pigra) living in a landscape fragmented by the expansion of agriculture and pastures for livestock in southeastern Mexico. In 2008, a complete census of the monkeys was carried out across the 2000-ha landscape matrix, and for every site where we observed monkeys, we recorded canopy height, tree basal area, food-source abundance, and distance to the nearest fragment. A total of 244 howler monkeys, distributed among 48 groups (including six solitary males) were counted in the matrix. Mean troop size was 5.6 ± 2.8 individuals, and the mode was three individuals. The highest number of troops and greatest howler monkey abundance were recorded in the isolated trees, the eucalyptus plantation, and orchards. A generalized linear model revealed that monkey abundance tended to be higher in matrix elements with higher canopy height, greater food availability, and closest to rainforest fragments. These results suggest that it is necessary to take into account the many elements of the landscape when drawing up conservation and habitat management plans, particularly in order to establish connectivity among the fragments and elements of the matrix with native trees.     

Ecophysiological traits may explain the abundance of climbing plant species across the light gradient in a temperate rainforest

Climbing plants are a key component of rainforests, but mechanistic approaches to their distribution and abundance are scarce. In a southern temperate rainforest, we addressed whether the dominance of climbing plants across light environments is associated with the expression of ecophysiological traits. In mature forest and canopy gaps, we measured leaf size, specific leaf area, photosynthetic rate, and dark respiration in six of the most abundant woody vines. Mean values of traits and their phenotypic change (%) between mature forest and canopy gaps were predictor variables. Leaf size and specific leaf area were not significantly associated with climbing plant dominance. Variation in gas-exchange traits between mature forest and canopy gaps explained, at least partly, the dominance of climbers in this forest. A greater increase in photosynthetic rate and a lower increase in dark respiration rate when canopy openings occur were related to the success of climbing plant species. Dominant climbers showed a strategy of maximizing exploitation of resource availability but minimizing metabolic costs. Results may reflect phenotypic plasticity or genetic differentiation in ecophysiological traits between light environments. It is suggested that the dominant climbers in this temperate rainforest would be able to cope with forest clearings due to human activities.     

Effects of Habitat Structure and Adjacent Habitats on Birds in Tropical Rainforest Fragments and Shaded Plantations in the Western Ghats, India

As large nature reserves occupy only a fraction of the earth’s land surface, conservation biologists are critically examining the role of private lands, habitat fragments, and plantations for conservation. This study in a biodiversity hotspot and endemic bird area, the Western Ghats mountains of India, examined the effects of habitat structure, floristics, and adjacent habitats on bird communities in shade-coffee and cardamom plantations and tropical rainforest fragments. Habitat and birds were sampled in 13 sites: six fragments (three relatively isolated and three with canopy connectivity with adjoining shade-coffee plantations and forests), six plantations differing in canopy tree species composition (five coffee and one cardamom), and one undisturbed primary rainforest control site in the Anamalai hills. Around 3300 detections of 6000 individual birds belonging to 106 species were obtained. The coffee plantations were poorer than rainforest in rainforest bird species, particularly endemic species, but the rustic cardamom plantation with diverse, native rainforest shade trees, had bird species richness and abundance comparable to primary rainforest. Plantations and fragments that adjoined habitats providing greater tree canopy connectivity supported more rainforest and fewer open-forest bird species and individuals than sites that lacked such connectivity. These effects were mediated by strong positive effects of vegetation structure, particularly woody plant variables, cane, and bamboo, on bird community structure. Bird community composition was however positively correlated only to floristic (tree species) composition of sites. The maintenance or restoration of habitat structure and (shade) tree species composition in shade-coffee and cardamom plantations and rainforest fragments can aid in rainforest bird conservation in the regional landscape.     

Effects of habitat transitions on rainforest bird communities across an anthropogenic landscape mosaic

We compared bird community responses to the habitat transitions of rainforest‐to‐pasture conversion, consequent habitat fragmentation, and post‐agricultural regeneration, across a landscape mosaic of about 600 km² in the eastern Australian subtropics. Birds were surveyed in seven habitats: continuous mature rainforest; two size classes of mature rainforest fragment (4–21 ha and 1–3 ha); regrowth forest patches dominated by a non‐native tree (2–20 ha, 30–50 years old); two types of isolated mature trees in pasture; and treeless pasture, with six sites per habitat. We compared the avifauna among habitats and among sites, at the levels of species, functional guilds, and community‐wide. Community‐wide species richness and abundance of birds in pasture sites were about one‐fifth and one‐third, respectively, of their values in mature rainforest (irrespective of patch size). Many measured attributes changed progressively across a gradient of increased habitat simplification. Rainforest specialists became less common and less diverse with decreased habitat patch size and vegetation maturity. However, even rainforest fragments of 1–3 ha supported about half of these species. Forest generalist species were largely insensitive to patch size and successional stage. Few species reached their greatest abundance in either small rainforest fragments or regrowth. All pastures were dominated by bird species whose typical native habitats were grassland, wetland, and open eucalypt forest, while pasture trees modestly enhanced local bird communities. Overall, even small scattered patches of mature and regrowth forest contributed substantial bird diversity to local landscapes. Therefore, maximizing the aggregate rainforest area is a useful regional conservation strategy.     

Foraging behaviour of a frugivorous bat helps bridge landscape connectivity and ecological processes in a fragmented rainforest

1. Landscape connectivity may greatly influence the distribution of animals when it alters their movements and their ability to reach food patches. Depending on their foraging behaviour, organisms may or may not adapt to anthropogenic changes in landscape connectivity and may eventually undergo local extinctions. 2. Recent studies underlined the need to use indicators of functional landscape connectivity based on the behaviour and movement abilities of studied animals to better link landscape structure to ecological processes in disturbed and fragmented areas. 3. The objectives of this study were: to elaborate an index of functional connectivity for Rhinophylla pumilio, a Neotropical understorey frugivorous bat; to use this index to investigate the possible mechanisms controlling its distribution and sustainability in a fragmented landscape; and to test whether this index could be applied to other species of the same guild. 4. We pursued a 10-year bat mist-net survey, coupled to local estimates of food availability, in a mature forest of French Guiana that was recently fragmented by the completion of a reservoir lake. The 18 sampling sites range from undisturbed continuous forest sites to small remote forest fragments. A connectivity value, based on radio-tracking surveys, was attributed to each site. Connectivity measures mean forest cover within neighbouring landscape units, weighted by the probability that bats would use them, as estimated by frequency distribution of flight distance data. 5. The abundance of R. pumilio was positively correlated with landscape connectivity and not correlated with local food availability. Its foraging strategy has evolved in response to the highly scattered distribution of its fruit resource. In spite of its high mobility, R. pumilio apparently failed to exploit a food resource that is distributed patchily over a low-connective habitat because its foraging movements are not well adapted to habitat disruptions. 6. The connectivity index contributed to explain general tendencies of abundance variations in other understorey frugivorous bats, although the spatial scale we examined was probably too small for these species. We make recommendations to adapt a functional connectivity index to species whose large-scale movements are difficult to survey.     

Current status of the habitat and population of the black howler monkey (Alouatta pigra) in Balancán, Tabasco, Mexico

We evaluated the habitat and populations of the black howler monkey (Alouatta pigra) in the municipality of Balancán, Tabasco, southeastern Mexico, using a combination of field surveys and remotely sensed data. We identified 21,937 ha of remnant vegetation composed of 1,348 fragments. Fragments separated by up to 200 m were grouped into "clusters" of fragments in accordance with the maximum observed open distance crossed by A. pigra. A total of 11% or 84 of the 772 clusters identified through remote sensing were selected at random, and for these we determined the vegetation type, canopy height, area, and distance to the closest human settlement. In these same 84 clusters, which included a total area of 9,817 ha, from October to June of 2006 we located a total of 1,064 black howler monkeys, including 228 troops and 49 solitary monkeys. A. pigra was found in 62 (74.7%) of all clusters visited, with a cumulative area of 6,032 ha. Troops varied in size from 2 to 15 individuals (average 6.0+/-2.9 ind/troop). Adults were 67% (n=716) of detected individuals, whereas juveniles were 20.5% (n=218) and infants were 12.5% (n=133). We found black howlers to occur at an ecological density of 10.8 ind/km(2), which is low in comparison with A. pigra in other fragmented and conserved sites. We found a statistically significant relationship between the area of clusters and the abundance of howler monkeys (r(2)=0.2, F=10.47, gl=3, P=0.002). In addition, the probability of finding A. pigra was greater in secondary vegetation, riparian vegetation, tropical dry forest, undisturbed tropical oak forest, and palm forest (F=12, gl=3, P<0.0001), as compared with disturbed tropical oak forest. Our results provide data on the distribution, abundance, and population structure of black howler monkeys in a fragmented landscape in the southeast of Mexico. These data are a necessary prerequisite for conservation planning for this species.     

Relative influence of size,connectivity and disturbance history on plant species richness and assemblages in fragmented grasslands

Questions: What is the relative influence of size, connectivity and disturbance history on plant species richness and assemblages of fragmented grasslands? What is the contribution of small fragments to the conservation of native species pool of the region? Location: Tandilia's Range, Southern Pampa, Argentina. Methods: Cover of plants was registered within 24 fragments of tall‐tussock grassland remnants within an agricultural landscape using modified Whittaker nested sampling. We analysed the influence of site variables related to disturbance history (canopy height, litter thickness) and fragment variables (size, connectivity) on species richness (asymptotic species richness, slope of the species–area curve) as well as on species assemblages by multiple regressions analysis and canonical correspondence analyses, respectively. Cumulative area was used for analysing whether small fragments or large fragments are more important to species diversity in the landscape. Results: Asymptotic species richness was significantly influenced by site variables, in particular by Paspalum quadrifarium's canopy height, but not by fragment variables. Species assemblages were also affected by site variables (12.2% of total variation), but no additional portion of the species assemblage variability was significantly explained by fragment size and connectivity. Sampling of several small fragments rendered more exotic and native species than sampling of few large fragments of the same total area. Conclusions: Our results agree with previous studies reporting low sensitivity of species diversity to size and isolation of grassland fragments in fragmented landscapes and high sensitivity of species diversity to local variables. The higher capture of regional native species pool by small grassland fragments than by few larger ones of equivalent accumulated area highlights the value of small fragments for conservation.     

Impacts of forest fragmentation on species composition and forest structure in the temperate landscape of southern Chile

Aim Few studies have explicitly examined the influence of spatial attributes of forest fragments when examining the impacts of fragmentation on woody species. The aim of this study was to assess the diverse impacts of fragmentation on forest habitats by integrating landscape‐level and species‐level approaches. Location The investigation was undertaken in temperate rain forests located in southern Chile. This ecosystem is characterized by high endemism and by intensive recent changes in land use. Method Measures of diversity, richness, species composition, forest structure and anthropogenic disturbances were related to spatial attributes of the landscape (size, shape, connectivity, isolation and interior forest area) of forest fragments using generalized linear models. A total of 63 sampling plots distributed in 51 forest fragments with different spatial attributes were sampled. Results Patch size was the most important attribute influencing different measures of species composition, stand structure and anthropogenic disturbances. The abundance of tree and shrub species associated with interior and edge habitats was significantly related to variation in patch size. Basal area, a measure of forest structure, significantly declined with decreasing patch size, suggesting that fragmentation is affecting successional processes in the remaining forests. Small patches also displayed a greater number of stumps, animal trails and cow pats, and lower values of canopy cover as a result of selective logging and livestock grazing in relatively accessible fragments. However, tree richness and β‐diversity of tree species were not significantly related to fragmentation. Main conclusions This study demonstrates that progressive fragmentation by logging and clearance is associated with dramatic changes in the structure and composition of the temperate forests in southern Chile. If this fragmentation process continues, the ability of the remnant forests to maintain their original biodiversity and ecological processes will be significantly reduced.     

Effects of forest successional status on microenvironmental conditions,diversity, and distribution of filmy fern species in a temperate rainforest

The vertical distribution of Hymenophyllaceae species has been related to microenvironmental variations around host trees. We addressed the questions: Do the vertical microenvironmental conditions within forest stands of differing successional statuses vary significantly? Does the diversity of Hymenophyllaceae species differ between forest successional statuses? Are the vertical distribution and diversity of Hymenophyllaceae species related more to humidity or light availability? Are there any interspecific differences in the desiccation tolerance of these species which can be related to their vertical distribution? We characterized the microhabitat conditions (vapor pressure deficit [VPD], air relative humidity [RH], and light availability [PAR]) and the vertical distribution of Hymenophyllaceae species in host trees, in both a secondary forest and an old‐growth temperate rainforest in Chile. Chlorophyll fluorescence was used to monitor the integrity of the photosynthetic apparatus during desiccation experiments. The stand basal area, tree height, and leaf area index were all significantly greater in the old‐growth forest stands, but VPD, RH, and PAR showed no significant differences between the two forests. Both successional statuses showed the same amount of filmy fern species in terms of both abundance and diversity. In both successional statuses VPD and RH decreased while PAR increased with the height of the hosts. Regardless of the forest's age, abundance and diversity of filmy ferns were greater in microsites of greater humidity and less light availability. Desiccation tolerance differed significantly among Hymenophyllaceae species. The distribution pattern could be better explained by the specific microenvironmental requirements and desiccation tolerance rather than the forest's successional status.     

Howling on the edge: Mantled howler monkey (Alouatta palliata) howling behaviour and anthropogenic edge effects in a fragmented tropical rainforest in Costa Rica

The function of long calling is a subject of interest across animal behaviour study, particularly within primatology. Many primate species have male‐specific long‐distance calls, including platyrrhines like the folivorous howler monkey (Alouatta spp.). Howler monkeys may howl to defend resources such as feeding trees or areas of rich vegetation from other monkey groups. This study tests the ecological resource defence hypothesis for howling behaviour in the mantled howler monkey (Alouatta palliata) and investigates how anthropogenic forest fragmentation may influence howling behaviour. More specifically, this study examines how howling bout rate, duration, precursors and tree species richness, DBH, and canopy cover vary in 100 m anthropogenic edge and interior forest zones at La Suerte Biological Research Station (LSBRS), a fragmented tropical rainforest in Costa Rica. Results show that tree species richness and canopy cover are higher in forest interior at this site, suggesting that monkeys should howl at greater rates in the interior to defend access to these higher‐quality vegetation resources. Overall, our results supported the ecological resource defence hypothesis. The main howl precursor was howling from neighbouring groups. Although howling rate did not differ between forest zones, howling bouts from forest interior were longer, had a greater number of howls per bout and were preceded by different precursors than howls from anthropogenic edge zones, including more howls from neighbouring groups. Our findings provide some of the first evidence for behavioural edge effects in primate vocal communication behaviour.     

Effects of Forest Fragmentation on the Abundance of <Emphasis Type="Italic">Colobus angolensis palliatus</Emphasis> in Kenya’s Coastal Forests

We documented the occurrence and abundance patterns of Angola black-and-white colobus (Colobus angolensis palliatus) in 46 coastal forest fragments ranging from 1 ha to >1400 ha in the Kwale District, Kenya. In field surveys conducted in 2001, we also recorded forest spatial, structural, resource, and disturbance characteristics to determine the effects of habitat quality and fragmentation and the factors most critical to the continued survival of the little-known species. We tested 13 hypotheses to explain variation in patch occupancy and abundance patterns of Colobus angolensis palliatus in relation to habitat attributes. Minimal adequate models indicated that the occurrence of colobus in forest fragments is positively associated with fragment area and canopy cover, whereas the density of colobus in occupied fragments is attributable to forest area, the proportion of forest change over the previous 12 yr, and the basal area of 14 major food trees. Large-scale illegal extraction of major colobus food trees in the District for human resource use, in both protected and unprotected forests, together with ongoing forest clearance and modification, are the major threats to Colobus angolensis palliatus in Kenya.     

Effects of fragments and landscape characteristics on the orchid bee richness (Apidae: Euglossini) in an urban matrix,southwestern Amazonia

Orchid bees are important pollinators in tropical forests. Although studies have already detected effects of habitat loss and forest fragmentation on bee assemblages, little is known about orchid bees in urban forest fragments. The aim of this study was to analyse the influence of forest fragments (size and edge index) and landscape features (forest cover area and built-up area around the forest fragments, connectivity and spatial distance from the urban center) on the abundance, richness and composition of orchid bees. Male bees were attracted by odoriferous baits and collected in ten forest fragments of different sizes. In total, we collected 3166 male bees belonging to 4 genera and 38 species. The increase of the built-up area and the reduction of the forest cover area around the forest fragments decreased the abundance and richness of bees. We recorded a smaller number of bees in areas closer to the urban center. We failed to find a significant relationship between abundance/richness of bees and forest fragment area, edge index, and connectivity. We observed that the faunistic dissimilarity was positively correlated with the geographic distance between forest fragments. The forest fragments that presented greater landscape dissimilarity also presented greater faunistic dissimilarity. Our results suggest that the matrix structure around the forest fragments is an important factor that influences the Euglossini bee assemblages inside these forest fragments. Based on our results, we believed that the conservation of fragments with a larger forest cover area and smaller built-up areas around them contribute to the maintenance of the diversity of orchid bees and their pollination services.     

The Importance of Tropical Rain Forest Fragments to the Conservation of Plant Species Diversity in Los Tuxtlas, Mexico

Of what value are forest fragments to the conservation of the tropical rain forest diversity for a landscape? We compared the changes in composition, diversity, and plant structure of 15 small (1–76 ha) relatively unprotected forest fragments with those of a large (700 ha) well protected fragment (LWPF) in Los Tuxtlas, Mexico. The trees, shrubs, lianas, palms, and herbs with dbh?≥?2.5 cm were sampled in 1000 m² at each site. For each ecological group (based on light requirements for germination: primary, secondary, and non-secondary light demanding, NSLD, species) and life form, estimates of species diversity, density, and basal area were analyzed using a stepwise multiple regression to determine whether there were any relationships between these variables and fragment characteristics (size, shape index, and isolation). The composition and plant structure of LWPF were different from those of the small fragments and large trees are absent from the canopy of the latter. Fragment size best explained the differences in composition and plant structure. Species composition in the largest fragments was similar to that of LWPF, but there was no significant difference in total richness between LWPF and the fragments, even though both the richness and abundance of secondary and NSLD species did differ. LWPF had more large primary trees in the canopy, and a greater abundance and basal area of palms and herbs. For tropical rain forest conservation, it is important to maintain the greatest possible number of large fragments and establish policies that prevent forest remnants from being further reduced in size and increasingly isolated from each other.     

Are fragments islands? Landscape context and density-area relationships in boreal forest birds

We investigated the role of matrix type as a determinant of change in bird densities with forest patch area (patch area effect) in two different Fennoscandian landscape types: mature forest fragments surrounded by cut-over or regenerating forest and true forested islands surrounded by water. Since the matrix of forested archipelagoes offers no resources to and impedes movement of forest birds, we predict that patch area effects on bird densities should be stronger on forested islands than in forest patches fragmented by forestry. We compiled correlation estimates of the bird density-patch area relationship from the literature and analyzed the data using meta-analysis. Combined correlation coefficients were significantly positive on islands but were not significantly different from 0 in fragments. Within-species comparisons also showed that correlations were consistently more positive on islands than in fragments. On islands but not in fragments, the densities of forest specialist species were more sensitive to area than were the densities of forest generalists, suggesting that specialists are more sensitive to changes in matrix quality. Migration status was only weakly associated with bird responses to island or fragment area. Thus, forest fragments do not function as true islands. We interpret this as the result of compensatory effects of the surrounding matrix in terms of availability of resources and enhanced connectivity (matrix quality hypothesis). A purely patch-centered approach seems an unrealistic framework to analyze population processes occurring in complex landscapes. The characteristics of the habitat matrix should therefore be explicitly incorporated into the assessment of species' responses to habitat fragmentation.     

Traits reveal how habitat‐quality gradients structure small mammal communities in a fragmented tropical landscape

Understanding the relationships among community structure, vegetation structure and availability of food resources are a key to unravelling the ecological processes that structure biological communities. In this study, we tested (i) whether the composition of small mammal communities changed across gradients in habitat quality in tropical forest fragments, and (ii) whether any observed change could be explained by the functional traits of species. We sampled 24 trapping grids in fragments of semi‐deciduous forest, in each of two 6‐month periods. We considered each trapping grid as a sampling unit, for which we collected three datasets: an environmental matrix (vegetation structure and food resource availability), the abundance of small mammal species (community structure) and a matrix of functional traits (ecological and morphological traits which express tolerance to habitat disturbance and trophic guild). We used an RLQ approach to evaluate the association between traits and environmental gradients. Forest‐specialist and scansorial–arboreal species were associated with more complex habitat that had greater litter and canopy cover and more fallen logs. In relation to trophic guilds, granivore (fruit seeds), insectivorous and omnivorous species were also associated with higher complexity habitat, while frugivores were associated with shrub cover and availability of fruits. We conclude that functional traits (habitat use, use of vertical strata and diet) provide valuable insights into the distribution of small mammals along gradients of habitat quality in tropical forest fragments. We highlight that communities studies in fragmented landscapes should investigate the different components of biodiversity not only in landscape‐scale but also in habitat scale. Abstract in Portuguese is available with online material.     

Species- and community-level responses to habitat spatial changes in fragmented rainforests: assessing compensatory dynamics in amphibians and reptiles

The rapid loss and degradation of tropical forests threatens the maintenance of biodiversity across different spatial scales. Nevertheless, the extirpation and population decline of some disturbance-sensitive species may be compensated for by colonization and proliferation of disturbance-adapted species, thus allowing distributions of community-level attributes (e.g., abundance and diversity) to be preserved in human-modified tropical landscapes. To test this poorly assessed hypothesis we evaluated species- and community-level responses of amphibians and reptiles to differences in forest patch (patch size, shape, and distance to water bodies) and landscape metrics (old-growth forest cover, degree of fragmentation, and matrix composition) in the fragmented Lacandona rainforest, Mexico. We found that the abundance of several amphibian and reptile species was strongly associated with forest patch and landscape attributes, being particularly higher in larger patches surrounded by a greater forest cover. Such changes at the species level generated notable changes in reptile communities. In particular, the abundance, diversity, and evenness of reptile communities were strongly related to patch size, patch shape, and matrix composition. Yet, because of compensatory dynamics in amphibians, this group showed weak responses at the community level. Despite such compensatory dynamics, our results indicate that forest loss at the patch and landscape levels represents the main threat to both amphibians and reptiles, thus indicating that to preserve herpetological communities in this biodiversity hotspot, conservation initiatives should be focused on preventing further deforestation.     

Amphibian and reptile communities of rainforest fragments: minimum patch size to support high richness and abundance

Information on animal communities inhabiting Neotropical fragmented landscapes is important for developing conservation strategies. The structure of amphibian and reptile communities in six tropical rainforest fragments (<20?ha) and two reference areas in continuous forest at Los Tuxtlas, Mexico was studied. A total of 3,481 individuals of 51 species of amphibians and reptiles were recorded across 12 bimonthly surveys during 2 years. Taxonomic composition was different between the smallest fragments and the reference areas. Six species were exclusive to large undisturbed forest and richness was significantly lower in the five smallest fragments (1.4–6.6?ha) compared with the largest patch, one or both of the reference areas. Amphibian abundance tended to be higher in large areas, while reptiles were more abundant in the five smallest fragments. Craugastor loki and Anolis uniformis were the dominant species in all sites, and particularly in the smaller fragments. Amphibian and reptile richness was positively related to larger patch sizes, deeper leaf litter, closed canopy cover, and higher relative humidity and negatively related to linear patch shape and high temperatures. Abundance of reptiles was positively associated to high temperatures, high density of woody debris, and closed canopy cover; it was negatively affected by linear patch shape, low humidity levels, and steeper slopes. While amphibian and reptile communities were strongly affected in vegetation fragments, these patches retained a considerable number of rainforest species. Fragments up to at least 17?ha have the potential for preserving communities with similar structure to those occurring in large tropical rainforests.     

Diversity of gall wasps (Hymenoptera: Cynipidae) associated with oak trees (Fagaceae: <Emphasis Type="Italic">Quercus</Emphasis>) in a fragmented landscape in Mexico

Habitat fragmentation reduces the available habitat area and increases both the distance between fragments and the amount of fragment edges. Therefore, there are more probabilities of plant population size reduction and species extinction. In the same way, biotic and abiotic changes associated with forest fragmentation can dramatically alter plant growth and phenological patterns. We conducted a 3-year study to analyze effects of habitat fragmentation and seasonal variation on host plant quality (quantity of leaves, diameter at breast height, tree height), gall abundance and species richness in a temperate oak forest. Our results show that host plant quality was significantly higher in isolated oaks and small fragments, increasing the abundance and species richness of oak gall wasp species in most fragmented habitats. Oak canopy cover is altered by forest fragmentation, there being higher production of leaves on trees that are more exposed to fragmentation, and can provide important resources for maintaining gall wasp species diversity in a fragmented landscape. We found higher gall wasp richness and abundance in autumn than in the spring, which matches with the higher quantity of leaves in this season.     

北京市域乡村人居林树冠覆盖及其区域差异分析

乡村人居林建设是落实新农村建设、实施乡村振兴战略和振兴农村生态文明的重要举措。以北京市为对象，基于北京市域2017年0.5m分辨率航空影像与2017年1：10万土地利用（LUCC）图等基础资源，在全市范围内随机选择260个行政村，从研究区域内乡村人居林树冠覆盖率、功能类型、斑块等级和景观格局特征四个层面展开区域差异特征分析。研究结果显示，北京市整体乡村人居林树冠覆盖率为18.32%，其中平原区和山区分别为18.40%和17.83%。在平原区范围内，乡村人居林树冠覆盖率呈近郊区（21.70%） > 远郊区（13.87%） > 延庆盆地区域（16.34%）；在山区内部，乡村人居林树冠覆盖率呈现低山区（24.45%） > 浅山区（16.55%） > 深山区（12.41%），太行山区（20.98%） > 燕山区（14.11%）。在乡村人居林功能类型分布中，片林为各分区最主要类型，在平原区和山区中分别占比55.75%和57.15%。在斑块等级结构方面，乡村人居林斑块总体呈现小而分散的特点，其中小斑块数目在区域中占比达93.03%，而各等级斑块在规模大小方面呈现"平分秋色"的特点。就景观格局指数特点而言，平原区内近郊区，山区内的深山区和燕山区乡村人居林斑块复杂程度、受人为干扰强度和多样性更高。综上特征，究其动因，农村居民点聚落规模、集聚形式和建设类型以及森林资源本底是影响乡村人居林建设条件的重要原因。     

Habitat Characteristics of Forest Fragments Determine Specialisation of Plant-Frugivore Networks in a Mosaic Forest Landscape

Plant-frugivore networks play a key role in the regeneration of sub-tropical forest ecosystems. However, information about the impact of habitat characteristics on plant-frugivore networks in fragmented forests is scarce. We investigated the importance of fruit abundance, fruiting plant species richness and canopy cover within habitat fragments for the structure and robustness of plant-frugivore networks in a mosaic forest landscape of South Africa. In total, 53 avian species were involved in fruit removal of 31 fleshy-fruiting plant species. Species specialisation was always higher for plants than for frugivores. Both species and network-level specialisation increased with increasing fruit abundance and decreased with increasing fruiting plant species richness and canopy cover within fragments. Interaction diversity was unaffected by fruit abundance and canopy cover, but increased slightly with increasing fruiting plant species richness. These findings suggest that especially the availability of resources is an important determinant of the structure of plant-frugivore networks in a fragmented forest landscape.