Invasibility of mature and 15-year-old deciduous forests by exotic plants

High species richness, resource availability and disturbance are community characteristics associated with forest invasibility. We categorized commonly measured community variables, including species composition, topography, and landscape features, within both mature and 15-year-old clearcuts in West Virginia, USA. We evaluated the importance of each variable for predicting the degree of forest invasion by early-establishing exotic invasive plants. Biotic variables, including overall richness (excluding exotic invasive species) and mutually exclusive native and exotic non-invasive species richness, were the strongest indicators of invasibility. Sites that were located on northeast-facing slopes, more mesic conditions, or in clearcuts were more likely to be invaded by exotic invasive plants. Invasion of clearcut sites was more dependent on available microsites (e.g., lower solar radiation, northeast-facing slopes, and lower elevations) within each site than on the condition of the surrounding landscape, whereas invasion into the mature forests was dependent more on the surrounding landscape (e.g., proximity to paved roads). Our results indicate that exotic invasive plant species in our study area respond similarly as other plant species to resource availability and that competitive interactions are relatively unimportant. Current invasion into this landscape is more likely to be a passive reaction to site conditions instead of a driver of change.     

Effects of forest modification on bird community composition and seed removal in a heterogeneous landscape in South Africa

Human disturbance threatens and modifies forest ecosystems worldwide. Previous studies have investigated the effects of human impact on local bird communities in disturbed forests, but we still lack information on how bird species richness and ecological processes respond to different forest modifications present at a landscape scale. In a heterogeneous South African landscape, we chose six types of indigenous scarp forest, differing in the intensity of human disturbance: continuous natural forests and natural forest fragments in nature reserves, forest fragments in eucalyptus plantations, fragments in the agricultural matrix, forest gardens and secondary forests in game reserves. In 36 study sites, we investigated the bird community using point counts and observed the seed removal of birds at the native tree species Celtis africana. Species richness did not differ among the forest types, but abundance varied significantly with most birds observed in fragments in the agricultural matrix, forest gardens, and secondary forests. The higher bird abundance in these forests was mainly due to forest generalists, shrubland and open country species whereas forest specialists were rarely present. Changes in species composition were also confirmed by multivariate analysis which clearly separated bird communities by forest type. Frugivore abundance in C. africana was highest in natural forest fragments, fragments in the agricultural matrix, forest gardens and secondary forests. The same trend was found for the estimated total number of fruits removed per C. africana tree, though the differences among forest types were not significant. Consequently, modified forests seem to maintain important ecological functions as they provide food sources for generalist species which may, due to their mobility, enhance natural plant regeneration. However, we could show that protected forest habitats are important refugees for specialist species sensitive to human disturbance.     

Community science data suggests that urbanization and forest habitat loss threaten aphidophagous native lady beetles

1. Community scientists have illustrated rapid declines of several aphidophagous lady beetle (Coccinellidae) species. These declines coincide with the establishment of alien coccinellids. We established the Buckeye Lady Beetle Blitz program to measure the seasonal occupancy of coccinellids within gardens across a wide range of landscape contexts. Following the Habitat Compression Hypothesis, we predicted that gardens within agricultural landscapes would be alien‐dominated, whereas captures of natives would be higher within landscapes encompassing a high concentration of natural habitat.
2. Within the state of Ohio, USA, community scientists collected lady beetles for a 7‐day period across 4 years in June and August using yellow sticky card traps. All identifications were verified by professional scientists and beetles were classified by three traits: status (alien or native), mean body length, and primary diet. We compared the relative abundance and diversity of coccinellids seasonally and determined if the distribution of beetles by size, status, and diet was related to landscape features.
3. Alien species dominated the aphidophagous fauna. Native aphidophagous coccinellid abundance was positively correlated with forest habitat while alien species were more common when gardens were embedded within agricultural landscapes. Urbanization was negatively associated with both aphidophagous alien and native coccinellids.
4. Synthesis and Applications: Our census of native coccinellid species within residential gardens—a widespread and understudied habitat—was enabled by volunteers. These data will serve as an important baseline to track future changes within coccinellid communities within this region. We found that native coccinellid species richness and native aphidophagous coccinellid abundance in gardens were positively associated with forest habitat at a landscape scale of 2 km. However, our understanding of when and why (overwintering, summer foraging, or both) forest habitats are important remains unclear. Our findings highlight the need to understand how declining aphidophagous native species utilize forest habitats as a conservation priority.

     

Settlements as a source for the spread of non-native plants into Central European suburban forests

Urbanization is considered as a major driver for biotic homogenization. Urbanization also promotes the dispersal of non-native species. This study examined the roles of suburban settlements and of the surrounding landscape composition for the spread of non-native plant species into adjacent mixed deciduous forests in Southern and Northwestern Switzerland. The number and abundance of native and non-native vascular plant species in both the ground vegetation and shrub layer were recorded in 15 forest sites situated adjacent to settlements and 15 control sites far from settlements. Various site and landscape characteristics were assessed in the surroundings (100 m radius) of the study sites. In both regions we found a higher number and larger abundance of non-native plant species in forest sites adjacent to settlements than in control forest sites. Furthermore, non-native plants were more frequently recorded close to roads and in sites surrounded by a large percentage cover of garden. All these effects were more pronounced in Southern Switzerland, a region with milder winter climate, than in Northwestern Switzerland. Our study showed that settlements are a source for the spread of non-native plant species into Central European suburban forests, and that the composition of the surrounding landscape matrix (e.g. traffic infrastructure, percentage cover of gardens) also affects the establishment of non-native plants.     

Garden and Landscape-Scale Correlates of Moths of Differing Conservation Status: Significant Effects of Urbanization and Habitat Diversity

Moths are abundant and ubiquitous in vegetated terrestrial environments and are pollinators, important herbivores of wild plants, and food for birds, bats and rodents. In recent years, many once abundant and widespread species have shown sharp declines that have been cited by some as indicative of a widespread insect biodiversity crisis. Likely causes of these declines include agricultural intensification, light pollution, climate change, and urbanization; however, the real underlying cause(s) is still open to conjecture. We used data collected from the citizen science Garden Moth Scheme (GMS) to explore the spatial association between the abundance of 195 widespread British species of moth, and garden habitat and landscape features, to see if spatial habitat and landscape associations varied for species of differing conservation status. We found that associations with habitat and landscape composition were species-specific, but that there were consistent trends in species richness and total moth abundance. Gardens with more diverse and extensive microhabitats were associated with higher species richness and moth abundance; gardens near to the coast were associated with higher richness and moth abundance; and gardens in more urbanized locations were associated with lower species richness and moth abundance. The same trends were also found for species classified as increasing, declining and vulnerable under IUCN (World Conservation Union) criteria. However, vulnerable species were more strongly negatively affected by urbanization than increasing species. Two hypotheses are proposed to explain this observation: (1) that the underlying factors causing declines in vulnerable species (e.g., possibilities include fragmentation, habitat deterioration, agrochemical pollution) across Britain are the same in urban areas, but that these deleterious effects are more intense in urban areas; and/or (2) that urban areas can act as ecological traps for some vulnerable species of moth, the light drawing them in from the surrounding landscape into sub-optimal urban habitats.     

Tropical paradox: a multi-scale analysis of the invasion paradox within Miami Rock Ridge tropical hardwood hammocks

The invasion paradox describes the scale dependence of native-exotic richness relationships (NERRs), where NERRs are negative at neighborhood scales and positive at landscape scales. However, a lack of tropical surveys and past failures to isolate potential confounding variables contribute to significant gaps in our understanding of the processes producing these patterns. We surveyed the vascular flora of 13 tropical hardwood hammocks for community characteristics (e.g., native and exotic species richness, vegetative cover) with a hierarchical sampling design. Using model selection, we determined which variables best predicted patterns of exotic species richness at each spatial scale of consideration. We found that native and exotic species richness were positively correlated at neighborhood scales, but negatively correlated at landscape scales. The latter result stands in stark opposition to the patterns published in the literature thus far. We found that natural disturbance history (as approximated by vegetative cover) was positively correlated with exotic species richness at intermediate and landscape scales only. Overall, hammock identity was the most important factor driving exotic species richness patterns at all spatial scales. Hammocks with highly-disturbed hydrologies, brought about by water management, had fewer native species and more exotic species than hammocks with more natural hydrological conditions. Our results are among the first from examination of subtropical communities, and may support the hypothesis that tropical and subtropical communities are subject to more intense biotic interactions. However, given our unique sampling design, our results do not reject the hypothesis that environmental heterogeneity drives the relationship between native and exotic species richness patterns.     

Bird community shifts related to different forest restoration efforts: A case study from a managed habitat matrix in Mexico

Although increased attention is being paid to animals when studying restoration processes, little is known on the effects that different restoration efforts have on birds. In this study we evaluated the variation of bird communities in a managed landscape that includes cropfields and two different restoration strategies. To evaluate possible differential effects of both restoration strategies (plus former-state and natural-state comparisons as controls), we compared their bird communities. After five growing seasons, bird species richness was highest in native forest remnants and lowest in cropfields. Although species richness values from the restoration treatment did not show differences in relation to those from the forest treatment, values for the reforestation treatment did. Bird densities were highest in the forests and alike in cropfield, reforestation, and restoration treatments. However, bird communities recorded in the restoration treatment were fairly even when compared to the reforestation treatment, and highest bird species composition similarity was recorded between the restoration and forest treatments. These results suggest that the studied restoration treatment attracts a higher number of bird species in relation to former states and thus enhance bird richness. Also, we demonstrate that restoration efforts that include more actions can affect more ecosystem components. In this study, nurse plants not only offered a quick growing structural vegetation component that enhanced habitat structure, but also provided abundant food resources for birds. Given the scarcity of comparable habitat matrices to replicate our study, our results should be taken with caution as they are not generalizable to all Mexican temperate forest conditions. Although further studies need to address whether restoration practices using Lupinus elegans positively affect bird primary population parameters (e.g., survival, reproduction), our results show that restoration practices that include nurse plants can promote rich bird communities after only 5 years from the implementation of restoration measures.     

Land use change has stronger effects on functional diversity than taxonomic diversity in tropical Andean hummingbirds

Land use change modifies the environment at multiple spatial scales, and is a main driver of species declines and deterioration of ecosystem services. However, most of the research on the effects of land use change has focused on taxonomic diversity, while functional diversity, an important predictor of ecosystem services, is often neglected. We explored how local and landscape scale characteristics influence functional and taxonomic diversity of hummingbirds in the Andes Mountains in southern Ecuador. Data was collected in six landscapes along a land use gradient, from an almost intact landscape to one dominated by cattle pastures. We used point counts to sample hummingbirds from 2011 to 2012 to assessed how local factors (i.e., vegetation structure, flowering plants richness, nectar availability) and landscape factors (i.e., landscape heterogeneity, native vegetation cover) influenced taxonomic and functional diversity. Then, we analyzed environment – trait relationships (RLQ test) to explore how different hummingbird functional traits influenced species responses to these factors. Taxonomic and functional diversity of hummingbirds were positively associated with landscape heterogeneity but only functional diversity was positively related to native vegetation coverage. We found a weak response of taxonomic and functional diversity to land use change at the local scale. Environment‐trait associations showed that body mass of hummingbirds likely influenced species sensitivity to land use change. In conclusion, landscape heterogeneity created by land use change can positively influence hummingbird taxonomic and functional diversity; however, a reduction of native vegetation cover could decrease functional diversity. Given that functional diversity can mediate ecosystem services, the conservation of native vegetation cover could play a key role in the maintenance of hummingbird pollination services in the tropical Andes. Moreover, there are particular functional traits, such as body mass, that increase a species sensitivity to land use change.     

Deconstructing the native–exotic richness relationship in plants

Aim Classic theory suggests that species‐rich communities should be more resistant to the establishment of exotic species than species‐poor communities. Although this theory predicts that exotic species should be less diverse in regions that contain more native species, macroecological analyses often find that the correlation between exotic and native species richness is positive rather than negative. To reconcile results with theory, we explore to what extent climatic conditions, landscape heterogeneity and anthropogenic disturbance may explain the positive relationship between native and exotic plant richness. Location Catalonia (western Mediterranean region). Methods We integrated floristic records and GIS‐based environmental measures to make spatially explicit 10‐km grid cells. We asked whether the observed positive relationship between native and exotic plant richness (R²= 0.11) resulted from the addition of several negative correlations corresponding to different environmental conditions identified with cluster analysis. Moreover, we directly quantified the importance of common causal effects with a structural equation modelling framework. Results We found no evidence that the relationship between native and exotic plant richness was negative when the comparison was made within environmentally homogeneous groups. Although there were common factors explaining both native and exotic richness, mainly associated with landscape heterogeneity and human pressure, these factors only explained 17.2% of the total correlation. Nevertheless, when the comparison was restricted to native plants associated with human‐disturbed (i.e. ruderal) ecosystems, the relationship was stronger (R²= 0.52) and the fraction explained by common factors increased substantially (58.3%). Main conclusions While our results confirm that the positive correlation between exotic and native plant richness is in part explained by common extrinsic factors, they also highlight the great importance of anthropic factors that – by reducing biotic resistance – facilitate the establishment and spread of both exotic and native plants that tolerate disturbed environments.     

The roles of biotic resistance and nitrogen deposition in regulating non-native understory plant diversity

Understanding the mechanisms that allow for plant invasions is important for both ecologists and land managers, due to both the environmental and economic impacts of native biodiversity losses. We conducted an observational field study in 2008 to examine the relationship between native and non-native forest understory plant species and to investigate the influence of soil nitrogen (N) on plant community richness and diversity. In 2009, we conducted a companion fertilization experiment to investigate how various forms of N deposition (inorganic and organic) influenced native and non-native species richness and diversity. We found that native species richness and diversity were negatively correlated with 1) non-native species richness and diversity and 2) higher total soil inorganic N. In the deposition experiment, adding organic N fertilizers decreased native richness and diversity compared to inorganic N fertilizers. Together, these results indicate that increasing soil N can be detrimental to native species; however, native species richness and diversity may counteract the N-stimulation of non-native species. Furthermore, the negative effects of organic N deposition on native plants may be just as strong, if not stronger, than the effects of inorganic N deposition.     

The importance of conserving biodiversity outside of protected areas in mediterranean ecosystems

Mediterranean-type ecosystems constitute one of the rarest terrestrial biomes and yet they are extraordinarily biodiverse. Home to over 250 million people, the five regions where these ecosystems are found have climate and coastal conditions that make them highly desirable human habitats. The current conservation landscape does not reflect the mediterranean biome's rarity and its importance for plant endemism. Habitat conversion will clearly outpace expansion of formal protected-area networks, and conservationists must augment this traditional strategy with new approaches to sustain the mediterranean biota. Using regional scale datasets, we determine the area of land in each of the five regions that is protected, converted (e.g., to urban or industrial), impacted (e.g., intensive, cultivated agriculture), or lands that we consider to have conservation potential. The latter are natural and semi-natural lands that are unprotected (e.g., private range lands) but sustain numerous native species and associated habitats. Chile has the greatest proportion of its land (75%) in this category and California-Mexico the least (48%). To illustrate the potential for achieving mediterranean biodiversity conservation on these lands, we use species-area curves generated from ecoregion scale data on native plant species richness and vertebrate species richness. For example, if biodiversity could be sustained on even 25% of existing unprotected, natural and semi-natural lands, we estimate that the habitat of more than 6,000 species could be represented. This analysis suggests that if unprotected natural and semi-natural lands are managed in a manner that allows for persistence of native species, we can realize significant additional biodiversity gains. Lasting biodiversity protection at the scale needed requires unprecedented collaboration among stakeholders to promote conservation both inside and outside of traditional protected areas, including on lands where people live and work.     

Influence of local and landscape factors on bumblebees in semi-natural meadows: a multiple-scale study in a forested landscape

Understanding the effects of local and landscape factors on bumblebees is relevant for the conservation of this group of pollinators. Bumblebees have been well-studied in agricultural landscapes of Western Europe, Asia and North America, but few studies have been developed on bumblebees in forest-dominated landscapes of Eastern Europe. We developed this study in 22 semi-natural meadows located in a patchy forested landscape of Estonia. We investigated the influence of habitat characteristics and landscape factors (calculated at four spatial scales: 250, 500, 1,000 and 2,000 m radius) on the total species richness and abundance of bumblebees. Correlation analysis, partial least squares (PLS) and stepwise forward-selection multiple regression analysis were applied in this study. The presence of a high diversity of flowering plants in semi-natural meadows may benefit the abundance of bumblebees. At the local level, patch area and shape seem to have positive and negative influences, respectively, on bumblebee species richness. At the landscape level, human settlements with the presence of gardens may favour bumblebee richness and abundance. Also, bumblebee species may increase with a high presence of meadows in the landscape, and may decrease with high percentages of forest and young forest. Overall, forested landscapes with a strong presence of edges and a diverse matrix may support a higher species richness and abundance of bumblebees. Both local and landscape factors should be considered when designing conservation strategies and agri-environmental measures.     

Economic Stratification Differentiates Home Gardens in the Maya Village of Pomuch,Mexico

Economic Stratification Differentiates Home Gardens in the Maya Village of Pomuch, Mexico. In this paper, we analyze if economic stratification of peasant families in a Maya village in the Yucatán Peninsula of Mexico influences species composition and structure of home gardens. Our general hypothesis was that composition and structure reflect a higher dependence on home garden produce of relatively poorer families as compared to more prosperous families. We registered the cultivated trees and herbs in samples of twelve home gardens of poorer and wealthier families that had similar assets in the 1980s, and classified them by principal use and geographic origin. Total species richness of cultivated herbs was highest in home gardens of the more prosperous families, whereas total species richness of trees was highest in home gardens of the poorer families. Average species richness of trees and herbs and species composition was similar in both economic strata. Poorer families cultivated relatively more trees for uses other than fruit than richer families. The average and total number of native tree species and density of trees with diameter at breast height of less than 10 cm was significantly higher in poorer families’ home gardens than in those of wealthier families. We conclude that economic stratification leads to different production strategies in home gardens. Richer families are comparatively more interested in obtaining fruit occasionally and emphasize diversity of herbaceous ornamentals. Poorer families emphasize different uses, favor the native flora, and increase tree density. Thereby they contribute more to biodiversity conservation than wealthier families.     

Native forest metacommunity structures in Uruguay shaped by novel land‐use types in their surroundings

We explore the effect of land‐use change from extensively used grasslands to intensified silvi‐ and agricultural monocultures on metacommunity structure of native forests in Uruguay. We integrated methods from metacommunity studies, remote sensing, and landscape ecology to explore how woody species distribution was influenced by land‐use change from local to regional scale. We recorded richness and composition of adult and juvenile woody species from 32 native forests, created land‐use maps from satellite image to calculate spatial metrics at landscape, class, and patch levels. We also analyzed the influence of land use pattern, climate, topography, and geographic distance between sites (d) on metacommunity, and created maps to visualize species richness and (dis)similarity between communities across the country. Woody species communities were distributed in a discrete pattern across Uruguay. Precipitation and temperature seasonality shaped species distribution pattern. Species richness and community dissimilarity increased from West to East. Latitude did not influence these patterns. Number of patches, landscape complexity, and interspersion and juxtaposition indexes determine woody species distribution at landscape level. Increasing areas covered by crops and timber plantation reduced species richness and increased community dissimilarity. The spatial metrics of native forest fragments at patch level did not influence metacommunity structure, species richness, and community dissimilarity. In conclusion, Uruguayan native forests display a high range of dissimilarity. Pressure of neighborhood land uses was the predominant factor for species assemblages. Conserving landscape structures that assure connectivity within and among native forest patches is crucial. On sites with rare target species, the creation of alliances between governmental institution and landowner complemented by incentives for biodiversity conservation provides opportunities to advance in species protection focused on those less tolerant to land‐use change.     

Frugivory,Post‐feeding Flights of Frugivorous Birds and the Movement of Seeds in a Brazilian Fragmented Landscape

Habitat fragmentation can break down the movement processes of frugivorous animals, thus influencing the relationship between plants and their seed dispersers by altering the number and identity of seed dispersers, and their relative contribution to seed dispersal. We studied the assemblages of frugivorous birds, their composition, species richness, and visitation rates to fruiting plants growing in the different landscape elements (forest fragments, live fences, and trees isolated in pastures) embedded in a Brazilian fragmented, agricultural landscape. By following the post‐feeding movements of frugivorous birds, we inferred the direction of seed movement from and to each of these landscape elements. Fruiting trees growing at different landscape elements were visited by frugivorous birds at similar rates. Isolated trees attracted a greater and distinct bird assemblage than trees in forest fragments or live fences. Judging by the post‐feeding flights of birds, the seeds of isolated trees were the most likely to reach all the landscape elements considered, but the contribution of isolated trees to the seeds falling in forested habitats or pastures depended on their degree of isolation. A few bird species were able to move widely, visiting fruiting plants in all landscape elements, and promoting long‐distance dispersal for plants. These few birds are of special interest because they are mobile links that connect habitats in fragmented landscapes with their seed dispersal services. Abstract in Spanish is available at http://www.blackwell‐synergy.com/loi/btp .     

Individual Species-Area Relationship of Woody Plant Communities in a Heterogeneous Subtropical Monsoon Rainforest

The spatial structure of species richness is often characterized by the species-area relationship (SAR). However, the SAR approach rarely considers the spatial variability of individual plants that arises from species interactions and species’ habitat associations. Here, we explored how the interactions of individual plants of target species influence SAR patterns at a range of neighborhood distances. We analyzed the data of 113,988 woody plants of 110 species from the Fushan Forest Dynamics Plot (25 ha), northern Taiwan, which is a subtropical rainforest heavily influenced by typhoons. We classified 34 dominant species into 3 species types (i.e., accumulator, repeller, or no effect) by testing how the individual species-area relationship (i.e., statistics describing how neighborhood species richness changes around individuals) of target species departs (i.e., positively, negatively, or with no obvious trend) from a null model that accounts for habitat association. Deviation from the null model suggests that the net effect of species’ interactions increases (accumulate) or decreases (repel) neighborhood species richness. We found that (i) accumulators were dominant at small interaction distances (<10–30 m); (ii) the detection of accumulator species was lower at large interaction distances (>30 m); (iii) repellers were rarely detected; and (iv) large-sized and abundant species tended to be accumulators. The findings suggest that positive species interactions have the potential to accumulate neighborhood species richness, particularly through size- and density-dependent mechanisms. We hypothesized that the frequently disturbed environment of this subtropical rainforest (e.g., typhoon-driven natural disturbances such as landslides, soil erosion, flooding, and windthrow) might create the spatial heterogeneity of species richness and promote positive species interactions.     

Forest fragmentation and loss reduce richness,availability, and specialization in tropical hummingbird communities

Hummingbirds are important pollinators of many native Neotropical plants but their abundance and diversity in landscapes dominated by intensive human uses such as agriculture have rarely been examined, despite such land‐uses prevailing in the tropics. We examined how tropical deforestation affects hummingbird community structure in premontane forest patches embedded in a tropical countryside of Coto Brus Canton, Costa Rica. We captured hummingbirds in fourteen landscapes representing a gradient in patch size and forest amount, and tested for the effects of these variables on (1) hummingbird captures at flowers (pollinator availability); (2) species richness; and (3) filtering of functional traits. After accounting for sampling effects, both hummingbird availability and species richness declined by 40% and 50%, respectively, across the gradient in deforestation that we observed (9–66% forest within 1000 m). Focal patch size was the strongest predictor, even after statistically accounting for the amount of forest and matrix composition of landscapes. These reductions in availability and richness were well predicted by functional traits; morphologically specialized species with the capacity to transport long‐distance outcrossed pollen and low functional redundancy within the pollinator network showed the greatest sensitivity to landscape change. We hypothesize that declines in hummingbird availability, diversity, and functional traits are important mechanisms driving the observed pollen limitation of ornithophilous flowers in fragmented tropical landscapes. Efforts to conserve large forest patches and enhance matrix permeability are critical for maintaining forest hummingbird communities and pollination services under current and predicted deforestation regimes.     

Relationships between spatial configuration of tropical forest patches and woody plant diversity in northeastern Puerto Rico

The destruction and fragmentation of tropical forests are major sources of global biodiversity loss. A better understanding of anthropogenically altered landscapes and their relationships with species diversity and composition is needed in order to protect biodiversity in these environments. The spatial patterns of a landscape may control the ecological processes that shape species diversity and composition. However, there is little information about how plant diversity varies with the spatial configuration of forest patches especially in fragmented tropical habitats. The northeastern part of Puerto Rico provides the opportunity to study the relationships between species richness and composition of woody plants (shrubs and trees) and spatial variables [i.e., patch area and shape, patch isolation, connectivity, and distance to the Luquillo Experimental Forest (LEF)] in tropical forest patches that have regenerated from pasturelands. The spatial data were obtained from aerial color photographs from year 2000. Each photo interpretation was digitized into a GIS package, and 12 forest patches (24–34 years old) were selected within a study area of 28 km². The woody plant species composition of the patches was determined by a systematic floristic survey. The species diversity (Shannon index) and species richness of woody plants correlated positively with the area and the shape of the forest patch. Larger patches, and patches with more habitat edge or convolution, provided conditions for a higher diversity of woody plants. Moreover, the distance of the forest patches to the LEF, which is a source of propagules, correlated negatively with species richness. Plant species composition was also related to patch size and shape and distance to the LEF. These results indicate that there is a link between landscape structure and species diversity and composition and that patches that have similar area, shape, and distance to the LEF provide similar conditions for the existence of a particular plant community. In addition, forest patches that were closer together had more similarity in woody plant species composition than patches that were farther apart, suggesting that seed dispersal for some species is limited at the scale of 10 km.     

Use of Tropical Dry Forests and Agricultural Areas by Neotropical Bird Communities

Agricultural activities represent a global threat to biodiversity, yet little is known about the relative importance of different agricultural land uses in relation to their wildlife communities. We explored bird community structure, diversity, and composition in a landscape dominated by primary tropical dry forest, and in three agricultural systems (i.e., tree orchards, herbaceous cropfields, cattle pastures) to evaluate the way in which birds use different habitats within the landscape. Tropical dry forests had the highest species richness and community evenness, although the bird community in tree orchards was also relatively species rich and even. Cattle pastures had more bird species than cropfields but both habitats were comparatively species poor with low evenness. Our results are related to habitat structure and the spatial location of sites within the landscape matrix. Based on our observations, we recommend including native tree species within agricultural systems and surrounding areas to provide additional resources for birds. Finally, we suggest promoting natural recruitment of native trees and shrubs within cattle pastures to provide suitable habitat for species that use tropical dry forest plants. Abstract in Spanish is available at http://www.blackwell‐synergy.com/loi/btp .     

Home Gardens Sustain Crop Diversity and Improve Farm Resilience in Candelaria Loxicha,Oaxaca, Mexico

Home gardens are land use units embedded in a larger land use system, in this case in Candelaria Loxicha, Oaxaca, Mexico. Using a combination of qualitative and quantitative methods, we investigated how home gardens are integrated into local farming practices and how these influence biodiversity. Our findings suggest that home gardens harbour high levels of biodiversity, which are maintained and enriched by farmers’ practices, particularly plant and seed exchange. Plant diversity is higher in younger home gardens and in home gardens where owners actively exchange plant material with other people. Through plant exchange, seed storage, and the dispersion of seeds and plants in different land uses, farmers encourage plant diversity and consequently increase the resilience of their farming system in changing climatic, demographic and economic conditions. Both men and women participate in the establishment, care and management of home gardens, but they are responsible for different plants and home garden functions. For economic reasons, the inhabitants of Candelaria Loxicha are increasingly engaging in international migration. Migrants, upon their return bring new ideas and plants that might transform the rural landscape.