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Forest Fragmentation (forest + fragmentation)

Distribution by Scientific Domains

Life Sciences	84%
Humanities and Social Sciences	8%

Distribution within Life Sciences

Conservation Science	27%
Ecology & Organismal Biology	22%

Selected Abstracts

Impact of Forest Fragmentation on Understory Plant Species Richness in Amazonia

CONSERVATION BIOLOGY, Issue 2 2003
Julieta Benítez-Malvido
In Central Amazonia, 9 to 19 years after fragmentation, we recorded species richness and net seedling recruitment rate in forest fragments of 1, 10, and 100 ha and in continuous forest. In 1991 all seedlings 5,100 cm tall within permanent 1-m2 plots in fragments and continuous forest were counted and grouped into tree, liana, palm, and herb life-form classes. In 1993 we manually removed all seedlings that were <1 m tall from the permanent plots. Six years and 5 months later ( 1999 ), all new seedlings recruited into the plots were counted, grouped into different life forms, and classified into distinct morphospecies. The species richness of recruited tree, liana, herb, and palm seedlings was lower in forest fragments than in continuous forest, with the 1-ha fragment having the poorest species richness. The total number of recruited individuals was 40% less than that previously present for all life forms, except lianas. Liana recruitment was 7% to 500% higher than the original abundance in the forest fragments and continuous forest. In general, species similarity was higher among fragments than between fragments and continuous forest, with the 1-ha fragment being less similar. Species rank/abundance curves showed that continuous forest species in all life forms tended to disappear in forest fragments, whereas common species in forest fragments were absent from continuous forest. Overall, our results suggest that the life-form composition and structure of the regenerative plant pool in fragments were shifting toward a species-poor seedling community. Losses of understory species diversity, but especially of tree seedlings, threaten the maintenance of rainforest biodiversity and compromise future forest regeneration. Resumen: La fragmentación de las selvas tropicales afecta severamente a a los árboles de gran porte, sin embargo, su efecto sobre otros estadíos y formas de vida de las plantas es poco conocido. En la Amazonia central, de 9 a 19 años después de la fragmentación, se registró la riqueza de especies y la tasa neta de reclutamiento de plántulas en fragmentos de selva de 1, 10, y 100 ha y en selva contínua. En 1991, todas las plántulas de 5,100 cm de altura dentro de cuadrantes permanentes de 1-m2 en los fragmentos y en la selva contínua, fueron contadas y agrupadas en diferentes formas de vida: árboles, lianas, palmas y hierbas. En 1993 se removieron manualmente todas las plántulas <1 m de altura dentro de los cuadrantes. Seis años y cinco meses más tarde (1999) se contaron todas las plántulas reclutadas dentro de los cuadrantes, se agruparon en diferentes formas de vida v se clasificaron en morfoespecies distintivas. La riqueza de especies de plántulas reclutadas en todas las formas de vida fue menor en los fragmentos que en la selva contínua, con el fragmento de 1 ha presentando la menor riqueza de especies. El número total de individuos reclutados fue 40% menor que los previamente presentes para todas las formas de vida, excepto lianas. El reclutamiento de lianas fué de 7 a 500% mayor que la abundancia original en los fragmentos y en la selva contínua. En general la similitud de especies fué mayor entre fragmentos que entre fragmentos y selva contínua, con el fragmento de 1-ha siendo el menos similar. Las curvas de rango/abundancia de especies, mostraron que las especies de selva contínua en todas las formas de vida tendieron a desaparecer de los fragmentos, mientras que las especies comunes en los fragmentos estuvieron ausentes en la selva contínua. En general, nuestros resultados sugieren que la composición de formas de vida y la estructura del banco regenerativo en fragmentos tienden a convertirse en una comunidad de plántulas pobre en especies. La pérdida de diversidad de especies del sotobosque, pero especialmente de plántulas de árboles, amenaza el mantenimiento de la biodiversidad y pone en peligro la regeneración futura de la selva. [source]

Linking Spatial Pattern and Ecological Responses in Human-Modified Landscapes: The Effects of Deforestation and Forest Fragmentation on Biodiversity

GEOGRAPHY COMPASS (ELECTRONIC), Issue 4 2009
John A. Kupfer
Studies of forest loss and fragmentation provide clear examples of the linkages between ecological pattern and process. Reductions in forest area lead to higher within-patch extinction rates, the eventual loss of area-sensitive species, and declines in species richness and diversity. Forest loss also results in increased isolation of remnants, lower among-patch immigration rates, and less ,rescue' from surrounding populations. Specific responses, however, are sometimes counterintuitive because they depend on life-history tradeoffs that influence population dynamics and species co-existence in heterogeneous landscapes, not just forest remnants. Thus, while fragmentation generally favours r-selected, generalist strategies, such as high dispersal and a wide niche breadth, ecological outcomes may be confounded by species-specific responses to conditions in the human-dominated matrix and the ways in which forest edges shape cross-landscape movements. Given that pressures on global forestlands continue to intensify due to growing population sizes, economic pressures, and needs for space and resources, successfully maintaining or restoring species will necessitate a combination of short- and long-term actions that address both habitat protection and restoration. Doing so will require an interdisciplinary approach that gives adequate attention to the manners by which forest loss and fragmentation affect population dynamics through changes in forest area, isolation, habitat quality, matrix properties, and edge effects as well as the synergistic interactions of fragmentation with climate change, human-altered disturbance regimes, species interactions and other drivers of species population declines. [source]

Vertical Stratification Responses of an Arboreal Dung Beetle Species to Tropical Forest Fragmentation in Malaysia

BIOTROPICA, Issue 5 2010
Daniel J. Tregidgo
ABSTRACT Little is known about how arboreal arthropods respond to forest disturbance. We assessed how rain forest fragmentation affected the vertical stratification of arboreal dung beetles in Peninsular Malaysia. An arboreal dung beetle species (Onthophagus sp.) moved closer to the forest floor in smaller fragments, suggesting a downward shift in its foraging possibly in response to fragmentation. [source]

Does Forest Fragmentation and Selective Logging Affect Seed Predators and Seed Predation Rates of Prunus africana (Rosaceae)?

BIOTROPICA, Issue 2 2008
Nina Farwig
ABSTRACT Forest fragmentation and selective logging can influence the life cycle of tropical tree species at several levels, e.g., by lowering pollination, by limiting seed dispersal, and by increasing seed predation. Understanding human-induced modifications in ecosystem processes such as seed predation is essential for conservation management of threatened species. We studied the impact of forest fragmentation and selective logging on seed predation of the endangered tree Prunus africana in the tropical rain forest of Kakamega, Kenya. We quantified the activity of seed predators in the main forest, forest fragments, and in sites of different logging intensity in the dry and rainy seasons of 2003 and 2006. Further, we performed predation experiments with single and groups of P. africana seeds in the same sites. We recorded a tendency toward higher activity of seed predators in the main forest compared to fragmented sites. Single seeds, in contrast to groups of seeds, had marginally significantly higher predation rates in intensively logged compared to moderately logged sites. Overall, predation rates showed little relationship to seed predator activity and were highly variable among years and seasons. Additional studies on seedling establishment and survival are needed to predict whether the endangered tree is able to maintain sustainable populations in Kakamega Forest. Only by studying all processes in the life cycle is it possible to develop sound management strategies for the species. [source]

Effects of Forest Fragmentation on Pollinator Activity and Consequences for Plant Reproductive Success and Mating Patterns in Bat-pollinated Bombacaceous Trees,

BIOTROPICA, Issue 2 2004
Mauricio Quesada
ABSTRACT Forest fragmentation and the resulting spatial isolation of tree species can modify the activity of pollinators and may have important implications for the reproductive success and mating systems of the plants they pollinate. The objectives of this study were to (1) evaluate the effect of forest fragmentation on pollinator activity in bat-pollinated bombacaceous trees and (2) determine the effects of forest fragmentation on reproductive success and mating systems of bombacaceous trees. We studied these parameters in three bombacaceous tree species in tropical seasonal forest of Chamela, Jalisco, Mexico, and Osa and Guanacaste, Costa Rica. For Ceiba aesculifolia, more visits were observed in fragments by both Glossophaga soricina and Leptonycteris curasoae. For Ceiba grandiflora, Musonycteris harrisoni visited flowers exclusively in forest and G. soricina visited more flowers in forest than in fragments; no difference was shown by L. curasoae. For Ceiba pentandra in Chamela, no differences were found in visitation by G. soricina between forest and fragments; L. curasoae visited significantly more flowers in forest. Ceiba pentandra received more visits by Phyllostomus discolor than G. soricina in Guanacaste, whereas no bat visitors were observed in Osa. Total mean flower production was greater in fragments than forest for C. aesculifolia, whereas no difference was observed for C. grandiflora. Fruit set was greater in forest than in fragments for C. grandiflora, whereas no difference was observed for C. aesculifolia. Outcrossing rates were high for C. aesculifolia and C. grandiflora in Chamela, and for C. pentandra in Guanacaste, independent of tree habitat, while C. pentandra in Osa showed a mixed-mating system. The effects of forest fragmentation on bat pollinators, plant reproductive success, and mating patterns varied depending upon the bombacaceous species. This variability was associated with the effects that forest fragmentation may have on differences in flowering patterns, bat foraging behavior, and plant self-incompatibility systems. RESUMEN La fragmentatión de bosques y el aislamiento espacial, producto de este fenómeno, pueden modificar la actividad de los polinizadores y pueden tener implicaciones importantes sobre el éxito reproductivo y los sistemas de apareamiento de las plantas que polinizan. Los objetivos de este estudio consisten en: (1) evaluar los efectos de la fragmentatión de bosque sobre la actividad de los polinizadores de árboles de Bombacaceas, y (2) determinar los efectos de la fragmentación sobre el éxito reproductivo y el sistema de apareamiento de árboles de Bombacaceas. Evaluamos estos parámetros en 3 especies de árboles de esta familia en bosques estacionales en Jalisco, México y Guanacaste y Osa, Costa Rica. Las flores de Ceiba aesculifolia fueron mas visitadas en fragmentos por Glossophaga soricina y Leptonycteris curasoae. En Ceiba grandiflora, Musonycteris harrisoni visitó flores exclusivamente en el bosque y G. soricina visitó mas flores en el bosque que en los fragmentos mientras que no hubo diferencias para L. curasoae. En Chamela, no hubo diferencias en la tasa de visitas de flores entre bosque y fragmentos para G. soricina en Ceiba pentandra mientras que L, curasoae visitó más flores en el bosque. En Guanacaste, C, pentandra recibio mas visitas de Phyllostomus discolor que de G. soricina mientras que no hubo visitas por murcielagos en Osa. La produccion total promedio de flores fue mayor en los fragmentos que en el bosque para C. aesculifolia mientras que no hubo diferencias para C. grandiflora. La proba-bilidad de que una flor produzca fruto fué mayor en el bosque que en los fragmentos para C. grandiflora pero no hubo diferencias en C. aesculifolia. La tasa de exocruzamiento fue aha para C. aesculifolia y C. grandiflora en Chamela, y para C. pentandra en Guanacaste, mientras que C. pentandra en Osa mostró un sistema de apareamiento mixto. Los efectos de la fragmentación de bosques sobre la polinización por murciélagos, la reproducción de plantas y sus patrones de apareamiento varían dependiendo de la especie de Bombacaceae. Esta variabilidad está asociada a los efectos que la fragmentación de bosques puede tener sobre diferencias en los patrones de floración, el comportamiento de forrajeo de los polinizadores, y los sistemas de incompatibilidad de las plantas. [source]

The effects of fragmentation on fluctuating asymmetry in passerine birds of Brazilian tropical forests

JOURNAL OF APPLIED ECOLOGY, Issue 6 2000
M. Anciães
Summary 1. ,Fluctuating asymmetry (FA) refers to the difference between the right and left sides in characters that should otherwise be bilaterally symmetrical, but whose expression is affected by epigenetic stress during development. Forest fragmentation may promote an increase in FA in isolated populations, by either genetic or environmental stress. FA may function as a biomonitor index in conservation biology if increased levels were observed in populations from fragmented habitats. 2. ,We tested the hypothesis that FA is higher in birds from small tropical forest patches than in large forest tracts. We measured wing and tarsus FA on mist-netted birds from seven fragments and seven continuous areas from south-eastern Atlantic rain forest in Brazil. We performed FA comparisons between fragments and control groups for the whole community, for individual foraging guilds and for the six most abundant species. 3. ,Wing and tarsus FA were significantly greater in fragments than continuous areas for the whole community and were both negatively correlated with forest fragment size. Differences in FA varied among foraging guilds, being more evident for insectivorous species, especially those feeding in or near the understorey. 4. ,FA levels increased significantly in forest fragments in at least one trait for five of the six most abundant species. There was no correlation between tarsus and wing asymmetries for the individuals of any species nor any difference between the degree of asymmetries of these characters. 5. ,We suggest that FA is a useful tool to assess the effects of fragmentation on forest birds, and may be applied in monitoring neotropical birds. FA indices might be profitably developed, particularly in species most threatened by fragmentation effects and when investigated in different morphological characters. [source]

Forest fragmentation and primates' survival status in non-reserved forests of the ,Kampala area', Uganda

AFRICAN JOURNAL OF ECOLOGY, Issue 2004
D. BarangaArticle first published online: 17 AUG 200
Abstract Previous primate studies have concentrated on the effects of forest disturbance on primate populations residing mainly in natural forest reserves. The present study was conducted in 20 non-reserved forest patches in the ,Kampala area', a forest-savanna-agricultural mosaic, to investigate the effects of forest fragmentation on the distribution and survival status of arboreal primates in the patches. Mpanga Forest Reserve, as the nearest to the forest patches, was used as a control. Primate census data revealed that the black-and-white colobus (Colobus guereza) was restricted in its distribution while redtail monkeys (Cercopithecus ascanius schmidti) were cosmopolitan. There was no significant relationship between forest patch size and red-tail population size, number of groups and group density decreased. Of the trees sampled, 70% were food species while 30% were nonfood species. Basal area of food tree species significantly increased with forest patch size (R2 = 0.5885) but its relationship with red-tail population size and group density (B = ,0.42784, R2 = 0.18305, P >,0.05) was not significant. [source]

Forest fragmentation, the decline of an endangered primate, and changes in host,parasite interactions relative to an unfragmented forest

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 3 2008
Thomas R. Gillespie
Abstract Forest fragmentation may alter host,parasite interactions in ways that contribute to host population declines. We tested this prediction by examining parasite infections and the abundance of infective helminths in 20 forest fragments and in unfragmented forest in Kibale National Park, Uganda. Over 4 years, the endangered red colobus (Procolobus rufomitratus) declined by 20% in fragments, whereas the black-and-white colobus (Colobus guereza) in fragments and populations of both colobines in unfragmented forest remained relatively stable. Seven nematodes (Strongyloides fulleborni, Strongyloides stercoralis, Oesophagostomum sp., an unidentified strongyle, Trichuris sp., Ascaris sp., and Colobenterobius sp.), one cestode (Bertiella sp.), and three protozoans (Entamoeba coli, Entamoebahistolytica/dispar, and Giardia sp.) were detected. Infection prevalence and the magnitude of multiple infections were greater for red colobus in fragmented than in unfragmented forest, but these parameters did not differ between forests for black-and-white colobus. Infective-stage colobus parasites occurred at higher densities in fragmented compared with unfragmented forest, demonstrating greater infection risk for fragmented populations. There was little evidence that the nature of the infection was related to the size of the fragment, the density of the host, or the nature of the infection in the other colobine, despite the fact that many of the parasites are considered generalists. This study suggests that forest fragmentation can alter host,parasite dynamics and demonstrates that such changes can correspond with changes in host population size in forest fragments. Am. J. Primatol. 70:222,230, 2008. © 2007 Wiley-Liss, Inc. [source]

Forest fragmentation relaxes natural nest predation in an Afromontane forest

ANIMAL CONSERVATION, Issue 4 2009
T. Spanhove
Abstract Nest predation is widely regarded as a major driver underlying the population dynamics of small forest birds. Following forest fragmentation and the subsequent invasion by species from non-forested landscape matrices, shifts in predator communities may increase nest predation near forest edges. However, effects of human-driven habitat change on nest predation have mainly been inferred from studies with artificial nests, despite being regarded as poor surrogates for natural ones. We studied variation in predation rates, and relationships with timing of breeding and characteristics of microhabitats and fragments, on natural white-starred robin Pogonocichla stellata nests during three consecutive breeding seasons (2004,2007) in a Kenyan fragmented cloud forest. More than 70% of all initiated nests were predated during each breeding season. Predation rates nearly quadrupled between the earliest and the latest nests within a single breeding season, increased with distance to the forest edge, and decreased with the edge-to-area ratio of forest fragments. These spatial relationships oppose the traditional perception of edge and fragmentation effects on nest predation, but are in line with results from artificial nest experiments in other East African forests. In case of inverse edge and fragmentation effects on nest predation, such as shown in this study, species that tolerate edges for breeding may be affected positively, rather than negatively, by forest fragmentation, while the opposite can be expected for species restricted to the forest interior. The possibility of inverse edge effects, and its conservation implications, should therefore be taken into account when drafting habitat restoration plans. [source]

Does Forest Fragmentation and Selective Logging Affect Seed Predators and Seed Predation Rates of Prunus africana (Rosaceae)?

Effects of Forest Fragmentation on Pollinator Activity and Consequences for Plant Reproductive Success and Mating Patterns in Bat-pollinated Bombacaceous Trees,

An Experimental Investigation of Landscape Resistance of Forest versus Old-Field Habitats to Emigrating Juvenile Amphibians

CONSERVATION BIOLOGY, Issue 5 2002
Betsie B. Rothermel
Larval amphibians,spotted salamander (Ambystoma maculatum), small-mouthed salamander (A. texanum), and American toad ( Bufo americanus ),were added to artificial pools in four dispersal arrays on forest edges. Each array consisted of a pool surrounded by a circular drift fence with pitfall traps and two 2.5 × 50 m enclosures (runs) extending into forest and old-field habitat. Juveniles captured at the circular fences were individually marked and released into either field or forest runs. We determined initial distance, initial rate, total distance, and net distance moved by juveniles in the field versus forest from recaptures in the runs. We also conducted 24-hour dehydration trials to compare the rates of evaporative water loss by spotted and small-mouthed salamanders in field and forest. Initial orientation of spotted salamanders and toads was significantly biased toward forest. Orientation of small-mouthed salamanders did not differ significantly from random expectations. The avoidance of open-canopy habitat by juvenile American toads in particular indicates that predictions of dispersal behavior based on adult habitat use may be misleading. Spotted salamanders moved almost four times farther and toads more than three times farther into the forest than into the field, and recapture rates of both species were much lower in the field. We attribute the lower recapture rates and shorter distances moved in the field to higher mortality due to desiccation or an abundance of predators. Juvenile spotted and small-mouthed salamanders experienced greater evaporative water loss in the field. Our data on movement behavior and dehydration rates suggest that old-field habitats offer greater landscape resistance to dispersing juveniles of some species. Thus, forest fragmentation is likely to reduce dispersal rates between local populations of these three species, with potentially negative consequences for population persistence in altered landscapes. Resumen: Utilizamos un enfoque experimental para investigar los efectos de la composición del paisaje sobre el éxito inicial de dispersión de anfibios juveniles. Colcamos larvas de anfibios (salamandras manchadas [Ambystoma maculatum] y A. texanum y sapo americano [Bufo americanus] ) en estanques artificiales en cuatro secuencias de dispersión en bordes de bosque. Cada secuencia consistió de un estanque rodeado por un cerco circular con trampas de fosa y dos encierros (corridas) de 2.5 × 50 m que se extendían hacia el hábitat de bosque y de campo viejo. Los juveniles capturados en los cercos circulares fueron marcados individualmente y liberados en las corridas de bosque o de campo. A partir de recapturas en las corridas, determinamos la distancia inicial, la tasa inicial, las distancia total y la distancia neta recorrida por juveniles en el campo versus el bosque. También realizamos pruebas de deshidratación de 24 horas para comparar las tasas de pérdida de agua por evaporación en salamandras en el campo y el bosque. La orientación inicial de Ambystoma maculatum y Bufo americanus estuvo significativamente sesgada hacia el bosque. La orientación inicial de A. texanum no fue significativamente diferente de las expectativas aleatorias. La evasión del hábitat abierto en particular por juveniles de sapo americano indica que las predicciones del comportamiento de dispersión basadas en el uso del hábitat por adultos pueden llevar a conclusiones erróneas. Las salamandras manchadas se movieron cuatro veces mas lejos y los sapos más de tres veces más lejos dentro del bosque que dentro del campo, y las tasas de recaptura de ambas especies fueron mucho menores en el campo. Atribuimos las bajas tasas de recaptura y las distancias menores a la mayor mortalidad debido a la desecación o a la abundancia de depredadores. Los juveniles de las dos especies de salamandras experimentaron mayor pérdida de agua por evaporación en los campos. Nuestros datos del comportamiento de movimiento y las tasas de deshidratación sugieren que los hábitats de campo viejo ofrecen mayor resistencia de paisaje para los juveniles dispersantes de algunas especies. Por tanto, es probable que la fragmentación de bosques reduce las tasas de dispersión entre poblaciones locales de estas tres especies, con consecuencias potencialmente negativas para la persistencia de la población en paisajes alterados. [source]

Synergistic Effects of Subsistence Hunting and Habitat Fragmentation on Amazonian Forest Vertebrates

CONSERVATION BIOLOGY, Issue 6 2001
Carlos A. Peres
These effects are likely to be considerably aggravated by forest fragmentation because fragments are more accessible to hunters, allow no (or very low rates of ,) recolonization from nonharvested source populations, and may provide a lower-quality resource base for the frugivore-granivore vertebrate fauna. I examined the likelihood of midsized to large-bodied bird and mammal populations persisting in Amazonian forest fragments of variable sizes whenever they continue to be harvested by subsistence hunters in the aftermath of isolation. I used data from a comprehensive compilation of game-harvest studies throughout Neotropical forests to estimate the degree to which different species and populations have been overharvested and then calculated the range of minimum forest areas required to maintain a sustainable harvest. The size distribution of 5564 Amazonian forest fragments,estimated from Landsat images of six regions of southern and eastern Brazilian Amazonia,clearly shows that these are predominantly small and rarely exceed 10 ha, suggesting that persistent overhunting is likely to drive most midsized to large vertebrate populations to local extinction in fragmented forest landscapes. Although experimental studies on this negative synergism remain largely unavailable, the prospect that increasingly fragmented Neotropical forest regions can retain their full assemblages of avian and mammalian species is unlikely. Resumen: La cacería de subsistencia tiene efectos negativos profundos sobre la diversidad de especies, la biomasa y estructura de las comunidades de vertebrados en bosques de la Amazonía que de otra forma están poco perturbadas. Estos efectos se agravan considerablemente por la fragmentación del bosque porque los fragmentos son más accesibles a los cazadores, no permiten la recolonización por poblaciones no cazadas o disminuyen las tasas de recolonizacíon y pueden proporcionar una base de recursos de menor calidad para la fauna de vertebrados frugívoro-granívoros. Examiné la posibilidad de persistencia de poblaciones de aves y mamíferos medianos a grandes en fragmentos de bosque de tamaño variable si continúan sujetos a la cacería de subsistencia como una consecuencia del aislamiento. Utilicé datos de una compilación extensiva de estudios de cacería en bosques neotropicales para estimar el grado en que diferentes especies y poblaciones han sido sobre explotadas y calculé el área de bosque minima requerida para mantener una cosecha sostensible. La distribucíon de tamaños de 5564 fragmentos de bosque amazónica, estimado a partir de imágues de Landsat de seis regiones del sur y del esté de la Amazonía brasileña indica claramente que estos fragmentós son principalmente pegueños y que rara vez exceden las lolta, lo que sugiere que la sobre cacería persistente probablemente lleve a la extincíon local de poblaciones de vertebrados de tamaño mediano a grande en paisajes boscosos fragmentados. Aunque estudios experimentales de este sinergismo negativo no están disponibles, la perspectiva de que las regiones neotropicales cada vez más fragmentadas, puedan retener las comunidades completas de aves y mamíferos poco es probable. [source]

Low Recruitment of Trees Dispersed by Animals in African Forest Fragments

CONSERVATION BIOLOGY, Issue 6 2001
N. J. Cordeiro
We compared adult and juvenile trees in forest transects in a 3500,ha submontane forest with those in four forest fragments of 521, 30, 9, and 0.5 ha. Preliminary results show that recruitment of seedlings and juveniles of 31 animal-dispersed tree species was more than three times greater in continuous forest and large forest fragments (,30 ha) than in small forest fragments (,9 ha), whereas recruitment of eight wind- and gravity-dispersed trees of the forest interior was unaffected. Recruitment of 10 endemic, animal-dispersed tree species was 40 times lower in small fragments than in continuous forest or large fragments. Counts of diurnal primates and birds in all five sites indicated that frugivorous species have declined with decreasing fragment size. These results are consistent with the idea that loss of dispersal agents depresses tree recruitment in the course of forest fragmentation. Resumen: Investigamos los efectos de la fragmentación del bosque en la desaparición de animales frugívoros y el reclutamiento de árboles dispersados por animales y viento en parches de bosques de 80 años de edad en las montañas del este de Usambara, Tanzania. Comparamos árboles adultos y juveniles en transectos de bosque en un bosque submontañoso de 3500 ha con transectos de cuatro fragmentos de bosque de 521, 30, 9 y 0.5 ha. Los resultados preliminares muestran que el reclutamiento de plántulas y juveniles especies de árboles dispersados por animales fue tres veces mayor en el bosque continuo y fragmentos grandes (,30 ha) que en fragmentos pequeños (,9 ha), mientras que el reclutamiento de ocho árboles dispersados por viento y gravedad del interior del bosque no fue afectado. El reclutamiento de 10 especies endémicas de árboles dispersados por animales fue 40 veces menor en los fragmentos pequeños que en el bosque continuo o en los fragmentos grandes. Los conteos de primates diurnos y aves en los cinco sitios indican que las especies frugívoras han disminuido con la disminución del tamaño del fragmento. Estos resultados son consistentes con la idea de que la pérdida de los agentes dispersores deprime el reclutamiento de los árboles en el transcurso de la fragmentación del bosque. [source]

The species-area relationship in the hoverfly (Diptera, Syrphidae) communities of forest fragments in southern France

ECOGRAPHY, Issue 2 2006
Annie Ouin
The effect of forest fragmentation was studied in hoverfly communities of 54 isolated forests (0.14,171 ha) in south west France. The positive relationship between species richness and wood patch area was investigated by testing the three hypotheses usually put forward to explain it: 1) the sampling effect hypothesis, 2) the patch heterogeneity hypothesis, 3) the hypothesis of equilibrium between distance from other patch (colonisation) and surface area of the patch (extinction). The syrphid species were divided into 3 ecological groups, based on larval biology as summarized in the "Syrph the Net" database: non forest species, facultative forest species and forest species. A total of 3317 adults belonging to 100 species, were captured in the 86 Malaise traps. Eight species were non forest (N=16), 65 facultative forest (N=2803) and 27 forest species (N=498). Comparison of the slopes of the species-area curves for species richness and species density per forest patch showed a strong sampling effect in the species-area relationship. Wood patch heterogeneity increased with wood patch area and positively influenced hoverflies richness. Less isolated wood patches presented high richness of forest species and low richness of non forest species. Only forest species richness seemed to respond to the equilibrium between surface area and isolation. Depending on which hypothesis explained best the species-area relationship, management recommendations to mitigate fragmentation effects were formulated at various spatial scales and for different stakeholders. [source]

Gall wasps and their parasitoids in cork oak fragmented forests

ECOLOGICAL ENTOMOLOGY, Issue 1 2007
GUILLEM CHUST
Abstract 1.,This paper explores the potential effects of host-plant fragmentation on cork oak gall wasp populations (Cynipidae, Hymenoptera) and on their predators, lethal inquilines, and parasitoids. To address this objective, galls were collected across a gradient of cork oak (Quercus suber) forest fragmentation in the East Pyrenees (Albera, Spain), and they were incubated to obtain the parasitism rates. 2.,Two hypotheses were tested: (1) Host-plant fragmentation may induce a decline in gall wasp populations because of area and isolation effects on local extinction and dispersal; as a consequence of that, parasitoids may decline even more strongly in fragmented habitats than their prey. (2) Host-plant fragmentation may cause a decline in gall wasp parasitoid populations that, in turn, can lead to an ecological release in their prey populations. 3.,Among the eight cork oak gall wasps sampled in the study area of Albera, the gall abundances of three species (Callirhytis glandium, Callirhytis rufescens, and Andricus hispanicus) were significantly related to forest fragmentation. The overall abundance of gall wasps was affected by a radius of , 890 m surrounding landscape, presenting constant abundances with forest loss until forest cover is reduced at , 40%; below that value the abundance increased rapidly. Three inquilines and 23 parasitoids species were recorded after gall incubation. In 25 cases, species of inquilines and parasitoids were newly recorded for the corresponding host in the Iberian peninsula. 4.,Although the overall parasitism rate was high (1.1), it was uncorrelated with fragmentation and with overall cynipid abundance. These results indicate that host-plant fragmentation was correlated with higher abundance of gall wasps, whereas the parasitism rate could not explain this hyper-abundance in small forest fragments. [source]

Geomorphic and dendroecological impacts of slushflows in central Gaspé Peninsula (Québec, Canada)

GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 4 2001
Sonya J. Larocque
Slushflows are rare phenomena in southeastern Canada. Here we report for the first time the occurrence of slushflows in a subalpine environment in eastern Canada (Mt. Albert, Gaspé Peninsula, Québec). Because nothing is known of their frequency- magnitude in the area, we reconstructed the chronology of slushflow events over the past century using dendrogeomorphic techniques based on impact scars, reaction wood and traumatic resin ducts. Slushflows contributed to the formation of a tongue-shaped accumulation of 17900 m2 at the outlet of a firstorder drainage basin. The slushflow boulder tongue was composed of heterogeneous-sized, angular and unoriented clasts, which are markedly different from the sediments of an adjacent alluvial fan. Although movements were initiated above the subalpine forest limit, slushflows induced forest fragmentation along the treed slope. Three slushflow events were identified over the past century, in 1925, 1964 and 1988, respectively, which indicate exceptional initiation conditions and considerable geomorphic activity of individual events. [source]

The effects of edge, fragment size and degree of isolation on avian species richness in highly fragmented forest in West Africa

IBIS, Issue 2 2007
S. MANU
Almost nothing is known of the effects of forest fragmentation on bird diversity within the heavily degraded and fragmented forest remnants in West Africa. We examined the effects of edge, fragment size and isolation on bird species richness in southwestern Nigeria where forest fragmentation is pronounced. In total, 122 km of line transects were used to survey birds and vegetation within 45 forest patches between January 2000 and March 2002: 197 species were recorded. Avian species number and total counts in forest patches were unrelated to fragment area (within the observed range of 14,445 ha), but were negatively influenced by degree of isolation and increasing distance from the edge. As the total area of forested land within 15 km of a patch fell from 4 to 0%, so 21% of species were lost. In total, six and zero species (of 154 recorded more than once) were consistently recorded in the larger and smaller forest fragments, respectively, and four and two bird species were consistently recorded in unisolated and isolated forest fragments, respectively, suggesting that the addition of ,edge' species did not compensate for loss of species sensitive to fragmentation. Diversity index was not affected by either fragment area or degree of isolation, but decreased with distance from the edge. When individual species counts were considered, 68% of species (n = 62) showed no significant effect of distance to edge. Of those 20 species which showed an effect, 12 were less common close to the edge. Most species (65%) did not respond significantly to increasing isolation but of those 22 species that did, 20 were less common in more isolated fragments. Ninety-seven per cent of species showed no significant response to area. As avian diversity and species composition, but not species number, were apparently insensitive to forest fragmentation, our findings suggest that fragmentation reduces the probability of occurrence of a wide range of West African bird species, rather than a subset of fragmentation-sensitive species. The greater apparent sensitivity of present-day West African forest bird communities to fragmentation rather than patch size might reflect previous extinctions of area-sensitive species. Minimizing further forest fragmentation might be the most effective means of conserving avian diversity in current West African landscapes where most remaining forest patches are small (i.e. < 500 ha). [source]

Fragmentation and pre-existing species turnover determine land-snail assemblages of tropical rain forest

JOURNAL OF BIOGEOGRAPHY, Issue 10 2009
Dinarzarde C. Raheem
Abstract Aim, The main aims of the study were: (1) to investigate the effect of fragment age in relation to other patch- and landscape-scale measures of forest fragmentation, and (2) to assess the relative importance of fragmentation, habitat degradation (i.e. degradation caused by selective logging and past shifting cultivation) and putative pre-existing species turnover in structuring current land-snail assemblages. Location, South-western Sri Lanka. Methods, The land-snail fauna was sampled using standardized belt transects. Fifty-seven transects were sampled in 21 lowland rain forest fragments (c. 1,33,000 ha). The spatial arrangement of fragments in the study area was explicitly considered in an effort to take into account the non-random nature of fragmentation and degradation and the possibility that current species composition may reflect patterns of species turnover that existed prior to fragmentation. The data set of 57 land-snail species and 28 environmental and spatial variables was analysed using canonical correspondence analysis and partial canonical correspondence analysis. Results, Fragment age, mean shape complexity (i.e. a landscape-scale measure of shape complexity), altitude, and the spatial variables x (longitude), y (latitude) and y2 explained significant variation in land-snail species composition. None of the three nominal variables quantifying habitat degradation was significantly correlated with variation in species composition. The independent effects of fragment age and mean shape complexity were similar. The combined effect of the spatial variables alone was larger than the independent effects of fragment age, mean shape complexity or altitude, but was of the same order of magnitude. The total variation explained by the spatial variables was comparable to the total non-spatial variation accounted for by fragment age, mean shape complexity and altitude. Main conclusions, Fragment age was found to be one of only two key determinants (the other was shape complexity at the landscape scale) driving fragmentation-related changes in community composition. The influence of pre-fragmentation patterns of species turnover on assemblage structure can be stronger than the effects of fragmentation measures, such as age, and may override the effects of forest degradation. Thus, strong patterns of pre-existing turnover may potentially confound interpretation of the effects of forest fragmentation and degradation. [source]

Effects of forest fragmentation on European birds: implications of regional differences in species richness

JOURNAL OF BIOGEOGRAPHY, Issue 4 2003
José Luis Tellería
Abstract Aim, In this paper, we adopted a large-scale approach to evaluate the effect of regional richness of forest birds on the number of bird species retained by forest fragments in several localities across Europe. Location, We studied bird assemblages in fourteen forest archipelagos embedded in agricultural matrices from southern Norway to central Spain. Tree composition varied from oak and beech forests of the northern localities to oak and pine xerophitic woodlands of the southern ones. The number of fragments in each forest archipelago ranged from eighteen to 211. Methods, We used the Gleason equation (s = a + z log A; where s and A are, respectively, the species richness and size of forest fragments and z the rate of species loss) to estimate the species richness for 1- and 15-ha fragments in each archipelago. The regional richness of forest birds was estimated by modelling the geographical distribution of species richness in the European atlas of breeding birds. Results, The latitudinal distribution of regional richness displayed a convex form, with the highest values being in central Europe. Along this gradient, the number of species retained by fragments and the rate of species loss was positively related to regional richness. In addition, the percentage of the regional pool of species sampled by fragments decreased in the southern localities. Main conclusions, Relationships between regional richness of forest birds and richness in fragments seem to explain why fragments in central Europe shelter more species than their southern counterparts. The decreased ability of southern forest fragments to sample the regional richness of forest birds, could be explained as an effect of the low abundance of many species in the Mediterranean, which could depress their ability to prevent extinction in fragments by a rescue effect. Alternatively, high beta diversity in the Mediterranean could produce undersampling by fragments of the regional pool of species. These regional differences in the response of bird assemblages to forest fragmentation are used to discuss the usefulness of large-scale, biogeographical approaches in the design of conservation guidelines. [source]

Forest fragmentation and primates' survival status in non-reserved forests of the ,Kampala area', Uganda

Insect herbivory declines with forest fragmentation and covaries with plant regeneration mode: evidence from a Mexican tropical rain forest

OIKOS, Issue 2 2010
Betsabé Ruiz-Guerra
The consequences of tropical forest fragmentation on herbivory are poorly understood. The limited evidence suggests that forest fragmentation can have positive, negative or neutral effects on herbivory. Inconsistencies may be partly explained by plant interspecific variation and differential responses related to plant life history. In this study we examined the effects of forest fragmentation and plant regeneration mode (shade-tolerant and light-demanding species) on sapling herbivory using a large sample of the community (97 species, representing 25% of the woody flora of the study site), and a subset of species shared by forest fragments and continuous forest. For the latter, we also analyzed the effects of species identity on variation in herbivory. Also, for the shared species we used two techniques to measure herbivory: standing herbivory (i.e. instantaneous, actual damage) and cumulative herbivory (i.e. damage, accumulated over time, on initially intact leaves). Insect herbivory was the predominant type of damage in the two forest types, and standing herbivory at both the community and the shared species level was significantly higher in continuous forest than in fragments. Considering shared species, both standing and cumulative herbivory were significantly higher in light-demanding than in shade-tolerant species. Cumulative herbivory also showed a significant interaction between forest fragmentation and plant regeneration mode, whereby a significant decline in herbivory in fragments was driven by reduced herbivory in shade-tolerant species, whereas for light-demanding species herbivory did not change significantly, due to contrasting species-specific responses. We conclude that tropical forest fragmentation reduces insect herbivory, but this depends on plant regeneration mode and species identity. These changes could have effects on plant regeneration and diversity in forest fragments via long-term demographic consequences. [source]

Scale-dependent responses to forest cover displayed by frugivore bats

OIKOS, Issue 11 2008
Naiara Pinto
Despite vast evidence of species turnover displayed by Neotropical bat communities in response to forest fragmentation, the exact shape of the relationship between fragment area and abundance for individual bat species is still unclear. Bats' ample variation in diet, morphology, and movement behaviour can potentially influence species' perception of the landscape. Thus, studies describing fragment area at a single spatial scale may fail to capture the amount of forest available from the perspective of individual bat species. In the present paper, we study the influence of forest cover on bats inhabiting a fragmented forest in Mexico, focusing on some of the most common frugivore species: Artibeus jamaicensis, Carollia spp. (C. brevicauda/C. perspicillata) and Sturnira spp. (S. lilium/S. ludovici). We quantified forest cover at scales ranging from 50 to 2000,m, and measured the influence of forest cover on bat capture success, a surrogate for abundance. The three species displayed positive and significant scale-dependent associations with forest cover. Abundance of A. jamaicensis increased with forest cover measured at scales ranging between 500 and 2000,m, while Carollia spp. responded more strongly to variation in forest cover measured at scales 100,500,m. For Sturnira spp., abundance was a function of presence of creeks near mist-netting sites, and amount of secondary forest present at a 200,m scale. The observed variation in responses to forest cover can be explained in light of interspecific differences in diet, home range, and body size. Our results illustrate a method for measuring the effect of forest fragmentation on mobile species and suggest that changes in abundance in fragmented landscapes emerge from the interaction between species' traits and landscape structure. [source]

Consequences of forest fragmentation for polyporous fungi at two spatial scales

OIKOS, Issue 2 2006
R. Penttilä
Greatly reduced area of old-growth forests and the very low amount of dead wood in managed forests in northern Europe have caused a marked decline in the populations of saproxylic species. It is less clear at which spatial and temporal scales these adverse changes are taking place, and more information is needed to reliably predict which species are especially sensitive to loss and fragmentation of habitat. Here we compare species richness, incidence of occurrence in forest fragments, and abundance of polyporous fungal species and species groups between two regions in Finland with contrasting histories of forestry and a marked difference in the amount and spatial configuration of old-growth forests. We also analyse the consequences of increasing loss of connectivity on the presence and abundance of polypores in a study region with a documented short-term history of old-growth fragmentation. Our results show that the species number, incidence of occurrence, and abundance of especially the rare, threatened, and near-threatened species are much lower in the old-growth fragments in Häme in southern Finland in comparison with Kuhmo in eastern Finland, most probably because of the longer history of intensive forestry in Häme. Among the rare species, the species that show the greatest difference between the two regions (at the scale of 500 km) also tended to respond most strongly to the more recent forest fragmentation within the study region in Kuhmo (at the scale of 50 km). Polypores associated with spruce seem to be more strongly affected by forestry than species associated with pine, possibly reflecting the differences in the natural dynamics of spruce-dominated and pine-dominated forests. [source]

Concurrent Management of an Exotic Species and Initial Restoration Efforts in Forests

RESTORATION ECOLOGY, Issue 4 2005
Stephen D. Murphy
Abstract One of the proximate results of forest fragmentation, and a cause of continued microenvironmental change and exacerbation of ecological problems, is increased invasions by weedy plant species. One such example is Alliaria petiolata (Brassicaceae), a serious pest threatening much of eastern North America. Alliaria petiolata impedes mitigation of fragmentation and restoration efforts because it tends to outcompete and possibly extirpate much of the native understory species on localized scales. As part of a strategy to address the problems of fragmented habitats, an experiment was conducted to determine whether Sanguinaria canadensis (Papaveraceae) could outcompete A. petiolata. Using an additive design, I transplanted S. canadensis at densities of 0, 1, 2, 3, 5, 7, 9, 11, 15, and 20 ramets/m2 in 1997 and allowed them to interact with initial A. petiolata densities of 128 seedlings and 31 rosettes/m2. As of 2000, multivariate analyses of variance with repeated measures and simple analyses of variance indicated that initial S. canadensis densities of as little as 5 ramets/m2 suppressed A. petiolata. Initial S. canadensis densities of 9 and 11 ramets/m2 resulted in the lowest numbers of late-spring seedlings, numbers and sizes of year 1 and 2 rosettes, numbers and gross areas of stem leaves, numbers of flowering individuals, number of flowers, number of fruits (siliques), and height at flowering. While it remains to be tested whether this will continue and if the reestablishment of S. canadensis will help reassemble forest ecosystems, the experiments indicated that transplanting S. canadensis was effective at mitigating the spread of A. petiolata. [source]

Impacts of Restored Patch Density and Distance from Natural Forests on Colonization Success

RESTORATION ECOLOGY, Issue 4 2003
Hans Jacquemyn
Abstract The reduction and fragmentation of forest habitats is expected to have profound effects on plant species diversity as a consequence of the decreased area and increased isolation of the remnant patches. To stop the ongoing process of forest fragmentation, much attention has been given recently to the restoration of forest habitat. The present study investigates restoration possibilities of recently established patches with respect to their geographical isolation. Because seed dispersal events over 100 m are considered to be of long distance, a threshold value of 100 m between recent and old woodland was chosen to define isolation. Total species richness, individual patch species richness, frequency distributions in species occurrences, and patch occupancy patterns of individual species were significantly different among isolated and nonisolated stands. In the short term no high species richness is to be expected in isolated stands. Establishing new forests adjacent to existing woodland ensures higher survival probabilities of existing populations. In the long term, however, the importance of long-distance seed dispersal should not be underestimated because most species showed occasional long-distance seed dispersal. A clear distinction should be made between populations colonizing adjacent patches and patches isolated from old woodland. The colonization of isolated stands may have important effects on the dynamics and diversity of forest networks, and more attention should be directed toward the genetic traits and viability of founding populations in isolated stands. [source]

Differences in diet and activity pattern between two groups of Alouatta palliata associated with the availability of big trees and fruit of top food taxa

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 8 2009
Jacob C. Dunn
Abstract The threat that forest fragmentation and habitat loss presents for several Alouatta taxa requires us to determine the key elements that may promote the persistence of howler monkeys in forest fragments and to evaluate how changes in the availability of these elements may affect their future conservation prospects. In this study we analyzed the relationship between the availability of both big trees of top food taxa (BTTFT) (diameter at breast height>60) and fruit of top food taxa (FrTFT) in the home ranges of two groups of Alouatta palliata mexicana occupying different forest fragments in Los Tuxtlas, Mexico, and their diet and activity pattern. Both study groups preferred big trees for feeding and the group with lower availability of BTTFT in their home range fed from more, smaller food sources. Furthermore, both study groups also increased the number of food sources when their consumption of fruit decreased, and the group with lower availability of FrTFT in their home range fed from more food sources. The increase in the number of food sources used under such conditions, in turn, set up a process of higher foraging effort and lower rest. In summary, our results support other studies that suggest that the availability of big trees and fruit may be two important elements influencing the persistence of howler monkeys in forest fragments. Am. J. Primatol. 71:654,662, 2009. © 2009 Wiley-Liss, Inc. [source]

Forest fragmentation, the decline of an endangered primate, and changes in host,parasite interactions relative to an unfragmented forest

Stress in Yucatan spider monkeys: effects of environmental conditions on fecal cortisol levels in wild and captive populations

ANIMAL CONSERVATION, Issue 5 2009
A. Rangel-Negrín
Abstract In the Yucatán Peninsula, spider monkeys Ateles geoffroyi yucatanensis are generally found in two contrasting conditions: large tracts of conserved forest or small fragments surrounded by human populations. In the present study, we analyzed fecal cortisol levels of spider monkeys to investigate whether environmental conditions have an influence on stress; specifically, we compared fecal cortisol across individuals living in conserved forests, fragmented forests and captive conditions (zoos and pets). Radioimmunoanalysis of fecal samples from 121 individuals indicated significant differences in mean cortisol for A. g. yucatanensis based on habitat type, with the lowest levels found in the conserved forest condition. The higher cortisol levels in both fragmented forest populations and in captive individuals may be the result of metabolic and behavioral stress. The mean male fecal cortisol concentration was significantly higher than that of females, and the fecal cortisol concentration was higher in the dry season compared with the wet season in a conserved habitat. Therefore, we emphasize the importance of considering sex and seasonality when monitoring fecal cortisol concentrations of spider monkeys, and more generally of frugivores, as they face a seasonal variation in food availability. Finally, our results suggest that forest fragmentation may create long-term stressors for spider monkeys, affecting the viability of populations living under such conditions. [source]