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Fragmented Forest (fragmented + forest)
Selected AbstractsThe effects of edge, fragment size and degree of isolation on avian species richness in highly fragmented forest in West AfricaIBIS, Issue 2 2007S. 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] Nest usurpation is an ,edge effect' for Carolina chickadees Poecile carolinensisJOURNAL OF AVIAN BIOLOGY, Issue 1 2002Paul F. Doherty During 1995,1997, we monitored Carolina chickadee Poecile carolinensis nests in a fragmented forest landscape in northcentral Ohio, USA. Nest success was positively correlated with woodlot area and most nest loss was due to nest destruction by house wrens Troglodytes aedon. During 1998 and 1999, we conducted an experiment in both large (>6.8 ha) and small (<6.8 ha) woodlots in which we gave chickadees a choice of nesting on edges of woodlots (preferred wren habitat) or in the center of woodlots. We found no difference in nest success between large and small woodlots, but regardless of woodlot size, nest success was lower on edges than in the center. In the experiment, 100% of nest loss was due to nest destruction by house wrens. Given a choice, Carolina chickadees preferred to nest centrally more often than on edges. These results suggest that in fragmented landscapes where house wrens are common, nest destruction by house wrens is a major cause of nest failure in the Carolina chickadee. Such edge-dependent interspecific nest-site usurpation has not been previously recognized as a potentially important selective factor in nest site selection. [source] Gap-crossing movements predict species occupancy in Amazonian forest fragmentsOIKOS, Issue 2 2009Alexander C. Lees In fragmented landscapes, species persistence within isolated habitat patches is governed by a myriad of species life-history, habitat patch and landscape characteristics. We investigated the inter-specific variation in non-forest gap-crossing abilities of an entire tropical forest-dependent avifauna. We then related this measure of dispersal ability to species life-history characteristics and occupancy data from 31 variable-sized forest patches sampled within the same fragmented forest landscape. A total of 5436 gap-crossing movements of 231 forest-dependent bird species were observed across ten linear forest gaps of varying widths, adjacent to large areas of undisturbed forest. Species persistence in isolated fragments was strongly linked to gap-crossing ability. The most capable gap-crossers were medium to large-bodied species in the large insectivore, frugivore and granivore guilds, matching the most prevalent subset of species in small forest patches. However, some competent gap-crossing species failed to occur in small patches, and minimum forest-patch area requirements were more important in determining patch occupancy for these species. Narrow forest gaps (4,70 m) created by roads and power-lines may become territory boundaries, thereby eliminating home-range gap-crossing movements for many forest species, but permit rarer dispersal events. Wider gaps (>70 m) may inhibit gap-crossing behaviour for all but the most vagile species. Although patch size and quality may be the most important factors in structuring species assemblages in forest fragments, our results show that the degree of patch isolation and permeability of the surrounding matrix also explain which species can persist in forest isolates. Reducing the number and width of forest-dividing gaps; maintaining and/or creating forest corridors and increasing matrix permeability through the creation and maintenance of ,stepping-stone' structures will maximise the species retention in fragmented tropical forest landscapes. [source] Scale-dependent responses to forest cover displayed by frugivore batsOIKOS, Issue 11 2008Naiara 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] Births in wild black and gold howler monkeys (Alouatta caraya) in Northern ArgentinaAMERICAN JOURNAL OF PRIMATOLOGY, Issue 3 2009Silvana Peker Abstract Previous studies on births in nonhuman primates suggest that births are expected to occur at night to avoid predators. Here, we describe birth-related behaviors in wild black and gold howler monkeys, Alouatta caraya and address the various ideas proposed in the literature about the timing of births in group-living nonhuman primates. We collected data on females' birth-related behaviors through continuous focal observations and scan samples. Focal observations on females giving birth were taken for the remainder of the day after noticing a female was in labor. We recorded behaviors and the spatial distribution of the whole group using scan samples taken every 10,min from sunrise to sunset the same day of birth. We recorded five births at the continuous forest (CF) over a 25 months period (January 2004,December 2004 and September 2005,September 2006) and two births in the fragmented forest (FF) over a 13 months period (September 2005,September 2006). From these, four births were during daylight (two at CF and two at FF) and three during the night at CF. Our descriptions of A. caraya births contribute to a growing data set on the timing of parturition in wild nonhuman primates and suggest that a clear pattern of nocturnal births is not universal across nonhuman primate species. Am. J. Primatol. 71:261,265, 2009. © 2008 Wiley-Liss, Inc. [source] Microhabitat Selection of three Forest Understory Birds in the Brazilian Atlantic RainforestBIOTROPICA, Issue 3 2010Miriam M. Hansbauer ABSTRACT When assessing fragmentation effects on species, not only habitat preferences on the landscape scale, but also microhabitat selection is an important factor to consider, as microhabitat is also affected by habitat disturbance, but nevertheless essential for species for foraging, nesting and sheltering. In the Atlantic Rainforest of Brazil we examined microhabitat selection of six Pyriglena leucoptera (white-shouldered fire-eye), 10 Sclerurus scansor (rufous-breasted leaftosser), and 30 Chiroxiphia caudata (blue manakin). We radio-tracked the individuals between May 2004 and February 2005 to gain home ranges based on individual fixed kernels. Vegetation structures in core plots and fringe plots were compared. In C. caudata, we additionally assessed the influence of behavioural traits on microhabitat selection. Further, we compared microhabitat structures in the fragmented forest with those in the contiguous, and contrasted the results with the birds' preferences. Pyriglena leucoptera preferred liana tangles that were more common in the fragmented forest, whereas S. scansor preferred woody debris, open forest floor (up to 0.5 m), and a thin closed leaf litter cover which all occurred significantly more often in the contiguous forest. Significant differences were detected in C. caudata for vegetation densities in the different strata; the distance of core plots to the nearest lek site was significantly influenced by sex and age. However, core sites of C. caudata in fragmented and contiguous forests showed no significant differences in structure. Exploring microhabitat selection and behavior may greatly support the understanding of habitat selection of species and their susceptibility to fragmentation on the landscape scale. Abstract in Portuguese is available at http://www.blackwell-synergy.com/loi/btp [source] Effects of the Surrounding Matrix on Tree Recruitment in Amazonian Forest FragmentsCONSERVATION BIOLOGY, Issue 3 2006HENRIQUE E. M. NASCIMENTO efectos de borde; especies pioneras; fragmentación de bosques; bosque lluvioso Abstract:,Little is known about how the surrounding modified matrix affects tree recruitment in fragmented forests. We contrasted effects of two different matrix types, Vismia - and Cecropia -dominated regrowth, on recruitment of pioneer tree species in forest fragments in central Amazonia. Our analyses were based on 22, 1-ha plots in seven experimental forest fragments ranging in size from 1 to 100 ha. By 13 to 17 years after fragmentation, the population density of pioneer trees was significantly higher in plots surrounded by Vismia regrowth than in plots surrounded by Cecropia regrowth, and the species composition and dominance of pioneers differed markedly between the two matrix types. Cecropia sciadophylla was the most abundant pioneer in fragments surrounded by Cecropia regrowth (constituting nearly 50% of all pioneer trees), whereas densities of species in Vismia -surrounded fragments were distributed more evenly. Thus the surrounding matrix had a strong influence on patterns of tree recruitment in Amazonian forest fragments. Resumen:,Se conoce poco del efecto de la matriz modificada circundante sobre el reclutamiento de árboles en bosques fragmentados. Contrastamos los efectos de dos tipos diferentes de matriz, vegetación secundaria dominada por Vismia- y Cecropia-, sobre el reclutamiento de especies de árboles pioneros en fragmentos de bosque en la Amazonía central. Nuestros análisis se basaron en 22 parcelas de 1 ha en siete fragmentos de bosque experimentales que varían entre 1 y 1000 ha. Entre 13 y 17 años después de la fragmentación, la densidad poblacional de árboles pioneros era significativamente mayor en parcelas rodeados por Vismia que en las parcelas rodeadas por Cecropia, y la composición y dominancia de especies pioneras fueron marcadamente diferentes en cada tipo de matriz. Cecropia sciadophylla fue la pionera más abundante en fragmentos rodeados por Cecropia (constituyó casi 50% de todos los árboles pioneros), mientras que las densidades de especies en los fragmentos rodeados por Vismia se distribuyeron más homogéneamente. Por lo tanto, la matriz circundante tiene una fuerte influencia sobre los patrones de reclutamiento de árboles en fragmentos de bosque Amazónicos. [source] Why is there discordant diversity in sengi (Mammalia: Afrotheria: Macroscelidea) taxonomy and ecology?AFRICAN JOURNAL OF ECOLOGY, Issue 1 2009Galen B. Rathbun Abstract The seventeen species of sengis or elephant-shrews form a well-defined clade of mammals endemic to Africa that occupy the extremes of terrestrial habitats, from coastal deserts to montane forests. Because of their isolation on Africa soon after the break-up of Gondwanaland, theoretically sengis initially evolved with little competition from other placental radiations. Their life history features include myrmecophagy, saltatorial gaits, no or limited use of nests, social monogamy, small litters of precocial young and absentee maternal care of neonates. These traits together are unique to the Macroscelidea and represent a wedding of features usually associated with either small antelopes or anteaters. Combined, these features define an adaptive syndrome that presumably has been relatively immune to competition from contemporary mammals, partially due to phylogenetic inertia. Yet paradoxically, the syndrome is well suited to a wide range of terrestrial habitats, resulting in low taxonomic diversity. Because of their unusual phylogeny and low species diversity, conservation interest is high for those sengis with relatively low densities in fragmented forests. Résumé Les 17 espèces de sengis (musaraignes éléphants) forment un clade bien déterminé de mammifères endémiques d'Afrique, qui occupe des habitats terrestres extrêmes allant de déserts côtiers à des forêts de montagne. En raison de leur isolement sur le continent africain très vite après la scission du Gondwana, les sengis ont théoriquement évolué au départ sans qu'il existe beaucoup de compétition avec les radiations d'autres placentaires. Les caractéristiques de leur histoire incluent de la myrmécophagie, des déplacements par bonds, un usage de nids limité, voire inexistant, la monogamie sociale, de petites portées de jeunes précoces et l'inexistence de soins maternels pour les nouveau-nés. Toutes ces caractéristiques sont uniques pour les Macroscélidés et représentent un regroupement de caractéristiques d'habitude associées à de petites antilopes ou à des fourmiliers. Combinées, ces caractéristiques définissent un syndrome d'adaptation qui, sans doute, fut relativement protégé de toute compétition avec des mammifères contemporains, à cause, en partie, de l'inertie phylogénétique. Mais, paradoxalement, ce syndrome est bien adaptéà une vaste gamme d'habitats terrestres, ce qui n'entraîne donc qu'une faible diversité taxonomique. En raison de leur phylogenèse inhabituelle et de la faible diversité entre ces espèces, l'intérêt de la conservation est considérable pour ces sengis dont la densité, dans des forêts fragmentées, est relativement faible. [source] Theory meets reality in fragmented forestsANIMAL CONSERVATION, Issue 5 2008W. F. Laurance No abstract is available for this article. [source] | ||||||||||||||||||||||