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Forest Interior (forest + interior)
Selected AbstractsLow Recruitment of Trees Dispersed by Animals in African Forest FragmentsCONSERVATION BIOLOGY, Issue 6 2001N. 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] Forest fragmentation relaxes natural nest predation in an Afromontane forestANIMAL CONSERVATION, Issue 4 2009T. 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] Forest bird diversity and ski-runs: a case of negative edge effectANIMAL CONSERVATION, Issue 1 2005Paola Laiolo Among tourist activities in the Alps, winter sports have a prominent role because of the large scale of changes they cause at the habitat and landscape level. We have analysed whether ski resorts lead to significant threats to the avian diversity in the coniferous forests of the western Italian Alps, by comparing the bird communities of plots located in (1) the forest interior, (2) forest at the edge of ski-runs and (3) forest at the edge of pastures (the latter two are anthropogenic elements of forest fragmentation). Ski-runs produce a negative edge effect in the study forests: plots at their edges present lower bird species richness and Shannon diversity than those located in the forest interior or at the edges of pastures. In particular, birds typical of ecotone habitats seem to favour forest plots set at the edge of pastures. Ski-run-edges are linear landscape features that create high contrast edges; conversely, vegetation structure is more complex at the edge of pastures, attracting a rich and diverse avifauna. In the study area, pastures tend to be abandoned whereas winter sport resorts are increasing in extent. Accordingly, there is a need for coordinated management and cooperation between sport- and land-management agencies, in order to preserve native biodiversity while simultaneously managing land for sport activities. [source] Birds on edge: avian assemblages along forest-agricultural boundaries of central Victoria, AustraliaANIMAL CONSERVATION, Issue 2 2001Monica J. Campi Habitat clearance generally produces fragmented landscapes. A major consequence is the creation of large amounts of new ,edge habitat', often of a kind not previously existing, such as abrupt forest- agricultural land interfaces. Much work from around the world suggests that proliferation of edge habitat seriously affects birds reliant on large forest blocks to persist, and the intrusion of edge specialists into areas they did not previously occupy. These processes often generate avifaunal gradients in which assemblages change from the interior to the edge. This effect is explored in the largest remnant block of box-ironbark forest of central Victoria, Australia (about 30,000 ha). Eight radially oriented survey lines were established around the periphery of the block. Along each survey line, five transects with long axes oriented parallel to the edge were positioned with midlines at 40 m, 160 m, 280 m and 400 m into the forest, and one transect 80 m into the agricultural land, yielding a total of 40 transects. Six identical transects were located deep within the forest (> 2 km). There was little evidence of a change in the avifauna from interior to edge, although mean richness was depressed in the edge habitats compared with forest interior transects. These results were essentially the same for ,all species' or ,forest dependent' species. Thus, there is little evidence for marked edge effects on the avifauna of these large forest blocks, although work in intermediate sized remnants (100-1000 ha) is needed to identify thresholds at which edge effects begin to be manifested. [source] Persisting Hyper-abundance of Leaf-cutting Ants (Atta spp.) at the Edge of an Old Atlantic Forest FragmentBIOTROPICA, Issue 6 2009Sebastian T. Meyer ABSTRACT Leaf-cutting ants (LCAs) profoundly benefit from edge creation in Neotropical forests, where they act as a keystone species and disturbance agent. In view of their poorly explored population dynamics, the question arises whether high densities of LCAs are a transitional or a persisting phenomenon. We studied the temporal variation of LCA colony densities at the edge of the Brazilian Atlantic forest. At physically stable edges of an old forest fragment, densities of Atta cephalotes and Atta sexdens (11 and five times higher in a 50 m edge zone in comparison with the forest interior) persisted over a 4-yr interval (2001,2005) with no significant difference in densities between years. Species-specific per colony growth rates ranged from 12 to ,5 percent/yr, suggesting that populations were approximately at equilibrium. High rates of colony turnover (little less than 50% in 4 yr) indicated an average colony life span of about 7 yr,a life expectancy considerably lower than previous estimates for Atta colonies. Stable, hyper-abundant populations of LCAs accord with the constantly high availability of palatable pioneer vegetation (the preferred food source of LCAs) at forest edges and are expected to persist in time as long as forests are characterized by high edge to interior ratios, with potentially long-lasting consequences for the ecosystem. [source] Wildlife habitat strips and native forest ground-active beetle assemblages in plantation nodes in northeast TasmaniaAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 4 2005Simon Grove Abstract, In Tasmania, plantation establishment is often concentrated in ,nodes', a practice that can result in a high degree of fragmentation of remaining native forest in these areas. In this study we examined the sensitivity of ground-active beetles to the effects of conversion of native forest to plantation in which remaining native forest is largely confined to narrow wildlife habitat strips. At five damp sclerophyll forest sites in northeast Tasmania, pitfall sampling was carried out along the middle axis of a wildlife habitat strip, in the young plantation surrounding the strip, and at three distances in from the edge of nearby continuous native forest. The study documented a rich fauna, particularly for carabids. Species composition varied among sites, emphasising the need for adequate regional reservation of native forest at appropriate spatial scales. While plots in plantations and strips supported similar numbers of species as continuous native forest, they usually differed in assemblage composition. In general, assemblages in strips appeared to be intermediate in composition between those of continuous native forest and plantations. Significant differences corresponding to a progressive change in assemblage composition with distance into continuous native forest from its edge were detected for one, possibly two, sites. Plots in strips were generally more similar in assemblage composition to those near the edge of continuous native forest than to those towards its interior. Within the study area, strips may promote the survival of species that otherwise associate with the edges of continuous native forest, but they may provide less effective habitat for species that associate with native forest interiors. However, they still harbour many native forest species which are rare or absent in plantations. Although only based on a short-term sampling program, the study implies that future strips in Tasmanian damp sclerophyll forest could better benefit some forest interior species if prescriptions were to specify wider strips. However, a clearer conservation outcome might be to ensure the continuance of a sufficiently comprehensive, adequate and representative network of native forest formal reserves (in addition to wildlife habitat strips) containing damp sclerophyll forest. These should be large enough to cater for forest interior species, and dispersed at a spatial scale appropriate to the rate of species turnover found among ground-active beetle assemblages in these forests. [source] | ||||||||||