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Isolated Forest Fragments (isolated + forest_fragment)
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] Species and structural diversity of church forests in a fragmented Ethiopian Highland landscapeJOURNAL OF VEGETATION SCIENCE, Issue 5 2010Alemayehu Wassie Abstract Question: Thousands of small isolated forest fragments remain around churches ("church forests") in the almost completely deforested Ethiopian Highlands. We questioned how the forest structure and composition varied with altitude, forest area and human influence. Location: South Gondar, Amhara National Regional State, Northern Ethiopia. Methods: The structure and species composition was assessed for 810 plots in 28 church forests. All woody plants were inventoried, identified and measured (stem diameter) in seven to 56 10 m x 10-m plots per forest. Results: In total, 168 woody species were recorded, of which 160 were indigeneous. The basal area decreased with tree harvest intensity; understorey and middle-storey density (<5 cm DBH trees) decreased with grazing; overstorey density (>5 cm DBH trees) increased with altitude. The dominance of a small set of species increased with altitude and grazing intensity. Species richness decreased with altitude, mainly due to variation in the richness of the overstorey community. Moreover, species richness in the understorey decreased with grazing intensity. Conclusions: We show how tree harvesting intensity, grazing intensity and altitude contribute to observed variations in forest structure, composition and species richness. Species richness was, however, not related to forest area. Our study emphasizes the significant role played by the remaining church forests for conservation of woody plant species in North Ethiopian Highlands, and the need to protect these forests for plant species conservation purposes. [source] Spatial and temporal variability in predation on rainforest primates: do forest fragmentation and predation act synergistically?ANIMAL CONSERVATION, Issue 3 2009M. T. Irwin Abstract Predation is a constant risk for most primates, impacting demography, population dynamics, activity patterns and social behaviour. Data are limited on both the rates of predation and its spatial and temporal variability. We present long-term observations of Cryptoprocta ferox predation on rainforest sifakas in Madagascar, Propithecus diadema at Tsinjoarivo (22 group years) and Propithecus edwardsi at Ranomafana (73 group years), derived from intensive observations based on ongoing behavioural studies. Average per capita offtake rates are relatively low (0.06,0.07), but temporal variability is high (kills are clumped in time). This is consistent with Cryptoprocta ecology; individual home ranges are much larger than sifaka ranges, and individuals may hunt in a subsection of their range until prey density is decreased, then move on. These results have broad implications. First, in terms of the evolution of anti-predator strategies, it now becomes important to ask: (1) whether average or peak predation rates determine the strength of selection and (2) whether antipredator strategies (e.g. vigilance, sleeping site selection) fluctuate interannually, reflecting recent experience. Second, in terms of population ecology, Cryptoprocta may have disproportionately large impacts on the (small) sifaka groups, even driving groups to extinction (as observed at both sites). Third, the disappearance of groups has important implications for conservation. When this happens in continuous forest (as at Ranomafana), home ranges will likely be re-filled over time, whereas in isolated forest fragments (as at Tsinjoarivo), recolonization is less likely. Thus, conservation planners should consider predation as a potentially important proximate cause of extirpation in fragmented landscapes, even when resource density and quality could otherwise sustain populations. Considering the effects of predation can be useful in (1) decisions regarding the allocation of limited conservation resources, including which landscapes to invest resources in and (2) investigating ways to increase resilience of prey species. [source] Importance of Interhabitat Gaps and Stepping-Stones for Lesser Woodcreepers (Xiphorhynchus fuscus) in the Atlantic Forest, BrazilBIOTROPICA, Issue 3 2008Danilo Boscolo ABSTRACT Translocation experiments showed that a woodcreeper bird species is able to move between isolated forest fragments, but this ability is limited by increasing interpatch distances. Larger distances (> 100 m) were overcome by using small stepping-stones (isolated trees), which enhance connectivity and are useful for the species conservation in fragmented landscapes. RESUMO Experimentos de translocação demonstraram que uma espécie de arapaçu é capaz de mover-se entre fragmentos florestais, mas essa habilidade é limitada por seu isolamento. Distâncias maiores que 100 m foram vencidas com o uso de árvores isoladas, as quais aumentam a conectividade e são úteis para a conservação dessa espécie em paisagens fragmentadas. [source] | ||||||||||