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1.
We conducted the first orangutan population census of Gunung Palung National Park, West Kalimantan, Indonesia, between April and September 2001. We used a refined line-transect nest-count methodology utilizing transect recounts to survey 69 km at 14 sites within the park and 14.2 km in the buffer zone. We present the first Bornean orangutan density estimate using complete site-specific parameters and long term monitoring of nest decay rates. Average orangutan density was 3.0 individuals/km2, with densities ranging from 2.4 ind/km2 in montane forest to 4.1 ind/km2 in primary peat swamp. In addition, we tested alternative approaches to calculation of the nest-duration parameter. The second count of each transect resulted in 30% higher density estimates overall. We conclude that recounts should be incorporated into standard line-transect methodology. We estimate there to be ≈2500 individual orangutans in Gunung Palung, indicating the importance of this site in plans to conserve a network of viable orangutan populations. While logging may reduce densities, disturbed forest both inside and adjacent to the park has high conservation value as orangutan habitat. Further research into long-term orangutan population persistence in disturbed forest is needed.  相似文献   

2.
We investigated the population density of Bornean orangutans Pongo pygmaeus pygmaeus and aspects of habitat quality in a selectively hand-logged peat swamp forest in West Kalimantan, Indonesia, and in a comparable unlogged forest nearby. We conducted orangutan nest surveys, measured different parameters of forest structure, recorded monthly changes in fruit availability, and noted the sex and the stage of maturity of orangutans encountered. Nest density, an index of orangutan population density, was 21% lower in the logged area. The forest, logged 2 years previously, had fewer large food trees and a greater number of canopy gaps. We discuss these differences in relation to the lower orangutan nest density in the logged forest. Significantly fewer adult orangutans were observed in the logged study area. We hypothesize that fully adult orangutans, particularly females, are the most severely affected by hand-logging.  相似文献   

3.
In order to design effective conservation measures for the orangutan, accurate information on their distribution and densities are needed. Nest counts along line transects allow for fairly accurate assessment of orangutan density. However, large sample sizes are needed to obtain accurate estimations of the decay rate of nests, preventing a rapid estimate. Moreover, due to the structure of tropical forests, nest numbers above and near the trail are underestimated. In this study, a rapid assessment method for the estimation of orangutan density is developed, allowing for the estimation of density with a single survey. Procedures are provided for estimating a correction factor which adjusts for underestimating nest numbers near the transect trail. Furthermore, we provide a shortcut to rapidly assess nest decay rate without the need for consecutive surveys. Finally, recommendations are made for determining orangutan density using two different techniques. These techniques incorporate correction factors and a shortcut to accurately assess orangutan density with only one or two visits to an area.  相似文献   

4.
The human footprint is increasing across the world’s natural habitats, causing large negative impacts on the survival of many species. In order to successfully mitigate the negative effects on species’ survival, it is crucial to understand their responses to human-induced changes. This paper examines the effect of one such disturbance, logging, on Sumatran orangutans – a critically endangered great ape. Orangutan population densities may decrease or remain stable after logging, but data on the effects of logging on the behavior of individuals is scant. Here, we provide individual-level behavioral data based on direct observations in 2003–2008 at the Ketambe (Sumatra, Indonesia) research area (partly subject to intense selective logging) in order to assess responses of Sumatran orangutans to logging. Logging significantly negatively affected forest structure and orangutan food resources, specifically important fallback and liana-derived foods. Individual orangutans behaved differently between logged and pristine forest; they moved more and rested less in logged forest. With the exception of figs, diet composition remained overall similar. Altogether, life after logging seems energetically more expensive for orangutans. Based on the results of this study, we provide recommendations for conservation research and guidelines for reduced-impact logging.  相似文献   

5.
Preservation of orangutan habitat can only be effective when their range requirements are taken into consideration. Here, the effect of the variation in fruit supply at different altitudes on the seasonal movements of orangutans is investigated. Transects were surveyed every 2 months from 1998 to 2000, at different altitudinal zones in the larger Ketambe area, Indonesia. The density of orangutan and sources of ripe fruit with soft pulp were determined along these transects. Both orangutan density and the availability of fruit varied considerably throughout the survey period at different altitudinal zones. The peaks in fruit production at different altitudes occurred in successive periods. For each altitudinal zone a significant correlation was found between orangutan density and the number of fruit sources, which shows that orangutans follow the production of fruit between these altitudinal zones within the boundaries of their home range. Orangutans with core areas in intermediate and highland areas depend seasonally on fruit production of lowland areas, and vice versa. Thus, conservation of large tracts of primary forest with a range of different altitudes is necessary to preserve the remaining orangutan population.  相似文献   

6.
Human disturbance of tropical rainforests may change pollinator communities indirectly as a result of changes in resource availability. We studied the mechanisms by which human disturbance affects a community of major pollinators, stingless bees, in Sarawak, Malaysia. We surveyed forest structure and flowering activity, and conducted a nest census and a bait-trap survey of stingless bees, both in primary forests and in forests disturbed by logging and shifting cultivation. The densities of late successional trees and large trees (diameter at breast height >50 cm) were higher in the primary forests than in the disturbed forests. The density of flowering trees was lower one year after logging, but recovered in old disturbed forests because of the active flowering of pioneer trees that became established after the disturbance. Stingless bees nest only in large trees, and nest density was positively correlated with the density of large trees. However, we found no relationship between the numbers of foragers and floristic parameters. Some species preferred nesting in dipterocarps, while others preferred dead trees. The results of the bait-trap survey also indicated that some species were abundant in the primary forests, whereas other species were abundant in the disturbed forests. These results suggest that human disturbance alters the species composition of the stingless bee community. Such changes in the bee community may affect the reproductive success of plants, and ultimately forest composition.  相似文献   

7.
Chinese village fengshui forests (VFF) are small remnant forest patches that coexist with natural villages. The indigenous residents protect the forest patches under traditional Chinese geomancy beliefs (namely fengshui). However, the VFF community features and conservation values and relationships with the indigenous people remain poorly understood. In this study, we evaluated tree species diversity conservation of regional VFF patches by sampling a 1200 m2 transect within each patch. We also tested our hypothesis that patch size did not significantly impact interior forest community features of well-protected VFF patches. Thirty-two well-protected VFF patches in the Pearl River Delta, China were investigated. The average coefficient of similarity between transects (CS) was employed to evaluate community heterogeneity. Five forest community parameters (tree species richness per 1200 m2, tree stem density, tree basal area density, Shannon–Wiener diversity index (SWI), and Simpson diversity index (SI)) were measured and compared with regional well-developed evergreen broadleaved, coniferous and coniferous-broadleaved mixed forests. The relationships between the five parameters versus patch size and elevation were analyzed. A total of 266 tree species comprised of 57 families were recorded in 32 transects, of which 258 (97%) species were indigenous and eight (3%) were exotic. Ten tree species were endangered, rare or nationally protected by the Chinese government, and 57 species were endemic to China. The average CS was 0.38; and the average five forest community parameter values were as follows: 46.8 for tree species richness; 3403 plants/ha for stem density, 49.1 m2/ha for basal area, 4.04 for SWI and 0.90 for SI. These values were consistent with well-developed evergreen broadleaved forests and greater than coniferous and coniferous-broadleaved forests. No significant correlation was detected between the five community parameters and patch area or elevation. We conclude that VFF patches preserve abundant tree species and heterogeneous habitats, which are important for maintaining regional biodiversity. The interior community features of VFF patches were not significantly affected by patch size. We recommend protection of both large and small VFF patches, which can be substantially enhanced by the preservation of associated traditional relic village cultures.  相似文献   

8.
To conserve tropical forests, it is crucial to characterise the disturbance threshold beyond which populations of tropical trees are no longer resilient. This approach is still not widely employed, especially with respect to the effects of moderate disturbances. Compensation effects, such as positive interactions among plants, are addressed even more rarely. We attempt to identify the extents to which the distribution of the keystone palm tree Ceroxylon echinulatum is regulated by various regimes of deforestation in a threatened tropical montane cloud forest in the North-West Andes of Ecuador. The demographic structure of this palm tree was examined in three habitats: old-growth forest, forest disturbed by selective logging, and deforested pasture. Patterns were related to stand structure, microclimate, and soil composition. Seedling desiccation owing to severe aboveground water stress led to the absence of juvenile palms in pastures, and thus was predictive of a near extinction of the species in this habitat. However, shade provided by dominant bunchgrass in pastures considerably reduced above- and belowground water stress by diminishing light intensity. Selective logging resulted in a higher density of individuals in disturbed forests than in old-growth forests, but was associated with a spoiled spatial structure. Therefore, the protection of residual old-growth forests is a prerequisite for the conservation of C. echinulatum, although secondary forests might act as provisional refuges that promote its resilience. The reduction of water stress by nurse grasses in pastures represents a promising approach to promote the resilience of tropical tree species and their associated communities after deforestation.  相似文献   

9.
The endemic Seram cockatoo, Cacatua moluccensis, was placed on Appendix I of CITES in response to declining trade statistics but in the absence of population data. We conducted population surveys and collected data on habitat structure at seven sites on Seram in 1998. Cockatoo densities ranged from 0.93 to 17.25 birds/km2 and averaged 7.9 birds/km2 across sites. We classified habitat into three types but found that cockatoo densities did not correspond closely to habitat differences across sites. Cockatoo abundance was significantly associated with presence of potential nest trees and strangling figs. Analysis of forest cover and landuse indicates that while most of the island is still covered in lowland forest, only 14% of these forests are protected and almost half the island is classified as logging concession. Conservation recommendations include better information and enforcement of laws protecting Seram cockatoos and resolution of boundary conflicts between parks and logging concessions.  相似文献   

10.
The response of most large carnivores to selective logging is poorly understood. On the one hand, selective logging may represent loss of important habitat, yet, on the other hand, selective logging may increase browse availability for a terrestrial ungulate prey base, thereby indirectly benefiting large carnivores. Using a camera trap-based sampling method, we estimate tiger density in two primary-selectively logged forest areas that straddle Kerinci Seblat National Park, Sumatra. We then investigate potential differences between the habitat use of tigers: within these study areas and forest types; and, within the finer-scale landscape features associated with these covariates. Across the mixed forest study areas, tiger density estimates (adult individuals/100 km2 ± S.E.) of 2.95 ± 0.56 and 1.55 ± 0.34 were produced. However, within these areas, tigers showed a preference for primary over degraded forest, and this was related to the greater accessibility of degraded forest sites to people, e.g., through their proximity to roads. Presently, the majority of Sumatran tigers occur within large tracts of primary forest, but these extend outside of the island’s protected area borders, and these unprotected forests are especially at risk from the high levels of deforestation in Sumatra. As forest is cleared, previously remote, and therefore safer, tracts of primary forest become accessible and, eventually, degraded. Yet, from our study, degraded forest in combination with primary forest supported sufficiently high tiger densities and can, therefore, make an important contribution to tiger conservation. It is therefore essential to lessen the detrimental effects of accessibility through increasing law enforcement and destroying ex-logging roads.  相似文献   

11.
Tree cavities are proposed to limit populations and structure communities of cavity-nesting birds. Although the greatest diversity of cavity-nesting birds is found in tropical and subtropical moist forests, little is known about how tropical logging affects the abundance of cavities or cavity-nesting birds. We compared the abundance of cavities and cavity nests between primary and selectively-logged subtropical moist Atlantic forest in Argentina, and conducted the first before-after controlled nest-box addition experiment to determine whether nest sites limit the breeding density of cavity-nesting birds in tropical or subtropical moist forest. Visual inspection of 86 cavities identified through ground-surveys revealed that only 19% were suitable for nesting birds, suggesting that cavity abundance may be overestimated in the literature on tropical forests. Suitable cavities were found in fewer than 1% of 1156 trees <60 cm dbh but 20% of 20 trees >100 cm dbh. Logged forest had half the basal area of primary forest, one third the density of large trees, nine times fewer cavities suitable for nesting birds, and 17 times fewer active nests. When we added nest boxes, nesting density increased on treatment plots but not on control plots in both logged and primary forest, suggesting that cavity supply can limit nest density even in relatively undisturbed forest. This is the first experiment to show how reduced cavity supply in logged tropical forest can limit breeding density of cavity-nesting birds. International initiatives such as forest certification should promote tropical timber management strategies that conserve large live cavity-bearing trees.  相似文献   

12.
In southern Africa the samango monkey Cercopithecus mitis is confined to small (< 500 ha) forest fragments and is considered a locally rare species. Monkey populations from 17 of Natal's forests were visited and 14 of these were censused using King's strip transect method. Enviromental correlates and disturbance factors affecting samango population density are examined. The results of this provincial census show that it may be possible to predict samango density according to the plant species richness and diversity of a forest. The potential effect of the latter on the vagaries of food abundance and availability and hence the primate carrying capacity of a forest are considered. The important conclusion is that forests in Natal with very high species richness and diversity values do not necessarily support high samango densities. In fact these forests appear to maintain population densities similar to those forests with low plant species richness and diversity (swamp and sand forests). This has important implications for the conservation and management of the species, since it high-lights the importance to its survival, of those, often young, forests that can maintain high population densities (coastal dune and coastal lowland forest). Furthermore, results of this study permit a more objective interpretation of the evaluation of the observed abundance of samango monkeys in different forest types, and in so doing may form the basis for sound management proposals in the future.  相似文献   

13.
This study investigated associations between the relative abundance of the threatened ngwayir (western ringtail possum, Pseudocheirus occidentalis) and anthropogenic disturbances at local and landscape scales within the publicly-managed jarrah (Eucalyptus marginata) forests of south-western Australia. Logging, fire, fox (Vulpes vulpes) control and forest fragmentation were investigated in relation to the relative abundance of ngwayir at 90 sites within an area of 285,000 ha east of Manjimup; the location of the last remaining substantial population of ngwayir in jarrah forest. Overall, ngwayir abundance was greatest in areas with limited anthropogenic disturbance. At the local-scale, ngwayir abundance was negatively associated with greater fire intensity. At the landscape-scale, it was positively associated with fox control and negatively associated with forest fragmentation and distance from non-remnant vegetation (i.e., agriculture and tree plantations). Abundance was also greatest in predominantly unlogged landscapes and in forests that had been regrowing for an average of 40 years since the landscape was most recently logged, in other words, where logging was historically least intense. Interactions between fox control efforts and forest fragmentation were also important. This study emphasises the importance of conducting research at appropriate spatial scales and to account for the synergistic effects of the causes of decline. An adaptive management approach to the mitigation of the agents of decline is recommended.Indirect evidence indicates that high value habitat for ngwayir has in all likelihood been selectively cleared for agriculture, owing to its fertile and productive nature. Habitat loss is, therefore, also likely to be a major cause of the modern decline of the species. While many jarrah forest areas that support remaining high abundances of the ngwayir have been incorporated into reserves, conservation of ngwayir habitat and populations outside reserves also will be essential for the recovery and long-term viability of the species.  相似文献   

14.
Logging and intense shifting cultivation have caused major degradation of tropical forests and loss of biodiversity. Understanding the direct and indirect effects of those land uses on plant biodiversity is essential to the restoration of tropical forests. We compared the species diversity, community composition and basal area of all stems ?1 cm dbh among 18 1-ha tropical lowland and montane rain forest plots with a well-recorded long-term history of shifting cultivation and logging on Hainan Island, south China. We also explored the relative importance of disturbance and environmental factors in determining forest recovery. We found that the species density and diversity in old growth forests were higher than in shifting cultivation fallows (55 years old) but lower than in logged forests (35–40 years since logging). The species composition of shifting cultivation fallows was distinct from other forest types but logged forests were similar to old growth forests, especially in lowland forests. Disturbance intensity was the most frequently important factor in determining species composition, species density, diversity, and basal area accumulation. Soil nutrient availability explained some of the variation in species composition and diversity. Stem density was related to multiple factors including disturbance history, soil nutrients, and distance to old-growth forest. In general, we found that disturbance intensity was a better predictor of forest structure and diversity than edaphic environmental variables, highlighting the importance of human impacts in shaping tropical forest successional pathways.  相似文献   

15.
Large flying-foxes in insular Southeast Asia are the most threatened of the Old World fruit bats due to high levels of deforestation and hunting and effectively little local conservation commitment. The forest at Subic Bay, Philippines, supports a rare, large colony of vulnerable Philippine giant fruit bats (Pteropus vampyrus lanensis) and endangered and endemic golden-crowned flying-foxes (Acerodon jubatus). These large flying-foxes are optimal for conservation focus, because in addition to being keystone, flagship, and umbrella species, the bats are important to Subic Bay’s economy and its indigenous cultures. Habitat selection information streamlines management’s efforts to protect and conserve these popular but threatened animals. We used radio telemetry to describe the bats’ nighttime use of habitat on two ecological scales: vegetation and microhabitat. The fruit bats used the entire 14,000 ha study area, including all of Subic Bay Watershed Reserve, as well as neighboring forests just outside the protected area boundaries. Their recorded foraging locations ranged between 0.4 and 12 km from the roost. We compared the bats’ use to the availability of vegetative habitat types, riparian areas, and bat trees. The fruit bats’ locations showed a preference for undisturbed forest types and selection against disturbed and agricultural areas. Bat locations also showed selection for particular fruiting/flowering bat trees. The bats showed strong preference for riparian areas; locations were in riparian areas over four times more than expected. From these results we recommend that management focus flying-fox conservation efforts on undisturbed forest and riparian areas.  相似文献   

16.
Unprecedented deforestation is currently underway in Southeast Asia. Since this trend is likely to continue, it is critical to determine the value of human-modified habitats (e.g., mixed-rural habitat) for conserving the regional native forest avifauna. The impacts of ongoing deforestation on the highly endemic avifauna (33%) of Sulawesi (Indonesia) are poorly understood. We sampled birds in primary and secondary forests in the Lore Lindu National Park in central Sulawesi, as well as the surrounding plantation and mixed-rural habitats. Species richness, species density and population density of forest birds showed a consistent decreasing trend in the following order: primary forests > secondary forests > mixed-rural habitat > plantations. Although primary forests contained the highest proportion (85%) of a total of 34 forest species recorded from our point count surveys, 40-yr old secondary forests and the mixed-rural habitat showed high conservation potential, containing 82% and 76% of the forest species, respectively. Plantations recorded only 32% of the forest bird species. Fifteen forest species had the highest abundance in primary forests, while two species had higher abundance outside primary forests. Our simulations revealed that all forest birds that were sensitive to native tree cover could be found in areas with at least 20% continuous native tree cover. Our study shows that although primary forests have the highest conservation value for forest avifauna, the potential of degraded habitats, such as secondary forests and the mixed-rural habitat, for conserving forest species can be enhanced with appropriate land use and management decisions.  相似文献   

17.
A consequence of isolation is increased susceptibility to catastrophe. Insect damage to fragmented and isolated forests has the potential to serve as a catastrophic force; such damage has increased worldwide due to climate change and fire suppression policies. We examined the response of endangered endemic Mt. Graham red squirrels to catastrophic insect damage due to moths, beetles, and introduced aphids. Insects changed the forest environment significantly for the endemic squirrel by reducing basal area and stem densities of live stems, while increasing number and basal area of standing dead stems. Availability of two major foods, fungi and tree seeds, declined in insect-damaged forests relative to trends in undamaged forests. Numbers of Mt. Graham red squirrels declined precipitously in insect-damaged forests suggesting a catastrophe. Conservation options are limited in such situations. Forest-insect induced catastrophes are likely to become more common in the near future as forest health declines due to past management tactics and climate change. Prudent conservation measures include the anticipation of insect outbreaks and effective forest treatments to decrease likelihood of such catastrophes to species of precarious conservation status, while avoiding abrupt changes to critical habitat.  相似文献   

18.
Southeast Asia experiences one of the highest rates of deforestation in the tropics due to agricultural expansion, logging, habitat fragmentation and urbanization, which are expected to result in species declines and extinctions. In particular, growing global demands for food, biofuel and other commodities are driving the rapid expansion of oil palm and paper-and-pulp industries at the expense of lowland dipterocarp forests, further jeopardizing Southeast Asian forest biotas. We synthesize recent findings on the effects of land-use changes on plants, invertebrates, vertebrates and ecosystem functioning/services in Southeast Asia. We find that species richness and abundance/density of forest-dependent taxa generally declined in disturbed compared to mature forests. Species with restricted ranges and those with habitat and foraging specialization were particularly vulnerable. Forest loss also disrupted vital ecosystem services (e.g. crop pollination). Long-term studies are needed to understand biotic sustainability in regenerating and degraded forests, particularly in the context of the synergistic or additive effects of multiple agents of biodiversity loss (e.g. invasive species and climate change). The preservation of large tracts of mature forests should remain the principal conservation strategy in the tropics. In addition, reforestation and reintroductions of native species, as well as improved connectivity among forest patches could enhance the conservation value of forest remnants in human-dominated landscapes.  相似文献   

19.
Effect of selective logging on vascular epiphyte diversity was investigated in a moist lowland forest of Eastern Himalaya. Three epiphytic groups viz. orchids, pteridophytes and non-orchid angiosperm epiphytes were specifically studied in closed, selectively logged and in unlogged forests with treefall gaps. Logging reduced the structural complexity of the forests and altered their microclimate. With logging, there was a general decline in richness and abundance of epiphytes except orchids. The abundance and species composition of pteridophytes and non-orchid angiosperm epiphytes were related to microclimate and substrate features while their richness were correlated only with canopy cover. In contrast, orchid species composition was related to forest structure. A combination of management strategies is required for conservation of all epiphyte groups. A mosaic of logged and unlogged forest patches with undisturbed forests in proximity would maintain the diversity of pteridophytes and other angiosperms. However, for full representation of orchids, it is necessary to maintain the structural diversity of the tree forms.  相似文献   

20.
Traditional biodiversity conservation approaches emphasize the protection of pristine forests. However, it has become increasingly difficult to secure large tracts of undisturbed forests, particularly in the developing tropics. This has led some conservation scientists and organizations to explore the conservation potential of human-modified habitats, such as selectively logged forests. On the other hand, other scientists have highlighted the perils of overselling the conservation value of degraded habitats and advocate for re-focusing of efforts and resources on protecting primary forests. While there are merits to both contentions, we argue that the “back to wilderness” paradigm has limited relevance in the Sundaland region. This is because: (1) primary forest only makes up a small minority of the remaining forest in the region and most of it is already protected by law; (2) vast areas of selectively logged forest are still susceptible to plantation conversion; and (3) selectively logged forest are important habitats for some of the world’s most endangered species. To meet both conservation and development goals, we suggest that tracts of selectively logged forest be assessed for their ecological value and forests of high conservation value be prioritized for better protection through their inclusion into existing protected area networks and/or improved sustainable forestry management.  相似文献   

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