Effects of forestry practices on vegetation structure and bird community of Kibale National Park, Uganda

I examined the lingering effects of past timber management practices on the vegetation structure and bird community of Kibale National Park, Uganda. I compared four forest treatments: unlogged native forest (UL), two that were selectively logged at low (LL) and high (HL) intensities in the 1960s, and a conifer plantation (PL). Forest-dependent birds were best represented at UL. LL was similar to UL in both vegetation structure and bird community composition, although some forest-dependent bird species were missing from the former. HL had significantly less canopy closure and lower tree density than other plots as a result of the combination of extensive secondary damage and natural disturbance patterns that prevented the reclosure of the forest canopy. Thirty-one percent of the forest-dependent bird species observed during the study were not detected at HL. At PL, bird species richness and bird abundance were about a third of those observed in other plots. There were significant correlations between heterogeneity of tree distribution (horizontal heterogeneity) and abundance and species richness of birds across plots. Abundance and species richness of all, forest-dependent, and forest generalist birds were highest in plots with intermediate measures of horizontal heterogeneity, which were mostly unlogged or lightly logged. If reduced-impact logging practices are not implemented during selective logging operations in tropical forests, consequent long-term changes in vegetation structure may result in significant declines in the populations of some forest-dependent species, as was observed in Kibale National Park.     

Mature Black Cherry Used as a Bioindicator of Ozone Injury

Incidence and severity of foliar symptoms due to ambient ozone exposures were documented on mature black cherry (Prunus serotina) in two National Parks [Great Smoky Mountains National Park (GRSM) and Shenandoah National Park (SHEN)] in the Appalachian Mountains of the eastern USA during the summer of 1991-1993. Three plots in each park containing 30 trees each (Big Meadows in SHEN had 60 trees) with 90 and 120 trees total trees were evaluated in GRSM and SHEN, respectively. Plots were established at different elevations adjacent to ozone monitoring stations. Samples of foliage were collected and three exposed branches from the upper- crown and three branches from the mid-to-lower crown were examined for symptoms of foliar ozone injury. Incidence was greatest in 1991 at both locations; 60% and 45% for GRSM and SHEN, respectively. In 1992 and 1993, incidence was very similar in both parks, with approximately 33% of the trees affected. Black cherry at the highest elevations exhibited the greatest amount of symptoms in both parks all three years of the study. These sites also exhibited the highest ozone concentrations. In addition, the percent of trees injured by ozone was positively correlated with SUM06 and W126. These results along with forest surveys and open-top chamber studies indicate that black cherry may be a reliable bioindicator of foliar injury due to ambient ozone.     

Bird species richness in a Bornean exotic tree plantation: A long-term perspective

To provide sustainable income from forestlands, large areas in the tropics are planted with “agricultural” trees, such as oil palm and rubber, and “industrial” trees, such as Acacia mangium and Gmelina arborea. To examine how native forest birds use such plantations, we surveyed in 2005 the avifauna at Sabah Softwoods, a plantation in southeastern Sabah, Malaysian Borneo. We focused on A. mangium, Albizia (Paraserianthes falcataria), oil palm (Elaeis guineensis), and logged native forest, and compared our results to those of a study conducted at the same plantation in 1982. The number of forest species in the industrial groves did not change dramatically between 1982 and 2005, even though the trees had been cropped several times and the plantation was, by 2005, completely surrounded by cleared land and far removed from primary forest. However, as is common in logged or isolated forests throughout the world, certain primary forest groups (e.g., muscicapine flycatchers) have been extirpated from the entire plantation area. The industrial groves also lacked some larger species of kingfisher, woodpeckers, and canopy frugivores. Nevertheless, numerous primary forest taxa (ca. 50% of species) were found in mature industrial tree groves. Albizia attracted the most species of birds, followed closely by Acacia. Both tree types underpinned relatively complex secondary forests that attracted forest birds. In contrast, younger groves of Acacia and Albizia held mainly open country and scrub species. Oil palm, as a remarkably simple and unusual habitat, attracted few bird species. Sustained occurrence of forest birds in all groves of exotic trees at Sabah Softwoods was substantially enhanced by the relatively rich avifauna of the logged native forest remaining in substantial stands throughout the plantation.     

Biodiversity and ecosystem function of tropical forest dung beetles under contrasting logging regimes

A key challenge for tropical conservation biologists is to assess how forest management practices affect biodiversity and associated ecosystem functions. Dung beetles (Scarabaeidae: Scarabaeinae) provide an ideal focal guild for such studies. We compared dung beetle assemblages and experimentally assessed rates of dung removal and seed burial in undisturbed forest, low-intensity selectively logged forest under sustainable forest management, and high-intensity logged forest, not under sustainable management in Malaysian Borneo. In total, 7923 individuals from 39 species of dung beetle were collected. There were no significant differences in abundance, biomass or diversity across sites. Species richness was significantly lower in the high-intensity logged sites. Beta diversity was low: of 35 species recorded in undisturbed forest sites, 32 were also captured in low-intensity sites and 29 in high-intensity sites. The environmental and vegetation variables measured had little influence on species composition. An average of 63–99% of dung was removed over 24 h. Mean dung and seed removal were significantly lower in the high-intensity logged sites. Dung removal rates were significantly and positively correlated with dung beetle species richness, but not with dung beetle biomass or abundance. However, the biomass of large-bodied, nocturnal dung beetles was positively correlated with dung removal. In contrast to previous studies, dung beetle biomass and abundance were not correlated with species richness, indicative of density compensation. Overall, dung beetle communities and associated ecosystem functions were robust to low-intensity but not high-intensity selective logging. These differences may be related to changes in the abundance and biomass of particular dung beetle species or guilds rather than community-wide measures of abundance and biomass, highlighting the need to move beyond simplistic biodiversity-ecosystem functioning correlations to understand the functional consequences of habitat modification in high-diversity ecosystems.     

The effects of reduced-impact logging practices on soil animal communities in the Deramakot Forest Reserve in Borneo

The effectiveness of reduced-impact logging practices on the maintenance of biodiversity in Borneo has been recognized for some organisms (e.g., mammals). We investigated the effects of reduced-impact logging and conventional selective logging practices on biodiversity by using soil fauna as indicators of disturbance. The study sites were the production forests of the Deramakot Forest Reserve and the Tangkulap Forest Reserve in Sabah, Malaysian Borneo (5°14–30′ N, 117°11–36′ E). We compared macro- and mesofauna in a pristine forest with no logging, a reduced-impact logged forest in Deramakot Forest Reserve, and a conventionally logged forest in Tangkulap Forest Reserve.The mean density of soil macrofauna (excluding ants) did not differ significantly among the three forest categories (nested ANOVA, p > 0.05). This tendency was also seen in the density and species richness of Oribatida and Collembola, which showed little difference among forest categories. Nonmetrical multidimensional scaling (NMS) ordination diagrams revealed a different community composition in conventionally logged forest sites compared with the other sites. The scores for the NMS first or second axis of soil fauna were correlated with one or more of the values for density, diversity, and species composition of trees. A RELATE test showed the congruence between trees and the Collembola and Oribatida community composition between sites. The results implied that the soil fauna community composition was related to tree communities. In conclusion, the impacts of logging on decomposers in the soil animal communities have been mitigated by the introduction of reduced-impact logging in Deramakot Forest Reserve through the protection of tree vegetation. It is important to consider monitoring the influence of selective logging on soil fauna with regard to the dynamics of the species (or group) composition because total density and species (or group) richness of soil fauna displayed only a marginal response to the different logging practices.     

Comparing bird community responses to forest fragmentation in two lowland Central American reserves

Habitat loss and fragmentation reduce diversity of tropical bird communities, but the predictability of how communities in fragments disintegrate over time remains unclear. We compared bird community changes of two lowland forest reserves, La Selva Biological Station (LSBS), Costa Rica and Barro Colorado Island (BCI), Panama, both approximately the same size (1500 ha) and at similar latitude (9-10 N) in Central America. Both reserves are losing bird species despite LSBS’s connection to an existing large park (incomplete isolation) and BCI’s favorable location within a largely forested landscape. We examined characteristics of guilds and species lost from the sites to determine whether patterns were similar, and thus predictable. Some of the same guilds declined at both reserves, particularly insectivores and ground/understory nesters. At LSBS mixed-species flock participants, forest species, and burrow-nesters also declined or became extirpated disproportionately. At BCI edge species became extirpated. Body mass was a poor predictor of species and guild loss at both sites, except for carnivores at La Selva. Thus, fragmentation appears to influence some guilds more than others, but which species decline or disappear in tropical forest fragments is also influenced by site-specific factors, mostly yet to be determined. We need to understand such idiosyncratic effects of fragmentation better, rather than rely on one-size-fits-all management plans to conserve bird communities in tropical forest fragments.     

Habitat structure and proximity to forest edge affect the abundance and distribution of forest-dependent birds in tropical coastal forests of southeastern Madagascar

Despite the fact that Madagascar is classified a biological `hotspot' due to having both high levels of species endemism and high forest loss, there has been no published research on how Madagascan bird species respond to the creation of a forest edge or to degradation of their habitat. In this study, we examined how forest bird communities and different foraging guilds were affected by patch habitat quality and landscape context (forest core, forest edge and matrix habitat) in the threatened littoral forests of coastal southeastern Madagascar. We quantified habitat use and community composition of birds by conducting 20 point counts in each landscape contextual element in October and November 2002. We found that littoral forest core habitats had significantly (p<0.01) more bird species than forest edge and matrix habitats. Thirty-one (68%) forest dependent species were found to be edge-sensitive. Forest edge sites had fewer species, and a higher representation of common species than forest interior sites. Twenty-nine species were found in the matrix habitat, and the majority of matrix-tolerant forest species had their greatest abundance within littoral forest edge habitats. Guild composition also changed with landscape context. Unlike other tropical studies with which we are familiar, we found that frugivorous species were edge-sensitive while sallying insectivores were edge-preferring. The majority of canopy insectivores (n=15, 88%), including all six endemic vanga species, were edge-sensitive. When habitat quality was assessed, the distributions of nine edge-sensitive species were significantly (p<0.01) affected by changes in habitat complexity and vegetation vertical structure in core or edge point counts. Therefore, we believe that changes in vegetation structure at the edge of littoral forest remnants may be a key indicator of mechanisms involved in edge sensitivity of forest dependent species in these forests. Our findings indicate that habitat fragmentation and degradation affect Madagascan bird communities and that these processes threaten many species. With continued deforestation and habitat degradation in Madagascar, we predict the further decline of many bird species.     

Supply of tree-holes limits nest density of cavity-nesting birds in primary and logged subtropical Atlantic forest

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.     

Does forest type and vegetation patchiness influence horizontal distribution of soil Collembola in two neighbouring forest sites?

The influence of forest type and heterogeneity of understory vegetation on the horizontal distribution of soil living Collembola was studied in two neighbouring mountain forest sites—a 180-year old beech forest and a 70-year old natural spruce forest. Four homogenous patches with different understory vegetation were chosen within each forest site and sampled 12 times between 1997 and 1998. A total of 56 collembolan species were identified, 51 in the beech forest and 48 in the spruce site. Twenty-three species were rare—they were recorded with low constancy and density. Although both forest sites differed in soil type, humus form and soil chemical parameters, the species composition of their collembolan communities was quite similar (77% shared species). Nevertheless, soil collembolan communities of both forest sites were clearly delimited on both qualitative (presence–absence) and quantitative (in density of individual species) levels as well as in terms of total collembolan density. Mean collembolan density reached 26 650–44 030 ind/m² in the beech patches compared to 44 470–68 050 ind/m² found in the spruce patches. Considerably higher densities of several species in one forest site may indicate more suitable habitat. In spite of similar species composition and minor differences in qualitative parameters among different vegetation patches within one forest site, there was clear variation in density of individual species, particularly between patches with and without herb vegetation. This could reflect different microclimatic conditions, additional litter supply from herbs or indirect interactions of Collembola with their roots.     

Visible Ozone Injury on Forest Trees in Great Smoky Mountains National Park, USA

During the summer of 1991 ozone injury trend plots in Great Smoky Mountains National Park, USA, consisting of mature black cherry, sassafras and yellow-poplar were established near three ozone monitors, ranging in elevation from 597-1265 m. Beginning in mid-August 1991-1993, three exposed branches each from the upper- and mid- to lower-crown of each tree were collected and evaluated for ozone injury. Of the trees examined, 63%, 52% and 36% exhibited some amount of foliar injury in 1991, 1992 and 1993, respectively. Ozone injury across species was the greatest at Cove Mountain in all three years of the study. Overall, across sites and years, 11, 12 and 11% of all leaves examined exhibited visible injury for black cherry, sassfras and yellow-poplar, respectively. The percentage of injured leaves per branch was greater in the mid- to lower-canopy for black cherry, across all sites. Trees for each species that exhibited the greatest or least amounts of visible injury did so in all three years of the study, indicating a differential sensitivity within each species population. No significant ozone exposure-tree response relationships were observed with any variable tested. These data indicate that ozone concentrations are high enough to cause visible symptoms to selected trees within Great Smoky Mountains National Park, USA.     

Diversity and abundance of selected animal species in undisturbed forest,selectively logged forest and plantations in East Kalimantan,Indonesia

Animal surveys were conducted in six habitat types within the timber concession of PT International Timber Corporation Indonesia, East Kalimantan. Species diversity was found to be similar in undisturbed forest and in 3- to 5-year-old selectively logged forest, although densities in the latter were considerably less. Both diversity and density declined drastically in forestry plantations, but certain of the species remaining caused significant damage to young trees. Although few animals were observed in areas where there was active road construction and timber felling, their densities in adjacent undisturbed forest areas did not increase, suggesting that the level of local migration actually is low. It is suggested that recolonisation of old logged forest can occur successfully provide that the level of hunting is low and that adjacent areas of undisturbed forest remain to provide a population pool from which colonists can spread.     

Simulating anthropogenic impacts to bird communities in tropical rain forests

We used an aggregated modelling approach to simulate the impacts of anthropogenic disturbances on the long-term dynamics of faunal diversity in tropical rain forests. We restricted our study to bird communities even though the approach is more general. We developed a model called BioDiv which simulated the establishment of hypothetical bird species in a forest. Our model was based on the results of a simple matrix model which calculated the spatio-temporal dynamics of a tropical rain forest in Malaysia. We analysed the establishment of bird species in a secondary forest succession and the impacts of 60 different logging scenarios on the diversity of the bird community. Of the three logging parameters (cycle length, method, intensity), logging intensity had the most servere impact on the bird community. In the worst case the number of bird species was reduced to 23% of the species richness found in a primary forest.     

Composition of the microbial communities in the mineral soil under different types of natural forest

Phospholipid fatty acid (PLFA) patterns were used to describe the composition of the soil microbial communities under 12 natural forest stands including oak and beech, spruce-fir-beech, floodplain and pine forests. In addition to the quantification of total PLFAs, soil microbial biomass was measured by substrate-induced respiration and chloroform fumigation-extraction. The forest stands possess natural vegetation, representing an expression of the natural site factors, and we hypothesised that each forest type would support a specific soil microbial community. Principal component analysis (PCA) of PLFA patterns revealed that the microbial communities were compositionally distinct in the floodplain and pine forests, comprising azonal forest types, and were more similar in the oak, beech and spruce-fir-beech forests, which represent the zonal vegetation types of the region. In the nutrient-rich floodplain forests, the fatty acids 16:1ω5, 17:0cy, a15:0 and a17:0 were the most prevalent and soil pH seemed to be responsible for the discrimination of the soil microbial communities against those of the zonal forest types. The pine forest soils were set apart from the other forest soils by a higher abundance of PLFA 18:2ω6,9, which is typical of fungi and may also indicate ectomycorrhizal fungi associated with pine trees, and high amounts of PLFA 10Me18:0, which is common in actinomycetes. These findings suggest that the occurrence of azonal forest types at sites with specific soil conditions is accompanied by the development of specific soil microbial communities. The study provides information on the microbial communities in undisturbed forest soils which may facilitate interpretation of data derived from managed or even damaged or degraded forests.     

Lowland rainforest avifauna and human disturbance: persistence of primary forest birds in selectively logged forests and mixed-rural habitats of southern Peninsular Malaysia

We compared the composition and structure of primary forest avifauna among primary forests, selectively logged forests and mixed-rural areas (e.g. villages and agricultural areas) of Peninsular Malaysia. We found that forests that were selectively logged at least 30 years ago contained only 73-75% of the 159 species of extant primary forest birds, with an increased proportion of dominant species. We estimated that only 28-32% of the primary forest species utilized the mixed-rural habitat, and that the number of species that bred in the agricultural landscapes might be even lower. The microhabitat of different species most affected their vulnerability to disturbance. Most small, arboreal frugivores and omnivores, and insectivores that fed from tree trunks, showed greater persistence in the mixed-rural habitat than ground dwelling bird species, which were affected most by disturbance. Resource abundance and variables that were closely related to forest disturbance such as the density of large trees, density of dead trees, canopy cover density and shrub volume influenced the distribution of the primary forest birds. Large primary forest reserves and a revision of short-cycle logging regimes (ca. 30 years) are needed if we are to conserve the lowland rainforest avifauna of Peninsular Malaysia and other parts of Southeast Asia.     

Bird community responses to reduced-impact logging in a certified forestry concession in lowland Bolivia

We studied bird community composition and abundance within the logged and unlogged forest areas of a certified forestry concession in lowland Bolivia. The logged forest was harvested using reduced-impact logging techniques between one and four years previously. We used canonical correspondence analysis to describe the relationship between selected environmental variables and bird species abundance data, and the Indicator Value procedure to test for associations between bird species and the logged and unlogged habitats. Approximately one-third of birds were restricted to either the logged or unlogged areas, with 20% of all species only encountered in, or significantly more abundant in, the unlogged areas of the concession. The majority of birds found in significantly higher abundance in the unlogged areas of the concession were associated with forest habitats dominated by large trees, or a high diversity of trees, providing dense canopy cover and deep leaf litter, with an understorey dominated by ferns. Over 40% of bird species that were significantly associated with the unlogged areas of the concession are of conservation concern. In contrast, the majority of birds associated with the logged areas of the concession are known to be relatively resilient to human disturbance. The majority of species which exhibited significant lower abundances in the logged areas of the concession belonged to insectivorous or frugivorous feeding guilds. We discuss whether current management practices within this certified concession are sustainable and how our results can be used to guide future research and inform better practice.     

Bayesian spatial modeling of data from avian point count surveys

We present a unified framework for modeling bird survey data collected at spatially replicated survey sites in the form of repeated counts or detection history counts, through which we model spatial dependence in bird density and variation in detection probabilities due to changes in covariates across the landscape. The models have a complex hierarchical structure that makes them suited to Bayesian analysis using Markov chain Monte Carlo (MCMC) algorithms. For computational efficiency, we use a form of conditional autogressive model for modeling spatial dependence. We apply the models to survey data for two bird species in the Great Smoky Mountains National Park. The algorithms converge well for the more abundant and easily detected of the two species, but some simplification of the spatial model is required for convergence for the second species. We show how these methods lead to maps of estimated relative density which are an improvement over those that would follow from past approaches that ignored spatial dependence. This work also highlights the importance of good survey design for bird species mapping studies.     

Local and landscape factors determine functional bird diversity in Indonesian cacao agroforestry

Large-scale intensification of smallholder cacao management is currently affecting the agroforestry landscapes of Sulawesi (Indonesia), the world’s third largest cacao producer. Little is known about how this shift from diverse plantations to full-sun cacao will affect functionally important biodiversity within the agroecosystem, and how this is related to landscape-wide patterns in land-use and natural ecosystems. We recorded birds in 43 cacao plots differing in woody and herbaceous vegetation as well as distance to forest in two valleys around the Lore Lindu National Park in Central Sulawesi. Species richness of frugivores and nectarivores decreased with increasing distance to forest, whereas granivorous birds increased in richness. Forest specialists, but not habitat generalists, responded positively to forest edge proximity. Species richness of all functional groups except seed eaters increased at higher density of tall shade trees. Greater species richness of shade trees was associated with higher species richness of frugivores and nectarivores, while herbaceous vegetation did not have a strong impact on the avifauna. The positive effect of shade trees was independent of distance to forest. In conclusion, our study shows the relative importance of local and landscape effects on bird diversity with shade trees being critical for bird conservation in cacao agroforestry landscapes.     

Peat swamp forest avifauna of Central Kalimantan, Indonesia: Effects of habitat loss and degradation

Peat swamp forest is a unique wetland ecosystem covering extensive areas in Southeast Asia that has received relatively little scientific attention and is now being lost at a rapid pace. This study examines the effects of anthropogenic degradation on bird communities in disturbed peat swamp forest habitats – namely, intact logged forest, a degraded forest fragment, and non-forest regrowth – in Central Kalimantan, Indonesia. Results show that species richness was significantly higher and species composition significantly different in intact logged forest in comparison to the degraded forest fragment and non-forested area. Nectarivore and tree foliage-gleaning insectivore abundance declined outside the intact forest, while the regrowth was dominated by the yellow vented bulbul, an open country insectivore–frugivore. Surveys reveal that large intact tracts of logged peat swamp forest can harbour threatened and near threatened bird species (36% of records) and thus play a role in their conservation, especially for a few habitat specialists. Given the extent of unmanaged degraded peatlands and continuing pressure to development them, urgent conservation actions are needed to rehabilitate and protect this ecosystem.     

Six years of habitat modification in a tropical rainforest margin of Indonesia do not affect bird diversity but endemic forest species

Studies on temporal changes of tropical bird communities in response to habitat modification are rare. We quantified changes in bird assemblages at the rainforest margin of Lore Lindu National Park, Central Sulawesi, over an interval of 6 years. Standardized bird counts were conducted in the years 2001/2002 and 2008 at 15 census points representing natural forest, secondary forest, agroforest and openland sites. Although overall species richness remained nearly identical, different species groups were affected unequally by habitat modification within the forest margin landscape. The mostly endemic forest species declined in abundance (72.0% of forest species) and were detected at fewer census points in 2008 (56.0%). In contrast, 81.8% of the solely widespread openland birds became more abundant and 63.6% of the species were recorded at a larger number of census points. Hence, recent human activities in the forest margin ecotone negatively affected species of high conservation value. Species richness turned out to be a poor indicator of habitat change, and our results underline the importance of considering species identities. Biotic homogenization as result of habitat conversion is a global phenomenon. In our study, the winners were widespread openland species, while the losers were endemic forest birds. In conclusion, our study shows that 6 years of land-use change had negative impacts on bird community structure and endangered species, but not on overall bird species richness.     

The effects of extreme forest fragmentation on the bird community of Singapore Island

Singapore Island suffered one of the highest known deforestation rates in the tropics from the mid-to-late 19th century when over 95% of its native lowland forest was cleared. We compared the current bird community structure and composition among three habitat types, i.e., old (>50 years, 7-935 ha) and young (?50 years, 29-49 ha) naturally regenerating secondary forests and abandoned wooded plantations (27-102 ha) dominated by exotic species. Forest patch area had the strongest influence on the current species richness. The overall bird richness was not greater in most mature forest patches, but 20 species were only found in the old secondary forests and five of these were found in <50% of these patches. The rapid decrease in the number of forest species in plantations was offset by an increase in the number of open habitat species. Comparisons with current bird communities in nearby mainland forest sites (Peninsular Malaysia) suggest that the forest avifauna of Singapore is depauperate. The preservation of larger mature and maturing forests is therefore required for conserving the extant forest avifauna in Singapore. Connecting isolated patches can also be envisioned to facilitate movements of forest birds that have low densities and restricted distribution.