Anthropogenic Forest Disturbance Research Articles

A global synthesis and conceptualization of the magnitude and duration of soil carbon losses in response to forest disturbances.

Forest disturbances are increasing around the globe due to changes in climate and management, deteriorating forests' carbon sink strength. Estimates of global forest carbon budgets account for losses of plant biomass but often neglect the effects of disturbances on soil organic carbon (SOC). Here, we aimed to quantify and conceptualize SOC losses in response to different disturbance agents on a global scale. Global. 1983-2022. Forest soils. We conducted a comprehensive global analysis of the effects of harvesting, wildfires, windstorms and insect infestations on forest SOC stocks in the surface organic layer and top mineral soil, synthesizing 927 paired observations from 151 existing field studies worldwide. We further used global mapping to assess potential SOC losses upon disturbance. We found that both natural and anthropogenic forest disturbances can cause large SOC losses up to 60 Mg ha-1. On average, the largest SOC losses were found after wildfires, followed by disturbances from windstorms, harvests and insects. However, initial carbon stock size, rather than disturbance agent, had the strongest influence on the magnitude of SOC losses. SOC losses were greatest in cold-climate forests (boreal and mountainous regions) with large accumulations of organic matter on or near the soil surface. Negative effects are present for at least four decades post-disturbance. In contrast, forests with small initial SOC stocks experienced quantitatively lower carbon losses, and their stocks returned to pre-disturbance levels more quickly. Our results indicate that the more carbon is stored in the forest's organic layers and top mineral soils, the more carbon will be lost after disturbance. Robust estimates of forest carbon budgets must therefore consider disturbance-induced SOC losses, which strongly depend on site-specific stocks. Particularly in cold-climate forests, these disturbance-related losses may challenge forest management efforts to sequester CO2.

Environmental Stress and the Primate Microbiome: Glucocorticoids Contribute to Structure Gut Bacterial Communities of Black Howler Monkeys in Anthropogenically Disturbed Forest Fragments

Animals living in anthropogenically disturbed habitats are exposed to environmental stressors which can trigger physiological reactions, such as chronic elevations of glucocorticoid hormones. Physiological responses to stressors may induce changes in the gut microbiome, most likely, facilitated by the gut–brain communication. Although these effects have been observed in humans and animal models, elucidating gut bacterial changes in wild animals under natural stressful conditions is still an ongoing task. Here we analyzed the association between physiological stress related to anthropogenic forest disturbance and changes in gut bacterial communities of black howler monkeys (Alouatta pigra) living in forest fragments in Mexico. We measured individuals’ fecal glucocorticoid metabolites (fGCMs) as an index of physiological stress and created inventories of fecal bacterial communities sequencing the 16S rRNA gene to assess gut microbiome change. We evaluated environmental stress by estimating differences in food availability – feeding tree diversity and biomass – in each group’s habitat. We found that both fGCMs and food availability indices were related to gut bacterial community shifts in black howler monkeys. Furthermore, using structural equation modeling, we found that a decrease in food availability, estimated through reductions in feeding tree basal area, increased fGCMs, which in turn induced increases in bacterial richness. Our findings show that the activation of the hypothalamic–pituitary–adrenal (HPA)-axis, which is a physiological response sensitive to environmental stressors such as the ecological disturbance of a habitat, contributes to structure the gut microbiome of arboreal primates in disturbed forests.

Assessing the Old-Growth Dependency of Two Saproxylic Beetle Species in the Southern Appalachian Mountains

AbstractThe southern Appalachian Mountains were intensively logged during the early 1900s, leaving little remaining old-growth forest. Much of the region is now second-growth forest, which may not be suitable to specialist saproxylic species. Moreover, if suitable habitat exists, poorly dispersing species may not be able to colonize it. To investigate this, we assessed the distribution and old-growth dependency of two low-mobility saproxylic beetles in Great Smoky Mountains National Park. Using both field surveys and community science data, we found Megalodacne heros (Say 1823) (Coleoptera: Erotylidae) to be limited to lower elevations regardless of disturbance history, while Phellopsis obcordata (Kirby 1837) (Coleoptera: Zopheridae) was restricted to inside or near old-growth forests. Although trees were generally smaller in second-growth, we detected no habitat limitation for P. obcordata: fungal hosts were present in second-growth areas and the beetle was present on trees as small as 11 cm in diameter. This suggests its distribution is shaped by its low dispersal capability and need for temporal continuity of deadwood habitat, therefore qualifying it as an indicator species. For P. obcordata, old-growth acted as refugia during landscape-wide, anthropogenic disturbances in the early 1900s, though we can draw no conclusions about M. heros from our dataset. The difference in sensitivity to human disturbance displayed between species may be linked to their relative dispersal abilities: P. obcordata is entirely flightless while M. heros is capable of some flight. This study highlights the value of using saproxylic invertebrates with limited dispersal ability for assessing impacts from anthropogenic forest disturbances.

The diversity and distribution of lianas under various disturbance regimes in Chilimo dry Afromontane forest, Ethiopia

Lianas contribute substantially to plant diversity and to local people’s livelihood in tropical forests around the world. However, their species composition and the factors that determine their distribution in dry Afromontane forests are less explored. In this study, we quantified the diversity and density of lianas under various anthropogenic disturbance levels in Chilimo dry Afromontane forest of Ethiopia. We also assessed their importance to the local people. All woody species ≥10 cm and lianas having ≥1 cm diameter size at the point of measurement were recorded in 72, 20 m × 20 m plots distributed on seven transect lines with 2 km distance between transects. We found twenty-four woody vines that belong to 19 genera and 15 families, having an overall density of 1358 liana stems per hectare. These lianas contributed about 25% to the woody plant diversity of the study forest. Six liana-climbing modes were recorded. Stem twiners were predominant in terms of species richness while Scrambler armed climbers were the most abundant species. Liana species richness and abundance were significantly different among the low, moderate, and high forest disturbance levels (p < 0.05) and Liana diversity significantly reduced in highly disturbed forest plots (p < 0.01). Human disturbance indirectly hinders liana assemblage, as liana species richness and abundance showed a positive relationship (p < 0.05) with tree species richness and abundance. The five most abundant species were Carissa spinarum, Rubus steudneri, Rosa abyssinica, Jasminum abyssinicum, and Urera hypselodendron. All the enumerated liana species identified had medicinal, veterinary, food, fence, traditional house construction, fuelwood, grazing, artisan work, and honeybee forage importance to the local residents. Carissa spinarum, Clematis simensis, and Rosa abyssinica were found to be the most important species to the local people having 2, 1.54 and 1.53 importance value index, respectively. There is a need of implementing effective forest management through strengthening the ongoing participatory forest management program to reverse the negative impacts of anthropogenic forest disturbances and to sustain dry Afromontane lianas and their roles in biodiversity and socioeconomic aspects.

A late Holocene record of human impacts on tropical environments from non-pollen palynomorphs, Albertine Rift, western Uganda

AbstractNon-pollen palynomorphs and elemental geochemistry data from Lake Kifuruka in western Uganda provide evidence of environmental change in the tropical African region since the beginning of the Holocene. The multi-proxy record presented here shows that dry conditions dominated the end of the Pleistocene evidenced by calcium enriched sediments and suppressed fungal taxa activity. Moist conditions dominated the early Holocene and persisted until just after 1960 cal yr BP. Elevated frequencies of individual fungal spore taxa associated with herbivory and soil erosion, includingSordaria-type,Sporormiella-type,Chaetomium-type, andGlomus-type, about 4300 cal yr BP suggests a significant environmental change that could be linked to human activities. A convergence of multiple proxy data, including microscopic charcoal, elemental geochemistry, and fungal spores, strongly support the occurrence of anthropogenic forest disturbance in the Albertine Rift about 4300 cal yr BP.

Allee effects and soil nutrient changes mediated by experimental plantings of a nonindigenous, temperate liana

Liana abundance worldwide has the potential to increase due to elevated atmospheric CO2 concentrations and continued anthropogenic forest disturbance. Temperate forests have relatively low liana diversity compared to tropical forests, and it is believed this discrepancy has allowed nonindigenous lianas to disrupt temperate native communities to a greater degree. Due to their nature as structural parasites upon trees, the influence of lianas on forest systems is disproportionately greater than their modest contributions to aboveground biomass, yet the establishment of lianas into temperate communities has not been well studied. We designed a fully factorial experiment to investigate how density (intraspecific competition) and growth orientation (climbing vs. creeping) would influence growth and biomass allocation in wintercreeper (Euonymus fortunei, Celastraceae) an exotic evergreen liana. We also quantified soil nutrients prior to planting and after 17 months of soil conditioning to determine if wintercreeper influences nutrient availability. We found evidence of Allee effects, in which the highest density treatment yielded significantly greater total biomass (in both roots and shoots), longer stems, and higher specific stem length. Soil analyses indicated that wintercreeper significantly altered soil nutrients, increasing C, N, P, Ca, and Mg over the course of the experiment. These findings support previous studies, which found that wintercreeper tends to grow best in dense monoculture populations. While founder populations may be slow to establish, Allee effects combined with wintercreeper’s ability to modify nutrient cycling may help account for this species’ recent recognition as a serious plant-pest following a century of widespread cultivation.

Recent Deforestation Pattern Changes (2000–2017) in the Central Carpathians: A Gray-Level Co-Occurrence Matrix and Fractal Analysis Approach

The paper explores the distribution of tree cover and deforested areas in the Central Carpathians in the central-east part of Romania, in the context of the anthropogenic forest disturbances and sustainable forest management. The study aims to evaluate the spatiotemporal changes in deforested areas due to human pressure in the Carpathian Mountains, a sensitive biodiverse European ecosystem. We used an analysis of satellite imagery with Landsat-7 Enhanced Thematic Mapper Plus (Landsat-7 ETM+) from the University of Maryland (UMD) Global Forest Change (GFC) dataset. The workflow started with the determination of tree cover and deforested areas from 2000–2017, with an overall accuracy of 97%. For the monitoring of forest dynamics, a Gray-Level Co-occurrence Matrix analysis (Entropy) and fractal analysis (Fractal Fragmentation-Compaction Index and Tug-of-War Lacunarity) were utilized. The increased fragmentation of tree cover (annually 2000–2017) was demonstrated by the highest values of the Fractal Fragmentation-Compaction Index, a measure of the degree of disorder (Entropy) and heterogeneity (Lacunarity). The principal outcome of the research reveals the dynamics of disturbance of tree cover and deforested areas expressed by the textural and fractal analysis. The results obtained can be used in the future development and adaptation of forestry management policies to ensure sustainable management of exploited forest areas.

High microhabitat heterogeneity drives high functional traits in forest birds in five protected forest areas in the urban mosaic of Durban, South Africa

Anthropogenic forest disturbance poses a significant threat to the persistence of wildlife. Generally, disturbance of forest environments alters vegetation structure, affecting specialised niche-dependent avian species. We investigated the influence of a comprehensive suite of vegetation structures on the taxonomic and functional diversity of avian forest species in five protected forest areas in the urban mosaic of eThekwini Municipality, Durban, South Africa during the austral breeding season of 2016. We conducted 135 fixed-radius point-count surveys between the vegetation classes of Indigenous Forest (IF) and Coastal Thicket/Dense Bush (TDB; a secondary wooded-habitat that represents regenerating Indigenous Forest), and recorded microhabitat structure covariates at each survey site. We conducted RLQ analyses to examine the association between avian functional traits and microhabitat structures present at each survey site. There was no significant difference in vegetation structure nor species richness between IF and TDB. Species with specialised ecological niches (e.g. large-bodied frugivores; small-bodied insectivores, cavity-nesters) were present in both IF and TDB, indicating that TDB in Durban represents an advanced stage of forest regeneration. We highlight the importance of both IF and TDB for providing critical habitat for both avian generalised and specialised functional traits in the forest patches in the urban mosaic. Crucially, we show that forested areas under conservation management in urbanised areas successfully provide species with a wide variety of functional traits critical to ecosystem functioning and human health.

The Behavioral Economics of Biodiversity Conservation Scientists

Values have a profound influence on the behaviour of all people, scientists included. Biodiversity is studied by ecologists, like myself, most of whom align with the “mission-driven” field of conservation biology. The mission involves the protection of biodiversity, and a set of contextual values including the beliefs that biological diversity and ecological complexity are good and have intrinsic value. This raises concerns that the scientific process might be influenced by biases toward outcomes that are aligned with these values. Retrospectively, I have identified such biases in my own work, resulting from an implicit assumption that organisms that are not dependent on natural habitats (e.g., forests) effectively do not count in biodiversity surveys. Finding that anthropogenic forest disturbance reduces the diversity of plant species dependent on shady forests can thus be falsely equated with more general biodiversity loss. Disturbance might actually increase overall plant diversity (i.e., including all of the species found growing in a particular place). In this paper I ask whether ecologists share values that are unrepresentative of broader society, I discuss examples of potential value-driven biases in biodiversity science, and I present some hypotheses from behavioral economics on possible psychological underpinnings of shared values and preferences among ecologists.

Identifying thresholds of logging intensity on dung beetle communities to improve the sustainable management of Amazonian tropical forests

Selective logging is the most widespread driver of tropical forest disturbance. As such, it is critically important to identify at which spatial scale logging intensity should be measured and whether there are clear thresholds in the relationship between logging intensity and its impacts on biodiversity or ecological processes. We address this using a robust before-and–after logging experimental design in the Brazilian Amazon, using a gradient of logging intensity measured at two different spatial scales. We assessed the impacts of selective logging using dung beetle communities and their ecological functions of dung removal and soil bioturbation. Our findings provide novel empirical evidence that biological consequences from Reduced Impact Logging (RIL) depend strongly on the scale at which logging intensity is measured: dung beetle local species richness and composition were strongly associated with logging intensity measured at a 10ha scale, while dung beetle-mediated soil bioturbation was more strongly associated with logging intensity measured across 90ha. Contrary to expectations, we found concave-shaped relationships between logging intensity and biodiversity and ecosystem functioning, demonstrating that sensitive dung beetle species and important processes may be lost following even low intensity anthropogenic forest disturbances. Taken together, these results suggest that production forests in the tropics need to reconsider the scale at which logging intensity is regulated, and put in place measures that further incentivise land sparing to enhance biodiversity conservation.

Soil Organic Matter Responses to Anthropogenic Forest Disturbance and Land Use Change in the Eastern Brazilian Amazon

Anthropogenic forest disturbance and land use change (LUC) in the Amazon region is the main source of greenhouse gas emissions to the atmosphere in Brazil, due to the carbon (C) and nitrogen (N) emitted from vegetation clearance. Land use conversion associated with management practices plays a key role in the distribution and origin of C in different soil organic matter (SOM) fractions. Here, we show how changing land use systems have influenced soil C and N stocks, SOM physical fractions, and the origin of SOM in the Santarém region of the eastern Brazilian Amazon. Soil C and N stocks were calculated for the surface layer of 0–30 cm. Anthropogenic disturbances to the standing forest, such as selective logging and wildfires, led to significant declines in soil C and N stocks. However, in the long-term, the conversion of the Amazon forest to pasture did not have a noticeable effect on soil C and N stocks, presumably because of additional inputs from pasture grasses. However, the conversion to cropland did lead to reductions in soil C and N content. According to the physical fractionation of SOM, LUC altered SOM quality, but silt and clay remained the combined fraction that contributed the most to soil C storage. Our results emphasize the importance of implementing more sustainable forest management systems, whilst also calling further attention to the need for fire monitoring systems, helping to ensure the resilience of C and N stocks and sequestration in forest soils; thereby contributing towards urgently needed ongoing efforts to mitigate climate change.

Demographic stimulation of the obligate understorey herb,Panax quinquefoliusL., in response to natural forest canopy disturbances

SummaryNatural and anthropogenic forest canopy disturbances significantly alter forest dynamics and lead to multi‐dimensional shifts in the forest understorey. An understorey plant's ability to exploit alterations to the light environment caused by canopy disturbance leads to changes in population dynamics. The purpose of this work was to determine if population growth of a species adapted to low light increases in response to additional light inputs caused by canopy disturbance, or alternatively, declines due to long‐term selection under low light conditions.To address this question, we quantified the demographic response of an understorey herb to three contrasting forest canopy disturbances (ice storms, tent caterpillar defoliation and lightning strikes) that encompass a broad range of disturbance severity. We used a model shade‐adapted understorey species,Panax quinquefolius, to parameterize stage‐based matrix models. Asymptotic growth rates, stochastic growth rates and simulations of transient dynamics were used to quantify the population‐level response to canopy disturbance. Life table response experiments were used to partition the underlying controls over differences in population growth rates.Population growth rates at all three disturbed sites increased in the transition period immediately after the canopy disturbance relative to the transition period prior to disturbance. Stochastic population models revealed that growth rates increased significantly in simulations that included disturbance matrices relative to those simulations that excluded disturbance. Additionally, transient models indicated that population size (n) was larger for all three populations when the respective disturbance matrix was included in the model.Synthesis. Obligate shade species are most likely to be pre‐adapted to take advantage of canopy gaps and light influx to a degree, and this pre‐adaptation may be due to long‐term selection under dynamic old growth forest canopies. We propose a model whereby population performance is represented by a parabolic curve where performance is maximized under intermediate levels of canopy disturbance. This study provides new evidence to aid our understanding of the population‐level response of understorey herbs to disturbances whose frequency and intensity are predicted to increase as global climates continue to shift.

Anthropogenic disturbance in tropical forests can double biodiversity loss from deforestation.

Concerted political attention has focused on reducing deforestation, and this remains the cornerstone of most biodiversity conservation strategies. However, maintaining forest cover may not reduce anthropogenic forest disturbances, which are rarely considered in conservation programmes. These disturbances occur both within forests, including selective logging and wildfires, and at the landscape level, through edge, area and isolation effects. Until now, the combined effect of anthropogenic disturbance on the conservation value of remnant primary forests has remained unknown, making it impossible to assess the relative importance of forest disturbance and forest loss. Here we address these knowledge gaps using a large data set of plants, birds and dung beetles (1,538, 460 and 156 species, respectively) sampled in 36 catchments in the Brazilian state of Pará. Catchments retaining more than 69–80% forest cover lost more conservation value from disturbance than from forest loss. For example, a 20% loss of primary forest, the maximum level of deforestation allowed on Amazonian properties under Brazil’s Forest Code, resulted in a 39–54% loss of conservation value: 96–171% more than expected without considering disturbance effects. We extrapolated the disturbance-mediated loss of conservation value throughout Pará, which covers 25% of the Brazilian Amazon. Although disturbed forests retained considerable conservation value compared with deforested areas, the toll of disturbance outside Pará’s strictly protected areas is equivalent to the loss of 92,000–139,000 km2 of primary forest. Even this lowest estimate is greater than the area deforested across the entire Brazilian Amazon between 2006 and 2015 (ref. 10). Species distribution models showed that both landscape and within-forest disturbances contributed to biodiversity loss, with the greatest negative effects on species of high conservation and functional value. These results demonstrate an urgent need for policy interventions that go beyond the maintenance of forest cover to safeguard the hyper-diversity of tropical forest ecosystems.

Mapping dynamics of deforestation and forest degradation in tropical forests using radar satellite data

Mapping anthropogenic forest disturbances has largely been focused on distinct delineations of events of deforestation using optical satellite images. In the tropics, frequent cloud cover and the challenge of quantifying forest degradation remain problematic. In this study, we detect processes of deforestation, forest degradation and successional dynamics, using long-wavelength radar (L-band from ALOS PALSAR) backscatter. We present a detection algorithm that allows for repeated disturbances on the same land, and identifies areas with slow- and fast-recovering changes in backscatter in close spatial and temporal proximity. In the study area in Madre de Dios, Peru, 2.3% of land was found to be disturbed over three years, with a false positive rate of 0.3% of area. A low, but significant, detection rate of degradation from sparse and small-scale selective logging was achieved. Disturbances were most common along the tri-national Interoceanic Highway, as well as in mining areas and areas under no land use allocation. A continuous spatial gradient of disturbance was observed, highlighting artefacts arising from imposing discrete boundaries on deforestation events. The magnitude of initial radar backscatter, and backscatter decrease, suggested that large-scale deforestation was likely in areas with initially low biomass, either naturally or since already under anthropogenic use. Further, backscatter increases following disturbance suggested that radar can be used to characterize successional disturbance dynamics, such as biomass accumulation in lands post-abandonment. The presented radar-based detection algorithm is spatially and temporally scalable, and can support monitoring degradation and deforestation in tropical rainforests with the use of products from ALOS-2 and the future SAOCOM and BIOMASS missions.

Monitoring anthropogenic disturbance trends in an industrialized boreal forest with Landsat time series

Human transformation of the terrestrial biosphere via resource utilization is a critical impetus for monitoring and characterizing anthropogenic change to vegetation condition. The primary objective of this research was to detect anthropogenic forest disturbance for a recent Landsat time series. A novel combination of an autonomous change detection procedure and spectral classification scheme was applied and tested in a landscape that has undergone significant resource development over the last 30 years. Anthropogenic disturbance was detected with greater than 93% accuracy. Most disturbances were correctly classified as within ±1 year. The signal of anthropogenic disturbance was significant in the landscape, accounting for more than 91% of all disturbances and 86% of total disturbed area during the 23-year study period. The study demonstrated a robust approach for examining historical disturbance trends related to human-modification of the environment.

Coming down from the trees: Is terrestrial activity in Bornean orangutans natural or disturbance driven?

The orangutan is the world's largest arboreal mammal, and images of the red ape moving through the tropical forest canopy symbolise its typical arboreal behaviour. Records of terrestrial behaviour are scarce and often associated with habitat disturbance. We conducted a large-scale species-level analysis of ground-based camera-trapping data to evaluate the extent to which Bornean orangutans Pongo pygmaeus come down from the trees to travel terrestrially, and whether they are indeed forced to the ground primarily by anthropogenic forest disturbances. Although the degree of forest disturbance and canopy gap size influenced terrestriality, orangutans were recorded on the ground as frequently in heavily degraded habitats as in primary forests. Furthermore, all age-sex classes were recorded on the ground (flanged males more often). This suggests that terrestrial locomotion is part of the Bornean orangutan's natural behavioural repertoire to a much greater extent than previously thought, and is only modified by habitat disturbance. The capacity of orangutans to come down from the trees may increase their ability to cope with at least smaller-scale forest fragmentation, and to cross moderately open spaces in mosaic landscapes, although the extent of this versatility remains to be investigated.

Large vertebrate responses to forest cover and hunting pressure in communal landholdings and protected areas of the Yucatan Peninsula, Mexico

AbstractAlthough tropical forest vertebrate populations are often heavily impacted by both habitat loss and subsistence hunting, in many human‐dominated landscapes their fate depends on the wider habitat matrix outside protected areas. This study used line‐transect surveys to examine patterns of vertebrate species richness and encounter rates (ER) throughout Mexico's Yucatan Peninsula across a broad spectrum of anthropogenic forest disturbances. Censuses were carried out at eight forest sites, including two localities within the Sian Ka'an Biosphere Reserve, a communally managed protected area, a private forest reserve and three communal‐tenure landholding units. Species richness increased with increasing forest cover in the surrounding landscape, but was not affected by the degree of hunting pressure. Responses to different forms of disturbance varied markedly across species and functional groups. Aggregate ER of old‐growth specialists were positively correlated with forest cover, but unrelated to hunting pressure. Hunting pressure was strongly related to aggregate ER of game species, particularly of preferred prey, and a meta‐analysis of species‐specific correlations showed a significant effect of hunting pressure on the ER across individual game species. Sampling within old‐growth forest of Sian Ka'an yielded relatively high ER for almost all species. In comparison, low ER were obtained for several species at Sian Ka'an sites consisting of a higher proportion of open habitat. Landholding units showed low relative abundances, but species ER varied depending on disturbance type. The communally managed reserve exhibited high ER for both game and non‐game species. Synthesis of these results with comparable data from 19 additional Mesoamerican sites shows that species‐specific ER found across the Yucatan Peninsula are within the ranges observed elsewhere, with a consistent pattern of lower abundances in hunted sites. It is critical that private, communal and public‐sector reserves are integrated into a coordinated management approach across the wider landscape in this biodiversity hotspot and throughout the Mesoamerican Biological Corridor.

Assessing Ecosystem Restoration Alternatives in Eastern Deciduous Hardwood Forests Using Avian Nest Survival

The effects of anthropogenic forest disturbance on avian populations are only starting to be understood, with most research focusing on community richness and species abundance. Monitoring nesting survival is becoming an important and increasingly reliable method for assessing habitat quality. We investigated nest survival and Brown-headed Cowbird nest parasitism of 18 Neotropical migratory bird species in experimentally managed mixed-oak forests in southeast Ohio. We monitored nests during one pre-treatment year and four post-treatment years in four treatment plots: thin, burn, thin + burn, and unmanipulated control. Nesting activity was lower in the first two post-treatment years, but returned to pre-treatment levels in the last two post-treatment years. Overall post-treatment nesting success in the thin and thin + burn treatments exceeded that in the control and burn plots. Ground and shrub nesting species responded negatively to burning alone, but were not affected by the other treatments. Understory nesting success was initially lower in the burn and thin + burn treatments than in the thin only treatment, but increased in the thin and thin + burn treatment in the final two years. Furthermore, we observed bird species nesting in the thin and thin + burn treatments in the final two years that had not been recorded in the previous three years. Hence, the thinned habitats attracted secondary scrub nesting species. Nest heights were significantly higher in burn and thin + burn treatments. We did not detect Brown-headed Cowbird parasitism until the third and fourth years post-treatment, but nest parasitism was still low at 4.1% of active nests. Our results suggest that combining selective harvests (thinning) with prescribed fire is the best of these forest management plans when considering avian nest survival.

Management Decentralization and Montane Forest Conditions in Tanzania

We examined how differences in local forest-management institutions relate to disparate anthropogenic forest disturbance and forest conditions among three neighboring montane forests in Tanzania under centralized, comanaged, or communal management. Institutional differences have been shaped by decentralization reforms. We conducted semistructured interviews with members of forest management committees, local government, and village households and measured anthropogenic disturbance, tree structure, and species composition in forest plots. We assessed differences in governance system components of local institutions, including land tenure, decision-making autonomy by forest users, and official and de facto processes of rule formation, monitoring, and enforcement among the three management strategies. We also assessed differences in frequencies of prohibited logging and subsistence pole cutting, and measures of forest condition. An adjacent research forest served as an ecological reference for comparison of forest conditions. Governance was similar for comanaged and centralized management, whereas communal managers had greater tenure security and decision-making autonomy over the use and management of their forest. There was significantly less illegal logging in the communal forest, but subsistence pole cutting was common across all management strategies. The comanaged forest was most disturbed by recent logging and pole cutting, as were peripheral areas of the larger centralized forest. This manifested in more degraded indicators of forest conditions (lower mean tree size, basal area, density of trees >or= 90 cm dbh, and aboveground biomass and higher overall stem density). Greater tenure security and institutional autonomy of the communal strategy contributed to more effective management, less illegal logging, and maintenance of good forest conditions, but generating livelihood benefits was a challenge for both decentralized strategies. Our results underscore the importance of well-designed institutional arrangements in forest management and illustrate mechanisms for improved forest governance and conservation in the context of Tanzanian decentralization reforms.

Rapid assessments of tropical dung beetle and butterfly assemblages: contrasting trends along a forest disturbance gradient

Abstract. 1. We carried out rapid assessments of the richness and diversity of fruit‐feeding butterflies (sampled with baited traps) and dung beetles (sampled with buffalo dung‐baited pitfall traps) at 20 sites across an anthropogenic forest disturbance gradient in Ba Be National Park, Vietnam.2. We investigated measures of diversity, richness, and functional composition for individual taxa in relation to the degree of disturbance, and verified whether dung beetles and butterflies showed congruent trends.3. For butterflies, overall species richness increased with forest disturbance, but the richness of rare species decreased. Species diversity was uncorrelated with disturbance.4. In dung beetles, species richness was unrelated to forest disturbance, but species diversity increased with forest disturbance. The richness of dung beetles in the telecoprid (roller) guild declined with forest disturbance.5. There was no significant correlation between dung beetles and butterflies across sites for either species richness or species diversity.6. Apparent effects of disturbance were thus sensitive to the particular metric used (species richness or diversity), the taxonomic group studied (butterflies or dung beetles), and the functional group investigated (different guilds of dung beetle).