Unlogged Forest Research Articles

Deadwood stocks increase with selective logging and large tree frequency in Gabon.

Deadwood is a major component of aboveground biomass (AGB) in tropical forests and is important as habitat and for nutrient cycling and carbon storage. With deforestation and degradation taking place throughout the tropics, improved understanding of the magnitude and spatial variation in deadwood is vital for the development of regional and global carbon budgets. However, this potentially important carbon pool is poorly quantified in Afrotropical forests and the regional drivers of deadwood stocks are unknown. In the first large-scale study of deadwood in Central Africa, we quantified stocks in 47 forest sites across Gabon and evaluated the effects of disturbance (logging), forest structure variables (live AGB, wood density, abundance of large trees), and abiotic variables (temperature, precipitation, seasonality). Average deadwood stocks (measured as necromass, the biomass of deadwood) were 65Mg ha-1 or 23% of live AGB. Deadwood stocks varied spatially with disturbance and forest structure, but not abiotic variables. Deadwood stocks increased significantly with logging (+38Mg ha-1 ) and the abundance of large trees (+2.4Mg ha-1 for every tree >60cm dbh). Gabon holds 0.74Pg C, or 21% of total aboveground carbon in deadwood, a threefold increase over previous estimates. Importantly, deadwood densities in Gabon are comparable to those in the Neotropics and respond similarly to logging, but represent a lower proportion of live AGB (median of 18% in Gabon compared to 26% in the Neotropics). In forest carbon accounting, necromass is often assumed to be a constant proportion (9%) of biomass, but in humid tropical forests this ratio varies from 2% in undisturbed forest to 300% in logged forest. Because logging significantly increases the deadwood carbon pool, estimates of tropical forest carbon should at a minimum use different ratios for logged (mean of 30%) and unlogged forests (mean of 18%).

Rill erosion in burned and salvage logged western montane forests: Effects of logging equipment type, traffic level, and slash treatment

Following wildfires, forest managers often consider salvage logging burned trees to recover monetary value of timber, reduce fuel loads, or to meet other objectives. Relatively little is known about the cumulative hydrologic effects of wildfire and subsequent timber harvest using logging equipment. We used controlled rill experiments in logged and unlogged (control) forests burned at high severity in northern Montana, eastern Washington, and southern British Columbia to quantify rill overland flow and sediment production rates (fluxes) after ground-based salvage logging. We tested different types of logging equipment—feller-bunchers, tracked and wheeled skidders, and wheeled forwarders—as well as traffic levels and the addition of slash to skid trails as a best management practice. Rill experiments were done at each location in the first year after the fire and repeated in subsequent years. Logging was completed in the first or second post-fire year. We found that ground-based logging using heavy equipment compacted soil, reduced soil water repellency, and reduced vegetation cover. Vegetation recovery rates were slower in most logged areas than the controls. Runoff rates were higher in the skidder and forwarder plots than their respective controls in the Montana and Washington sites in the year that logging occurred, and the difference in runoff between the skidder and control plots at the British Columbia site was nearly significant (p=0.089). Most of the significant increases in runoff in the logged plots persisted for subsequent years. The type of skidder, the addition of slash, and the amount of forwarder traffic did not significantly affect the runoff rates. Across the three sites, rill sediment fluxes were 5–1900% greater in logged plots than the controls in the year of logging, and the increases were significant for all logging treatments except the low use forwarder trails. There was no difference in the first-year sediment fluxes between the feller-buncher and tracked skidder plots, but the feller-buncher fluxes were lower than the values from the wheeled skidder plots. Manually adding slash after logging did not affect sediment flux rates. There were no significant changes in the control sediment fluxes over time, and none of the logging equipment impacted plots produced greater sediment fluxes than the controls in the second or third year after logging. Our results indicate that salvage logging increases the risk of sedimentation regardless of equipment type and amount of traffic, and that specific best management practices are needed to mitigate the hydrologic impacts of post-fire salvage logging.

Temporal Decay in Timber Species Composition and Value in Amazonian Logging Concessions.

Throughout human history, slow-renewal biological resource populations have been predictably overexploited, often to the point of economic extinction. We assess whether and how this has occurred with timber resources in the Brazilian Amazon. The asynchronous advance of industrial-scale logging frontiers has left regional-scale forest landscapes with varying histories of logging. Initial harvests in unlogged forests can be highly selective, targeting slow-growing, high-grade, shade-tolerant hardwood species, while later harvests tend to focus on fast-growing, light-wooded, long-lived pioneer trees. Brazil accounts for 85% of all native neotropical forest roundlog production, and the State of Pará for almost half of all timber production in Brazilian Amazonia, the largest old-growth tropical timber reserve controlled by any country. Yet the degree to which timber harvests beyond the first-cut can be financially profitable or demographically sustainable remains poorly understood. Here, we use data on legally planned logging of ~17.3 million cubic meters of timber across 314 species extracted from 824 authorized harvest areas in private and community-owned forests, 446 of which reported volumetric composition data by timber species. We document patterns of timber extraction by volume, species composition, and monetary value along aging eastern Amazonian logging frontiers, which are then explained on the basis of historical and environmental variables. Generalized linear models indicate that relatively recent logging operations farthest from heavy-traffic roads are the most selective, concentrating gross revenues on few high-value species. We find no evidence that the post-logging timber species composition and total value of forest stands recovers beyond the first-cut, suggesting that the commercially most valuable timber species become predictably rare or economically extinct in old logging frontiers. In avoiding even more destructive land-use patterns, managing yields of selectively-logged forests is crucial for the long-term integrity of forest biodiversity and financial viability of local industries. The logging history of eastern Amazonian old-growth forests likely mirrors unsustainable patterns of timber depletion over time in Brazil and other tropical countries.

Efectos de diferentes métodos de corta de bosque nativo en el paisaje

This research consist on a public opinion study to find out, how three target groups - domestic tourists, foreign tourists and local communities- perceive different silvicultural methods of native forests. The analyzed logging systems are: uniform protection cuts, selective thinning, selective cuts, and protection cuts in strips. The studies were performed in three different regions: La Araucania, Los Rios and Magallanes. The overall objective of the study was to analyze the effects of the different cutting methods on the landscape and the social perception of these impacts. The general hypothesis is that sustainable interventions in native forests are not affecting significantly the landscape and may, even, be preferred to unlogged forests. The methodology consists of structured and semi -structured interviews, based on different sets of photographs of the different logging systems presented to, and evaluated by respondents. The total number of interviewed was 317 persons among domestic tourists, foreign tourists and local community members visiting protected areas. The selected sample has an error of 5.2 % at a confidence level of 95 %. In addition, an exploratory online survey w as conducted with the same questions being addressed to general public represented by a random sample of 509 persons. Most respondents spoke favorably for the sustainable management of native forests, i.e. a balanced use and protection of forests. The results show that sustainable intervened native forests are equally or even more preferred landscapes that natural forests without intervention. Therefore, well-managed forests can be considered landscapes with scenic value, attractive for tourists.

Recovery of biomass and merchantable timber volumes twenty years after conventional and reduced-impact logging in Amazonian Brazil

Concerns about the sustainability of tropical forestry motivated this study on post-logging timber and carbon dynamics over a 20-year period in Paragominas, Pará, Brazil. Previously unlogged forest was subjected to conventional logging (CL), reduced-impact logging (RIL), or was set aside as an unlogged control. All trees ⩾25cm DBH and all trees of commercial species ⩾10cm DBH were monitored in a 24.5ha plot in each treatment, with a 5.25ha subplot in each for monitoring all trees ⩾10cm DBH. Above-ground biomass and bole volumes of merchantable species were tracked based on 10 inventories made between 1993 and 2014. Pre-logging biomass and bole volumes of commercial species were estimated as 237, 231, and 211Mgha−1, and 78, 80, and 70m3ha−1, in the RIL, CL, and unlogged plots, respectively. One year after logging, biomass was reduced 14% by RIL and 24% by CL with corresponding merchantable species volume reductions of 21% and 31%. By 2014, biomass and bole volumes of commercial species had recovered 95% and 98% of their pre-logging stocks in the RIL plot but only 76% and 72% in the CL plot, respectively; timber volumes from large trees (⩾50cm DBH) were only recovered to 81% in the RIL plot and to 53% in the CL plot. Over the first twenty years after logging, average volume increments from commercial species were substantially higher in the RIL plot (0.72m3ha−1year−1) than in the CL plot (0.08m3ha−1year−1). Recovery of both biomass and timber volumes were temporarily reversed between 2009 and 2014 due to a 4-fold increase in annual mortality rates in the RIL plot and a 5.5-fold increase in the CL plot (as well as a 3-fold increase in the control plot), all presumably related to the extreme drought of 2010. Our findings support the claim that use of RIL techniques accelerates rates of biomass and timber stock recovery after selective logging.

Investigating the effect of selective logging on tree biodiversity and structure of the tropical forests of Papua New Guinea

Abstract: Unsustainable exploitation of tropical forest resources is raising worldwide concern. In Papua New Guinea (PNG) timber harvesting has been identified as a major contributor to deforestation and forest degradation but its impact on biodiversity is still poorly understood. In this study we investigated the effect of selective logging on tree taxonomic composition, structure and diversity of PNG forests. We used data from 101 one-hectare permanent sample plots (PSPs) belonging to two vegetation types: low altitude forests on plains and fans (type P) and low altitude forests on uplands (type H). We used multivariate techniques to test for significant differences in species composition between plots of different vegetation types and disturbance regimes, identifying the tree taxa to which these differences could be ascribed. ANOVA was used to test for differences between logged-over and unlogged forest PSPs with respect to biodiversity (richness, Shannon’s diversity, Pielou’s evenness) and stand structure (stem density, basal area - BA). Temporal trends of forest features were analyzed using linear regression. Significant differences in taxonomic composition were found between logged-over and unlogged plots of the H type (p = 0.04). No differences were found in richness, diversity and evenness between logged-over and unlogged forest plots, while stem density was higher in the latter (421 ± 153 stems ha-1). Greater BA was found in unlogged forests (30.28 ± 4.45 m2 ha-1) of the H type when compared to the logged-over stands (15.52 ± 4.04 m2 ha-1). We detected positive trends in richness (0.55 ± 0.19 taxa ha-1 yr-1) and diversity after logging. Furthermore, H type forest exhibited positive trends in stem density (9 ± 1 stems ha-1 yr-1) and BA (0.42 ± 0.06 m2 ha-1 yr-1) with elapsed time since harvesting. Our analysis highlights some significant effects of logging activities on biodiversity and structure of PNG forests. Additionally, forests exhibited a significant recovery with respect to richness, diversity and stand structure. These preliminary results will be compared with data collected by the forthcoming National Forest Inventory in order to assess and monitor the effects of human activities and ecological factors on PNG forest biodiversity and develop appropriate conservation measures and sustainable management strategies.

Long-term effects of selective logging on dipterocarp populations in the Pasoh Forest Reserve, Malaysia

Background: Selective logging alters tree growth, mortality and recruitment, and the subsequent population dynamics of trees. However, little information is available on how tree populations reduce local extinction in logged forests.Aims: We evaluated the effects of selective logging on tree performance and population dynamics of five dominant dipterocarp species in the Pasoh Forest Reserve, Malaysia.Methods: We used demographic data derived from a forest that was selectively logged in 1958 as well as those from an unlogged primary forest and constructed population transition matrix models to project the population dynamics.Results: The dipterocarp species studied showed minor differences in mortality and diameter growth, but there was a large difference in recruitment between logged and unlogged forest; populations in the logged forest had 10 times slower recruitment rates into the smallest size class than those in the primary forest. Population size structures differed between the two forest types but, despite a large difference in the recruitment rates, there were only minor differences in both asymptotic- and matrix-projected population growth rates.Conclusions: A single selective logging event had only minor impacts on the growth rates of dipterocarp trees in the Pasoh forest. But at the same time it had a large impact on the size structure of the dipterocarp populations through a reduction in recruitment showing that the impacts of selective logging are still seen on dipterocarp population after 50 years.

Factors influencing tree diversity and compositional change across logged forests in the Solomon Islands

Tropical forests in the Solomon Islands have been heavily logged in the last century. However, little is known about forest recovery dynamics across this region. Extrapolating findings from logged forests in tropical mainlands or large continental landbridge islands to isolated archipelagos such as the Solomons is inappropriate because succession and diversification patterns and processes differ between the former and latter. We compared the taxonomic diversity and composition of trees between unlogged forest and sites that were logged 10, 30 and 50years previously to provide an indication of the potential dynamics of these forests following timber harvesting. The distance to logging roads and to unlogged forest influenced post-logging recovery, emphasising the importance of edge effects in previously logged forests. At least in the first 50years after logging, tree-community composition did not appear to converge toward that in unlogged forests over time. Although species assemblages in logged forests generally tend to shift from light demanding-pioneers to old-growth species over time, a long-lived pioneer Campnosperma brevipetiolata dominated the forest even 50years after logging. We suggest that recovery of the tree community in logged forests has been hindered by the persistence of C. brevipetiolata, and suggest that it could be thinned via careful silviculture techniques to enhance growth of mature-phase forest species. Removal of such persistent, long-lived pioneer trees could potentially help to accelerate recovery of heavily logged forests.

Leaf litter decomposition rates in degraded and fragmented tropical rain forests of Borneo

AbstractPreviously extensive tracts of primary rain forest have been degraded by human activities, and we examined how the effects of forest disturbance arising from habitat fragmentation and commercial selective logging affected ecosystem functioning in these habitats by studying leaf litter decomposition rates in litter bags placed on the forest floor. The rain forests of Borneo are dominated by trees from the family Dipterocarpaceae, and we compared leaf litter decomposition rates of three dipterocarp species at eight forest fragment sites (area 3–3529 ha) that had different histories of disturbance pre‐fragmentation: four fragments had been selectively logged prior to fragmentation and four had been formed from previously undisturbed forest. We compared these logged and unlogged forest fragments with sites in continuous forest that had been selectively logged (two sites) and fully protected and undisturbed (two sites). After 120 d, undisturbed continuous forest sites had the fastest rates of decomposition (52% mass loss). Forest fragments formed from unlogged forest (32% mass loss) had faster decomposition rates than logged forest fragments (28% mass loss), but slower rates than continuous logged forest (39% mass loss). Leaves of a light‐demanding species (Parashorea malaanonan) decomposed faster than those of a shade‐tolerant species (Hopea nervosa), but decomposition of all three dipterocarp species that we studied responded similarly to logging and fragmentation effects. Reduced decomposition rates in logged and fragmented forest sites may affect nutrient cycling and thus have detrimental consequences for forest regeneration. Conservation management to improve forest quality should be a priority, particularly in logged forest fragments.

Persistence of mammals in a selectively logged forest in Malaysian Borneo

Many tropical mammals with important functional roles in forest ecosystems are threatened with extinction, yet how they respond to increasingly prevalent habitat disturbance, such as selective logging, is not well understood. We deployed 43 motion-triggered camera traps in 2013 and 2014 in unlogged forest and in a forest logged three decades previously in Malaysian Borneo. We used camera trap photographs to assess whether selective logging influenced the local abundance of medium to large-bodied ground-dwelling mammals. We focused our study on six locally common species: sambar deer, (Rusa unicolor), yellow muntjac (Muntiacus atherodes), chevrotains (Tragulus spp.), banded civet (Hemigalus derbyanus), Malay civet (Viverra tangalunga), and pig-tailed macaque (Macaca nemestrina). Occupancy models were used to estimate local abundance. None of the mammals in our study exhibited decreased abundance in logged forest, although yellow muntjac and pig-tailed macaque were associated with canopy height. Contiguous forest connects these two areas, allowing animal movement between them, potentially explaining the lack of responses. The elapsed time since logging may have further influenced our findings. The effects of logging on mammal local abundance may no longer detectable after 30 years. Overall, our results demonstrate the importance of regenerating forest as habitat for medium- to large-sized mammal species.

Trade-off between Desiccation and Predation Risk in the Blue Ridge Two-lined Salamander (Eurycea wilderae)

There has been increased attention on amphibian declines over the past two decades, and many researchers agree that the primary factor responsible for this decline is habitat fragmentation and degradation. A number of studies have begun to address the impacts of forest management practices on amphibian populations; however, information about behavioral responses of amphibians to forestry practices such as logging is still needed. Using laboratory experiments, I investigated the behavioral choices of Blue Ridge Two-lined Salamanders (Eurycea wilderae) when presented with dry and moist environments (representing logged and unlogged forests) both with and without predators. When no predator was present, E. wilderae preferred a moist environment. When a predator was present in the moist environment, the adult E. wilderae preferred to remain in the less suitable dry environment, while juveniles displayed no clear choice. After logging, E. wilderae are faced with a decision between two adverse environments, wit...

Effect of reduced-impact logging on seedling recruitment in a neotropical forest

Seedling growth and survival are critical for tropical rainforest regeneration. Alterations to natural disturbance regimes, such as those brought about by logging, have the potential to shift relative species abundances and the community composition of forests, resulting in population declines for commercially valuable species. Timber operations therefore need to minimise such changes if long-term sustainability is to be achieved within the industry. Reduced-impact logging (RIL) has been promoted widely as an alternative management strategy to conventional selective logging, as it employs practices that decrease the negative impacts of logging within forests. However, the long-term sustainability of RIL, including the influence it has on the regeneration of species targeted for timber extraction, is still uncertain. Here we undertake a comparative study in Iwokrama forest, Guyana, examining seedling densities of four commercially valuable and two pioneer tree species in unlogged, 1.5years and 4.5years postharvest forest plots to ascertain how seedling regeneration is effected by RIL. We find that RIL had either a neutral or positive impact on the density of seedlings of timber species when compared to unlogged forest, with pioneer species densities remaining rare. We conclude that the forestry practices associated with RIL have little effect on the natural regeneration rates of key commercially valuable tree species in logged neotropical forests.

Towards the development of multifunctional molecular indicators combining soil biogeochemical and microbiological variables to predict the ecological integrity of silvicultural practices.

SummaryThe impact of mechanical site preparation (MSP) on soil biogeochemical structure in young larch plantations was investigated. Soil samples were collected in replicated plots comprising simple trenching, double trenching, mounding and inverting site preparation. Unlogged natural mixed forest areas were used as a reference. Analysis of soil nutrients, abundance of bacteria and gas exchanges unveiled no significant difference among the plots. However, inverting site preparation resulted in higher variations of gas exchanges when compared with trenching, mounding and unlogged natural forest. A combination of the biological and physicochemical variables was used to define a multifunctional classification of the soil samples into four distinct groups categorized as a function of their deviation from baseline ecological conditions. According to this classification model, simple trenching was the approach that represented the lowest ecological risk potential at the microsite level. No relationship was observed between MSP method and soil bacterial community structure as assessed by high‐throughput sequencing of bacterial 16S rRNA gene; however, indicator genotypes were identified for each multifunctional soil class. This is the first identification of multifunctional molecular indicators for baseline and disturbed ecological conditions in soil, demonstrating the potential of applied microbial ecology to guide silvicultural practices and ecological risk assessment.

Microclimatic edge effects in a recently harvested forest: Do remnant forest patches create the same impact as large forest areas?

Microclimatic forest influence (edge effects into open or regenerating areas) occurs within harvested forest, but the depth and magnitude may change depending on the design of the harvested area. This is an important consideration for managers, because gradients in microclimate can significant affect the ability of species to recolonise following disturbance. One harvesting method that can increase the amount of forest influence is aggregated retention. This technique involves leaving groups of trees (aggregates) within the harvested area, thus increasing the amount of regenerating forest that is near to an edge and therefore under forest influence. However, differences in the scale of forest influence generated from aggregates compared to unlogged forests surrounding harvested areas have not been tested. Understanding the ability of retained aggregates to generate forest influence is important in designing and implementing aggregated retention harvesting practices.This study tested whether retained aggregates generated similar levels of forest influence as mature forest surrounding harvested areas. Microclimatic forest influence was examined by monitoring spatial changes in air temperature and relative humidity along transects running from within standing mature forest into harvested forest. Intact forest and aggregate transects were located in the direction of maximum expected forest influence (south-facing edges). Results showed that forest influence was mostly similar in both depth and magnitude regardless of the type of forest from which it was generated. Temporal examination of forest influence showed that it changed throughout the day and across the year, with peaks in magnitude occurring during the middle of the day, and in months close to the equinoxes. Shade derived from standing trees was a potential driver of temporal patterns in microclimatic forest influence.At its peak magnitude, the microclimatic forest influence observed will likely have significant impacts on habitat suitability and thus, presumably, species recolonisation after disturbance. Results indicated that aggregated retention is an effective method for generating forest influence within harvested areas. Therefore, aggregated retention has the potential to be a valuable harvesting technique to alter microclimate and have beneficial impacts on the recovery of harvested forests.

Facing complexity in tropical conservation: how reduced impact logging and climatic extremes affect beta diversity in tropical amphibian assemblages

AbstractBiodiversity in pristine forest biomes is increasingly disturbed by human activity. Drivers such as logging and climate extremes are thought to collectively erode diversity, but their interactions are not well understood. However, ignoring such complexities may result in poor conservation management decisions. Here, we present the first study dealing with the complexity arising from the effects of interactions of two increasingly important disturbance factors (selective logging and climatic extreme events) on beta diversity patterns at different scales. Specifically, we examined extensive amphibian assemblage datasets obtained within a quasi‐experimental pre‐/post‐harvesting scheme in the lowland rainforests of Central Guyana. Changes in small‐scale patterns of beta diversity were not detectable at the higher landscape level, indicating that local‐scale dynamics are more informative for evaluating disturbance impacts. The results also underscore the importance of including abundance data when investigating homogenization or heterogenization effects, which should be considered when designing post‐logging impact assessments and selecting impact indicators. Moreover, logging should be regarded as a multifaceted driver that contributes to changes in biodiversity patterns in different ways, depending on interactions with other drivers. The effects of extreme climate events were significantly more pronounced in unlogged forest, while logged forest assemblages appeared buffered due to the presence of novel habitats. Imprudent post‐logging renaturation measures may thus counteract conservation targets. These findings highlight the fact that indicator bias and unaccounted interactions between multiple drivers can lead to misguided management strategies.

Does selective logging change ground-dwelling beetle assemblages in a subtropical broad-leafed forest of China?

Selective logging with natural regeneration is advocated as a near-to-nature strategy and has been implemented in many forested systems during the last decades. However, the efficiency of such practices for the maintenance of forest species are poorly understood. We compared the species richness, abundance and composition of ground-dwelling beetles between selectively logged and unlogged forests to evaluate the possible effects of selective logging in a subtropical broad-leafed forest in southeastern China. Using pitfall traps, beetles were sampled in two naturally regenerating stands after clearcuts (ca. 50 years old, stem-exclusion stage: selectively logged 20 years ago) and two mature stands (> 80 years old, understory re-initiation stage: selectively logged 50 years ago) during 2009 and 2010. Overall, selective logging had no significant effects on total beetle richness and abundance, but saproxylic species group and some abundant forest species significantly decreased in abundance in selectively logged plots compared with unlogged plots in mature stands. Beetle assemblages showed significant differences between selectively logged and unlogged plots in mature stands. Some environmental characteristics associated with selective logging (e.g., logging strategy, stand age, and cover of shrub and moss layers) were the most important variables explaining beetle assemblage structure. Our results conclude that selective logging has no significant impacts on overall richness and abundance of ground-dwelling beetles. However, the negative effects of selective logging on saproxylic species group and some unlogged forest specialists highlight the need for large intact forested areas for sustaining the existence of forest specialist beetles.

Survey of the reptiles of the montane forests near Dorrigo on the north coast of New South Wales

Reptile surveys were conducted in the early 1990s in the Dorrigo Forest Management Area, an area formerly comprising timber-production forests managed by the Forestry Commission of New South Wales. The surveys consisted of searches for reptiles along 54 transects together with targeted surveys. Twenty-two 500 m transects were located in previously logged forest and 32 in unlogged forest. Each transect was surveyed twice at an average seven days apart in the spring-summer of 1993 by two persons simultaneously for a duration of 90 min each. A total of 26 reptile species were detected during systematic surveys and 22 reptile species during targeted diurnal searches and opportunistic sightings. The highest species richness and density of reptiles were recorded in the logged New England Hardwood and Gorge Red Gum forest types. The Moist Hardwood type, with a closed mid-canopy had the lowest reptile species richness and density. Neither species richness nor number of individuals varied significantly with loggin...

Sleeping Sites of Spider Monkeys (Ateles geoffroyi) in Logged and Unlogged Tropical Forests

Selective logging can have negative effects on biodiversity and on key ecological processes such as seed dispersal and forest regeneration. Yet, the effect that timber extraction has on animal behavior and habitat use is poorly known. We tested whether the density, distribution, and composition of sleeping sites used by spider monkeys (Ateles geoffroyi) differed between two logged and two unlogged forest sites in the Calakmul region, southeastern Mexico. We recorded a total of 74 sleeping sites (0.11 sleeping sites/ha). The density of sleeping sites did not differ between forest conditions. Most (97%) sleeping sites were located in medium-stature semievergreen forest, and only 3% in low-stature seasonally inundated forest. In three of four sites, the number of sleeping sites in core areas was significantly greater than expected by chance, showing an aggregated spatial distribution, particularly in areas containing a greater density of feeding trees. About half (51%) of the sleeping sites were composed of a single large tree (mean ± SD diameter at breast height, 42.2 ± 21.9 cm) from a small number of tree species, such as Lonchocarpus castelloi, Bucida buceras, and Lysiloma latisiliquum. These results suggest that the current level of timber extraction seems to have no effect on the density, distribution, and composition of sleeping sites. Nevertheless, because the species that were selected as sleeping trees are subject to timber extraction, the availability of sleeping sites is expected to decrease in coming decades, potentially modifying the habitat use of this primate species.

Effect of selective logging on soil organic carbon dynamics in tropical forests in central and western Africa

Changes in soil organic carbon (SOC) as a consequence of selective logging activities are often neglected in tropical areas, even within activities that aim to promote the permanence of forest C stocks (e.g. REDD+). In this context, we assessed the magnitude of the impact of selective logging on the SOC levels in three chronosequences in Ghana, Cameroon and Gabon. In each chronosequence, from unlogged forest to forest that was selectively logged at different times in the past, adjacent plots were investigated by sampling the soil at various depths to 1 m. Both SOC concentrations and stocks drastically decrease after selective logging in all sites. The 0–5 cm depth represents the layer with the most evident SOC decreases, particularly in the first and second decades after selective logging. The SOC loss is later stabilised, but the C levels remain lower than those of the unlogged forest 45–50 years after selective logging. In all the investigated chronosequences, the SOC levels are strongly affected by selective logging and the soils continue losing C for many years. In conclusion, SOC measurements should be used to provide precise C emission-removal estimates also for forests managed using sustainable management practices.

Selective logging: Do rates of forest turnover in stems, species composition and functional traits decrease with time since disturbance? – A 45 year perspective

Selective logging, the targeted harvesting of timber trees in a single cutting cycle, is globally rising in extent and intensity. Short-term impacts of selective logging on tropical forests have been widely investigated, but long-term effects on temporal dynamics of forest structure and composition are largely unknown. Understanding these long-term dynamics will help determine whether tropical forests are resilient to selective logging and inform choices between competing demands of anthropogenic use versus conservation of tropical forests. Forest dynamics can be studied within the framework of succession theory, which predicts that temporal turnover rates should decline with time since disturbance. Here, we investigated the temporal dynamics of a tropical forest in Kibale National Park, Uganda over 45years following selective logging. We estimated turnover rates in stems, species composition, and functional traits (wood density and diameter at breast height), using observations from four censuses in 1989, 1999, 2006, and 2013, of stems ⩾10cm diameter within 17 unlogged and 9 logged 200×10m vegetation plots. We used null models to account for interdependencies among turnover rates in stems, species composition, and functional traits. We tested predictions that turnover rates should be higher and decrease with increasing time since the selective logging event in logged forest, but should be less temporally variable in unlogged forest. Overall, we found higher turnover rates in logged forest for all three attributes, but turnover rates did not decline through time in logged forest and was not less temporally variable in unlogged forest. These results indicate that successional models that assume recovery to pre-disturbance conditions are inadequate for predicting the effects of selective logging on the dynamics of the tropical forest in Kibale. Selective logging resulted in persistently higher turnover rates, which may compromise the carbon storage capacity of Kibale’s forest. Selective logging effects may also interact with effects from other global trends, potentially causing major long-term shifts in the dynamics of tropical forests. Similar studies in tropical forests elsewhere will help determine the generality of these conclusions. Ultimately, the view that selective logging is a benign approach to the management of tropical forests should be reconsidered in the light of studies of the effects of this practice on long-term forest dynamics.