Pre-logging Levels Research Articles

Recovery of species composition over 46 years in a logged Australian tropical forest following different intensity silvicultural treatments

Currently, more than 400 million hectares of tropical forests worldwide are now being managed for timber production. Understanding the long-term responses of tropical forests to management practices is critical for managing tropical forests sustainably. To investigate the responses of tropical forest dynamics to different silvicultural treatment intensities, permanent plots were established in 1967 in an Australian tropical forest with four treatments: selective logging only as a control and selective logging followed by three differing intensity silvicultural treatments in 1969. We investigated changes in the number of species, species dominance, and species composition of trees (DBH ≥ 10 cm) from 1967 to 2015. Before selective logging, the number of tree species did not differ between the treatments, ranging from 70 to 75. Selective logging alone had small immediate effects on the number of species and species abundance distributions. After silvicultural treatment, the number of species in the low-intensity treatment, medium-intensity treatment and high-intensity treatment were reduced to 48, 42, and 18 respectively. The number of species in the control, low-intensity, and medium-intensity treatments recovered to their pre-logging levels within 46 years, but recovery in the high-intensity treatment was incomplete due to much greater initial species loss through silvicultural treatment. Silvicultural treatments increased species dominance, with the differences being progressively more marked as the level of treatment intensity increased. Over 46 years, tree species abundance distribution in the silvicultural treatments became more even and largely returned to pre-logging conditions, with more rapid recovery after low and intermediate silvicultural treatments. Following silvicultural treatments, species composition in the logging only, low-intensity and medium-intensity silvicultural treatments did not change markedly, whereas species composition was substantially altered by high-intensity silvicultural treatment and was subsequently distinct from the other treatments. Within 46 years following treatments, species composition in the high intensity treatment showed a recovery trajectory towards pre-logging conditions, leading to increased species compositional similarity among the four treatments. Increasing the intensity of silviculture treatment led to greater time required for recovery of species diversity, composition and compositional similarity. We recommend that high-intensity silvicultural treatments should be avoided if rapid recovery of species diversity and composition is the desired management outcome in tropical rainforests similar to those in our study area.

Quantifying uncertainty about forest recovery 32-years after selective logging in Suriname

The inclusion of managed tropical forests in climate change mitigation has made it important to find the sustainable sweet-spot for timber production, carbon retention, and the quick recovery of both. Here we focus on recovery of aboveground carbon and timber stocks over the first 32years after selective logging with the CELOS Harvest System in Suriname. Our data are from twelve 1-ha permanent sample plots in which growth, survival, and recruitment of trees ≥15cm diameter were monitored between 1978 and 2012. We evaluate plot-level changes in basal area, stem density, aboveground carbon, and timber stock in response to average timber harvests of 15, 23, and 46m3ha−1. We use a linear mixed-effects model in a Bayesian framework to quantify recovery time for aboveground carbon and timber stock, as well as annualized increments for both. Our statistical models accounted for the uncertainty associated with the height and biomass allometries used to estimate aboveground carbon and increased precision of annualized aboveground carbon increments by including data from forty-one plots located elsewhere on the Guiana Shield. The probabilities of aboveground carbon recovery to pre-logging levels 32years after harvests of 15, 23 and 46m3ha−1 were 45%, 40%, and 24%, respectively. Net aboveground carbon increment for logged forests across all harvest intensities was 0.64MgCha−1yr−1, more than twice the rate observed in unlogged forests (0.26MgCha−1yr−1). The probabilities of timber stock recovery at the end of the 32-year period were highest after harvest intensities of 15 and 23m3ha−1 (with 80% probability) and lowest after the harvest of 46m3ha−1 (with 70% probability). Timber stock recovery across all harvest intensities was driven primarily by residual tree growth. Application of the legal cutting limit of 25m3ha−1 will require more than 70 and 40years to recover aboveground carbon and timber stocks, respectively, with 90% probability. Based on the low recruitment rates of the twelve species harvested, the 25year cutting cycle currently implemented in Suriname is too short for long-term timber stock sustainability. We highlight the value of propagating uncertainty from individual tree measurements to statistical predictions of carbon stock recovery. Ultimately, our study reveals the trade-offs that must be made between timber and carbon services as well as the opportunity to use carbon payments to enable longer cutting rotations to capture carbon from forest regrowth.

Carnation Creek watershed experiment—long‐term responses of coho salmon populations to historic forest practices

AbstractThe Carnation Creek project is a long‐term study of the effects of forestry practices on a small coastal watershed (11 km2) located in southwestern Vancouver Island. Initiated in 1970, this pretreatment versus post‐treatment case study consists of 5 years of preharvest, 6 years of during‐harvest, and now, 34 years of postharvest research. Forty‐one percent of the watershed was clearcut from 1976 to 1981. One tributary sub‐basin (1.1 km2) was left as an unharvested reference drainage. Riparian treatments varied from clearcuts to a variable‐width buffer. Fish population responses to logging have been complex, and specific to species and life stages. Stream warming due partly to riparian harvest increased the growth and survival of juvenile coho salmon and elevated smolt production by 65% for nearly three decades. These relatively short‐term thermal benefits offset the effects of riparian clearcutting which included accelerated bank erosion, streambed scour, loss of stable in‐stream wood, and sediment movement downstream. Landslides in 1984 greatly amplified these effects but took more than 20 years to propagate downstream to reduce fish habitat complexity and increase streambed instability and sediment transport over the entire portion inhabited by anadromous salmon. These delayed impacts have surpassed the thermal‐related benefits for coho salmon. Fry‐to‐smolt overwinter survival has declined from a mean of 50% between 1982 and 2004 to 15% since 2005. Coho salmon smolt production has consequently been reduced to below prelogging levels. Results show that forestry‐related alterations may take decades to fully develop and persist for decades longer without watershed and stream channel restoration.

Recruitment, growth and recovery of commercial tree species over 30 years following logging and thinning in a tropical rain forest

Sustainable production of timber from commercial species across felling cycles is a core challenge for tropical silviculture. In this study, we analysed how the intensity and type (harvesting and thinning) of silvicultural interventions affect: (a) recruitment of small stems (5cm⩽DBH<15cm), (b) increment of future crop trees (15cm⩽DBH<50cm) and (c) recovery of harvestable growing stocks (DBH⩾50cm) of 52 commercial timber species in the Tapajós National Forest, Brazil. Intervention intensities comprised logging (on average 61m3ha−1) and associated damage to remaining trees (1982) and thinning (refinement) to reduce basal area at the stand level (1993/1994). These interventions together resulted in a gradient of reduction in basal-area from 19 to 53% relative to pre-logging stocks. Trees (DBH⩾5cm) were measured on eight occasions in 41 permanent sample plots of 0.25ha each. The dynamics were analysed at the stand level over 30years and compared among treatments (including unlogged forest) and to pre-logging stands. Recruitment and growth temporarily increased following interventions and recovery of harvestable growing stock decreased with intervention intensity. Harvesting substantially increased recruitment of small stems relative to the unlogged forest, but recruitment rates decreased over time and did not increase following thinning. Gross increment of future crop trees was higher in logged than in unlogged forest and increased over time with high intensity of follow-up thinning, where it remained significantly higher than in control plots over time. Increased recruitment rates and volume increments were mainly driven by long-lived pioneer species, changing the composition of the growing stock. In 2012, recovery of harvestable growing stock of the 22 species harvested in 1982 varied between 19% and 57% in logged treatments relative to pre-logging levels. When considering an additional group of 30 species that were not harvested in the permanent sample plots but are now potentially commercial, relative recovery increased enough to support a second harvest under the present regulations (maximum harvest of 30m3ha−1), except for treatment with high thinning intensity where stocks were still less than 30% relative to pre-harvest levels. In contrast, light and medium thinning intensity promoted recovery of harvestable growing stock. These findings indicate that intensive thinning should be avoided and silvicultural interventions oriented towards future crop trees of target species should be adopted. This may enhance recovery and reduce unintended changes in composition of the commercial growing stock.

Avian responses to selective logging shaped by species traits and logging practices.

Selective logging is one of the most common forms of forest use in the tropics. Although the effects of selective logging on biodiversity have been widely studied, there is little agreement on the relationship between life-history traits and tolerance to logging. In this study, we assessed how species traits and logging practices combine to determine species responses to selective logging, based on over 4000 observations of the responses of nearly 1000 bird species to selective logging across the tropics. Our analysis shows that species traits, such as feeding group and body mass, and logging practices, such as time since logging and logging intensity, interact to influence a species' response to logging. Frugivores and insectivores were most adversely affected by logging and declined further with increasing logging intensity. Nectarivores and granivores responded positively to selective logging for the first two decades, after which their abundances decrease below pre-logging levels. Larger species of omnivores and granivores responded more positively to selective logging than smaller species from either feeding group, whereas this effect of body size was reversed for carnivores, herbivores, frugivores and insectivores. Most importantly, species most negatively impacted by selective logging had not recovered approximately 40 years after logging cessation. We conclude that selective timber harvest has the potential to cause large and long-lasting changes in avian biodiversity. However, our results suggest that the impacts can be mitigated to a certain extent through specific forest management strategies such as lengthening the rotation cycle and implementing reduced impact logging.

Carbon Stocks and Fluxes in Tropical Lowland Dipterocarp Rainforests in Sabah, Malaysian Borneo

Deforestation in the tropics is an important source of carbon C release to the atmosphere. To provide a sound scientific base for efforts taken to reduce emissions from deforestation and degradation (REDD+) good estimates of C stocks and fluxes are important. We present components of the C balance for selectively logged lowland tropical dipterocarp rainforest in the Malua Forest Reserve of Sabah, Malaysian Borneo. Total organic C in this area was 167.9 Mg C ha−1±3.8 (SD), including: Total aboveground (TAGC: 55%; 91.9 Mg C ha−1±2.9 SEM) and belowground carbon in trees (TBGC: 10%; 16.5 Mg C ha−1±0.5 SEM), deadwood (8%; 13.2 Mg C ha−1±3.5 SEM) and soil organic matter (SOM: 24%; 39.6 Mg C ha−1±0.9 SEM), understory vegetation (3%; 5.1 Mg C ha−1±1.7 SEM), standing litter (<1%; 0.7 Mg C ha−1±0.1 SEM) and fine root biomass (<1%; 0.9 Mg C ha−1±0.1 SEM). Fluxes included litterfall, a proxy for leaf net primary productivity (4.9 Mg C ha−1 yr−1±0.1 SEM), and soil respiration, a measure for heterotrophic ecosystem respiration (28.6 Mg C ha−1 yr−1±1.2 SEM). The missing estimates necessary to close the C balance are wood net primary productivity and autotrophic respiration.Twenty-two years after logging TAGC stocks were 28% lower compared to unlogged forest (128 Mg C ha−1±13.4 SEM); a combined weighted average mean reduction due to selective logging of −57.8 Mg C ha−1 (with 95% CI −75.5 to −40.2). Based on the findings we conclude that selective logging decreased the dipterocarp stock by 55–66%. Silvicultural treatments may have the potential to accelerate the recovery of dipterocarp C stocks to pre-logging levels.

Long-term responses of rainforest erosional systems at different spatial scales to selective logging and climatic change

Long-term (21-30 years) erosional responses of rainforest terrain in the Upper Segama catchment, Sabah, to selective logging are assessed at slope, small and large catchment scales. In the 0.44 km(2) Baru catchment, slope erosion measurements over 1990-2010 and sediment fingerprinting indicate that sediment sources 21 years after logging in 1989 are mainly road-linked, including fresh landslips and gullying of scars and toe deposits of 1994-1996 landslides. Analysis and modelling of 5-15 min stream-suspended sediment and discharge data demonstrate a reduction in storm-sediment response between 1996 and 2009, but not yet to pre-logging levels. An unmixing model using bed-sediment geochemical data indicates that 49 per cent of the 216 t km(-2) a(-1) 2009 sediment yield comes from 10 per cent of its area affected by road-linked landslides. Fallout (210)Pb and (137)Cs values from a lateral bench core indicate that sedimentation rates in the 721 km(2) Upper Segama catchment less than doubled with initially highly selective, low-slope logging in the 1980s, but rose 7-13 times when steep terrain was logged in 1992-1993 and 1999-2000. The need to keep steeplands under forest is emphasized if landsliding associated with current and predicted rises in extreme rainstorm magnitude-frequency is to be reduced in scale.

Longer-term water use of native eucalyptus forest after logging and regeneration: The Coranderrk experiment

The Coranderrk Project, located 70 km east of Melbourne, is Australia’s longest-running paired catchment study. Three small catchments (“Slip Creek”, “Blue Jacket Creek”, and “Picaninny Creek”) originally carrying old growth mountain ash and mixed species have been gauged since 1958. In 1971/72 Picaninny Creek catchment was substantially clear-felled and regenerated, predominantly with mountain ash (Eucalyptus regnans). The annual flow increased for the next 3 years (relative to the control), reaching a peak of almost 300 mm increase relative to the control catchment. Flow then declined; 8 years after the logging the annual flow had returned to pre-logging levels. Annual flow then continued to decline with a maximum reduction of around 200 mm per annum. Thirty-four years after logging the flow was still below the pre-treatment flow and showing no sign of recovery, although there were year to year variations associated with rainfall and drought. In 1972/73 Blue Jacket Creek had a “sawmiller selection” cutting in which approximately 50% of the basal area was removed. The response was a similar but muted version of the Picaninny Creek response. A statistical analysis used 1 year of the pre-treatment period to establish error limits. This showed that in both cases there was a statistically significant increase in flow followed by a statistically significant decrease in flow relative to old growth. Measurement of two of the catchments is continuing.

Sediment deposition in streams adjacent to upland clearcuts and partially harvested riparian buffers in boreal forest catchments

The rates of fine sediment deposition were compared among three logged and three reference stream reaches 2–3 years before and 3–4 years after logging to assess the environmental impacts of partial harvesting as a novel riparian management strategy for boreal forest streams. The partial-harvest logging resulted in 10, 21 and 28% average basal area removal from riparian buffers at the three logged sites, adjacent to upland clearcut areas. No significant differences from pre-logging or reference-site sedimentation patterns were detected for two of the three logged sites. At the site with the most intense riparian logging (WR2), significant increases of 3–5 times higher than pre-logging or reference levels were detected in fine inorganic sediment (250–1000 μm) load and accumulation in the first year after logging, but no significant change was detected in fine organic sediments or very fine sediments (0.5–250 μm). The increased inorganic sediment deposition at WR2 was temporary with no significant differences from reference or pre-logging levels detectable by summer of the second post-logging year. Logging impacts on fine sedimentation in streams appeared to have been mitigated by careful logging practices including winter harvesting in riparian areas to reduce ground disturbance, and a tendency to avoid immediate (within 3–5 m) stream-side areas. Where it is feasible and advisable to conduct partial harvesting in riparian buffers of boreal forest streams, the logging can be conducted without posing significant risk of increased sediment inputs to streams when careful logging practices are followed.

Temporal and Spatial Turbidity Patterns Over 30 Years in a Managed Forest of Western Washington1

Abstract: Forest practices have progressively changed over the last 30 years in the Pacific Northwest to address water quality concerns. There have been some assessments of these new management practices made at a site scale but very few studies have attempted to evaluate their efficacy at reducing cumulative sediment production at a watershed scale. Such an evaluation is difficult due to the spatial and temporal variability in sediment delivery and transport processes. Due to this inherent variability, detecting a response to management changes requires a long‐term data record. We utilized a water quality dataset collected over 30 years at four locations in the Deschutes River watershed (western Washington) to assess trends in turbidity and whether sediment control procedures implemented over this time period had any detectable influence. The sample sites ranged from small headwater streams (2.4 and 3.0 km2) to the mainstem of the Deschutes River (150 km2). Declining trends in turbidity were detected at all the permanently monitored sites. The mainstem Deschutes River site, which integrates sediment processes from the entire study watershed, showed dramatic declines in turbidity even with continued active forest management. For the small basins, logging and road construction occurred in the 1970s and 1980s and turbidity declined thereafter, achieving prelogging levels by 2000. There are no temporal trends in flow that could be responsible for the observed trends in turbidity. Our results suggest that increased attention to reducing sediment production from roads and minimizing the amount of road runoff reaching stream channels has been the primary cause of the declining turbidity levels observed in this study.

Effects of selective logging on tropical forest tree growth

We combined measurements of tree growth and carbon dioxide exchange to investigate the effects of selective logging on the Aboveground Live Biomass (AGLB) of a tropical rain forest in the Amazon. Most of the measurements began at least 10 months before logging and continued at least 36 months after logging. The logging removed ∼15% of the trees with Diameter at Breast Height (DBH) greater than 35 cm, which resulted in an instantaneous 10% reduction in AGLB. Both wood production and mortality increased following logging, while Gross Primary Production (GPP) was unchanged. The ratio of wood production to GPP (the wood Carbon Use Efficiency or wood CUE) more than doubled following logging. Small trees (10 cm &lt; DBH &lt; 35 cm) accounted for most of the enhanced wood production. Medium trees (35 cm &lt; DBH &lt; 55 cm) that were within 30 m of canopy gaps created by the logging also showed increased growth. The patterns of enhanced growth are most consistent with logging‐induced increases in light availability. The AGLB continued to decline over the study, as mortality outpaced wood production. Wood CUE and mortality remained elevated throughout the 3 years of postlogging measurements. The future trajectory of AGLB and the forest's carbon balance are uncertain, and will depend on how long it takes for heterotrophic respiration, mortality, and CUE to return to prelogging levels.

Regeneration changes in tree species abundance, diversity and structure in logged and unlogged subtropical rainforest over a 36-year period

The long-term effects of logging treatments on rainforest regeneration are difficult to quantify due to compounding interactions with natural dynamics, site characteristics and tree species. The aim of this study was to examine regeneration differences over a 36-year period in stands subjected to various levels of disturbance ranging from natural, through an increasing intensity of individual tree removal to intensive logging. Multivariate and univariate analyses of trees ≥10 cm diameter at 1.3 m above the ground (dbh) showed that regeneration responses were generally correlated with disturbance gradient. In the undisturbed controls there were gradual changes that had no significant effects on tree species richness and diversity, stem density, or diameter distribution. Gradual changes were also observed during the early stages of regeneration following logging. However, in logged sites changes in tree species richness and diversity, stem density and diameter distribution became more rapid with time, and significant changes were observed. Similar regeneration events across site and disturbance levels resulted in three identifiable stages. In the first stage, lasting about 10 years, stem density of abundant shade tolerant trees decreased with no discernable changes in tree species richness. In the second stage, also lasting about 10 years, tree species richness and diversity, as well as stem density decreased to minima due to localised species turnover and net mortality. In the third stage, recruitment surpassed mortality and reversed the net loss of both species and stems, as tree species assemblages began to return to pre-disturbance levels. Sites subjected to individual tree selective logging returned to their pre-logging states in all aspects within 35 years of logging, but diameter distribution of trees ≥40 cm dbh showed low density compared to that observed in the controls. After 15–30 years, sites subjected to more intensive logging returned to their pre-logging levels of stem densities, species abundance and richness, but after 35–44 years of regeneration this sites had low species diversity and high densities of both the small sized stems and shade intolerant tree species. More intensively logged sites also had a low density of shade tolerant tree species compared to the controls. This suggests that the restoration of forest structure takes considerably longer than the restoration of tree species richness and abundance following logging in these forests. A high rate of stand basal area growth and a modest diameter distribution of lager trees ≥40 cm dbh were observed in moderate tree selection logging. This indicates high timber production potential at moderate tree selection rate in this type of forest. However, if the stem size distribution of larger trees is to be maintained, a logging cycle longer than 50 years is necessary.

Dynamics of Tree Diversity in Undisturbed and Logged Subtropical Rainforest in Australia

In subtropical rainforest in eastern Australia, changes in the diversity of trees were compared under natural conditions and eight silvicultural regimes over 35 years. In the treated plots basal area remaining after logging ranged from 12 to 58 m^{2}/ha. In three control plots richness differed little over this period. In the eight treated plots richness per plot generally declined after intervention and then gradually increased to greater than original diversity. After logging there was a reduction in richness per plot and an increase in species richness per stem in all but the lightest selective treatments. The change in species diversity was related to the intensity of the logging, however the time taken for species richness to return to pre-logging levels was similar in all silvicultural treatments and was not effected by the intensity of treatment. These results suggest that light selective logging in these forests mainly affects dominant species. The return to high diversity after only a short time under all silvicultural regimes suggests that sustainability and the manipulation of species composition for desired management outcomes is possible.

A comparison of orang-utan density in a logged and unlogged forest on Sumatra

Several studies have shown that there is a strong decline in orang-utan densities shortly after logging. Nevertheless, there is little information on whether orang-utan densities return to their pre-logging values when logged forest is left to recover. This study investigates the orang-utan density in a 22-year-old selectively logged forest and compares it with the orang-utan density in a nearby ecologically similar primary forest. The results show that the orang-utan density did not differ significantly between primary forest and the selectively logged forest. Since we found no difference in fruit availability between the selectively logged and primary forest, we suggest that the selectively logged forest regenerated sufficiently well to sustain pre-logging levels of orang-utans. This study confirms previous studies that suggest fruit availability is the best ecological predictor of orang-utan densities and found a positive overall correlation between orang-utan density and fruit availability. The food attraction hypothesis, which explains local fluctuations in orang-utan density as a result of variation in fruit availability, was not supported.

Impacts of plantation development, harvesting schedules and rotation lengths on the rare snail Tasmaphena lamproides in northwest Tasmania: a population viability analysis

Tasmaphena lamproides is a rare snail found in northwest Tasmania. The species is eliminated by logging but re-establishes a population in ∼20-year-old native forest regeneration and builds up to pre-logging levels by ∼60 years. Major plantation development is planned within the range of the species. It is unlikely that T. lamproides will reinvade areas converted to plantation. To aid the conservation of T. lamproides the managing authority planned to retain a “biodiversity spine” (i.e. a string of contiguous coupes (logging units) that would be regenerated to native forest rather than converted to plantation) within areas earmarked for major plantation development. A PVA was used to assess the comparative impacts of different forest management scenarios. The management scenarios modelled involved differing levels of reservation, differing levels of native forest regeneration or conversion to plantation, different rotation lengths for native forest regeneration and different temporal patterns of logging of native forest. In a forest block with a major reserve simulations indicated that the population would decline to around 50% of the original population and thereafter remain fairly stable. For a forest block earmarked for plantation development where no major reserves occurred, simulations indicated the population would undergo a steep decline to around 20% of the original population. The extent of the recovery of the population before re-harvesting of the native forest coupes depended on the extent of the biodiversity spine. The probability of reaching low absolute population levels (<one or two thousand individuals) varied with the degree of plantation development but not linearly. Increasing the length of the rotation of native forest coupes lowered the probability of reaching low absolute numbers as did increasing the spread of logging of coupes over the length of the rotation rather than logging all of the coupes over a short time span. The model allows the managing authority to design a management scenario that meets a specific quantitative goal, such as a less than 10% probability of numbers falling below 1000 individuals. It also allows them to choose between a mix of different forest management strategies that could all potentially provide the same level of conservation benefit.

Short-term impacts of logging on understorey vegetation in a jarrah forest

Summary In 1985, new silvicultural treatments were implemented in jarrah (Eucalyptus marginata) forests available for wood production. As part of a scientific investigation into the ecological impacts of two of these treatments, gap cutting and shelterwood cutting, a survey was conducted 4 years after logging to examine the effects of these treatments on understorey vegetation species richness and abundance. Sampling scale was found to be an important factor affecting the results and subsequent interpretation of impacts. At the coupe scale, native plant species richness in unlogged coupe buffers was similar to that in adjacent logged patches. However, the mean number of species per 1 m2 was 20%-30% higher in the unlogged buffers than the logged patches. At all sampling scales, the abundance (number of individual plants) of native plants was 20%-35% higher in the buffers, but the abundance of introduced (weed) species was significantly higher in the logged patches. The abundance of weeds, which are mostly annual grasses and short-lived herbs, is likely to diminish with time. The time to recovery of native species abundance and the ecological significance of this is uncertain. Given the reported low seedling regeneration rate and limited dispersal capacity of many woody shrubs and perennial herbs, they are unlikely to return to pre-logging levels in the medium term. We attribute the reduction in the abundance of native plants mainly to mechanical soil disturbance, which ranged from 60% to 80% of the area of logged coupes, physical damage to the vegetation associated with logging and to intense heating of the topsoil during the post-logging silvicultural burn. Recommendations are made for reducing the negative impacts of logging operations on the understorey.

Nitrogen export from a watershed subjected to partial salvage logging.

Logging has been shown to induce nitrogen (N) leaching. We hypothesized that logging a watershed that previously exhibited forest decline symptoms would place additional stress on the ecosystem and result in greater N loss, compared to harvesting vigorous forests. We conducted a 10-year (1988 to 1998) assessment of N export from the Baldwin Creek watershed in southwestern Pennsylvania that was partially clearcut to salvage dead and dying northern red oak. N export from the watershed increased significantly following salvage logging operations and did not completely return to prelogging levels by the end of the study period. The largest annual NO3-N export of 13 kg/ha was observed during the first year after harvesting, an increase of approximately 10 kg/ha. Compared to data from other Appalachian Mountain watersheds in North Carolina, West Virginia, and Pennsylvania, calculated N loss for Baldwin Creek was considerably greater. Longer periods of reduced N uptake due to slow revegetation of salvage logged areas, coupled with increased amounts of N available to leaching, could have accounted for the large N losses observed for Baldwin Creek. Salvage logging of dead and dying trees from forested watersheds in this region appears to have the potential to result in much larger N losses than previously reported for harvest of healthy stands.

Simulated effects of logging on carbon storage in dipterocarp forest

Summary 1. As the role of forestry‐based options for reducing or mitigating greenhouse gas emissions is debated by policymakers, there is a need to inform the debate by synthesizing existing information on carbon dynamics in tropical forest systems and by applying this information to a range of possible interventions in forestry. 2. To investigate the consequences of reductions in logging damage for ecosystem carbon storage, we constructed a model to simulate changes in biomass and carbon pools following logging of primary dipterocarp forests in south‐east Asia. We adapted a physiologically driven tree‐based model of natural forest gap dynamics (FORMIX) to simulate forest recovery following logging. 3. Following selective logging, simulated ecosystem carbon storage declined from prelogging levels (213 Mg C ha−1) to a low of 97 Mg C ha−1, 7 years after logging. Carbon storage in biomass approached prelogging levels about 120 years after logging. 4. The relationship between fatal stand damage and ecosystem carbon storage was not linear, with biomass recovery following logging severely limited by 50–60% stand damage. 5. Results from simulations suggest that when 20–50% of the stand is killed during logging, replacing persistent forest species with pioneer tree species can reduce the site's potential for carbon storage by 15–26% over 40–60 years. 6. Reducing fatal damage from 40% to 20% of the residual stand, as was the case with a pilot project in Malaysia, was associated with an increase of 36 Mg C ha−1 in mean carbon storage over 60 years. 7. Efforts to monitor and verify the benefits, either through carbon sequestration in new growth or carbon retention in existing biomass, of offset projects involving tropical forests and natural forest management should focus on above‐ground biomass, particularly the large trees. Selection of the most appropriate allometric equations for a site and species is important because of their influence on biomass estimates.

Effects of variable-intensity logging and the influence of habitat variables on the distribution of the Greater Glider Petauroides volans in montane forest, southeastern New South Wales

Populations of arboreal marsupials were assessed in forests before and after logging at different levels of logging intensity to determine the sensitivity of these species to habitat disturbance. The logging treatments imposed were unlogged controls and two intensities of integrated logging for sawlogs and woodchips. The mean basal area of trees retained in logged blocks ranged from 83% to 35% of pre-logging levels. The objective of the study was to develop better methods for managing arboreal marsupials within the wood production forests of southeastern New South Wales. Seven species of arboreal marsupials were recorded during the study, but the Greater Glider Petauroides volans was the only species recorded in sufficient numbers for analysis (86% of all records). No significant differences were observed between the treatments in counts of the Greater Glider before and after logging. However, given the observed trend and an a priori expectation of a decline in numbers of this species following intensive logging, a one-tailed statistical test was applied which resulted in a significant difference at P = 0.08 for the contrast between the unlogged controls and the most intensively logged treatment. The existence of a threshold in logging intensity within the range of 21 % to 39% retention of tree basal area, below which numbers of the Greater Glider suffer a marked decline, was inferred on the basis of comparisons with the results of other studies. Factors other than logging were important in determining the distribution of the Greater Glider. Elevation, in particular, was a significant environmental variable, with Greater Gliders more likely to occur in forests above 845 m a.s.1. The presence and absence of particular tree species also influenced the distribution of the Greater Glider. Forests containing Manna Gum E. viminalis and Mountain Gum E. dalrympleana were highly preferred compared to forests with a high proportion of E. obliqua. The presence of E. cypellocarpa appeared to improve the quality of habitat for the Greater Glider in forests dominated by E. obliqua. This study has shown that Greater Glider populations can be maintained at or near pre-logging levels when at least 40% of the original tree basal area is retained thoughout logged areas and when the usual practice of retaining unlogged forest in riparian strips is applied.

Changes following 60 years of selective timber harvesting in the Budongo Forest Reserve, Uganda

The controlled extraction of timber from the Budongo Forest Reserve began in the 1930s. From the start of the operations it was intended that the timber should be harvested on a sustainable yield basis and the first of several 10-year working plans for the forest was drawn up in 1933. This paper documents the volume of timber removed, the date of logging, date of arboricide treatment and volume of arboricide applied in most compartments in the forest. Four species of mahogany formed about 65% of the timber extracted and this remained almost constant over the years despite attempts to encourage the use of other species by the Uganda Forest Department. Forest type maps made from sets of aerial photographs taken in 1951 and 1990 showed an increase in ‘mixed forest’ at the expense of ‘ Cynometr forest’; one of the major aims of the arboricide treatment. Ordination of the basal areas of the common tree species showed that the geographical position of a compartment explained more of the variation in species distribution than the variation between adjacent logged and unlogged compartments. A more detailed inventory of all species of tree in eight compartments across the forest showed greater species richness in the west of the forest and greater species richness in logged compartments. Measures of forest structure showed that more than 50 years is required for the forest to recover to pre-logging levels.