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Silvicultural treatment effects on commercial timber volume and functional composition of a selectively logged Australian tropical forest over 48 years
... Forest logging, when performed in an intense and/or unplanned manner, can hinder the process of tree establishment and growth, natural regeneration, and consequently, forest maintenance (Francez et al., 2013). Although there are studies indicating that species diversity is little affected after logging Jardim et al., 2008;Baraloto et al., 2012;Jardim and Quadros, 2016;Naves et al., 2020), several studies report changes in the original floristic structure and composition (Ruschel, 2008;Reis et al., 2010;Hirai et al., 2012), which may alter the community profile in the long term (Karsten et al., 2013;Darrigo et al., 2016;Hu et al., 2020). ...
... There was a decrease in floristic similarity in all strata and stages of development of the forest in relation to the initial post-logging conditions, indicating the effect of this anthropic disturbance on the composition of species. Variation in floristic composition after a disturbance is mainly associated with species gain and loss after intervention; generally, these changes occur during the initial forest recovery phase (Hu et al., 2018(Hu et al., , 2020. At km 114 of the Tapajós National Forest, this same variation in floristic composition was observed after the application of different intensities of silvicultural treatments. ...
... The disturbance of the forest structure (canopy openings) modifies the amount of light and heat that penetrates the canopy, with species being favored or disadvantaged to different degrees (de Avila et al., 2015). In general, the greatest changes in the natural regeneration structure of a post-disturbance forest are seen in the early years (Carvalho et al., 2004;de Carvalho et al., 2017); however, depending on the intensity at which it occurs, the changes may persist for a long time (Hu et al., 2018(Hu et al., , 2020. ...
Several studies indicate that the Amazon rainforest is home to the greatest biodiversity of tree species on the planet. The unique quality of this forest typology is under constant threat of change owing to the behavior of climate variables and different anthropic activities that occur in the biome itself. Therefore, it is essential to conduct studies that clarify the factors that affect the formation of forests in this ecosystem and to validate the use of forest resources by society through appropriate forest management practices. Thus, this study aimed to answer how the structure, composition and floristic diversity of the forest are influenced by forest logging in different phases of development of a local Amazonian forest, and whether there is a relationship between these attributes and regional and global climate factors. This study assessed the dynamics of natural regeneration of 36 permanent plots over 33 years after logging in the Tapajós National Forest in Belterra, State of Pará, Brazil. The plots studied were measured in 1981, 1983, 1985, 1987, 1992, 1997, 2007, and 2012. All individuals with height greater than 30 cm and diameter at breast height <10 cm were monitored in three regeneration strata (seedlings, saplings, and small trees) and three forest classes (gap-phase forest, growing forest, and old-growth forest). Density, floristic similarity according to the Sørensen Index, and floristic diversity according to the Hill series were analyzed. Climate variables such as mean annual compensated temperature; total annual precipitation, and Oceanic Niño Index were correlated with the mortality, recruitment, and density of growing trees. An ANOVA for count data verified that the density of individuals differed over time since logging among the regeneration strata and forest classes analyzed. Likewise, the diversity profiles generated from the Hill series were significantly different from each other, and the floristic similarity varied between regeneration strata over time. For the forest classes, the similarity values ranged between 50% and 96%. The gap-phase forest areas had the lowest similarity values, with some 100% dissimilar surveys. However, there was an exponential reduction in similarity over time in the different forest classes. The results indicate that logging promotes significant changes in floristic structure and diversity in different strata of natural regeneration and forest classes over time. Additionally, no correlation was found between climate variables and the natural regeneration dynamics in the Tapajós National Forest.
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... There are few woody lianas, but climbing palms (Calamus muelleri H. Wendl.) are abundant in the understory and subcanopy. Further information about the study site and changes in species composition over the 48 years can be found in Hu et al. (2018Hu et al. ( , 2020. ...
... Following selective logging in 1968, four treatments were applied in September 1969. Thinning practices were originally designed to promote the proportion, recruitment and growth of commercial timber species, predominantly Flindersia species (Hu et al., 2020). The objective of different intensity thinning practices was to assess which thinning intensity would promote the highest commercial timber volume. ...
... paper, low grade construction timber). From this perspective, our study also suggests that there is high potential of sustainably managed tropical secondary forests to act as substantial carbon sinks as well as reservoirs for forest biodiversity provided that there are sufficiently long logging rotation periods (Putz et al., 2012;Hu et al., 2018;Hu et al., 2020). Unfortunately, cutting cycles are often far too short (Dauber et al., 2005). ...
... Further, greater gap frequency and higher understory light in logged forests compared to unlogged forests can benefit species with specific life-history strategies and related functional traits (Baraloto et al., 2012;Döbert et al., 2017;Addo-Fordjour et al., 2020), and impact ecosystem services of logged forests. The species that benefit most from these environmental shifts immediately after logging are typically fast-growing, light-demanding pioneer species (de Carvalho et al., 2017) that tend to have low wood density (Baraloto et al., 2012;Hu et al., 2020) and abiotic seed dispersal (Rahayu et al., 2022;Carvalho et al., 2022), in contrast to the shade-tolerant species that are typically slow-growing and tend to have high wood density and animal-dispersed seeds. Thus, these species may have a competitive advantage and regenerate in higher abundances in early life stages soon after logging. ...
... Other studies that have explored how selective logging impacts functional composition in tropical forests found that logged forests have reduced wood density (Baraloto et al., 2012;Hu et al., 2020) and differences in dispersal mode and life-history strategy (Döbert Points refer to the proportion of timber individuals per 20×20 m plot. Boxes represent inter-quartile range (IQR), lines in the center represent the median. ...
... By knowing the volume of logs needed, we can estimate how much the area of NF and PF must be prepared to meet these requirements, as shown in Figure 3. In Figure 4, a silvicultural system is shown where harvesting is carried out as land preparation and then replanting and maintaining trees for a certain period before finally being harvested again [35], [36], [37]. The logs coming from the natural forest are used in the first 5 years. ...
This study aims to explore the potential for biomass-based power plant to accelerate the development of renewable energy to replace the role of fossil energy in Merauke district, South Papua Province. The method used in this study is, first, to collect data and analyze the load on the grid system and the portion of the energy mix as well as the availability of woody biomass from forest areas by making a simulation of the development of a 2 x 12 MW Biomass Power Plant. Second, by conducting experiments to obtain woodchip conversion, as the fuel of the Biomass Power Plant, from the wood log and conversion from Biomass Power Plant capacity to the required biomass plantation area. The results provide an overview of the big potency for developing biomass-based power generation by utilizing biomass from the local industrial plantation forest and show the energy transition towards energy independence. This study can be useful for policy makers and opportunities for entrepreneurs or suppliers of wood biomass, as well. For the future, in terms of fuel efficiency, it is necessary to reduce the plantation area as a source of biomass for power plants by reducing the moisture content of the woodchip to increase the calorific value and utilizing the forest residue. Furthermore, the comparison cost study between fossil power plant and biomass power plant, as well as the strategy for preserving the plantation to ensure a steady biomass supply is conducted.
... In both silvicultural and restoration approaches, thinning assumes that tree growth is negatively related to tree density (Brown et al., 2019;Dwyer et al., 2010) due to competition for resources including water, light, nutrients and space (Bhandari et al., 2021;Craine & Dybzinski, 2013). Commercial thinning to liberate selected trees from surrounding competitors has been found to increase tree growth (David et al., 2019;Guariguata, 1999;Hu et al., 2020). Thinning to promote large tree vigour and enhance old growth habitat features for ecosystem restoration has been trialled in a limited range of forest types with variable effects (Hood et al., 2018;Puettmann et al., 2016;Skov et al., 2005). ...
Large tree decline is occurring globally with critical implications for biodiversity and carbon sequestration. Restoration thinning is a potential management action to accelerate tree growth and promote large tree development in forests, yet trials have been limited and results have been mixed.
We conducted a large‐scale trial to determine whether restoration thinning could accelerate the development of large trees in river red gum forests in Australia that had experienced widespread woody thickening and a decline of large trees due to long‐term commercial timber harvesting and river regulation.
Thinning was conducted on 44 9‐ha plots by removing trees <40 cm diameter from around retained trees at a range of spacings. Initial tree densities ranged from ~260 to ~1860 trees per ha and 8%–86% of trees were removed by thinning. We monitored 1980 trees prior to thinning, and annually for 5 years post‐thinning. We tested the effects of thinning intensity on diameter growth of different sized trees and explored whether long‐ and short‐term water availability affected outcomes.
Thinning promoted the growth of small trees <56 cm diameter, especially in drier sites during wet years. Higher thinning intensities reduced the growth rates of large trees (no smaller than 79.5 cm diameter) in wetter sites.
For medium‐ and large‐sized trees, long‐ and short‐term water availability were stronger drivers of tree growth than competition due to tree density.
Synthesis and applications. Restoration thinning may accelerate tree growth in young river red gum forests where all trees are small. But restoration thinning may be ineffective or detrimental in multi‐aged forests where the goal is to promote the growth rates of trees that are already medium to large in size.
... Although high-grading can be financially beneficial for landholders in the short-term (Jay and Dillon 2016), this practice produces stands with limited potential for future timber production, and declining genetic and ecological value over time (Florence 1996). If landholders can be encouraged to better manage their native forests, silvicultural thinning treatments could greatly improve productivity by increasing the proportion and growth of trees with commercial boles, as well as increasing log quality and size (Burgess and Catchpoole 2016; Jay and Dillon 2016; Hu et al. 2020;Lewis et al. 2020a;Francis et al. 2020a). Currently, only a small proportion of private native forests are managed with silvicultural thinning. ...
Historically, Queensland’s private native forests have supplied between 40 and 70% of the hardwood resource to the state’s primary processors. Hardwood timber production from state-owned native forests and plantations in Queensland has decreased substantially in recent decades, increasing the hardwood timber industry’s reliance on private native forests. However, timber production opportunities from these forests are poorly understood. This study assessed the future wood supply capacity from private native forests in southern Queensland assuming alternative levels of landowner interest in management for timber production and willingness to invest in silvicultural treatment. Commercial and harvestable private native forests in southern Queensland were classified into six forest types and their spatial distributions were assessed. Potential growth rates for each forest type were estimated based on available literature and expert opinion, and their ability to supply logs to industry with and without silvicultural treatments was projected. Commercial and harvestable private native forests were found to cover an area of approximately 1.9 M ha in southern Queensland, of which spotted gum (693,000 ha) and ironbark (641,500 ha) forest types are most common. The private native forest estate is distributed over 17,665 landholdings (LotPlans), with 17% of these accounting for 66% of the commercial and harvestable resource. Most private native forests have not been actively managed for timber production and are in poor condition. Nevertheless, they presently have the potential to supply between about 150,000 and 250,000 m ³ of logs to industry per annum. Silvicultural treatments were found to have the potential to increase the mean annual increment of these forests by a factor of between two and four, indicating substantial opportunities to increase harvestable log volumes in the medium and long-term. Private native forests in southern Queensland could potentially more than compensate for the supply gap left by the declining area of state-owned native forests that are available for timber harvesting. Actual forest management performed and log volumes supplied to market will depend on the forest management decisions of thousands of individual landholders, which are influenced by their heterogeneous management objectives, the policy environment, perceptions of sovereign risk, timber markets and the long payback periods in forestry. An accommodating forest policy environment and landholder willingness to invest in forest management could maintain and potentially increase private hardwood log supply to industry, which would support farm income diversification and regional employment opportunities.
... Similarly, dominant thinning had the lowest QMD since the largest trees were removed. Thinning treatments altering size distributions of trees not only affect stand structure but may also affect stand value following thinning (Clune, 2013;Hu et al., 2020). ...
... Similarly, dominant thinning had the lowest QMD since the largest trees were removed. Thinning treatments altering size distributions of trees not only affect stand structure but may also affect stand value following thinning (Clune, 2013;Hu et al., 2020). ...
Pre-commercial (PCT) and commercial thinning (CT) are important silvicultural tools applied to spruce-fir (Picea-Abies) forests, a key forest type in the northeastern portion of North America. However, the long-term influences of CT, particularly when combined with PCT, are relatively unknown, except for a few specific locations in the region. Utilizing the repeated measurements from replicated experimental research sites (n = 15) initiated in the early 2000s throughout Maine, we quantified the influence of contrasting thinning treatments on spruce-fir stands with prior PCT and without a prior PCT (NoPCT). Thinning treatments at the nine sites with a prior PCT were a combination of multiple entry timings (immediate, 5-, and 10-year delay) and removal intensities (0, 33, and 50 % relative density reduction). At the six NoPCT sites, the CT treatments were a combination of thinning methods (dominant, crown, and low) and removal intensities (0, 33, and 50 %). The most effective CT in terms of large tree response, sawlog volume, and stand value were immediate CT rather than delayed treatments after PCT, and low thinning in NoPCT stands. Dominant thinning in NoPCT showed detrimental effects on residual stand conditions leading to the lowest yield and generated product values. In general, the earlier CT entry in PCT stands led to greater long-term benefits of the treatment in terms of tree size, merchantable volume, and financial value of the stand. No thinning treatment significantly enhanced cumulative total volume or merchantable volume or financial value compared to unthinned controls because even though thinning enhanced sawlog production, unthinned stands produced more pulpwood and studwood. Although we did not find significant economic benefits of CT in stands with or without PCT, light low thinning in NoPCT, and light crown thinning without delay in PCT could be an optimal strategy to maximize the average merchantable stem size without compromising the total stand value, while providing additional benefits to stand composition and generating mid-rotation revenue. Overall, the findings highlight some complexities and challenges with effective thinning regimes in highly shade-tolerant conifer species.
... The currently population structures of P. amabilis varied widely among the four forests (Fig. 4b). High-intensity disturbances can cause population declines (Kennard et al., 2002;Kennard, 2004;Hu et al., 2020). The developmental history of P. amabilis populations in abandoned farmland secondary forests coincides with the land use history ( Fig. 3c; Fig. 4), where intensive logging activities have been officially encouraged since the 1950 s, converting native forests to agricultural lands and causing extensive forest destruction that has brought many plant species close to extinction (Wu, 1980, Tang et al., 2011. ...
Potential suitable habitats for relict species are facing critical reductions due to intensified anthropogenic disturbances and climate change. These facts not only pose new challenges, but also call for a paradigm shift for the effective conservation of relict plant species. We investigated in situ population structures and regeneration status under varying management scenarios for Pseudolarix amabilis, a relict conifer endemic to China. We also re-evaluated the conservation status of P. amabilis using our latest in situ population census data. We found that the conservation status of P. amabilis is more pessimistic than expected. Hence, wild P. amabilis populations urgently need to be considered for conservation. More concretely, intensive and frequent anthropogenic disturbances reduce population recruitment, but a reduced population recruitment also occurs at places where human activities have been strictly prohibited. Comparing with other management scenarios, the populations in fengshui forests showed good regeneration, since the moderate anthropogenic disturbances in these forests. Therefore, fengshui forests can serve as a conservation paradigm of P. amabilis since they echo the optimum regime where anthropogenic disturbances occur.
... Although tree species, size, locations, and disturbance regimes can affect the MAIs (Nguyen-The et al., 1998), MAIs are commonly used to measure the timber growth and yield performance in the whole forests with or without logging (Gräfe et al., 2020;Hu et al., 2020). MAI in Table 2 is for whole natural forests, combing the growth of many tree species with their mortality. ...
The management of tropical forests can achieve multiple purposes. Here, we assessed timber production, bioenergy generation, and emission reductions through the management of production forest for timber and bioenergy production in Southeast Asia between 2000 and 2060 through a comparative study between the conventional and reduced impact logging (RIL) systems. Whilst producing an average of 35.1 million cubic metres per year (m³ year⁻¹) of wood products, the adoption of the RIL can result in emission reductions of 96.6 teragrams of carbon dioxide (TgCO2) over a 60-year period. Apart from deforestation, emissions from logging operations were the second-highest source of emissions, indicating that attention should be made to improve the efficiency of logging machinery whilst reducing deforestation and forest degradation. When combining all emissions together, total emission reductions were estimated at 229.9 TgCO2, 215.4 TgCO2, and 207.9 TgCO2 annually during the Paris Agreement between 2020 and 2030 if compared to coal, diesel, and natural gas, respectively. Southeast Asia could generate about US2.3 billion year⁻¹ under the result-based payment of the REDD+ scheme at a carbon price of US$10. Introducing tax exemptions or financial incentives for carbon and environmental taxes and/or energy tax could materialise the RIL-based forest management.
... Although tree species, size, locations, and disturbance regimes can affect the MAIs (Nguyen-The et al., 1998), MAIs are commonly used to measure the timber growth and yield performance in the whole forests with or without logging (Gräfe et al., 2020;Hu et al., 2020). MAI in Table 2 is for whole natural forests, combing the growth of many tree species with their mortality. ...
Global efforts have been made to manage tropical forests for timber production and climate change mitigation. This study assessed carbon emission reductions through the improved forest management and the substitution of fossil fuels with wood biomasses under the conventional (CVL) and reduced impact logging (RIL) systems in
Southeast Asia between 2000 and 2060. During this period, carbon emissions from logging and deforestation in the region were approximately 10% of carbon emissions from tropical deforestation. By adopting the RIL, 96.6 Tg CO2 of emissions can be reduced, while producing 35.1 million m3 year−1 of wood products. If woody biomasses are used to substitute the combustion of coal, diesel, or natural gas for bioenergy production, total emission reductions could be 229.9, 215.4, or 207.9 Tg CO2 annually during the Paris Agreement, respectively. Depending on chosen carbon price, management of natural forests in Southeast Asia could generate about US$2.1–2.3 billion annually over 10 years between 2020 and 2030. Although costs for bioenergy production from wood biomass remain the concern, enabling global policies, emerging sustainability markets, and financial incentives through carbon tax, environmental tax, and energy tax could materialize the sound management of tropical forests for long-term timber production and climate change mitigation.
... During timber production, short harvesting cycles quickly release much of the stored carbon back into the atmosphere, negating the initial carbon sequestration. Low-intensity management of livelihood native forests, for example through selective extraction, preserves biomass by allowing long-term carbon sequestration and natural vegetation succession while also benefitting biodiversity (Crane, 2020;Hu et al., 2020;Noormets et al., 2015). Alternative livelihood measures should be supported in the interim period before harvesting, to avoid the continued conversion of forest with high carbon stocks elsewhere leading to a net emission of CO 2 . ...
Urgent solutions to global climate change are needed. Ambitious tree‐planting initiatives, many already underway, aim to sequester enormous quantities of carbon to partly compensate for anthropogenic CO2 emissions, which are a major cause of rising global temperatures. However, tree planting that is poorly planned and executed could actually increase CO2 emissions and have long‐term, deleterious impacts on biodiversity, landscapes and livelihoods. Here, we highlight the main environmental risks of large‐scale tree planting and propose 10 golden rules, based on some of the most recent ecological research, to implement forest ecosystem restoration that maximizes rates of both carbon sequestration and biodiversity recovery while improving livelihoods. These are as follows: (1) Protect existing forest first; (2) Work together (involving all stakeholders); (3) Aim to maximize biodiversity recovery to meet multiple goals; (4) Select appropriate areas for restoration; (5) Use natural regeneration wherever possible; (6) Select species to maximize biodiversity; (7) Use resilient plant material (with appropriate genetic variability and provenance); (8) Plan ahead for infrastructure, capacity and seed supply; (9) Learn by doing (using an adaptive management approach); and (10) Make it pay (ensuring the economic sustainability of the project). We focus on the design of long‐term strategies to tackle the climate and biodiversity crises and support livelihood needs. We emphasize the role of local communities as sources of indigenous knowledge, and the benefits they could derive from successful reforestation that restores ecosystem functioning and delivers a diverse range of forest products and services. While there is no simple and universal recipe for forest restoration, it is crucial to build upon the currently growing public and private interest in this topic, to ensure interventions provide effective, long‐term carbon sinks and maximize benefits for biodiversity and people.
... Silvicultural treatments are another SFM measure [17]. While the effect of silvicultural treatments on the commercial timber volume of tropical forests has been investigated in various studies [18][19][20][21][22], the effects of silvicultural practices on carbon dynamics in both commercial and non-commercial stands is not well understood. ...
Sustainable forest management activities, such as future crop tree (FCT) release treatments, became part of the REDD+ strategy to avoid carbon emissions from forests. FCT release treatments are intended to achieve increased growth of FCTs by removing competitor trees. This initially leads to a reduction of the forest carbon pool and represents a carbon debt. We estimated that the time it takes for FCTs to offset the carbon debt through increased growth on experimental sites of 10 km 2 in Belize, Guyana, Suriname, and Trinidad and Tobago. We further investigated whether the costs of treatment can be compensated by the generated financial carbon benefits. An average of 2.3 FCT per hectare were released through the removal of an average of 3.3 competitors per hectare. This corresponds to an average above ground biomass (AGB) deficit of 2.3 Mg FCT −1. Assuming a 30% increase in growth, the FCT would need on average 130 years to offset the carbon loss. For carbon prices from US 4.2 to 8.4 FCT −1. Assuming a carbon price of US$ 10 Mg CO 2 e −1 , the additional increment required would be between 5.8 and 11.4 Mg tree −1 , thus exceeding the biological growth potential of most individual trees. The release of FCTs does not ensure an increase in forest carbon stocks, and refinancing of treatment costs is problematic.
Many natural forests in Southeast Asia are degraded following decades of logging. Restoration of these forests is delayed by ongoing logging and tropical cyclones, but the implications for recovery are largely uncertain. We analysed meteorological, satellite and forest inventory plot data to assess the effect of Typhoon Doksuri, a major tropical cyclone, on the forest landscapes of central Vietnam consisting of natural forests and plantations. We estimated the return period for a cyclone of this intensity to be 40 years. Plantations were almost twice as likely to suffer cyclone damage compared to natural forests. Logged natural forests (9–12 years after cessation of government-licensed logging) were surveyed before and after the storm with 2 years between measurements and remained a small biomass carbon sink (0.1 ± 0.3 Mg C ha ⁻¹ yr ⁻¹ ) over this period. The cyclone reduced the carbon sink of recovering natural forests by an average of 0.85 Mg C ha ⁻¹ yr ⁻¹ , less than the carbon loss due to ongoing unlicensed logging. Restoration of forest landscapes in Southeast Asia requires a reduction in unlicensed logging and prevention of further conversion of degraded natural forests to plantations, particularly in landscapes prone to tropical cyclones where natural forests provide a resilient carbon sink.
This article is part of the theme issue ‘Understanding forest landscape restoration: reinforcing scientific foundations for the UN Decade on Ecosystem Restoration’.
Enrichment of selectively logged rainforest by planting seedlings of commercially valuable species is often recommended to improve productivity, ecological functioning, and biodiversity. However, the survival and subsequent growth of enrichment plantings depend on how they respond to competition from neighbours. For successful forest restoration or commercial forest management, the challenge is to determine appropriate frequencies and intensities of silvicultural interventions, principally competition reduction. In this study, we use long-term data (49–60 years) from four enrichment planting experiments established after selective logging and girdling of non-commercial trees in a tropical rainforest in north Queensland, Australia, to assess the effects of competition on the survival and growth of enrichment plantings. We found that residual overwood development severely reduced the survival, diameter and volume growth of two widely planted rainforest species - Flindersia brayleyana (Rutaceae) and Agathis robusta (Araucariaceae). Both species responded well to overstory removal, either as an initial treatment or thereafter. Use of Hegyi’s competition index confirmed the strong suppressive effect of neighbours. The most abundant competitor was the fast-growing, early-secondary species Acacia aulacocarpa, which only became apparent after cessation of silvicultural treatments, 7 years after planting. Our results reaffirm the importance of an initial or early-age removal of the competing overstory for the success of enrichment planting. Further silvicultural treatments may be required for extended periods to control excessively increased overwood basal area and to remove late emerging pioneer or early secondary species.
Forest degradation accounts for ~70% of total carbon losses from tropical forests. Substantial emissions are from selective logging, a land-use activity that decreases forest carbon density. To maintain carbon values in selectively logged forests, climate change mitigation policies and government agencies promote the adoption of reduced-impact logging (RIL) practices. However, whether RIL will maintain both carbon and timber values in managed tropical forests over time remains uncertain. In this study, we quantify the recovery of timber stocks and aboveground carbon at an experimental site where forests were subjected to different intensities of RIL (4, 8, and 16 trees/ha). Our census data span 20 years postlogging and 17 years after the liberation of future crop trees from competition in a tropical forest on the Guiana Shield, a globally important forest carbon reservoir. We model recovery of timber and carbon with a breakpoint regression that allowed us to capture elevated tree mortality immediately after logging. Recovery rates of timber and carbon were governed by the presence of residual trees (i.e., trees that persisted through the first harvest). The liberation treatment stimulated faster recovery of timber albeit at a carbon cost. Model results suggest a threshold logging intensity beyond which forests managed for timber and carbon derive few benefits from RIL, with recruitment and residual growth not sufficient to offset losses. Inclusion of the breakpoint at which carbon and timber gains outpaced postlogging mortality led to high predictive accuracy, including out-of-sample R2 values >90%, and enabled inference on demographic changes postlogging. Our modeling framework is broadly applicable to studies that aim to quantify impacts of logging on forest recovery. Overall, we demonstrate that initial mortality drives variation in recovery rates, that the second harvest depends on old growth wood, and that timber intensification lowers carbon stocks.
This conference, organized by CIRAD, CIFOR and ECOFOR, under the aegis of IUFRO, was held in Montpellier from 15 to 18 November 2011. It took place in the context of the international year of forests and was attended by over 170 researchers and students. Seventy-two talks were given. Following the conference, the organizers were keen to publish this overview highlighting the main topics discussed.
Maintenance, in as natural a state as possible, of many of the world's 400 million ha of officially designated tropical production forests will ironically require silvicultural intensification in selected portions of some landscapes. Hopefully these intensively managed forests will continue to support abundant biodiversity and continue to provide many other environmental services, but profitable management is key to their survival as forests. While an increasing proportion of the growing global demand for forest products will be satisfied by plantations, most natural forests will certainly not be spared from harvesting. Even if the profitability of natural forest management can be increased through silvicultural interventions, it will remain difficult to financially justify natural forest management where there are high opportunity costs of retaining forests in lieu of other land uses (e.g. oil palm plantations, soybean fields or cattle ranches). That said, it is also important to recognise that these opportunity costs vary by orders of magnitude across the landscape. Areas of difficult access and adverse terrain yield lower profits from any landuse, with the magnitude of effect inversely proportional to the required capital investments. For this reason, natural forests mostly remain in swamps, on steep slopes and in remote areas. Unfortunately, these adverse conditions are also not conducive to environmentally-sound and profitable natural forest management. Whereas in many temperate and boreal forests, especially on private lands, environmentally-concerned foresters are working against the trend towards increased intensity of management and the consequent forest simplification, natural forest management in the tropics is still not common. Instead, timber exploitation (log mining) is likely to continue for the foreseeable future in much of the tropics. Here we focus on one tropical forest where the transition from exploitation to management occurred in response to a combination of governmental policies and the business interests of a private concessionaire. An important step in the transition from unnecessarily destructive timber mining to responsible forest management is employment of reduced-impact logging (RIL) techniques. Some costs of RIL are recovered by increased efficiency but loggers are not spontaneously adopting sound harvesting practices out of enlightened self-interest, at least not of the short-term financial variety. Furthermore, while low intensity, single-tree selection RIL harvests are environmentally benign, this gentle approach is neither very profitable nor sustainable where commercial timber species regenerate in canopy openings larger than those created by low intensity single tree selection. In most forests, other silvicultural interventions are needed to maintain timber yields and profits. Payments for environmental services (e.g. carbon sequestration) may cover some of the foregone costs of very low intensity timber stand management, but those payments are unlikely to be available for the vast majority of production forests in the tropics. To sustain yields and profits, one possible option is to increase intensity of tropical silviculture. The end of the continuum of silvicultural intensification is the conversion of natural forests into plantation monocultures, which we consider deforestation and do not cover further here. Between plantation conversion and single-tree selection using RIL is a wide variety of silvicultural interventions that tropical foresters all learn about in school but seldom see applied outside of experimental plots. Approaches such as shelterwoods, group selection and liberation thinning all have received substantial attention from researchers but have generally not been adopted by forest industries. Here we focus on enrichment planting, which is at the intensive end of natural forest management. Although enrichment planting, which is more completely referred to as plantation conversion by enrichment planting, has a long history of
Virgin rainforests generally have higher levels of tree stocking and basal area than Asian and African rainforests but are less species rich than the former. Mortality is generally <1% but exceeds the rate of recruitment so that there is a trend to lower species richness and basal area, with time. Such declines could result from environmental stability at the scale of the samples and from climatic trends and short-term drought events. There is generally a fall in the Shannon-Wiener index of diversity while evenness and uniformity generally rise, changes largely a consequence of the fall in species numbers. The immediate effects of logging are the reduction in the numbers of trees, reductions in basal area and an apparent reduction in the number of species. The latter effect is largely a consequence of small sample size and the constraint of the lower diameter limit in plot assessment. It does, however, have the effect of lowering diversity and raising evenness. The after-logging response is to increase species numbers and the diversity index on all but lightly logged plots. There is a consistent rise in basal area resulting from lessened mortality and enhanced recruitment and tree growth. The response following silvicultural treatment is much more marked with significant rises (from low levels) in species numbers and diversity and generally a rise in uniformity but a fall in evenness. Again there is a marked rise in basal area. A certain level of disturbance in the rainforest is necessary for maintenance of a high level of diversity. Logging generally provides this disturbance to a sufficient degree and leaves the rainforest as an intact and viable ecosystem with enhanced potential for production. -from Authors
Restoring the functions of disturbed forest to mitigation climate change is a main topic of policy makers. Better understanding of factors that directly influence post-disturbance forest biomass recovery is urgently needed to guide forest restoration and management. In this study, we examine changes in forest stand structure, wood density and biomass of forests recovering from different anthropogenic disturbances that represent forest land-use types in subtropical China: plantation, twice-logged and once-logged secondary forests, and compare them with undisturbed old-growth forest. Stand structure and wood density in all disturbed forests were evidently different from that of old-growth forest, even after 50-year regrowth. Forest biomass increased along plantation, twice-logged, once-logged and old-growth forests, with total living biomass (TLB) ranging from 150.8 ± 4.6 to 278.4 ± 1.5 Mg ha−1, aboveground biomass from 111.8 ± 4.2 to 204.1 ± 1.5 Mg ha−1 and coarse-root biomass from 33.0 ± 0.9 to 71.0 ± 0.8 Mg ha−1. However, fine-root biomass was highest in plantation (5.99 ± 0.52 Mg ha−1) and lowest in once-logged forest (3.35 ± 0.19 Mg ha−1). Both changes in stand structure and functional trait (wood density) directly determine forest biomass recovery according to the result that 10.6, 35.5 and 8.2 % of variation in TLB over the disturbance gradient were independently explained by basal area (
Currently, about 400 million hectares of tropical moist forests worldwide are designated production forests, about a quarter of which are managed by rural communities and indigenous peoples. There has been a gradual impoverishment of forest resources inside selectively logged forests in which the volume of timber extracted over the first cutting cycle was mostly from large, old trees that matured over a century or more and grew in the absence of strong anthropological pressures. In forests now being logged for a second and third time, that volume has not been reconstituted due in part to the lack of implementation of post-logging silvicultural treatments. This depletion of timber stocks renders the degraded forests prone to conversion to other land uses. Although it is essential to preserve undisturbed primary forests through the creation of protected areas, these areas alone will not be able to ensure the conservation of all species on a pan-tropical scale, for social, economic and political reasons. The conservation of tropical forests of tomorrow will mostly take place within human-modified (logged, domesticated) forests. In this context, silvicultural interventions are considered by many tropical foresters and forest ecologists as tools capable of effectively conserving tropical forest biodiversity and ecosystem services while stimulating forest production. This systematic review aims to assess past and current evidence of the impact of silviculture on tropical forests and to identify silvicultural practices appropriate for the current conditions in the forests and forestry sectors of the Congo Basin, Amazonia and Southeast Asia.
This systematic review will undertake an extensive search of literature to assess the relative effectiveness of different silvicultural interventions on timber production and the conservation value of forests, and to determine whether there is a relationship between sustainability of timber harvesting and the maintenance/conservation of other ecosystem services and biodiversity in production forests. Data will be extracted for meta-analysis of at least sub-sets of the review questions. Findings are expected to help inform policy and develop evidence-based practice guidelines on silvicultural practices in tropical forests.
Variation in wood specific gravity (WSG) within and across species of tropical trees is poorly studied in relation to vegetation change during tropical forest succession. We investigated WSG of 91 species in eight long‐term plots along a successional chronosequence in north‐eastern Costa Rica.
Radial changes in WSG were described by the rate of change (slope) along the stem radius. Significant radial changes were found in 42 of 74 species, with 37 species exhibiting increases from inner to outer wood, and five exhibiting decreases. Radial increases were commonly observed in species with inner WSG below 0·5, whereas radial decreases were observed in species with inner WSG above 0·7.
Wood specific gravity weighted by cross‐sectional area (wWSG) varied four‐fold among species. Species classified as second‐growth specialists had lower wWSG, lower inner and outer WSG, and higher slopes than old‐growth specialists; successional generalists showed intermediate trait values.
Among 18 species sampled in both second‐ and old‐growth forests, four species (22%) showed significant variation in wWSG between forest types. Of 33 widely sampled species, seven species (21%) showed a significant effect of stem diameter on wWSG.
Second‐growth plots had lower stand‐level wWSG and more pronounced radial increases than old‐growth plots. Individual tree biomass for species with radial increases and low WSG was substantially underestimated when based on unweighted WSG compared with wWSG.
Wood specific gravity varied with successional stage at multiple levels: within species, among successional specialist groups, and across plots of varying ages. Radial increases in WSG are common among trees in early and intermediate stages of tropical forest succession. This trait may confer growth advantages early in succession and increased resistance to physical or biotic damage during later successional stages.
Minimizing the deleterious environmental impacts of logging and other silvicultural treatments is the primary conservation goal in tropical forests managed for timber production. While it is always environmentally beneficial to minimize unnecessary damage, more intensive silviculture should not be discouraged in tropical forests in which regeneration and growth of commercially valuable timber species requires such treatments. Failing to regenerate commercial species may render forests more susceptible to conversion to other, more lucrative land uses. Increasing the intensity of silviculture may also decrease the total area of forest exploited for timber, thereby reducing the impacts of over-hunting, timber theft, wildfires, colonization, and conversion, which are facilitated by the increased accessibility of logged areas.
Forest dynamics after timber harvesting is a major issue for tropical forest managers and communities. Timber harvesting provides income to communities and governments and resources to industry but it has also been identified as a potential contributor to deforestation and degradation of tropical forests. In Papua New Guinea (PNG) harvesting is primarily occurring in accessible primary forests however, the fate of these forests under current harvesting practices is poorly understood.In this study we investigated the impacts of selective harvesting on stand structure, growth and dynamics, recovery and degradation, and species diversity. We also assessed the impacts of forest fire after the 1997–98 El Nino on basal area (BA) growth and mortality rates of natural tropical forests in PNG. For this study we used data from 118 (105 in selectively harvested and 13 in un-harvested forest), one-hectare permanent sample plots distributed across the country and measured for over 15years by the PNG Forest Research Institute (PNGFRI). We analysed data from 84 of these plots in harvested forest to examine temporal trends in stand condition following harvesting. Mortality rates were investigated in 10 of the 21 plots in harvested forest that were burned during the 1997–98 El Nino drought with sufficient data for analyses. We tested a model developed in Queensland tropical forests to determine whether or not a critical threshold residual BA existed for the recovery of harvested tropical forests in PNG. Results from a logarithmic regression analysis of the relationship between starting BA (BA at first census) and stand BA increment after selective harvesting showed a positive increase in BA growth (r2=0.74, p
Large areas of African moist forests are being logged in the context of supposedly sustainable management plans. It remains however controversial whether harvesting a few trees per hectare can be maintained in the long term while preserving other forest services as well. We used a unique 24 year silvicultural experiment, encompassing 10 4 ha plots established in the Central African Republic, to assess the effect of disturbance linked to logging (two to nine trees ha(-1) greater than or equal to 80 cm DBH) and thinning (11-41 trees ha(-1) greater than or equal to 50 cm DBH) on the structure and dynamics of the forest. Before silvicultural treatments, above-ground biomass (AGB) and timber stock (i.e. the volume of commercial trees greater than or equal to 80 cm DBH) in the plots amounted 374.5 ± 58.2 Mg ha(-1) and 79.7 ± 45.9 m(3) ha(-1), respectively. We found that (i) natural control forest was increasing in AGB (2.58 ± 1.73 Mg dry mass ha(-1) yr(-1)) and decreasing in timber stock (-0.33 ± 1.57 m(3) ha(-1) yr(-1)); (ii) the AGB recovered very quickly after logging and thinning, at a rate proportional to the disturbance intensity (mean recovery after 24 years: 144%). Compared with controls, the gain almost doubled in the logged plots (4.82 ± 1.22 Mg ha(-1) yr(-1)) and tripled in the logged + thinned plots (8.03 ± 1.41 Mg ha(-1) yr(-1)); (iii) the timber stock recovered slowly (mean recovery after 24 years: 41%), at a rate of 0.75 ± 0.51 m(3) ha(-1) yr(-1) in the logged plots, and 0.81 ± 0.74 m(3) ha(-1) yr(-1) in the logged + thinned plots. Although thinning significantly increased the gain in biomass, it had no effect on the gain in timber stock. However, thinning did foster the growth and survival of small- and medium-sized timber trees and should have a positive effect over the next felling cycle.
1. Current thinking holds that wood density mediates a tradeoff between strength and economy of construction, with higher wood density providing higher strength but at higher cost.
2. Yet the further away wood fibres are from the central axis of the trunk, the more they increase the strength of the trunk; thus, a fat trunk of low-density wood can achieve greater strength at lower construction cost than a thin trunk of high-density wood.
3. What then are the countervailing advantages of high wood density?
4. We hypothesize that high wood density is associated with lower maintenance costs due to lower trunk surface area, as surface area correlates with maintenance respiration.
5. This advantage would be particularly important to long-lived trees and could in part explain why they tend to have high wood density.
6. High wood density has also been associated with lower risk of trunk breakage, xylem implosion and pathogen invasion, but we argue that these relationships are not causal and instead reflect correlated selection on other traits of value to long-lived trees.
7. This revaluation of the costs and benefits of high wood density has important implications for understanding tree life-history evolution, functional diversity, forest carbon stocks and the impacts of global change.
Disturbances are widespread and may affect community assembly, species composition, (functional) diversity and hence ecosystem processes. It remains still unclear to what extent disturbance‐mediated species changes scale‐up to changes in community functional properties, especially for species‐rich tropical forests.
A large‐scale field experiment was performed in which the dynamics of 15 000 stems >10 cm in diameter was monitored for 8 years in 44 one‐ha forest plots. Twelve functional effect and response traits were measured for the most dominant tree species. The effects of different intensities of disturbance caused by logging and silvicultural treatments on the species and functional diversity of a Bolivian tropical forest community were evaluated, along with how these changes were driven by underlying demographic processes.
Disturbance treatments did not affect species diversity or functional diversity indices based on multiple traits related to primary productivity and decomposition rate. This result suggests that species richness is conserved, and trait variation is maintained, which can buffer the community against environmental change.
In contrast, disturbance intensity affected the average plant trait values in the community (the community‐weighted mean) for seven of 12 traits evaluated. At high disturbance intensity, the community had a lower wood density of stem and branches, lower leaf toughness and dry matter content, but higher specific leaf area and leaf N‐ and P concentration, with the value of these traits changing on average 6% over the 8‐year period. The functional spectrum of the community changed, therefore, from ‘slow’, conservative, shade‐tolerant species towards ‘fast’, acquisitive, light‐demanding species. These functional changes in mean trait values may enhance primary productivity and decomposition rate in the short term.
Temporal changes in community functional properties were mainly driven by recruitment, and little by mortality or survival.
Synthesis . Moderate levels of (logging) disturbance neither affected species diversity nor functional diversity per se in the 8‐year period after logging. Disturbance did, however, change the functional community composition towards ‘fast’ species with more acquisitive traits, thus potentially fuelling primary productivity and nutrient and carbon cycling. In conclusion, tropical forest management may contribute to conserving functional biodiversity of trees while providing forest resources.
1. Niche theory proposes that species differences underlie both coexistence within communities and the differentiation in species composition among communities via limiting similarity and environmental filtering. However, it has been difficult to extend niche theory to species‐rich communities because of the empirical challenge of quantifying niches for many species. This has motivated the development of functional and phylogeny‐based approaches in community ecology, which represent two different means of approximating niche attributes.
2. Here, we assess the utility of plant functional traits and phylogenetic relationships in predicting community assembly processes using the largest trait and phylogenetic data base to date for any set of species‐rich communities.
3. We measured 17 functional traits for all 4672 individuals of 668 tree species co‐occurring in nine tropical rain forest plots in French Guiana. Trait variation was summarized into two ordination axes that reflect species niche overlap.
4. We also generated a dated molecular phylogenetic tree based on DNA sequencing of two plastid loci ( rbcL and matK ) comprising 97% of the individuals and 91% of the species in the plots.
5. We found that, on average, co‐occurring species had greater functional and, to a lesser extent, phylogenetic similarity than expected by chance.
6. We also found that functional traits and their ordination loadings showed significant, albeit weak, phylogenetic signal, suggesting that phylogenetic distance provides pertinent information on niche overlap in tropical tree communities.
7. Synthesis . We provide the most comprehensive examination to date of the relative importance of environmental filtering and limiting similarity in structuring tropical tree communities. Our results confirm that environmental filtering is the overriding influence on community assembly in these species‐rich systems.
Uncertainty in biomass estimates is one of the greatest limitations to models of carbon flux in tropical forests. Previous comparisons of field-based estimates of the aboveground biomass (AGB) of trees greater than 10 cm diameter within Amazonia have been limited by the paucity of data for western Amazon forests, and the use of site-specific methods to estimate biomass from inventory data. In addition, the role of regional variation in stand-level wood specific gravity has not previously been considered. Using data from 56 mature forest plots across Amazonia, we consider the relative roles of species composition (wood specific gravity) and forest structure (basal area) in determining variation in AGB.
Mean stand-level wood specific gravity, on a per stem basis, is 15.8% higher in forests in central and eastern, compared with northwestern Amazonia. This pattern is due to the higher diversity and abundance of taxa with high specific gravity values in central and eastern Amazonia, and the greater diversity and abundance of taxa with low specific gravity values in western Amazonia. For two estimates of AGB derived using different allometric equations, basal area explains 51.7% and 63.4%, and stand-level specific gravity 45.4% and 29.7%, of the total variation in AGB. The variation in specific gravity is important because it determines the regional scale, spatial pattern of AGB. When weighting by specific gravity is included, central and eastern Amazon forests have significantly higher AGB than stands in northwest or southwest Amazonia. The regional-scale pattern of species composition therefore defines a broad gradient of AGB across Amazonia.
Most tropical forests outside protected areas have been or will be selectively logged so it is essential to maximize the conservation values of partially harvested areas. Here we examine the extent to which these forests sustain timber production, retain species, and conserve carbon stocks. We then describe some improvements in tropical forestry and how their implementation can be promoted.
A simple meta-analysis based on >100 publications revealed substantial variability but that: timber yields decline by about 46% after the first harvest but are subsequently sustained at that level; 76% of carbon is retained in once-logged forests; and, 85–100% of species of mammals, birds, invertebrates, and plants remain after logging. Timber stocks will not regain primary-forest levels within current harvest cycles, but yields increase if collateral damage is reduced and silvicultural treatments are applied.
Given that selectively logged forests retain substantial biodiversity, carbon, and timber stocks, this “middle way” between deforestation and total protection deserves more attention from researchers, conservation organizations, and policy-makers. Improvements in forest management are now likely if synergies are enhanced among initiatives to retain forest carbon stocks (REDD+), assure the legality of forest products, certify responsible management, and devolve control over forests to empowered local communities.
In this review, we highlight the main biotic and abiotic factors that influence the patterns of Neotropical secondary forest successions, referred as the woody vegetation that regrows after complete forest clearance due to human activities. We focus on both patterns of species replacement and various processes that occur during succession, and suggest that the sequence of processes may be predictable even if species composition is not. We describe forest recovery with respect to old-growth conditions, which we define as the structure, function, and composition of the original forest before conversion, and we examine this recovery process within the context of type and intensity of past land use. The various phases of the recovery process are described in detail: from factors affecting early colonization, changes in light and soil properties, soil–vegetation feedbacks at initial and later successional stages, biomass accumulation, forest productivity, rates of species accumulation, and species composition. The consensus of these analyses is that the regenerative power of Neotropical forest vegetation is high, if propagule sources are close by and land use intensity before abandonment has not been severe. Nevertheless, the recovery of biophysical properties and vegetation is heavily dependent on the interactions between site-specific factors and land use, which makes it extremely difficult to predict successional trajectories in anthropogenic settings. We attempt, throughout this review, to integrate the structural and functional characteristics of secondary succession as a way to enhance our ability both to predict and manage successional forest ecosystems due to their increasing importance as timber sources, providers of environmental services, and templates for restoration purposes.
Forest structure and floristic composition were studied in a series of 0.5 ha natural forest plots at four sites near Porto Trombetas in Pará State, Brazil, 11–12 years after being subjected to differing levels of above-ground biomass harvest and removal. In addition to undisturbed control plots, experimental treatments included: removal of most trees ≥45 cm DBH (low intensity harvest); removal of trees <20 and ≥60 cm DBH (moderate intensity harvest); clear-cutting (100% above-ground biomass removal). Post-harvest basal area growth generally increased with harvest intensity, and total basal areas for trees ≥5 cm DBH were, at the time of our study, 60% (in the clear-cut) to about 80% of those in the control plots. Biomass harvests stimulated recruitment and growth of residual trees, particularly in the smaller diameter classes, but had little effect on species richness for small trees, seedlings, vine, herbs, and grasses. Species richness for trees ≥15 cm DBH was greater in the control and low-intensity (74–75 species) than in the moderate intensity (47 species) and clear-cut (26 species) treatment plots. While the tree flora within all harvest treatments was broadly similar to the undisturbed (control) plots and included similar numbers of species of the major plant families typical of the surrounding forests, the more intensive harvest treatments, especially the clear-cut, were dominated by a higher proportion of short-lived, early successional tree species.
Wood density is an important variable in estimates of forest biomass and greenhouse-gas emissions from land-use change. The mean wood density used in estimates of forest biomass in the Brazilian Amazon has heretofore been based on samples from outside the “arc of deforestation”, where most of the carbon flux from land-use change takes place. This paper presents new wood density estimates for the southern and southwest Brazilian Amazon (SSWA) portions of the arc of deforestation, using locally collected species weighted by their volume in large local inventories. Mean wood density was computed for the entire bole, including the bark, and taking into account radial and longitudinal variation. A total of 403 trees were sampled at 6 sites. In the southern Brazilian Amazon (SBA), 225 trees (119 species or morpho-species) were sampled at 4 sites. In eastern Acre state 178 trees (128 species or morpho-species) were sampled at breast height in 2 forest types. Mean basic density in the SBA sites was 0.593 ± 0.113 (mean ± 1 S.D.; n = 225; range 0.265–0.825). For the trees sampled in Acre the mean wood density at breast height was 0.540 ± 0.149 (n = 87) in open bamboo-dominated forest and 0.619 ± 0.149 (n = 91) in dense bamboo-free forest. Mean wood density in the SBA sites was significantly higher than in the bamboo dominated forest but not the dense forest at the Acre site. From commercial wood inventories by the RadamBrasil Project in the SSWA portion of the arc of deforestation, the wood volume and wood density of each species or genus were used to estimate average wood density of all wood volume in each vegetation unit. These units were defined by the intersection of mapped forest types and states. The area of each unit was then used to compute a mean wood density of 0.583 g cm−3 for all wood volume in the SSWA. This is 13.6% lower than the value applied to this region in previous estimates of mean wood density. When combined with the new estimates for the SSWA, this gave an average wood density of 0.642 g cm−3 for all the wood volume in the entire Brazilian Amazon, which is 7% less than a prior estimate of 0.69 g cm−3. These results suggest that current estimates of carbon emissions from land-use change in the Brazilian Amazon are too high. The impact on biomass estimates and carbon emissions is substantial because the downward adjustment is greater in forest types undergoing the most deforestation. For 1990, with 13.8 × 103 km2 of deforestation, emissions for the Brazilian Amazon would be reduced by 23.4–24.4 × 106 Mg CO2-equivalent C/year (for high- and low-trace gas scenarios), or 9.4–9.5% of the gross emission and 10.7% of the net committed emission, both excluding soils.
Premise of the study:
In a previous paper, we questioned the traditional interpretation of the advantages and disadvantages of high wood density (Functional Ecology 24: 701-705). Niklas and Spatz (American Journal of Botany 97: 1587-1594) challenged the biomechanical relevance of studying properties of dry wood, including dry wood density, and stated that we erred in our claims regarding scaling.
Methods:
We first present the full derivation of our previous claims regarding scaling. We then examine how the fresh modulus of rupture and the elastic modulus scale with dry wood density and compare these scaling relationships with those for dry mechanical properties, using almost exactly the same data set analyzed by Niklas and Spatz.
Key results:
The derivation shows that given our assumptions that the modulus of rupture and elastic modulus are both proportional to wood density, the resistance to bending is inversely proportional to wood density and strength is inversely proportional with the square root of wood density, exactly as we previously claimed. The analyses show that the elastic modulus of fresh wood scales proportionally with wood density (exponent 1.05, 95% CI 0.90-1.11) but that the modulus of rupture of fresh wood does not, scaling instead with the 1.25 power of wood density (CI 1.18-1.31).
Conclusions:
The deviation from proportional scaling for modulus of rupture is so small that our central conclusion remains correct: for a given construction cost, trees with lower wood density have higher strength and higher resistance to bending.
Inventories of tree species are often conducted to guide conservation efforts in tropical forests. Such surveys are time consuming, demanding of expertise, and expensive to perform and interpret. Approaches to make survey efforts simpler or more effective would be valuable. In particular, it would be good to be able to easily identify areas of old-growth forest. The average density of the wood of a tree species is closely linked to its successional status. We used tree inventory data from eastern Borneo to determine whether wood density can be used to quantify forest disturbance and conservation importance. The average density of wood in a plot was significantly and negatively related to disturbance levels, with plots with higher wood densities occurring almost exclusively in old-growth forests. Average wood density was unimodally related to the diversity of tree species, indicating that the average wood density in a plot might be a better indicator of old-growth forest than species diversity. In addition, Borneo endemics had significantly heavier wood than species that are common throughout the Malesian region, and they were more common in plots with higher average wood density. We concluded that wood density at the plot level could be a powerful tool for identifying areas of conservation priority in the tropical rain forests of Southeast Asia.
The biomass of tropical forests plays an important role in the global carbon cycle, both as a dynamic reservoir of carbon, and as a source of carbon dioxide to the atmosphere in areas undergoing deforestation. However, the absolute magnitude and environmental determi- nants of tropical forest biomass are still poorly understood. Here, we present a new synthesis and interpolation of the basal area and aboveground live biomass of old-growth lowland tropical forests across South America, based on data from 227 forest plots, many previously unpublished. Forest biomass was analyzed in terms of two uncorrelated factors: basal area and mean wood density. Basal area is strongly affected by local landscape factors, but is relatively invariant at regional scale in moist tropical forests, and declines significantly at the dry periphery of the forest zone. Mean wood density is inversely correlated with forest dynamics, being lower in the dynamic forests of western Amazonia and high in the slow-growing forests of eastern Amazonia. The combination of these two factors results in biomass being highest in the moderately seasonal, slow growing forests of central Amazonia and the Guyanas (up to 350Mgdry weightha� 1) and declining to 200- 250Mgdry weightha� 1 at the western, southern and eastern margins. Overall, we estimate the total aboveground live biomass of intact Amazonian rainforests (area 5.76 � 106km2 in 2000) to be 93 � 23PgC, taking into account lianas and small trees. Including dead biomass and belowground biomass would increase this value by approximately 10% and 21%, respectively, but the spatial variation of these additional terms still needs to be quantified.
Wood density plays a central role in the life-history variation of trees, and has important consequences for mechanical properties of wood, stem and branches, and tree architecture. Wood density, modulus of rupture, modulus of elasticity, and safety factors for buckling and bending were determined for saplings of 30 Bolivian rain forest tree species, and related to two important life-history axes: juvenile light demand and maximum adult stature. Wood density was strongly positively related to wood strength and stiffness. Species safety factor for buckling was positively related to wood density and stiffness, but tree architecture (height : diameter ratio) was the strongest determinant of mechanical safety. Shade-tolerant species had dense and tough wood to enhance survival in the understorey, whereas pioneer species had low-density wood and low safety margins to enhance growth in gaps. Pioneer and shade-tolerant species showed opposite relationships between species traits and adult stature. Light demand and adult stature affect wood properties, tree architecture and plant performance in different ways, contributing to the coexistence of rain forest species.
An analysis of data from 212 permanent sample plots provided no evidence of any decline in rainforest productivity after three cycles of selection logging in the tropical rainforests of north Queensland. Relative productivity was determined as the difference between observed diameter increments and increments predicted from a diameter increment function which incorporated tree size, stand density and site quality. Analyses of variance and regression analyses revealed no significant decline in productivity after repeated harvesting. There is evidence to support the assertion that if any permanent productivity decline exists, it does not exceed six per cent per harvest.
Lianas (woody climbing plants) often abound in tropical forests after selective logging and other disturbances. Liana cutting is an often-prescribed but seldom applied silvicultural treatment designed to foster the growth of future crop trees (hereafter: FCTs). Small-scale studies indicate that this treatment is effective, but little is known about its efficiency (i.e., proportions of lianas missed) or financial cost effectiveness at operational scales. To fill these gaps, we worked in a commercial forest concession in Belize where FCTs and trees to be felled were liberated from lianas in 500–1000 ha annual timber harvest blocks. We found that field crews assigned this and inventory-related tasks spent 11.8% of their time cutting lianas from FCTs at a cost of 0.11 investment per tree a net present value of US $161.38 and a profitability index of 1467 for export quality timber. These results argue for the application of this inexpensive and effective treatment in managed forests where lianas abound.
One third of contemporary tropical forests is designated by national forest services for timber production. Tropical forests are also increasingly affected by anthropogenic disturbances. However, there is still much uncertainty around the capacity of tropical forests to recover their timber volume after logging as well as other disturbances such as fires, large blow-downs and extreme droughts, and thus on the long-term sustainability of logging. We developed an original Bayesian hierarchical model of Volume Dynamics with Differential Equations (VDDE) to infer the dynamic of timber volumes as the result of two ecosystem processes: volume gains from tree growth and volume losses from tree mortality. Both processes are expressed as explicit functions of the forest maturity, i.e. the overall successional stage of the forest that primarily depends on the frequency and severity of the disturbances that the forest has undergone. As a case study, the VDDE model was calibrated with data from Paracou, a long-term disturbance experiment in a neotropical forest where over 56 ha of permanent forest plots were logged with different intensities and censused for 31 years. With this model, we could predict timber recovery at Paracou at the end of a cutting cycle depending on the logging intensity, the rotation cycle length, and the proportion of commercial volume. The VDDE modelling framework developed presents three main advantages: (i) it can be calibrated with large tree inventories which are widely available from national forest inventories or logging concession management plans and are easy to measure, both on the field and with remote sensing; (ii) it depends on only a few input parameters, which can be an advantage in tropical regions where data availability is scarce; (iii) the modelling framework is flexible enough to explicitly include the effect of other types of disturbances (both natural and an-thropogenic: e.g. blow-downs, fires and climate change) on the forest maturity, and thus to predict future timber provision in the tropics in a context of global changes.
Identifying long-term impacts of logging disturbance on rainforests is crucial for biodiversity conservation. In this study, we evaluated changes in tree diversity and dynamics as well as species responses over 48 years in a subtropical rainforest subject to intensive logging in north-eastern New South Wales (NSW) Australia. Some areas of this forest were intensively logged (≥70% of basal area removal) as part of silvicultural practices, in conjunction with other activities such as herbicide application and enrichment planting. Measurements between 1966 and 2014 of trees ≥ 10 cm dbh were undertaken in permanent plots in undisturbed and disturbed (logged) areas. In undisturbed areas, absence of logging and occurrence of minimal natural perturbations induced stable tree diversity and dynamics during the 48-year period. In disturbed areas, tree diversity, dynamics and species responses differed profoundly over time, and from undisturbed areas. Distinct trends were grouped in three post-disturbance periods. A first period in which tree removal and damage during logging operations induced constraining conditions that reduced richness, diversity, dominance, tree density, basal area and recruitment. A second period was characterised by a decline of tree density and basal area after post-logging mortality, but they both recovered in subsequent years. During this second period, richness and diversity increased and species responses such as colonisation, adaptation, facilitation, and inter- and intraspecific competition were exhibited. Finally, there was a third period in which species abundance (shade-tolerant and –intolerant species) increased, and richness and tree density surpassed levels in undisturbed areas. This diversity recovery was induced by species colonisation (from different functional groups), species re-appearance and interspecific competition. We found disturbance from intensive logging was the underlying mechanism for changes in tree diversity and the stimulus of numerous species interactions and responses at population and community levels. In disturbed areas, 48 years of species responses promoted partial recovery of richness, species abundance and tree density. However, stand basal area was still lower than in undisturbed areas, and species dominance and floristic composition differ from 1966 conditions. In conclusion, intensive logging impacts still persist in disturbed areas, and more species responses are likely to occur during ongoing recovery.
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 32 years 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 !15 cm 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 46 m 3 ha À1. 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 32 years after harvests of 15, 23 and 46 m 3 ha À1 were 45%, 40%, and 24%, respectively. Net aboveground carbon increment for logged forests across all harvest intensities was 0.64 Mg C ha À1 yr À1 , more than twice the rate observed in unlogged forests (0.26 Mg C ha À1 yr À1). The probabilities of timber stock recovery at the end of the 32-year period were highest after harvest intensities of 15 and 23 m 3 ha À1 (with 80% probability) and lowest after the harvest of 46 m 3 ha À1 (with 70% probability). Timber stock recovery across all harvest intensities was driven primarily by residual tree growth. Application of the legal cutting limit of 25 m 3 ha À1 will require more than 70 and 40 years to recover aboveground carbon and timber stocks, respectively, with 90% probability. Based on the low recruitment rates of the twelve species harvested, the 25 year 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.
Subtropical forests are globally important in providing ecological goods and services, but it is not clear whether functional diversity and composition can predict aboveground biomass in such forests. We hypothesized that high aboveground biomass is associated with high functional divergence (FDvar, i.e., niche complementarity) and community-weighted mean (CWM, i.e., mass ratio; communities dominated by a single plant strategy) of trait values. Structural equation modeling was employed to determine the direct and indirect effects of stand age and the residual effects of CWM and FDvar on aboveground biomass across 31 plots in secondary forests in subtropical China. The CWM model accounted for 78, 20, 6 and 2% of the variation in aboveground biomass, nitrogen concentration in young leaf, plant height and specific leaf area of young leaf, respectively. The FDvar model explained 74, 13, 7 and 0% of the variation in aboveground biomass, plant height, twig wood density and nitrogen concentration in young leaf, respectively. The variation in aboveground biomass, CWM of leaf nitrogen concentration and specific leaf area, and FDvar of plant height, twig wood density and nitrogen concentration in young leaf explained by the joint model was 86, 20, 13, 7, 2 and 0%, respectively. Stand age had a strong positive direct effect but low indirect positive effects on aboveground biomass. Aboveground biomass was negatively related to CWM of nitrogen concentration in young leaf, but positively related to CWM of specific leaf area of young leaf and plant height, and FDvar of plant height, twig wood density and nitrogen concentration in young leaf. Leaf and wood economics spectra are decoupled in regulating the functionality of forests, communities with diverse species but high nitrogen conservative and light acquisitive strategies result in high aboveground biomass, and hence, supporting both the mass ratio and niche complementarity hypotheses in secondary subtropical forests.
Managed forests are important landscape components in tropical regions and may contribute to biodiversity conservation. Yet, managing tropical forests sustainably requires an understanding of ecosystem responses to silvicultural interventions. We investigated how silvicultural intervention intensity affects tree species composition and diversity over 30 years in the Brazilian Amazon by comparing them to pre-logging conditions and to an unlogged control. The interventions comprised logging in 1982 and thinning in 1993-1994 and ranged in intensity from 19 to 53% reduction in the original basal area (BA). Trees with diameter at breast height (DBH) ≥ 5 cm were measured on eight occasions in 41 permanent sample plots of 0.25 ha each. Silvicultural intervention intensity influenced both tree species composition and its trajectory within 30 years. In contrast, tree species diversity was not impaired. High intervention intensities (with BA reduction > 6.6 m² ha–1) had a substantial influence on the community of trees (DBH ≥ 10 cm), which did not show signs of return to pre-logging species composition. The reduction of BA through harvesting damage and thinning had a stronger effect on species composition than logging of mature trees itself. Thus, damage should be kept to a minimal level and strong thinning interventions should be avoided. This may enhance ecosystem recovery and maintenance of biodiversity at other trophic levels. Since current permitted harvesting intensities in the Brazilian Amazon are lower than the lowest intensity examined in our study, legal harvesting practices are unlikely to cause substantial, long-term changes in tree species composition.
The paper deals with the effect of treatment on cut-over forests which carry a reasonable stocking of advance growth, and is not directly concerned with problems of regeneration. The general basis of silvicultural treatment is outlined, and the importance of using standing tree values as a criterion of the effect of treatment and the economics of the operation is stressed.
Vast expanses of the world’s tropical forests have been or will be impacted by the cutting and harvest of trees for timber. We evaluate the environmental impacts of such ‘selective logging’ in natural forests and conclude that these logged forests typically retain most of their biodiversity and associated ecosystem functions, as well as their carbon, climatic and soil-hydrological services. Unfortunately, the values of logged forests are often overlooked in conservation plans and related research, leaving them vulnerable to further degradation, including post-logging clearing, fires and hunting. Because logged tropical forests are very extensive, functionally important, and provide core ecosystem services, efforts to expand their role in conservation strategies are urgently needed. Key priorities are improving harvest practices to reduce negative impacts on ecosystem functions and services, and preventing the rapid conversion and loss of logged forests.
Although the regulations are imperfectly enforced, logging firms in the Brazilian Amazon are subject to forest management regulations intended to reduce environmental damage and protect future forest productivity. Additionally, voluntary best practices firms adopt to achieve environmental performance that exceed regulatory requirements are largely limited to reduced impact logging (RIL) systems that reduce harvest damage relative to conventional logging systems used by a large majority of firms in the region. Existing regulations combined with best practices may not be adequate to ensure sustained yields. This inadequacy is an important issue as Brazil implements an ambitious program of forest concessions on public lands. We analyze the profitability and environmental outcomes of best logging practices and proposed sustainability requirements. We propose two operational definitions of sustainability (the first focusing on sustaining stand-level timber volumes and the other focusing on sustaining species-level volumes within the stand) based on sustaining timber inventories across cutting cycles rather than on sustaining overall harvest yields. RIL is shown to be profitable for loggers and increase the timber available for future harvests. While volume predicted to be available for the second and third harvests are significantly lower than the available timber in the unlogged forest, the second and third harvests are projected to be profitable and have the potential for sustainability despite high opportunity costs. However, as harvesting is repeated into the future, results show the composition of the harvest shifts from higher-value shade-tolerant and emergent species toward a greater reliance on longer-lived, lower-value pioneer species. This shift may create pressure to expand the forest base under management in order to continue to supply high-value species or increase the risk of timber trespass in conservation units and areas under community or indigenous management.
Using data from a logging experiment in the eastern Brazilian Amazon region, we develop a matrix growth and yield model that captures the dynamic effects of harvest system choice on forest structure and composition. Multinomial logistic regression is used to estimate the growth transition parameters for a 10-year time step, while a Poisson regression model is used to estimate recruitment parameters. The model is designed to be easily integrated with an economic model of decisionmaking to perform tropical forest policy analysis. The model is used to compare the long-run structure and composition of a stand arising from the choice of implementing either conventional logging techniques or more carefully planned and executed reduced-impact logging (RIL) techniques, contrasted against a baseline projection of an unlogged forest. Results from "log and leave" scenarios show that a stand logged according to Brazilian management requirements will require well over 120 years to recover its initial commercial volume, regardless of logging technique employed. Implementing RIL, however, accelerates this recovery. Scenarios imposing a 40-year cutting cycle raise the possibility of sustainable harvest volumes, although at significantly lower levels than is implied by current regulations. Meeting current Brazilian forest policy goals may require an increase in the planned total area of permanent production forest or the widespread adoption of silvicultural practices that increase stand recovery and volume accumulation rates after RIL harvests.
The establishment of commercial tree regeneration is currently a focus for concern regarding the sustainability of logging in the tropical forests of Bolivia. This study compared the density, species composition, and growth of sawtimber species seedling and sapling regeneration 14 months following selection logging. Areas sampled included logging gaps, logging roads, skid trails, and log landings. Areas not disturbed by logging were also sampled as controls. The abundance and composition of competing vegetation in tree regeneration plots was also measured. The highest density and greatest initial height growth rates of tree regeneration were observed on areas with the greatest amount of soil disturbance, including log landings and logging roads. This trend was largely due to the higher densities of two common, light-seeded, shade-intolerant species, Anadenanthera colubrina and Astronium urundeuva. Despite having higher light availability than other sites, tree regeneration of all species was poor in logging gaps. Logging gaps were quickly colonized by competing vegetation, particularly lianas, where they had a percent cover 2.5 times that in undisturbed sites. Regeneration of some commercial species in these forests appears to respond more favorably to disturbances that exceed those provided by single tree selection logging. Despite the better initial establishment and growth of a few species on areas with soil disturbance caused by logging, the lack of regeneration of other commercial tree species and the increasing colonization of all sites by competing plants indicate the need for post-harvest competition control treatments to ensure vigorous commercial species regeneration that will contribute to the sustainable management of this forest.
Use of reduced-impact logging (RIL) techniques has repeatedly been shown to reduce damage caused by logging. Unfortunately, these techniques do not necessarily ameliorate the low growth rates of many commercial species or otherwise assure recovery of the initial volume harvested during the next cutting cycle. In this study, we analyze the effect of logging and application of additional silvicultural treatments (liana cutting and girdling of competing trees) on the growth rates on trees in general and on of future crop trees (FCTs) of 24 commercial timber species. The study was carried out in a moist tropical forest in Bolivia, where we monitored twelve 27-ha plots for 4 years. Plots received one of four treatments in which logging intensity and silvicultural treatments were varied: control (no logging); normal (reduced-impact) logging; normal logging and low-intensity silviculture; and, increased logging intensity and high-intensity silviculture. Tree growth rates increased with intensity of logging and silvicultural treatments. The growth rates of FCTs of commercial species were 50–60% higher in plots that received silvicultural treatments than in the normal logging and control plots. Responses to silvicultural treatments varied among functional groups. The largest increase in growth rates was observed in FCTs belonging to the partially shade-tolerant and the shade-tolerant groups. These results indicate that silvicultural treatments, in addition to the use of RIL techniques, are more likely to result in a higher percentage of timber volume being recovered after the first cutting cycle than RIL alone.
Silvicultural treatments are generally performed to improve yields of commercially valuable tree species by increasing their recruitment and growth rates. In this study we analyze the effects of three different sets of silvicultural treatments on the densities and growth rates of seedlings, saplings and poles of 23 commercial tree species in a moist tropical forest in Bolivia. The treatments vary in intensity of logging and silviculture application, and are compared to a control treatment. Silvicultural treatments applied were liberation of future crop trees from lianas and neighboring competing trees, soil scarification and stand refinements. Treatments were applied to twelve 27-ha plots. In each plot 4 transects were established to assess the density and growth of the regeneration of the 23 commercial species. Effects were measured 1 and 4 years after treatment application and were described using three ecological guilds; shade-tolerant species, partially shade-tolerant species, and long-lived pioneers. We found that the intensive silviculture treatment had the largest impact on the density and growth rates of the regeneration of the commercial species. Overall, the density of regeneration of the commercial species was higher in the control treatment than in the logged treatments 1 year after treatment application, but 3 years later these differences had disappeared. Nevertheless, there were marked shifts in densities when different size classes were considered. In nearly all treatments, the number seedlings decreased over time, while the number of saplings and poles increased. Overall shade-tolerant species were more abundant than the other two ecological guilds. Treatment had a positive effect on density only for long-lived pioneers. Growth of commercial tree regeneration was strongly affected by treatment and was highest in the intensive silvicultural treatment plots where growth of long-lived pioneers was twice that of shade-tolerant species and partial shade-tolerant species. Apart from silvicultural treatments and ecological guild, light availability had the strongest effect on growth rates. These results show that different silvicultural treatments have different effects on the regeneration of commercial tree species and that ecological guilds-specific treatments should be considered in management plans for sustainable timber production in tropical lowland forests.
The lowland rain forests of Central America are poorly known from the standpoint of management for timber production. We studied the stand dynamics of a logged Costa Rican rain forest under three different regimes of post-logging silvicultural treatment. The site was located on low hills with Ultisols in Holdridge's Tropical Wet Forest life zone. The Pentaclethra macroloba-dominated forest had been high graded before planned management began. Management of the 540 × 540 m (29.2 ha) experimental area began with a timber harvest in the whole area during 1989–1990, 4 trees ha−1 being cut overall for 10.1 m3 ha−1. The experimental plots were 180 × 180 m (3.24 ha), comprising a 100 × 100 m (1.0 ha) central permanent sample plot (PSP) with a 40-m wide buffer strip. Two types of post-harvest silvicultural treatment: liberation/refinement (in 1991) and shelterwood (in 1992) were applied under a complete randomized block design with three replicates, using logged but untreated plots as controls. PSP data reported are for the 1988–1996 period for individuals with ≥10 cm DBH. The most marked changes in forest structure were caused by silvicultural treatment, basal area under the liberation/refinement treatment being reduced to ca. 65% of its probable mature forest value. Recruitment exceeded mortality in the years following intervention under all three treatments, but forest structural recovery was slowest under the liberation/refinement treatment. Post-intervention mortality rates appeared higher under the liberation/refinement treatment than under the control or shelterwood treatments, though differences were not statistically significant. In relation to tree attributes, mortality rates increased with decreasing DBH increment, crown illumination and quality of crown form. Commercial DBH increments were higher under the liberation/refinement treatment than in control plots during the 1993–1996 period. On the basis of its response to intervention during the first seven years of management, the forest appears resilient and productive; trends over time in mortality rates under the most intense silvicultural regime require close attention however. Pentaclethra-dominated forests are important components of the productive forest resources of Costa Rica and Nicaragua and, given current deforestation rates in areas such as southern Nicaragua, it is now urgent that the existing biophysical knowledge of these forests be applied to forest conservation and management.
Silvicultural treatments are often needed in selectively logged tropical forest to enhance the growth rates of many commercial tree species and, consequently, for recovering a larger proportion of the initial volume harvested over the next cutting cycle. The available data in the literature suggest, however, that the effect of silvicultural treatments on tree growth is smaller in dry forests than in humid forest tree species. In this study, we analyze the effect of logging and application of additional silvicultural treatments (liana cutting and girdling of competing trees) on the growth rates of future crop trees (FCTs; i.e., trees of current and potentially commercial timber species with adequate form and apparent growth potential). The study was carried out in a tropical dry forest in Bolivia where a set of 21.25-ha plots were monitored for 4 years post-logging. Plots received one of four treatments that varied in intensity of both logging and silvicultural treatments as follows: normal (reduced-impact) logging; normal logging and low-intensity silviculture; increased logging intensity and high-intensity silviculture; and, unlogged controls. The silvicultural treatments applied to FCTs involved liberation from lianas and overtopping trees. Results showed that rates of FCT stem diameter growth increased with light availability, logging intensity, and intensity of silvicultural treatments, and decrease with liana infestation degree. Growth rate increment was larger in the light and intensive silvicultural treatment (22¿27%). Long-lived pioneer species showed the strongest response to intensive silviculture (50% increase) followed by total shade-tolerant species (24%) and partial shade-tolerant species (10%). While reduced-impact logging is often not sufficient to guarantee the sustainability of timber yields, application of silvicultural treatments that substantially enhanced the growth rates of FCTs will help move the management of these forests closer to the goal of sustained yield
Queensland timbers: their nomenclature, density and lyctid susceptibility
- M L Cause
- E J Rudder
- W T Kynaston
Cause, M.L., Rudder, E.J., Kynaston, W.T., 1989. Queensland timbers: their nomenclature, density and lyctid susceptibility. Queensland: Techncial Pamphlets, pp. 2.
Repairing the rainforest Wet Tropics Management Authority and Biotropica Australia Pty. Ltd
- S Goosem
- N I J Tucker
Goosem, S., Tucker, N.I.J., 2013. Repairing the rainforest Wet Tropics Management
Authority and Biotropica Australia Pty. Ltd., Cairns.