Logging Gaps Research Articles

Corrigendum to: Removal of Woody Debris from Logging Gaps Influences Soil Physical and Chemical Properties in the Short Term: A Case Study in Central Amazonia

Corrigendum to: Removal of Woody Debris from Logging Gaps Influences Soil Physical and Chemical Properties in the Short Term: A Case Study in Central Amazonia

Removal of Woody Debris from Logging Gaps Influences Soil Physical and Chemical Properties in the Short Term: A Case Study in Central Amazonia

Abstract Generally, woody residues generated from logging remain on site, although recently, forest managers have been harvesting this material for energy generation. We evaluated the impact on an Oxisol’s physical and chemical properties after removal of residues (coarse woody debris, CWD) from logging-created gaps. The logging operations occurred on private timberland in the Central Amazon. Eighteen months after creation of the gaps, soil samples were taken up to 150 cm depth in each treatment: mature undisturbed forest (FOR), gaps with residues retained on site (RET), and gaps with removal of large branches greater than 10 cm in diameter that were from logging (REM). Clay content, up to 20 cm depth, was higher in RET and REM soils than in FOR soils. Soil bulk density values increased progressively from areas of FOR to RET and REM at 0–5 cm. The highest carbon and nutrient contents were observed in the 0–5 and 5–10 cm soil layers of RET. In the 10–30 cm depth, the contents of all nutrients, except phosphorus, were higher in REM soils. According to these short-term results, it is not possible to affirm categorically that the removal of CWD has a negative impact on the nutrient status of soils in gaps created by logging operations.

Prior Position- and ZWD-Constrained PPP for Instantaneous Convergence in Real-Time Kinematic Application

PPP using Kalman filter typically takes half an hour to achieve high positioning precision, which is required for small movements detection. Many dataset gaps due to temporary GPS receiver signal loss challenge the feasibility of PPP in GPS applications for kinematic precise positioning. Additional convergence time is needed before PPP reaches the required precision again. In this study, Partial parameters were estimated by using the position and ZWD as prior constraint. The solved partial parameters were applied to initialize the Kalman filter for PPP instantaneous re-convergence. A set of bridge GPS data with logging gaps were used to validate the re-convergence performance of improved PPP. The results show that the displacements from position-constrained PPP with initialized variance are 0.14 m, 0.09 m and 0.05 m, which are much better than those from standard PPP. The precision of displacement from position- and ZWD-constrained PPP with initialized variance is slightly improved when compared with that from position-constrained PPP with initialized variance at all 3 surveying points. The bridge experiment verifies that the displacement time series of improved PPP instantaneously converges at the first epoch of all signal reacquired, in contrast, standard PPP deviates by meters. This finding suggests that improved PPP can successfully deal with the GPS data logging gaps for instantaneous convergence.

Technical and financial evaluation of enrichment planting in logging gaps with the high-value species Swietenia macrophylla and Handroanthus serratifolius in the Eastern Amazon

Enrichment planting in logging gaps is an important silvicultural treatment to ensure long-term wood production in tropical forests. Knowledge on environmental and economic aspects of enrichment planting with high commercial value timber species in logging gaps is scarce, which creates uncertainty for decision makers about the method effectiveness. To contribute to the debate, this work aimed to evaluate technically and financially enrichment planting of Swietenia macrophylla and Handroanthus serratifolius in logging gaps to serve as a model in the recovery and production increase of these species in future cutting cycles. An experiment on enrichment planting was established in 46 logging gaps in 2009 and measurements of planted individuals were done in 2011, 2014, and 2017. A cost-benefit analysis using net present value (NPV) and a sensitivity analysis were carried out on different interest rates for the production of roundwood and sawnwood. Eight years after planting, individuals of Swietenia and Handroanthus presented a diameter at breast height of 7.88 ± 1.41 cm and 5.20 ± 1.00 cm, and a Periodic Annual Increment (PAI) of 0.98 ± 0.38 cm year−1 and 0.65 ± 0.22 cm year−1, respectively. At the last measurement, Swietenia and Handroanthus individuals had a survival percentage of 51% and 24% and a mortality rate of 8% and 16% year−1, respectively. NPV was positive for Swietenia in roundwood and sawnwood harvested at 60 and 90 years after planting (2nd and 3rd cutting cycles) and for Handroanthus in sawnwood harvested 90 years after planting. Once increasing PAI in 10% and 20%, Swietenia presented the highest NPVs and Handroanthus was profitable with harvest in 60 years and PAI increasing 20%. Based on these results, a model of Swietenia and Handroanthus production and conservation through enrichment planting in logging gaps was built.

Responses in growth and dynamics of the shade-tolerant species Theobroma subincanum to logging gaps in the Eastern Amazon

Aim of study: To assess responses of the shade-tolerant species Theobroma subincanum in relation to canopy gaps created by reduced impact logging (RIL).Materials and methods: A managed forest in themunicipality ofMoju, Pará state,Brazil, harvested in 1997 through RIL was monitored during 12 years (1998-2010). Nine logging gaps were selected and classified in small, medium, and large. Four 10 m x 50 m strips starting from the gap’s border towards the forest and following the directions of cardinal points were installed. Each strip was divided in five 10 m x 10 m plots. Density, diameter distribution (DBH ≥ 5 cm with intervals = 5 cm), and diameter growth were measured.Main results: No significant changes in seedling density of T. subincanum were found, and its diameter distribution followed the reverse “J” shape during all monitoring time. T. subincanum presented diameter growth of 0.15 cm year-1 with highest Periodic Annual Increment in diameter up to three years, and stabilization in nine years after RIL. The species responded to a growth gradient inversely proportional to the gap’s border distance (p = 0.001) but not to gap size and plots direction in cardinal points around the gap.Research highlights: Shade-tolerant species such as T. subincanum have sensible and positive growth responses to disturbances caused by RIL even when seedlings received low amounts of indirect sunlight. These positive responses should be considered in the management of production forests.Keywords: Ecological group; forest management; diameter distribution; reduced impact logging (RIL).

Tree regeneration after fire and logging in sub-alpine forest on the southeastern Tibetan Plateau

Forest ecosystems provide environmental services that benefit human communities. Despite their importance, forests have experienced deforestation and land-use changes that are particularly severe in the tropics and subtropics. Increasing concern about forest sustainability management and conservation supports the need for studies on forest recovery after deforestation. Many studies have estimated that recovery of forest structure, species composition and richness takes more than 50 years to reach a state similar to that of adjacent undisturbed forests. To date, most of these studies were carried out in the tropics and at high latitudes. However, less is known about the recovery process of sub-alpine forest after deforestation. The natural sub-alpine forest on the southeastern Tibetan Plateau is an important ecosystem, which ranges from 3000 to 4400 m above the sea level (a.s.l.), and these forests were disturbed by human before 1998. In the forests near the town of Lulang, Smith fir ( Abies georgei var. smithii ) is the dominant tree species above 3500 m a.s. l. The climate is mainly influenced by the Indian monsoon and westerlies. In summer, the Indian monsoon brings abundant precipitation to our study area. The winter climate is controlled by the westerlies producing cold and dry conditions. According to the instrumental record from the Nyingchi meteorological station, mean annual temperature and total annual precipitation are 8.9°C and 672.7 mm, respectively. This area has experienced a significant warming trend during the past five decades. Our study focused on logged and burnt sites of Smith fir forests (3460–3865 m a.s. l.) near Lulang in Nyingchi. Three and five rectangular plots (30 m ´ 30 m) were established in the logged (azimuth angle: 326°–328°) and fire-affected (azimuth angle: 243°–260°) gaps, respectively. Global Positioning System (GPS) was used to record the locations of the 8 plots. For each plot, the upper and lower sides were perpendicular to the direction of slope aspect. The lower-left side of each plot was regarded as the origin for each sampling grid. To assess the regeneration in each plot, we tagged all of the trees and measured their position coordinates ( x and y ). The tree species were also recorded. The ages of the gaps were estimated by taking increment cores from nearby adult trees surrounding the gap and examining the synchronous and abrupt growth release events. These cores were then air dried, carefully sanded, and crossdated in the lab. The ring-width series were measured under the Lintab 6 system (Rinntech, Heidelberg, Germany). We used several methods to estimate the age of each tree. For the seedlings and saplings, we estimated their age by counting the number of bud scars along the main stem. For the adult trees, we used the increment borer to get a core (close to the pith) at the base of the trunk. The ages of these samples were obtained by counting the number of rings under the stereomicroscope. The date of the burnt gap formation was estimated as 1942 and the logging gap formed in 1991, both based on abrupt growth release of nearby adult trees surrounding the gaps after fire and logging. According to the surveyed data and tree age, we obtained the decadal recruitment series for each tree species. In the burnt gaps (southwestern facing slope), we found that the regenerated tree species mainly consist of spruce ( Picea likiangensis var . linzhiensis ), juniper ( Sabina squamata ) and oak ( Quercus aquifolides ). In the logged site (northwestern facing slope), the regenerated tree species is mainly Smith fir. Compared with the natural Smith fir forest, the tree density is lower in the burnt and logged sites. In summary, once the forest on the southeastern Tibetan Plateau is logged or burnt, it will take longer time to recover to undisturbed Smith fir forest.

Post-harvesting silvicultural treatments in canopy logging gaps: Medium-term responses of commercial tree species under tending and enrichment planting

Technical and scientific information on medium-term effects of post-logging silvicultural interventions on the recovery of harvestable growing stocks are hardly available. To mitigate uncertainties about these effects our study aimed to answer the following question: “What is the medium-term effect of post-harvest silvicultural treatments on mortality, growth, and the structure of commercial tree species in canopy logging gaps under tending and enrichment planting?” we study individuals planted and naturally regenerated in 72 logging gaps opened tree felling during reduced-impact logging among different silvicultural treatments: (1) natural regeneration tending (TNER); (2) enrichment planting in logging gaps (EP1); (3) enrichment planting in logging gaps previously cleaned of harvesting residuals (EP2). Mortality increased through time, EP1 presented the highest mortality rates of all treatments in the first, sixth and 11th year, TNER had the lowest at the same period. TNER and EP2 presented the highest basal area and EP2 the highest periodic annual increment. Effects of the silvicultural treatment TNER were positive, since it presented the highest survival and a high mean basal area of the initial trees. The medium-term effects of silvicultural treatments applied over individuals of commercial trees in logging gaps indicate higher survival and growth that reflected in the structure of treated individuals when compared to standard procedures of reduced impact-logging, these results bring positive outcomes to reach more sustainable future cutting cycles in the Brazilian Amazon and other tropical forests worldwide.

Rapid recovery of thermal environment after selective logging in the Amazon

Selective logging is one of the most widespread pattern of disturbance in tropical forests but has a much lower detrimental impact on forest structure than wildfires and conversion to farmland. Thus, logged tropical forest represents critical strongholds of global biodiversity. The ability of these forests to rapidly recover their baseline thermal environmental conditions will markedly influence their conservation value, particularly under global climate change. We investigated the impacts of commercial selective logging on the forest thermal environment in the Brazilian Amazon by relating canopy disturbance from logging to ambient understorey and ground surface temperatures. Specifically, we assessed the impact of selective logging on the forest thermal heterogeneity; how much post-harvest time is required for the thermal environment of logging gaps and logging roads return to unlogged primary forest levels; and the spatial availability of surface microclimates considering time of recovery since logging. Logging gaps following 1 year of recovery had a hotter understorey ambient than all other environments, especially during peak midday temperatures. Compared to the unlogged understorey, logging gaps after 3 years of recovery were only marginally warmer, and logging gaps after 5 years of recovery were slightly cooler. Older wide roads (5 years; 6 m) experienced very similar understorey thermal conditions than both narrow roads (3 m) after 1-5 years of recovery, and unlogged forest. Ground surface temperatures exhibited the largest discrepancies among all environments. The temperature range spanned by surface microclimates notably increased during peak midday heat in logging gaps following 1 year of recovery. Additionally, the proportion of cool area was smaller in younger logging gaps, but the average size of cool patches and their spatial aggregation was similar to that in unlogged forest. Although commercial selective logging can severely damage tropical forest structure, we found that the forest can fairly rapidly regain its thermal environment. Post-logging forest management should carefully focus on preventing fire incursions and illegal activities with special attention to those 3-5 years post-harvest. Thermal homeostasis in selectively logged tropical forests can be vital for long-term maintenance of global biodiversity under contemporary scenarios of climate change.

Natural regeneration of tree species in the Eastern Amazon: Short-term responses after reduced-impact logging

Forest management for timber production has improved in tropical forests with the adoption of a polycyclic silvicultural system (PSS) where harvesting is carried out using reduced-impact logging (RIL). In this study, the natural regeneration of forests harvested under RIL restrictions was assessed in three different sites of the Eastern Amazon two years after logging. A total of 7987 seedlings and saplings belonging to 197 species were sampled through 951 plots of 2×2m in 11 different natural and logging created environments. Light-demanding commercial species presented their highest density in logging environments such as logging gaps, skid trails, and borders of log decks. Shade-tolerant commercial species were more common in natural and logging gaps. Regarding the densities of harvested species in the three study sites, only 26.3% were represented by ⩾5 individuals and 28.1% were completely absent in the surveys two years after logging. These results suggest a lack of natural regeneration of the current commercial tree species in the Eastern Amazon. Therefore, post-harvesting silvicultural treatments as enrichment planting and the tending of the natural regeneration in logging gaps should be applied to ensure the regeneration of these species.

Vertebrate herbivores are the main cause of seedling mortality in a logged African rainforest—implications for forest restoration

AbstractHigh seedling mortality can limit tropical forest regeneration after disturbance, such as selective logging. However, causes of seedling mortality are often poorly understood although this information is critical for designing appropriate restoration methods. We studied seedling mortality in a rainforest in Uganda where natural recovery has failed after selective logging carried out 40 years earlier and the sites are dominated by herbaceous vegetation. We established an experiment where seeds of 12 indigenous tree species were sown into different‐sized logging gaps in order to capture factors that cause early seedling mortality. We examined whether seedling mortality was influenced by vegetation cover (VC), vertebrate herbivores (VHs), gap size, or forest compartment and recorded causes of mortality. We found that seedling mortality was in general high but showed high tree species‐specific variation (ranging from 19 to 92% six months after emergence). VHs, particularly rodents, were the most important cause of mortality. Rotting caused mortality particularly in smaller gaps, but elephant trampling, drying, being washed away by rain and falling debris were only minor mortality causes. Dense VC was not a considerable barrier to seedling survival, but by providing shelter for rodents, it indirectly increased seedling herbivory. Our results show that high seedling mortality on logged sites can limit forest regeneration and rodents in particular can be a significant factor causing high seedling mortality.

Differential Performance between Two Timber Species in Forest Logging Gaps and in Plantations in Central Africa

To develop silvicultural guidelines for high-value timber species of Central African moist forests, we assessed the performance of the pioneer Milicia excelsa (iroko, Moraceae), and of the non-pioneer light demander Pericopsis elata (assamela, Fabaceae) in logging gaps and in plantations in highly degraded areas in south-eastern Cameroon. The survival and size of each seedling was regularly monitored in the silvicultural experiments. Differences in performance and allometry were tested between species in logging gaps and in plantations. The two species performance in logging gaps was significantly different from plantations and concurred with the expectations of the performance trade-off hypothesis but not with the expectations of species light requirements. The pioneer M. excelsa survived significantly better in logging gaps while the non-pioneer P. elata grew significantly faster in plantations. The high mortality and slow growth of M. excelsa in plantations is surprising for a pioneer species but could be explained by herbivory (attacks from a gall-making psyllid). Identifying high-value native timber species (i) with good performance in plantations such as P. elata is of importance to restore degraded areas; and (ii) with good performance in logging gaps such as M. excelsa is of importance to maintain timber resources and biodiversity in production forests.

马尾松（Pinus massoniana）人工林不同大小林窗对土壤不同形态活性有机碳的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 马尾松(Pinus massoniana)人工林林窗对土壤不同形态活性有机碳的影响 DOI: 10.5846/stxb201402070221 作者: 作者单位: 四川农业大学林学院生态林业研究所,四川农业大学林学院生态林业研究所,四川农业大学林学院,四川农业大学林学院生态林业研究所,四川农业大学林学院生态林业研究所,四川农业大学林学院生态林业研究所,四川农业大学林学院生态林业研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家科技支撑计划课题 (2011BAC09B05); 国家自然科学基金(31370628); 国家自然科学基金(31300528) Effects of gap size in Pinus massoniana plantations on different soil labile organic carbon fractions Author: Affiliation: Sichuan Agricultural University,,Sichuan Agricultural University,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:研究了四川盆地低山丘陵区马尾松人工林不同大小林窗对表层土壤活性有机碳(水溶性有机碳、微生物量碳、易氧化碳)含量、分配比例及碳库管理指数的影响。结果表明:(1)林窗下土壤微生物量碳含量与分配比例较林下土壤有所升高,而水溶性有机碳与易氧化碳含量及水溶性有机碳分配比例有所降低。(2)林窗大小显著影响林窗中心土壤活性有机碳含量与分配比例。随林窗面积增大,水溶性有机碳、微生物量碳与易氧化碳含量呈现较为一致的升高趋势;水溶性有机碳和微生物量碳分配比例也升高,易氧化碳分配比例先下降后升高,稳定态碳先升高后降低;总体表现为较大林窗(900-1225m2)微生物活性强,活性有机碳含量高,且有机碳库稳定性较好。(3)土壤碳库管理指数随林窗面积增大无显著变化,但与各形态活性有机碳含量及总有机碳含量显著相关,说明土壤碳库管理指数能够相对全面地反映林窗大小对土壤碳库的影响。 Abstract:Large areas of P. massoniana plantations are often assumed to have serious ecological problems such as reduced biodiversity and soil degradation. Logging gaps are an efficient practice used to solve these problems. We investigated how the size of forest gaps in P. massoniana plantations influenced the characteristics of different soil labile organic carbon fractions and the carbon management index. Compared with those in P. massoniana plantations, the content and proportion of microbial biomass carbon increased, while the content of water-soluble organic carbon and readily oxidizable carbon, and the proportion of water-soluble organic carbon decreased in forest gaps. The size of the forest gap had significant effects on the content and proportion of labile organic carbon fractions. With the increasing size of forest gaps, the content of water-soluble organic carbon, microbial biomass carbon, and readily oxidizable carbon increased. The proportions of water-soluble organic carbon and microbial biomass carbon increased, the proportion of readily oxidizable carbon first decreased and then increased and the non-labile carbon proportion first increased and then decreased. The content and proportion of labile organic carbon and the stability of organic carbon were relatively higher in larger (900-1225 m2) gaps. The carbon management index was not significantly affected by forest gap size, which positively correlated with the content of different soil labile organic carbon fractions and soil total organic carbon. The effects of forest gap size on soil organic carbon were relatively significant in larger (900-1225 m2) forest gaps in terms of a higher stability of organic carbon and a greater amount of microbial biomass carbon and water-soluble organic carbon. This suggests that 900-1225 m2 gaps might provide optimal logging gap size for the conservation of ecological functions and natural regeneration in P. massoniana plantations. 参考文献 相似文献 引证文献

Enrichment of Logging Gaps with a High Conservation Value Species (Pericopsis elata) in a Central African Moist Forest

In central Africa, most of the timber species require high light at the seedling stage for survival and growth. Forest managers face a regeneration shortage of these light-demanding timber species. To achieve long-term sustainability, there is a need for enrichment methods combining low cost and high species performance. The aim of this study was to assess the performance of Pericopsis elata seedlings in enriched logging gaps in Cameroon. Over five years; the survival and size of each seedling was monitored in 27 logging gaps that were either left without maintenance or cleared. Gaps were relatively small with an average total area of 155 m2. We found that planted seedlings of P. elata performed well in logging gaps. Even without any maintenance 61% of the planted seedlings survived after five years with an average annual diameter increment of 0.28 cm. P. elata appeared to be a good candidate species for enrichment in logging gaps. We demonstrated that the seedlings of P. elata tolerated a wide range of soil conditions but that their performance was strongly influenced by light availability (gap clearance), suggesting potentially improved performance of P. elata in high light environments such as in plantation or larger gaps.

Regeneration in canopy gaps of tierra-firme forest in the Peruvian Amazon: Comparing reduced impact logging and natural, unmanaged forests

Reduced impact logging (RIL) has been promoted as a cornerstone in sustainable forest management in the tropics, although the ecological implications of RIL guidelines are poorly understood. This study aims to identify the impact of RIL on the regeneration of commercial timber species by comparing the regeneration dynamics of logging gaps with naturally occuring canopy gaps. In the concession of Consorcio Forestal Amazonico in the region of Ucayali in the Peruvian Amazon, a total of 210 circular sample plots were established in 35 gaps in unmanaged natural forest and 35 canopy gaps in forest managed according to RIL guidelines. The size of each canopy gap was estimated by establishing a polygon that followed the vertical projection of the edge of the gap. Three circular plots of 100 m2 were established within each canopy gap. The center points of the plots were placed at the stump, mid-trunk and crown of the fallen tree. It appeared that the total abundance of seedlings did not differ significantly between logging gaps and natural canopy gaps. Instead the response to logging varied between species groups. The Clarisia sp. species group had a significant negative response to logging, while Ormosia sp., Aniba sp., Ocotea sp., Qualea sp. and Terminalia sp. were significantly more abundant in gaps of logged-over forest. A direct effect of seed tree retention on seedling abundance could not be detected statistically. Possible reasons for observed differences between untouched and logged forest and consequences of observed patterns for long-term forest development and management were discussed. It was concluded that issuing and enforcing strict guidelines on sustainable forest management is no guarantee for preserving species composition in tropical forests.

SELECTIVE LOGGING AND DAMAGE TO UNHARVESTED TREES IN A HYRCANIAN FOREST OF IRAN

Selective logging in mature hardwood stands of Caspian forests often causes physical damage to residual trees through felling and skidding operations, resulting in a decline in bole quality and subsequent loss of tree value. This study evaluated the logging damage to residual trees following logging operations. A total density of 5.1 trees/ha and 17.3 m3/ha of wood were harvested. On average, 9.8 trees were damaged for every tree extracted, including 8 trees destroyed or severely damaged. The most common types of damage included uprooted stems, stem wounds to the cambial layer, and bark scrapes. Damage to trees sustained along skid trails was found to be significantly more than the damage that incurred within logging gaps and winching areas. The results of this study suggest that logging practices also need to be accompanied by close supervision of field personnel and post-logging site inspections to be implemented properly.

Contrasting taxonomic and functional responses of a tropical tree community to selective logging

Summary1. Considerable debate surrounds the extent to which tropical forests can be managed for resource extraction while conserving biodiversity and ecosystem properties, which depend on functional composition. Here we evaluate the compatibility of these aims by examining the effects of logging on taxonomic and functional diversity and composition in a tropical forest.2. Twenty years after selective logging, we inventoried 4140 stems regenerating in logging gaps and adjacent undisturbed areas, and we integrated a database of 13 functional traits describing leaf and wood economics of tropical trees.3. We found no differences in taxonomic and functional richness among habitats, but logging gaps had significantly higher taxonomic and functional evenness.4. Logging also effected striking, long‐term changes in both species and functional composition. In particular, the xylem density of recruits in logging gaps was 6% less than in unlogged forests, leaves were 11% less tough and had 6–13% greater mineral nutrient concentrations.5. Synthesis and applications. Our results suggest that managers of tropical forests should limit overall surface area converted to logging gaps by creating fewer, larger gaps during selective logging, to reduce impacts on the taxonomic and functional composition of the regenerating stand.

Regeneration patterns of Eastern white pine (Pinus strobus L.) in hardwood-dominated forests in Virginia, USA

Eastern white pine (Pinus strobus L.) is a moderately shade-tolerant species that co-occurs with hardwood tree species in many forests of the eastern United States, as well as in pure stands. The species is valued for its timber, as well as for wildlife and recreation. Regeneration of this species is somewhat unpredictable and often occurs in patches of similarly-aged cohorts. We described the regeneration patterns of this species and examined their relation to environmental variables within hardwood forests of southwestern Virginia, USA. An average of 5.3 white pine patches per ha were observed in this study. The majority of patches consisted of saplings (85%), with 9% of patches in pole size classes, and 6% in seedling size classes. The average density of patches was 43.5 stems with an average age of 20 years. The size of patches averaged 80.6 m2. The total density of seedlings and the number of regeneration patches of all sizes of regeneration (seedlings, saplings, and poles) in plots was related to the surrounding density of large white pine trees (potential seed trees). The density of seedlings or patches was not significantly related to current vegetation cover or soil surface cover variables, but more than half of regeneration patches were located in or adjacent to old canopy gaps, most of which were old logging gaps. While seedling regeneration may occur within the understory of these forests near seed trees, advancement to the sapling and pole stage appears to be associated with canopy gap formation.

Diameter Growth of Juvenile Trees after Gap Formation in a Bolivian Rain Forest: Responses are Strongly Species‐specific and Size‐dependent

ABSTRACTWe evaluated growth responses to gap formation for juvenile individuals of three canopy rain forest species: Peltogyne cf. heterophylla, Clarisia racemosa and Cedrelinga catenaeformis. Gaps were formed during selective logging operations 7 yr before sampling in a Bolivian rain forest. We collected wood samples for tree‐ring analyses at different distances to the stump (<10, 10–40 and >40 m) and from trees with different diameters (5–30 cm diameter at breast height [dbh]). Tree‐rings width was measured in at least two radii and converted to average diameter growth. Changes in 7‐yr median diameter growth before and after selective logging were analyzed. Diameter growth rates significantly increased by 0.7–0.8 mm/yr after gap formation for P. heterophylla and C. catenaeformis, but not for C. racemosa. We applied a multiple regression analysis to explain variation in growth responses of P. heterophylla and C. catenaeformis by distance to logging gap and tree size. For P. heterophylla we found that growth increase occurring close to logging gaps was strongest for large juvenile trees (20–25 cm dbh) and almost absent in small juveniles. For C. catenaeformis, variation in growth responses was not related to tree size or distance to gaps. Our results show that growth responses to gap formation strongly differ across species and tree sizes. This finding calls for caution in the interpretation of growth releases in tree‐ring series, as gap formation does not necessarily invoke growth responses and if such growth responses occur, their strength is species‐ and size specific.

The impact of community-based forest management on timber treeregeneration in north-eastern Honduras, with specific reference tobig-leaf mahogany (Swietenia macrophylla)

Reduced-impact logging is used to minimise the negative effects of selective logging. However, it has been suggested that low-impact logging may create too little disturbance for the regeneration of the light-demanding timber tree species, hence compromising forest productivity. This study evaluates the impact of low-intensity, non-mechanised, certified community forest management on timber tree regeneration. Particular attention was paid to big-leaf mahogany (Swietenia macrophylla), which has a regeneration pattern linked with large-scale disturbances. Logging gaps were compared to natural treefall gaps of an unlogged forest. There were more species of the light-demanding timber trees, but fewer individuals of the shade-tolerant timber species in the certified forest logging gaps, compared to unlogged forest treefall gaps. Furthermore, significant differences were found in the environmental characteristics of the logging and natural treefall gaps, although these only partially explained the differences in timber regeneration. Mahogany was found in over half of the logged forest gaps, whilst being nearly absent in the natural treefall gaps. However, all mahoganies in the established logging gaps were seedling-sized, indicating that regeneration may be hampered due to competing vegetation. The results of the study suggest that low-impact forest management may, at least in the short term, favour light-demanding species over the shade-tolerant ones, similarly to conventional forest management.

Growth responses of neotropical trees to logging gaps

Summary 1. Modelling growth strategies among tropical trees is an important objective in predicting the response of tree dynamics to selective logging and in gaining insights into the ecological processes that structure tree communities in managed tropical forests. 2. We developed a disturbance index to model the effects of distance to and area of logging gaps on stem radial growth rates. This index was tested using census data of 43 neotropical tree species, representing a variety of life‐history strategies and developmental stages, from a selectively logged forest at Paracou, French Guiana. Growth strategies were analyzed in light of two indicators: the inherent species growth rate (when disturbance index is null) and the species reaction (change in growth rate) to logging gaps. 3. Across species, the predicted inherent growth rates in unlogged forest ranged from 0·25 to 6·47 mm year−1, with an average growth of 2·29 mm year−1. Ontogenetic shifts in inherent growth rate were found in 26 of the 43 species. 4. Species growth response to logging gaps varied widely among species but was significantly positive for 27 species. The effect of ontogeny on growth response to logging was retained for 14 species, and species with inherent fast growth rate (5 mm year−1) responded less to logging gap disturbances than did species with slow inherent growth (1 mm year−1). 5. Functional traits explained 19–42% of the variation in the inherent growth rate and in species’ response across all developmental stages. Whereas maximum diameters and seed mass were strong predictors of inherent growth rate, maximum height, wood density, mode of germination and stem architecture were additionally involved in tree growth response. 6. Synthesis and applications: This study provides a necessary framework for developing predictive post‐logging growth models for the thousands of species comprising tropical forests and is sufficiently general to apply to a broad range of managed tropical forests.