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We evaluated the impacts of selective logging on tree regeneration one, four, and eight years after harvests in Antimary State Forest in the State of Acre, Brazil. We inventoried tree seedlings, saplings, and poles (>50 cm tall to

Nature conservation through sustainable forest management is challenged in the tropics by unnecessarily destructive but selective logging and diminishing timber yields. Silvicultural treatments beyond reduced-impact logging are often recommended to increase timber stocking, tree growth, and profits. Despite lack of large-scale and long-term scientific support, Indonesia has embarked on large-scale silvicultural intensification. To fill this information gap, we assessed the timber, carbon, and tree species composition consequences of different silvicultural practices in dipterocarp forests in Kalimantan, Indonesia. With data from 30 1-ha sample plots monitored for up to 20 years after silvicultural intervention coupled with a new forest growth and yield model simulation (SILFOR), we evaluated the long–term consequences of the following silvicultural practices: once logged with a minimum cutting diameter (MCD) of 60 cm (L60); once logged followed by under-planting with seedlings of commercial timber species (L60UP); twice logged with MCDs of 60 cm and then 40 cm (L60L40); and, twice logged followed by strip planting along cleared lines (L60L40SP). The results indicate that timber yields will not be sustained by L60 or L60L40 even if cutting cycles are extended from the current minimum of 30 years to 60 years. In contrast, yields from enrichment planted logged-over forests will recover to levels higher than the first cut if cutting cycles are extended to 50 years for L60UP and to 40 years for L60L40SP. Under these intensive silvicultural regimes, biomass carbon stocks also recover to primary forests levels, but with increased representation of commercial species. Although silviculturally successful, the financial consequences of these approaches to management intensification remain to be scrutinized.

Bastin et al.’s estimate (Reports, 5 July 2019, p. 76) that tree planting for climate change mitigation could sequester 205 gigatonnes of carbon is approximately five times too large. Their analysis inflated soil organic carbon gains, failed to safeguard against warming from trees at high latitudes and elevations, and considered afforestation of savannas, grasslands, and shrublands to be restoration., Funding: Supported by the Texas A&M Sid Kyle Global Savanna Research Initiative (T.W.B.); Swiss National Science Foundation (20FI20_173691) (N.B.); Centre National pour la Recherche Scientifique CNRS PICS 2018-2020 (RESIGRASS) (E.B.); CNPq (Brazil, 303179/2016-3) (G.D.); CNPq (Brazil) (G.W.F.); CNPq (Brazil, 303988/2018-5) (A.F.); NASA award NNX17AK14G (F.F.); NSF award 1354943 (W.A.H.); Fundação de Amparo à Pesquisa do Estado de Minas Gerais (Brazil, 2016/13232-5) (S.L.S.); the Office of the Royal Society (IC170015) (C.E.R.L.); CNPq (Brazil, 310345/2018-9) (G.E.O.); the Spanish Government (FIROTIC, PGC2018-096569-B-I00) (J.G.P.); the National Research Foundation (ACCESS, 114695) (N.S.); CNPq (Brazil, 303568/2017-8) (F.A.O.S.); NSF awards 1342703 and 1926431 (C.J.S. and D.M.G.); NSF award EAR-1253713 (C.A.E.S.); Deutsche Forschungsgemeinschaft grant 5579 POEM (V.M.T.); and USDA-NIFA Sustainable Agricultural Systems Grant 12726253 (J.W.V.)

The selective logging that characterizes most timber extraction operations in the tropics leaves large patches of logging blocks (i.e., areas allocated for harvesting) intact, without evidence of direct impacts. For example, in ~10,000 ha sampled in 48 forest management enterprises in Africa (Gabon, Republic of Congo, and the Democratic Republic of Congo), Indonesia, Suriname, and Mexico, an average of 69% (range 20–97%) of the area in logging blocks was not directly affected by timber harvests. The proportion of intact forest within logging blocks decreased very slightly with increases in harvest intensity in the accessed portion of the logging blocks (9–86 m3 ha−1) but decreased strongly with harvest intensity in entire logging blocks (0.3–48.2 m3 ha−1). More forest was left intact in areas farther from roads, on slopes >40%, and within 25 m of perennial streams, but the effect sizes of each of these variables was small (~8%). It is less clear how much of the intact forest left after one harvest will remain intact through the next. Conservation benefits without reductions in timber yields will derive from better management planning so that sensitive and ecologically critical areas, such as steep slopes and riparian buffers, constitute large and permanent proportions of the intact forest in selectively logged landscapes in the tropics.

Tropical forests are globally important for both biodiversity conservation and the production of economically valuable wood products. To deliver both simultaneously, two contrasting approaches have been suggested: one partitions forests (sparing); the other integrates both objectives in the same location (sharing). To date, the ‘sparing or sharing’ debate has focused on agricultural landscapes, with scant attention paid to forest management. We explore the delivery of biodiversity and wood products in a continuum of sparing-to-sharing scenarios, using spatial optimization with set economic returns in East Kalimantan, Indonesia—a biodiversity hotspot. We found that neither sparing nor sharing extremes are optimal, although the greatest conservation value was attained towards the sparing end of the continuum. Critically, improved management strategies, such as reduced-impact logging, provided larger conservation gains than altering the balance between sparing and sharing, particularly for endangered species. Ultimately, debating sparing versus sharing has limited value while larger gains remain from improving forest management. To achieve both biodiversity conservation and timber production in tropical forests, this modelling study finds that improved management has much more impact than the choice between sparing forests or sharing forest land for both purposes.

Tropical dry forests (TDF) are highly threatened ecosystems that are often fragmented due to land-cover change. Using plot inventories, we analyzed tree species diversity, community composition and aboveground biomass patterns across mature (MF) and secondary forests of about 25 years since cattle ranching ceased (SF), 10–20-year-old plantations (PL), and pastures in a TDF landscape in Ecuador. Tree diversity was highest in MF followed by SF, pastures and PL, but many endemic and endangered species occurred in both MF and SF, which demonstrates the importance of SF for species conservation. Stem density was higher in PL, followed by SF, MF and pastures. Community composition differed between MF and SF due to the presence of different specialist species. Some SF specialists also occurred in pastures, and all species found in pastures were also recorded in SF indicating a resemblance between these two land-cover types even after 25 years of succession. Aboveground biomass was highest in MF, but SF and Tectona grandis PL exhibited similar numbers followed by Schizolobium parahyba PL, Ochroma pyramidale PL and pastures. These findings indicate that although species-poor, some PL equal or surpass SF in aboveground biomass, which highlights the critical importance of incorporating biodiversity, among other ecosystem services, to carbon sequestration initiatives. This research contributes to understanding biodiversity conservation across a mosaic of land-cover types in a TDF landscape.

Concerns about the sustainability of tropical forestry motivated this study on post-logging timber and carbon dynamics over a 20-year period in Paragominas, Para, Brazil. Previously unlogged forest was subjected to conventional logging (CL), reduced-impact logging (RIL), or was set aside as an unlogged control. All trees ⩾25 cm DBH and all trees of commercial species ⩾10 cm DBH were monitored in a 24.5 ha plot in each treatment, with a 5.25 ha subplot in each for monitoring all trees ⩾10 cm DBH. Above-ground biomass and bole volumes of merchantable species were tracked based on 10 inventories made between 1993 and 2014. Pre-logging biomass and bole volumes of commercial species were estimated as 237, 231, and 211 Mg ha−1, and 78, 80, and 70 m3 ha−1, in the RIL, CL, and unlogged plots, respectively. One year after logging, biomass was reduced 14% by RIL and 24% by CL with corresponding merchantable species volume reductions of 21% and 31%. By 2014, biomass and bole volumes of commercial species had recovered 95% and 98% of their pre-logging stocks in the RIL plot but only 76% and 72% in the CL plot, respectively; timber volumes from large trees (⩾50 cm DBH) were only recovered to 81% in the RIL plot and to 53% in the CL plot. Over the first twenty years after logging, average volume increments from commercial species were substantially higher in the RIL plot (0.72 m3 ha−1 year−1) than in the CL plot (0.08 m3 ha−1 year−1). Recovery of both biomass and timber volumes were temporarily reversed between 2009 and 2014 due to a 4-fold increase in annual mortality rates in the RIL plot and a 5.5-fold increase in the CL plot (as well as a 3-fold increase in the control plot), all presumably related to the extreme drought of 2010. Our findings support the claim that use of RIL techniques accelerates rates of biomass and timber stock recovery after selective logging.

To assess the impacts of a low-intensity selective timber harvest on a palm community in Belize, we mapped logging infrastructure (i.e., roads, log landings, skid trails, and stumps) and measured palm regeneration 1 year after a timber harvest carried out using reduced-impact logging (RIL) practices. We sampled palms across a gradient of increasing harvest impact severity from areas not directly affected by logging, in felling gaps, on secondary and primary skid trails, and on log landings. We used generalised linear mixed-effect models fitted in a Bayesian framework and applied a non-metric multi-dimensional scaling of the ecological distances between sites to evaluate differences in palm seedling regeneration density and species composition, respectively. The harvest of an average of 2.5 trees ha−1 caused 0.4% of the forest to be converted to log landings, 0.7% and 3.6% to roads and skid trails, and 2.3% to felling gaps, which left 93.0% of the 350 ha harvest block with no direct impacts of logging. The difference in abundance and species composition of palm regeneration in unlogged areas compared to felling gaps and skid trails was small, but log landings had markedly lower densities. These results highlight that the impacts of selective logging are minor at least where harvest intensities are low and RIL practices are employed. If further reductions in canopy opening and soil disturbance are desired, we recommend that logs be cable-yarded (i.e., winched) the final 20 m to skid trails instead of driving to the tree stumps. We estimate that implementation of this practice would reduce total skid trail coverage from 3.6% to 2.9% and overall forest disturbance from 7.0% to 6.3%. However, further reductions in disturbance might be inimical to the maintenance of palms and will certainly not favour regeneration of light-demanding commercial timber species (e.g., Swietenia macrophylla).

Tropical forests are crucial in terms of biodiversity and ecosystem services, but at the same time, they are major sources of revenue and provide livelihoods for forest-dependent people. Hopes for the simultaneous achievement of conservation goals and poverty alleviation are therefore increasingly placed on forests used for timber extraction. Most timber exploitation is carried out unsustainably, which causes forest degradation. Two important mechanisms have emerged to promote sustainable forest management: certification and community-based forest management (CFM). We synthesize the published information about how forest certification and CFM perform in terms of environmental, social, and economic variables. With the caveat that very few published studies meet the standards for formal impact evaluation, we found that certification has substantial environmental benefits, typically achieved at a cost of reduced short-term financial profit, and accompanied by some improvement to the welfare of neighboring communities. We found that the economic and environmental benefits of CFM are understudied, but that the social impacts are controversial, with both positive and negative changes reported. We identify the trade-offs that likely caused these conflicting results and that, if addressed, would help both CFM and certification deliver the hoped-for benefits. (Resume d'auteur)

Attempts to restore savannas are often thwarted by the resprouting of unwanted woody plants after they are top-killed by fire or mechanical treatments. In an effort to reduce stump sprouting of native to the region but invasive Quercus hemisphaerica (laurel oak) and Q. nigra (water oak) in an area being restored to longleaf pine (Pinus palustris) savanna, we treated 5–19 cm diameter stumps in ways opposite to the recommended practices for coppice management. Specifically, we created high stumps (1 m) and split half longitudinally (1 m-split); we also cut a sample at ground level (0 m), as recommended for coppice management. Over the 9-year observation period about 45% of the stumps died, with no treatment or species effects. Survival of individual sprouts was higher for Q. nigra than Q. hemisphaerica. In both species, sprouts from the 1 m stumps suffered the highest mortality rates, followed by the 0 m and 1 m-split treatments; number of sprouts per stump followed the same pattern (1 m > 0 m > 1 m-split). Root collar sprouts were more likely to survive than those that emerged higher on the stump or from rhizomes, and sprout mortality decreased with stump diameter in Q. nigra but not Q. hemisphaerica. Sprout survival decreased but sprout growth increased with canopy openness. About 40% of all sprouts were from rhizomes. Contrary to our expectation, wood decay was rare in all sprouts, regardless of their diameter or the height from which they emerged. These results confirm the benefits of treating stumps with herbicides to reduce unwanted trees in savannas undergoing restoration.

We compared stump sprouting by three common timber species in Suriname on the basis of sprout origins on stumps, sprout densities, and sprout height:diameter ratios. We then compared some leaf and stem functional traits of 15&ndash, 18-month-old resprouts and nearby conspecific saplings of the same height (0.5&ndash, 3.5 m) but unknown age. Stumps of Dicorynia guianensis Amsh. (29&ndash, 103 cm in diameter) produced the most sprouts (x = 9.2/stump), followed by the 50&ndash, 71 cm diameter stumps of Eperua falcata Amsh. (10.6/stump), and the 30&ndash, 78 cm diameter Qualea rosea Amsh. (5.9/stump), sprout density did not vary with stump diameter. Sprouts emerged from the lower, middle, and upper thirds of the stumps of all three species, but not from the vicinity of the exposed vascular cambium in Qualea. With increased resprout density, heights of the tallest sprout per stump tended to increase but height:diameter ratios increased only in Dicorynia. Compared to conspecific saplings, sprouts displayed higher height-diameter ratios, higher leaf-to-wood mass ratios (LWR), and lower wood densities, but did not differ in leaf mass per unit area (LMA) or leaf water contents. These acquisitive functional traits may reflect increased resprout access to water and nutrients via the extensive root system of the stump. That we did not encounter live stump sprouts from the previous round of selective logging, approximately 25 years before our study, suggests that stump sprouts in our study area grow rapidly but do not live long.

We evaluate the effects of “Water and Forest Producers” (PAF), a payment for ecosystem services project, on forest cover outcomes in a watershed serving the Rio de Janeiro region of Brazil. We apply propensity score matching and regression to 81 beneficiary properties on 8848 ha and 398 control properties on 33,748 ha. We estimate the average treatment effect on the treated for changes in rates of reforestation and deforestation, and the resulting change in forest cover. Over the first 7 years of PAF (2010–2016), our results indicate that the project increased forest cover on participating properties by only 136 ha (95% confidence intervals of 8–265 hectares), or 1.5% relative to our estimate of the counterfactual scenario without PAF. Impacts on forest cover were caused mostly by reduced deforestation rather than reforestation. “Placebo” impact tests estimated using pre-intervention data indicate that our results are robust. The observed forest cover benefit came at the per-hectare cost of $32,963 ($16,917-$560,367) paid mostly with off-site mitigation funds. Semi-structured interviews with PAF beneficiaries suggest that the limited impacts of PAF may be the result of mostly enrolling properties that likely would have remained forested even without the project.

Large trees in the tropics are reportedly more vulnerable to droughts than their smaller neighbours. This pattern is of interest due to what it portends for forest structure, timber production, carbon sequestration and multiple other values given that intensified El Niño Southern Oscillation (ENSO) events are expected to increase the frequency and intensity of droughts in the Amazon region. What remains unclear is what characteristics of large trees render them especially vulnerable to drought-induced mortality and how this vulnerability changes with forest degradation. Using a large-scale, long-term silvicultural experiment in a transitional Amazonian forest in Bolivia, we disentangle the effects of stem diameter, tree height, crown exposure and logging-induced degradation on risks of drought-induced mortality during the 2004/2005 ENSO event. Overall, tree mortality increased in response to drought in both logged and unlogged plots. Tree height was a much stronger predictor of mortality than stem diameter. In unlogged plots, tree height but not crown exposure was positively associated with drought-induced mortality, whereas in logged plots, neither tree height nor crown exposure was associated with drought-induced mortality. Our results suggest that, at the scale of a site, hydraulic factors related to tree height, not air humidity, are a cause of elevated drought-induced mortality of large trees in unlogged plots. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications'.

When 2 Mha of Amazonian forests are disturbed by selective logging each year, more than 90 Tg of carbon (C) is emitted to the atmosphere. Emissions are then counterbalanced by forest regrowth. With an original modelling approach, calibrated on a network of 133 permanent forest plots (175 ha total) across Amazonia, we link regional differences in climate, soil and initial biomass with survivors’ and recruits’ C fluxes to provide Amazon-wide predictions of post-logging C recovery. We show that net aboveground C recovery over 10 years is higher in the Guiana Shield and in the west (21 ±3 Mg C ha-1) than in the south (12 ±3 Mg C ha-1) where environmental stress is high (low rainfall, high seasonality). We highlight the key role of survivors in the forest regrowth and elaborate a comprehensive map of post-disturbance C recovery potential in Amazonia. DOI: http://dx.doi.org/10.7554/eLife.21394.001, eLife digest The Amazon rainforest in South America is the largest tropical forest in the world. Along with being home to a huge variety of plants and wildlife, rainforests also play an important role in storing an element called carbon, which is a core component of all life on Earth. Certain forms of carbon, such as the gas carbon dioxide, contribute to climate change so researchers want to understand what factors affect how much carbon is stored in rainforests. Trees and other plants absorb carbon dioxide from the atmosphere and then incorporate the carbon into carbohydrates and other biological molecules. The Amazon rainforest alone holds around 30% of the total carbon stored in land-based ecosystems. Humans selectively harvest certain species of tree that produce wood with commercial value from the Amazon rainforest. This “selective logging” results in the loss of stored carbon from the rainforest, but the loss can be compensated for in the medium to long term if the forest is left to regrow. New trees and trees that survived the logging grow to fill the gaps left by the felled trees. However, it is not clear how differences in the forest (for example, forest maturity), environmental factors (such as climate or soil) and the degree of the disturbance caused by the logging affect the ability of the forest ecosystem to recover the lost carbon. Piponiot et al. used computer modeling to analyze data from over a hundred different forest plots across the Amazon rainforest. The models show that the forest’s ability to recover carbon after selective logging greatly differs between regions. For example, the overall amount of carbon recovered in the first ten years is predicted to be higher in a region in the north known as the Guiana Shield than in the south of the Amazonian basin where the climate is less favorable. The findings of Piponiot et al. highlight the key role the trees that survive selective logging play in carbon recovery. The next step would be to couple this model to historical maps of logging to estimate how the areas of the rainforest that are managed by selective logging shape the overall carbon balance of the Amazon rainforest. DOI: http://dx.doi.org/10.7554/eLife.21394.002

Better stewardship of land is needed to achieve the Paris Climate Agreement goal of holding warming to below 2 °C; however, confusion persists about the specific set of land stewardship options available and their mitigation potential. To address this, we identify and quantify "natural climate solutions" (NCS): 20 conservation, restoration, and improved land management actions that increase carbon storage and/or avoid greenhouse gas emissions across global forests, wetlands, grasslands, and agricultural lands. We find that the maximum potential of NCS-when constrained by food security, fiber security, and biodiversity conservation-is 23.8 petagrams of CO2 equivalent (PgCO2e) y-1 (95% CI 20.3-37.4). This is ≥30% higher than prior estimates, which did not include the full range of options and safeguards considered here. About half of this maximum (11.3 PgCO2e y-1) represents cost-effective climate mitigation, assuming the social cost of CO2 pollution is ≥100 USD MgCO2e-1 by 2030. Natural climate solutions can provide 37% of cost-effective CO2 mitigation needed through 2030 for a >66% chance of holding warming to below 2 °C. One-third of this cost-effective NCS mitigation can be delivered at or below 10 USD MgCO2-1 Most NCS actions-if effectively implemented-also offer water filtration, flood buffering, soil health, biodiversity habitat, and enhanced climate resilience. Work remains to better constrain uncertainty of NCS mitigation estimates. Nevertheless, existing knowledge reported here provides a robust basis for immediate global action to improve ecosystem stewardship as a major solution to climate change.

Sea level rise elicits short- and long-term changes in coastal plant communities by altering the physical conditions that affect ecosystem processes and species distributions. While the effects of sea level rise on salt marshes and mangroves are well studied, we focus on its effects on coastal islands of freshwater forest in Florida's Big Bend region, extending a dataset initiated in 1992. In 2014–2015, we evaluated tree survival, regeneration, and understory composition in 13 previously established plots located along a tidal creek; 10 plots are on forest islands surrounded by salt marsh, and three are in continuous forest. Earlier studies found that salt stress from increased tidal flooding prevented tree regeneration in frequently flooded forest islands. Between 1992 and 2014, tidal flooding of forest islands increased by 22%–117%, corresponding with declines in tree species richness, regeneration, and survival of the dominant tree species, Sabal palmetto (cabbage palm) and Juniperus virginiana (southern red cedar). Rates of S. palmetto and J. virginiana mortality increased nonlinearly over time on the six most frequently flooded islands, while salt marsh herbs and shrubs replaced forest understory vegetation along a tidal flooding gradient. Frequencies of tidal flooding, rates of tree mortality, and understory composition in continuous forest stands remained relatively stable, but tree regeneration substantially declined. Long-term trends identified in this study demonstrate the effect of sea level rise on spatial and temporal community reassembly trajectories that are dynamically re-shaping the unique coastal landscape of the Big Bend.

When net deforestation declines in the tropics, attention will be drawn to the composition and structure of the retained, restored, invaded, and created forests. At that point, the seemingly inexorable trends toward increased intensities of exploitation and management will be recognized as having taken their tolls of biodiversity and other forest values. Celebrations when a country passes this ‘forest transition’ will then be tempered by realization that what has been accepted as ‘forest’ spans the gamut from short-rotation mono-clonal stands of genetically engineered trees to fully protected old growth natural forest. With management intensification, climate change, species introductions, landscape fragmentation, fire, and shifts in economics and governance, forests will vary along gradients of biodiversity, novelty of composition, stature, permanence, and the relative roles of natural and anthropogenic forces. Management intensity will increase with the increased availability of financial capital associated with economic globalization, scarcity of wood and other forest products, demand for biofuels, improved governance (e.g., security of property rights), improved accessibility, and technological innovations that lead to new markets for forest products. In a few places, the trend toward land-use intensification will be counterbalanced by recognition of the many benefits of natural and semi-natural forests, especially where forest-fate determiners are compensated for revenues foregone from not intensifying management. Land-use practices informed by research designed and conducted by embedded scientists will help minimize the tradeoffs between the financial profits from forest management and the benefits of retention of biodiversity and the full range of environmental services.

Adoption of reduced-impact logging (RIL) methods could reduce CO2 emissions by 30-50% across at least 20% of remaining tropical forests. We developed two cost effective and robust indices for comparing the climate benefits (reduced CO2 emissions) due to RIL. The indices correct for variability in the volume of commercial timber among concessions. We determined that a correction for variability in terrain slope was not needed. We found that concessions certified by the Forest Stewardship Council (FSC, N = 3), when compared with noncertified concessions (N = 6), did not have lower overall CO2 emissions from logging activity (felling, skidding, and hauling). On the other hand, FSC certified concessions did have lower emissions from one type of logging impact (skidding), and we found evidence of a range of improved practices using other field metrics. One explanation of these results may be that FSC criteria and indicators, and associated RIL practices, were not designed to achieve overall emissions reductions. Also, commonly used field metrics are not reliable proxies for overall logging emissions performance. Furthermore, the simple distinction between certified and noncertified concessions does not fully represent the complex history of investments in improved logging practices. To clarify the relationship between RIL and emissions reductions, we propose the more explicit term 'RIL-C' to refer to the subset of RIL practices that can be defined by quantified thresholds and that result in measurable emissions reductions. If tropical forest certification is to be linked with CO2 emissions reductions, certification standards need to explicitly require RIL-C practices.

Interventions designed to reduce emissions of atmospheric heat-trapping gases from tropical forest degradation are more likely to succeed if based on previous experiences and if they are clearly linked to other on-going conservation and development initiatives. Links between forest management certification, climate change mitigation, and forest product legality assurance already being made on the ground by forest auditors should be recognized and enhanced. Similar synergies are also important at the international policy level, but we focus at the forest level and on the decisions of individual workers and the effectiveness of forest auditors. We stress how designs of linked conservation interventions should be based on theories of change that recognize the complexity of issues at stake across the hierarchy of actors and re-contextualize the processes so as to direct them towards emission-reductions and other desired outcomes. We posit the need to invest in building the capacity of both those responsible for and affected by forest loss and degradation for more efficient and accountable implementation of REDD+ and related conservation interventions.

Comparisons of the costs of reduced-impact (RIL) and conventional logging (CL) based on new data from Gabon and 10 previously published studies revealed that some tropical forest operators should adopt RIL out of financial self-interest but many may require other motivation. Among the comparisons in which costs were expressed per cubic meter of harvested timber, three reported lower costs for RIL, one showed identical costs with CL, and six reported RIL to be more costly.

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.

Selective logging is an important socio-economic activity in the Congo Basin but one with associated environmental costs, some of which are avoidable through the use of reduced-impact logging (RIL) practices. With increased global concerns about biodiversity losses and emissions of carbon from forest in the region, more information is needed about the effects of logging on forest structure, composition, and carbon balance. We assessed the consequences of low-intensity RIL on above-ground biomass and tree species richness in a 50 ha area in northwestern Gabon. We assessed logging impacts principally in 10 randomly located 1-ha plots in which all trees ⩾10 cm dbh were measured, identified to species, marked, and tagged prior to harvesting. After logging, damage to these trees was recorded as being due to felling or skidding (i.e., log yarding) and skid trails were mapped in the entire 50-ha study area. Allometric equations based on tree diameter and wood density were used to transform tree diameter into biomass. Logging was light with only 0.82 trees (8.11 m3) per hectare extracted. For each tree felled, an average of 11 trees ⩾10 cm dbh suffered crown, bole, or root damage. Skid trails covered 2.8% of the soil surface and skidding logs to the roadside caused damage to an average of 15.6 trees ⩾10 cm dbh per hectare. No effect of logging was observed on tree species richness and pre-logging above-ground forest biomass (420.4 Mg ha−1) declined by only 8.1% (34.2 Mg ha−1). We conclude from these data that with harvest planning, worker training in RIL techniques, and low logging intensities, substantial carbon stocks and tree species richness were retained in this selectively logged forest in Gabon.

Soil characteristics are important drivers of variation in wet tropical forest structure and diversity, but few studies have evaluated these relationships in drier forest types. Using tree and soil data from 48 and 32 1ha plots, respectively, in a Bolivian moist and dry forest, we asked how soil conditions affect forest structure and diversity within each of the two forest types. After correcting for spatial effects, soil-vegetation relationships differed between the dry and the moist forest, being strongest in the dry forest. Furthermore, we hypothesized that soil nutrients would play a more important role in the moist forest than in the dry forest because vegetation in the moist forest is less constrained by water availability and thus can show its full potential response to soil fertility. However, contrary to our expectations, we found that soil fertility explained a larger number of forest variables in the dry forest (50 percent) than in the moist forest (17 percent). Shannon diversity declined with soil fertility at both sites, probably because the most dominant, shade-tolerant species strongly increased in abundance as soil fertility increased.

Large-scale wildfires are expected to accelerate forest dieback in Amazonia, but the fire vulnerability of tree species remains uncertain, in part due to the lack of studies relating fire-induced mortality to both fire behavior and plant traits. To address this gap, we established two sets of experiments in southern Amazonia. First, we tested which bark traits best predict heat transfer rates (R) through bark during experimental bole heating. Second, using data from a large-scale fire experiment, we tested the effects of tree wood density (WD), size, and estimated R (inverse of cam- bium insulation) on tree mortality after one to five fires. In the first experiment, bark thickness explained 82% of the variance in R, while the presence of water in the bark reduced the difference in temperature between the heat source and the vascular cambium, perhaps because of high latent heat of vaporization. This novel finding provides an important insight for improving mechanistic models of fire-induced cambium damage from tropical to temperate regions. In the second experiment, tree mortality increased with increasing fire intensity (i.e. as indicated by bark char height on tree boles), which was higher along the forest edge, during the 2007 drought, and when the fire return inter- val was 3 years instead of one. Contrary to other tropical studies, the relationship between mortality and fire intensity was strongest in the year following the fires, but continued for 3 years afterwards. Tree mortality was low ( � 20%) for thick-barked individuals ( � 18 mm) subjected to medium-intensity fires, and significantly decreased as a function of increasing tree diameter, height and wood density. Hence, fire-induced tree mortality was influenced not only by cambium insulation but also by other traits that reduce the indirect effects of fire. These results can be used to improve assessments of fire vulnerability of tropical forests.

As in many other developing countries, the state government of Acre, Brazil, is developing a program for compensating forest holders (such as communities of rubber tappers and indigenous peoples as well as small, medium and large private land holders) reducing their emission of atmospheric heat-trapping gases by not deforesting. We describe and then apply to Acre a method for estimating carbon stocks by land cover type. We then compare the results of our simple method, which is based on vegetation mapping and ground-based samples, with other more technically demanding methods based on remote sensing. We estimated total biomass carbon stocks by multiplying the measured above-ground biomass of trees >10 cm DBH in each of 18 forest types and published estimates for non-forest areas, as determined by measurement of 44 plots throughout the state (ranging from 1 to 10 ha each), by land-cover area estimated using a geographical information system. State-wide, we estimated average above-ground biomass in forested areas to be 246 ± 90 Mg ha −1 ; dense forest showed highest (322 ± 20 Mg ha −1 ) and oligotrophic dwarf forest ( campinarana ) the lowest biomass (20 ± 30 Mg ha −1 ). The two most widespread forest types in Acre, open canopy forests dominated by either palms and bamboo (for which ground-based data are scant), support an estimated 246 ± 44 and 224 ± 50 Mg ha −1 of above-ground biomass, respectively. We calculate the total above-ground biomass of the 163,000 km 2 State of Acre to be 3.6 ± 0.8 Pg (non-forest biomass included). This estimate is very similar to two others generated using much more technologically demanding methods, but all three methods, regardless of sophistication, suffer from lack of field data.

Damage to the Fukushima Nuclear Power Plant by the recent earthquake and tsunami that hit northern Japan should stimulate consideration of alternative sources of energy. In particular, if managed appropriately, the 25.1 million ha of Japanese forests could be an important source of wood biomass for bioenergy production. Here, we discuss policy incentives for substituting wood bioenergy for nuclear power, thereby creating a safer society while better managing the forest resources in Japan.

The State of Florida (USA) is especially threatened by sea level rise due to extensive low elevation coastal habitats (approximately 8,000 km2 < 1 m above sea level) where the majority of the human population resides. We used the Sea Level Affecting Marshes Model (SLAMM) simulation to improve understanding of the magnitude and location of these changes for 58,000 ha of the Waccasassa Bay region of Florida’s central Gulf of Mexico coast. To assess how well SLAMM portrays changes in coastal wetland systems resulting from sea level rise, we conducted a hindcast in which we compared model results to 30 years of field plot data. Overall, the model showed the same pattern of coastal forest loss as observed. Prospective runs of SLAMM using 0.64 m, 1 m and 2 m sea level rise scenarios predict substantial changes over this century in the area covered by coastal wetland systems including net losses of coastal forests (69%, 83%, and 99%, respectively) and inland forests (33%, 50%, and 88%), but net gains of tidal flats (17%, 142%, and 3,837%). One implication of these findings at the site level is that undeveloped, unprotected lands inland from the coastal forest should be protected to accommodate upslope migration of this natural community in response to rising seas. At a broader scale, our results suggest that coastal wetland systems will be unevenly affected across the Gulf of Mexico as sea level rises. Species vulnerable to these anticipated changes will experience a net loss or even elimination.

Changes in land-uses, fire regimes, and climate are expected to promote savanna expansion in the Amazon Basin, but most studies that come to this conclusion fail to define “savanna” clearly or imply that natural savannas of native species will spread at the expense of forest. Given their different conservation values, we sought to differentiate between species-diverse natural savannas and other types of fire-maintained grass-dominated vegetation that replaced tropical forests between 1986 and 2005 in 22,500 km 2 of eastern lowland Bolivia. Analysis of Landsat TM and CBERS-2 satellite imagery revealed that, in addition to 1200 km 2 (7.1%) of deforestation for agriculture and planted pastures, 1420 km 2 (8.4%) of forest was replaced by derived savannas. Sampling in 2008 showed that natural savannas differed from forest-replacing derived savannas floristically, in soil fertility, and in fuel loads. Natural savannas typically occurred on sandy, acidic, nutrient-poor soils whereas most derived savannas were on comparatively fertile soils. Fuel loads in derived savannas were twice those of natural savannas. Natural savannas supported a diversity of grass species, whereas derived savannas were usually dominated by Guadua paniculata (native bamboo), Urochloa spp. (exotic forages), Imperata brasiliensis (native invasive), Digitaria insularis (native ruderal), or the native fire-adapted herb Hyptis suaveolens (Lamiaceae). Trees in derived savannas were forest species (e.g., Anadenanthera colubrina ) and fire-tolerant palms ( Attalea spp.), not thick-barked species characteristic of savanna environments (e.g., Curatella americana ). In addressing tropical vegetation transitions it is clearly important to distinguish between native species-diverse ecosystems and novel derived vegetation of similar structure.

"In this review paper, we assess the economical, governance, and technical conditions that shape forest management in tropical Latin America with particular regard to efforts to reduce forest-based carbon emissions. We provide a framework for discussions about ways to improve forest management that achieve environmental objectives while promoting local and national development and contributing to local livelihoods. We argue that many management practices that lead towards sustainability are only likely to be adopted where there is good governance backed by financial incentives for effective enforcement of management regulations. We propose some policy interventions designed to lower net greenhouse gas emissions by decreasing rates of forest degradation and increasing carbon stock recovery in logged-over or otherwise degraded forests. Implementation of REDD+ could provide critical compensation to forest users for improved management practices in the absence of, or in combination with other economic incentives."

Inclusion of improved forest management as a way to enhance carbon sinks in the Copenhagen Accord of the United Nations Framework Convention on Climate Change (December 2009) suggests that forest restoration will play a role in global climate change mitigation under the post-Kyoto agreement. Although discussions about restoration strategies often pertain solely to severely degraded tropical forests and invoke only the enrichment planting option, different approaches to restoration are needed to counter the full range of degrees of degradation. We propose approaches for restoration of forests that range from being slightly to severely degraded. Our methods start with ceasing the causes of degradation and letting forests regenerate on their own, progress through active management of natural regeneration in degraded areas to accelerate tree regeneration and growth, and finally include the stage of degradation at which re-planting is necessary. We argue that when the appropriate techniques are employed, forest restoration is cost-effective relative to conventional planting, provides abundant social and ecological co-benefits, and results in the sequestration of substantial amounts of carbon. For forest restoration efforts to succeed, a supportive post-Kyoto agreement is needed as well as appropriate national policies, institutional arrangements, and local participation.

To illustrate the importance of theories-of-change (ToCs) for evaluation of conservation interventions, we consider the global ToC from the Forest Stewardship Council (FSC) and then develop a more explicit ToC focused on the sustained timber yield (STY) aspiration for natural forest management in Indonesia. We use these ToCs to consider certification implementation processes vis-&agrave, vis indicators for STY extracted from FSC&rsquo, s Indonesian Stewardship Standard that mentions STY explicitly in 45 and implicitly in 21 of 237 indicators. Analysis of 38 audit reports about 23 enterprises (2001&ndash, 2017) revealed that only 77 of 504 major non-conformities assigned by auditors addressed STY. This apparent lack of attention to STY is surprising given the exhaustion of timber stocks in many production forests and the closure of many forest enterprises over the past two decades, but our ToC reveals numerous unsatisfied and unsatisfiable assumptions in certification that preclude detection of unsustainable harvests. Furthermore, compliance with governmental regulations on harvest intensities does not allow full timber recovery. To sustain yields, logging intensities need to be reduced and/or silvicultural treatments applied to increase yields, both of which reduce short-term profits. Declining yields might be accepted if the capacity of logged forests to grow timber is not impaired, but forest abandonment due to timber stock depletion is worrisome if it fosters illegal forest conversion.

Predicting responses of vegetation to environmental factors in human-altered tropical ecosystems requires an understanding of the controls on plant population expansion across landscapes (i.e., long-distance dispersal) as well as of factors affecting recruitment at local scales (i.e., microsite conditions). We studied the roles of light availability, habitat type, soil disturbance, and seed dispersal in a selectively logged forest in lowland Bolivia where the exotic forage grass Urochloa (Panicum) maxima is abundant on roads and log landings but does not invade felling gaps or unlogged forest. Shade-house trials and seed addition experiments with U. maxima revealed that this C 4 grass thrives in high light but also grows in partial shade (10% full sun, but not 1% full sun), and that felling gaps, but not undisturbed forest, are suitable for grass establishment. To determine if seed dispersal by logging vehicles explains the discrepancy between actual and potential grass recruitment sites, we collected grass seeds that fell from trucks onto log landings located long distances (> 500 m) from established grass populations. Trucks dispersed an estimated 1800 alien grass seeds per log landing during the early dry season; automobiles also transported seeds of grass (135 seeds/vehicle). The seeds collected (and relative abundances) were the exotics U. (Panicum) maxima (97%) and Urocbloa (Brachiaria) brizantha (2%), and the pan-tropical weeds Sorghum halapense (1%) and Rottboellia cochinchinensis (0.2%). Grasses invade this forest where disturbance coincides with seed dispersal by motor vehicles, while dispersal limitation apparently prevents invasion of many sites otherwise suitable for grass recruitment (i.e., felling and natural gaps).

Changes in above-ground biomass (AGB) of 17 1 ha logged plots of terra firme rain forest in the eastern Amazon (Brazil, Paragominas) were monitored for four years (2004–2008) after reduced-impact logging. Over the same time period, we also monitored two 0.5 ha plots in adjacent unlogged forest. While AGB in the control plots changed little over the observation period (increased on average 1.4 Mg ha −1 ), logging resulted in immediate reductions in ABG that averaged 94.5 Mg ha −1 (±42.0), which represented 23% of the 410 Mg ha −1 (±64.9) present just prior to harvesting. Felled trees (dbh > 55 cm) accounted for 73% (±15) of these immediate losses but only 18.9 Mg ha −1 (±8.1) of biomass was removed in the extracted logs. During the first year after logging, the annual AGB balance (annual AGB gain by recruitment and growth − annual AGB loss by mortality) remained negative (−31.1 Mg ha −1 year −1 ; ±16.7), mainly due to continued high mortality rates of damaged trees. During the following three years (2005–2008), average net AGB accumulation in the logged plots was 2.6 Mg ha −1 year −1 (±4.6). Post-logging biomass recovery was mostly through growth (4.3 ± 1.5 Mg ha −1 year − 1 for 2004–2005 and 6.8 ± 0.9 Mg ha −1 year − 1 for 2005–2008), particularly of large trees. In contrast, tree recruitment contributed little to the observed increases in AGB (1.1 ± 0.6 Mg ha −1 year −1 for 2004–2005 and 3.1 ± 1.3 Mg ha −1 year −1 for 2005–2008). Plots with the lowest residual basal area after logging generally continued to lose more large trees (dbh ≥70 cm), and consequently showed the greatest AGB losses and the slowest overall AGB gains. If 100% AGB recovery is desired and the 30-year minimum cutting cycle defined by Brazilian law is adhered to, current logging intensities (6 trees ha −1 ) need to be reduced by 40–50%. Such a reduction in logging intensity will reduce financial incomes to loggers, but might be compensated for by the payment of environmental services through the proposed REDD (reduced emissions from deforestation and forest degradation) mechanism of the United Nations Framework Convention on Climate Change.

We test the hypotheses proposed by Gentry and Schnitzer that liana density and basal area in tropical forests vary negatively with mean annual precipitation (MAP) and positively with seasonality. Previous studies correlating liana abundance with these climatic variables have produced conflicting results, warranting a new analysis of drivers of liana abundance based on a different dataset. We compiled a pan-tropical dataset containing 28,953 lianas (Z2.5cmdiam.) from studies conducted at 13 Neotropical and 11 Paleotropical dry to wet lowland tropical forests. The ranges in MAP and dry season length (DSL) (number of months with mean rainfall o100mm) represented by these datasets were 860‐7250mm/yr and 0‐7mo, respectively. Pan-tropically, liana density and basal area decreased significantly with increasing annual rainfall and increased with increasing DSL, supporting the hypotheses of Gentry and Schnitzer. Our results suggest that much of the variation in liana density and basal area in the tropics can be accounted for by the relatively simple metrics of MAP and DSL.

Understanding the proximate causes of post-fire conifer mortality due to smoldering duff fires is essential to the restoration and management of coniferous forests throughout North America. To better understand duff fire-caused mortality, we investigated tree stress and radial growth following experimental fires in a long-unburned forest on deep sands in northern Florida, USA. We burned basal fuels surrounding 80 mature Pinus palustris Mill. in a randomized experiment comparing the effects of basal burning treatments on stem vascular meristems; surficial roots; root and stem combinations; and a non-smoldering control. We examined the effects of duration of lethal temperatures (>60 8C) on subsequent pine radial growth and root non-structural carbohydrates (starch and sugar). Duff and mineral soil temperatures in the experimental fires consistently exceeded 60 8C for over an hour following ignition, with lethal temperatures of shorter duration recorded 20 cm below the mineral soil surface. Duff heating was best explained by day-of-burn Oe horizon moisture (P = 0.01), although little variation was explained (R 2 = 0.24). Post-fire changes in latewood radial increment in the year following fires was related to duration of temperatures >60 8C 10 cm deep in the mineral soil (P = 0.07), but explained little variability in post-fire growth (R 2 = 0.17). In contrast, changes in non-structural carbohydrate content in coarse roots (2–5 mm diameter) 120 days following burning were more strongly correlated with the duration of lethal heating 5 cm below the mineral soil surface (P = 0.02; R 2 = 0.53). Results from this study implicate the role of mineral soil heating in the post-fire decline of

The distributions of 17 tree species with seeds or fruits that are commonly eaten or otherwise used by humans were studied in reference to anthropogenic soils in a seasonally dry lowland tropical forest in Bolivia. Two types of anthropogenic dark earths (ADEs) were identified: terra preta (TP: darkened with charcoal fragments and with abundant pottery shards) and terra mulata (TM: somewhat darkened but with little or no pottery). In 216ha, we compared the densities of trees 410cmdbh of useful species in nine TP patches, three TM patches, and six areas with nonanthropogenic soils (N-ADE). The TP, which covers approximately 20 percent of the sample area, has higher contents of organic matter, extractable P, and extractable Ca than N-ADE soils, as well as higher pH and extractable P than TM. TM has organic matter and Ca contents similar to N-ADE soils but significantly less extractable K. In general, TP has higher nutrient content than surrounding soils, both at the surface (0‐10cm) and deeper in the profile (40‐50cm). Despite these differences in soil fertility and contrary to our expectations, none of the 17 tree species were concentrated on TP perhaps because interactions between local dispersal agents and natural disturbances have masked historical patterns. Alternatively, past inhabitants of the study area may have enriched forests with useful tree species in areas where they were not practicing the intensive soil husbandry that results in ADEs.

If global policies intended to promote forest conservation continue to use the definition of “forest” adopted in 2001 by the United Nations Framework Convention on Climate Change (an area of >0.05‐1 ha with >10‐30% cover of plants >2‐5 m tall at maturity), great quantities of carbon and other environmental values will be lost when natural forests are severely degraded or replaced by plantations but technically remain “forests.” While a definition of “forest” that is globally acceptable and appropriate for monitoring using standard remote sensing options will necessarily be based on a small set of easily measured parameters, there are dangers when simple definitions are applied locally. At the very least, we recommend that natural forest be differentiated from plantations and that for defining “forest” the lower height limit defining “trees” be set at more than 5 m tall with the minimum cover of trees be set at more than 40%. These changes will help reduce greenhouse gas emissions from what is now termed forest “degradation” without increasing monitoring costs. Furthermore, these minor changes in the definition of “forest” will promote the switch from degradation to responsible forest management, which will help mitigate global warming while protecting biodiversity and contributing to sustainable development.

While research continues on the causes, consequences, and rates of deforestation and forest degradation in the tropics, there is little agreement about what exactly is being lost, what we want back, and to whom the ‘we’ refers. Particularly unsettling is that many analyses and well-intended actions are implemented in fogs of ambiguity surrounding definitions of the term ‘forest’—a problem that is not solely semantic; with development of markets for biomass carbon, vegetation classification exercises take on new relevance. For example, according to the basic implementation guidelines of the Kyoto Protocol, closed canopy natural forest could be replaced by monoclonal plantations of genetically engineered exotic tree species and no deforestation would have occurred. Following these same guidelines, carbon credits for afforestation could be available for planting trees in species-rich savannas; these new plantations would count towards a country moving towards the ‘forest transition,’ the point at which there is no net ‘forest’ loss. Such obvious conflicts between biodiversity conservation and carbon sequestration might be avoided if ‘forest’ was clearly defined and if other vegetation types and other ecosystem values were explicitly recognized. While acknowledging that no one approach to vegetation classification is likely to satisfy all users at all scales, we present an approach that recognizes the importance of species composition, reflects the utility of land-cover characteristics that are identifiable via remote sensing, and acknowledges that many sorts of forest degradation do not reduce carbon stocks (e.g., defaunation) or canopy cover (e.g., over-harvesting of understory nontimber forest products).

A major impediment to the sustainable management of tropical dry forests in Bolivia is the scarcity of natural regeneration of commercial timber tree species. Where regeneration is present, true seedlings of many species are outnumbered by vegetative sprouts from roots, broken stems, and the stumps of felled trees. This study evaluates the importance of resprouts promoted by logging operations for the regeneration of commercially important canopy tree species. The objectives of the study were: (1) to characterize stump and root sprouting behaviors of canopy tree species harvested for timber; (2) to quantify the effect of logging on relative abundances and growth rates of stump sprouts, root sprouts, and true seedlings; (3) to relate the species-specific probabilities of stump sprouting to stump diameter and stump height; and (4) to explore how sprouting varies with the ecological requirements of canopy tree species. The study was carried out 1–5 years after logging of a privately owned land in a Bolivian tropical dry forest. Twenty-seven of the 31 species monitored resprouted at least occasionally, among which Centrolobium microchaete (Leguminosae-Fabaceae) and Zeyheria tuberculosa (Bignoniaceae) were the most frequent stump sprouters, and Acosmium cardenasii (Leguminosae-Fabaceae) and C. microchaete were the most frequent root sprouters. In all species the number of sprouts declined with increasing stump diameter and stump height. The probability of stump resprouting differed among species but did not vary consistently with stump diameter, except in Z. tuberculosa in which it declined. Approximately 45% of juveniles

SummaryWhile around 20% of the Amazonian forest has been cleared for pastures and agriculture, one fourth of the remaining forest is dedicated to wood production [1]. Most of these production forests have been or will be selectively harvested for commercial timber, but recent studies show that even soon after logging, harvested stands retain much of their tree-biomass carbon and biodiversity [2,3]. Comparing species richness of various animal taxa among logged and unlogged forests across the tropics, Burivalova et al. [4] found that despite some variability among taxa, biodiversity loss was generally explained by logging intensity (the number of trees extracted). Here, we use a network of 79 permanent sample plots (376 ha total) located at 10 sites across the Amazon Basin [5] to assess the main drivers of time-to-recovery of post-logging tree carbon (Table S1). Recovery time is of direct relevance to policies governing management practices (i.e., allowable volumes cut and cutting cycle lengths), and indirectly to forest-based climate change mitigation interventions.

Ilex VomitoriaAit. (Yaupon): A Native North American Source of a Caffeinated and Antioxidant-Rich Tea. Yaupon holly (Ilex vomitoria Ait.) is a caffeine-containing shrub native to the southeastern United States where its leaves and twigs were traditionally used to prepare a stimulating and healthful beverage by Amerindians and more recent colonists. For a variety of mostly socioeconomic and cultural reasons, widespread consumption of yaupon tea ceased by the late 19th century, but the species is widely used in ornamental horticulture. Given the environmental damage associated with other caffeine crops, we believe that disuse of this species is unfortunate, and we report on traits that consumers may consider valuable. We found that total foliar biomass, caffeine, and antioxidant production all increased with nitrogen fertilization in one common ornamental yaupon cultivar, ‘Nana.’ Increasing light availability was associated with increased antioxidant activity but not with the decreased caffeine production predicted by the carbon/nutrient balance hypothesis for secondary metabolite production. We also found the highest caffeine concentrations in another yaupon cultivar, ‘Pendula,’ but suggest that the wide range of chemical variation offered by wild-type yaupon populations renders them more suitable as sources for the development of high caffeine-producing varieties. The results of this study suggest that yaupon is a viable caffeine alternative for North Americans living within its range on the southeastern coastal plain.

We investigated the distribution of sand pine (Pinus clausa) seedlings in relation to the locations of hardwoods and palmettos that had resprouted in five recently clear-cut and one burned stand in sand pine scrub vegetation in Ocala National Forest (Florida, USA). We also studied how the shade and mechanical support provided by the taller resprouts affect the allometry and biomechanics of sand pine seedling stems. Although soil surface temperatures were higher and soil moisture contents (0–5 cm) were lower in open than in covered microsites, sand pine seedling densities did not vary in relation to proximity to resprouted hardwoods and palmettos. There was no apparent nurse plant effect on sand pine seedling distributions, but seedlings that grew up under the resprouts had larger whole stem flexibilities, greater height:diameter ratios, and less tapered stems. In response to the mechanical support and shade of neighboring plants, sand pine seedlings grow taller per unit investment in stem tissue, thereby shortening the period during which they presumably suffer from above-ground competition. This biomechanical plasticity increases the rates at which sand pine seedlings can overtop their resprouted competitors.

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.

Sea-level rise threatens low-lying coastal ecosystems globally. In Florida, USA, salinity stress due to increased tidal flooding contributes to the dramatic and well documented decline of species-rich coastal forest areas along the Gulf of Mexico. Here, we present the results of a study of coastal forest stand dynamics in thirteen 400 m² plots representing an elevation gradient of 0.58-1.1 m affected by tidal flooding and rising sea levels. We extended previously published data from 1992-2000 to 2005 to quantify the full magnitude of the 1998-2002 La Nina-associated drought. Populations of the dominant tree species, Sabal palmetto (cabbage palm), declined more rapidly during 2000-2005 than predicted from linear regressions based on the 1992-2000 data. Dramatic increases in Juniperus virginiana (Southern red cedar) and S. palmetto mortality during 2000-2005 as compared with 1995-2000 are apparently due to the combined effects of a major drought and ongoing sea-level rise. Additionally, coastal forest stands continued to decline in species richness with increased tidal flooding frequency and decreasing elevation. Stable isotope (H, O) analyses demonstrate that J. virginiana accesses fresher water sources more than S. palmetto. Carbon isotopes reveal increasing δ¹³C enrichment of S. palmetto and J. virginiana with increased tidal flooding and decreased elevation, demonstrating increasing water stress in both species. Coastal forests with frequent tidal flooding are unable to support species-rich forests or support regeneration of the most salt-tolerant tree species over time. Given that rates of sea-level rise are predicted to increase and periodic droughts are expected to intensify in the future due to global climate change, coastal forest communities are in jeopardy if their inland retreat is restricted.