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International audience; Forests that regrow naturally on abandoned fields are important for restoring biodiversity and ecosystem services, but can they also preserve the distinct regional tree floras? Using the floristic composition of 1215 early successional forests (≤20 years) in 75 human-modified landscapes across the Neotropic realm, we identified 14 distinct floristic groups, with a between-group dissimilarity of 0.97. Floristic groups were associated with location, bioregions, soil pH, temperature seasonality, and water availability. Hence, there is large continental-scale variation in the species composition of early successional forests, which is mainly associated with biogeographic and environmental factors but not with human disturbance indicators. This floristic distinctiveness is partially driven by regionally restricted species belonging to widespread genera. Early secondary forests contribute therefore to restoring and conserving the distinctiveness of bioregions across the Neotropical realm, and forest restoration initiatives should use local species to assure that these distinct floras are maintained.

International audience; Tropical forests disappear rapidly because of deforestation, yet they have the potential to regrow naturally on abandoned lands. We analyze how 12 forest attributes recover during secondary succession and how their recovery is interrelated using 77 sites across the tropics. Tropical forests are highly resilient to low-intensity land use; after 20 years, forest attributes attain 78% (33 to 100%) of their old-growth values. Recovery to 90% of old-growth values is fastest for soil (12 decades). Network analysis shows three independent clusters of attribute recovery, related to structure, species diversity, and species composition. Secondary forests should be embraced as a low-cost, natural solution for ecosystem restoration, climate change mitigation, and biodiversity conservation.

Tropical forests are globally important, but it is not clear whether biodiversity enhances carbon storage and sequestration in them. We tested this relationship focusing on components of functional trait biodiversity as predictors. Data are presented for three rain forests in Bolivia, Brazil and Costa Rica. Initial above-ground biomass and biomass increments of survivors, recruits and survivors + recruits (total) were estimated for trees ≥10 cm d.b.h. in 62 and 21 1.0-ha plots, respectively. We determined relationships of biomass increments to initial standing biomass (AGBi), biomass-weighted community mean values (CWM) of eight functional traits and four functional trait variety indices (functional richness, functional evenness, functional diversity and functional dispersion). The forest continuum sampled ranged from ‘slow’ stands dominated by trees with tough tissues and high AGBi, to ‘fast’ stands dominated by trees with soft, nutrient-rich leaves, lighter woods and lower AGBi. We tested whether AGBi and biomass increments were related to the CWM trait values of the dominant species in the system (the biomass ratio hypothesis), to the variety of functional trait values (the niche complementarity hypothesis), or in the case of biomass increments, simply to initial standing biomass (the green soup hypothesis). CWMs were reasonable bivariate predictors of AGBi and biomass increments, with CWM specific leaf area SLA, CWM leaf nitrogen content, CWM force to tear the leaf, CWM maximum adult height Hmax and CWM wood specific gravity the most important. AGBi was also a reasonable predictor of the three measures of biomass increment. In best-fit multiple regression models, CWMHmax was the most important predictor of initial standing biomass AGBi. Only leaf traits were selected in the best models for biomass increment; CWM SLA was the most important predictor, with the expected positive relationship. There were no relationships of functional variety indices to biomass increments, and AGBi was the only predictor for biomass increments from recruits. Synthesis. We found no support for the niche complementarity hypothesis and support for the green soup hypothesis only for biomass increments of recruits. We have strong support for the biomass ratio hypothesis. CWMHmax is a strong driver of ecosystem biomass and carbon storage and CWM SLA, and other CWM leaf traits are especially important for biomass increments and carbon sequestration. Fil: Finegan, B.. Production and Conservation in Forests Programme; Costa Rica Fil: Peña Claros, Marielos. Facultad de Ciencias Agrícolas. Instituto Boliviano de Investigación Forestal; Bolivia. Wageningen University. Forest Ecology and Forest Management Group; Países Bajos Fil: de Oliveira, Alexandre. Universidade de São Paulo. Departamento de Ecologia; Brasil Fil: Ascarrunz, Nataly. Facultad de Ciencias Agrícolas. Instituto Boliviano de Investigación Forestal; Bolivia Fil: Bret Harte, M. Syndonia. University of Alaska. Institute of Arctic Biology; Estados Unidos Fil: Carreno Rocabado, Geovana. Facultad de Ciencias Agrícolas. Instituto Boliviano de Investigación Forestal; Bolivia. Wageningen University. Forest Ecology and Forest Management Group; Países Bajos Fil: Casanoves, Fernando. Biostatistics Unit; Costa Rica Fil: Diaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Eguiguren Velepucha, Paul. Production and Conservation in Forests Programme; Costa Rica Fil: Fernandez, Fernando. Production and Conservation in Forests Programme; Costa Rica Fil: Licona, Juan Carlos. Facultad de Ciencias Agrícolas. Instituto Boliviano de Investigación Forestal; Bolivia Fil: Lorenzo, Leda. Universidade de São Paulo. Departamento de Ecologia; Brasil Fil: Salgado Negret, Beatriz. Production and Conservation in Forests Programme; Costa Rica. Instituto Alexander von Humboldt; Colombia Fil: Vaz, Marcel. Universidade de São Paulo. Departamento de Ecologia; Brasil Fil: Poorter, Lourens. Facultad de Ciencias Agrícolas. Instituto Boliviano de Investigación Forestal; Bolivia. Wageningen University. Forest Ecology and Forest Management Group; Países Bajos

Amazonian Dark Earths (ADE) are the result of human modification of the Amazonian landscape since pre-Columbian times. ADE are characterized by increased soil fertility compared to natural soils. In the Amazonian forest, soil fertility influences understory herb and fern species composition. However, little research has been done to evaluate the effect of ADE on the composition of the understory community. We evaluated the effects of ADE and soil in 36 plots (150 m × 4 m) established in a Bolivian moist forest (La Chonta). For each plot, we determined soil nutrients, and the composition, richness, and abundance of terrestrial fern, angiosperm herb, and understory palm species. We found that the presence of ADE created a gradient in soil nutrients and pH that affected the understory species composition especially of ferns and palms. Additionally, the higher nutrient concentration and more neutral soil pH on ADE soils caused a decrease of ferns species richness. We therefore conclude that the current composition of the understory community in this particular Bolivian forest is a reflection of past human modifications of the soil.

Aim Tropical forests store 25% of global carbon and harbour 96% of the world's tree species, but it is not clear whether this high biodiversity matters for carbon storage. Few studies have teased apart the relative importance of forest attributes and environmental drivers for ecosystem functioning, and no such study exists for the tropics. Location Neotropics. Methods We relate aboveground biomass (AGB) to forest attributes (diversity and structure) and environmental drivers (annual rainfall and soil fertility) using data from 144,000 trees, 2050 forest plots and 59 forest sites. The sites span the complete latitudinal and climatic gradients in the lowland Neotropics, with rainfall ranging from 750 to 4350¿mm¿year-1. Relationships were analysed within forest sites at scales of 0.1 and 1 ha and across forest sites along large-scale environmental gradients. We used a structural equation model to test the hypothesis that species richness, forest structural attributes and environmental drivers have independent, positive effects on AGB. Results Across sites, AGB was most strongly driven by rainfall, followed by average tree stem diameter and rarefied species richness, which all had positive effects on AGB. Our indicator of soil fertility (cation exchange capacity) had a negligible effect on AGB, perhaps because we used a global soil database. Taxonomic forest attributes (i.e. species richness, rarefied richness and Shannon diversity) had the strongest relationships with AGB at small spatial scales, where an additional species can still make a difference in terms of niche complementarity, while structural forest attributes (i.e. tree density and tree size) had strong relationships with AGB at all spatial scales. Main conclusions Biodiversity has an independent, positive effect on AGB and ecosystem functioning, not only in relatively simple temperate systems but also in structurally complex hyperdiverse tropical forests. Biodiversity conservation should therefore be a key component of the UN Reducing Emissions from Deforestation and Degradation strategy.

Atmospheric carbon dioxide records indicate that the land surface has acted as a strong global carbon sink over recent decades1, 2, with a substantial fraction of this sink probably located in the tropics3, particularly in the Amazon4. Nevertheless, it is unclear how the terrestrial carbon sink will evolve as climate and atmospheric composition continue to change. Here we analyse the historical evolution of the biomass dynamics of the Amazon rainforest over three decades using a distributed network of 321 plots. While this analysis confirms that Amazon forests have acted as a long-term net biomass sink, we find a long-term decreasing trend of carbon accumulation. Rates of net increase in above-ground biomass declined by one-third during the past decade compared to the 1990s. This is a consequence of growth rate increases levelling off recently, while biomass mortality persistently increased throughout, leading to a shortening of carbon residence times. Potential drivers for the mortality increase include greater climate variability, and feedbacks of faster growth on mortality, resulting in shortened tree longevity5. The observed decline of the Amazon sink diverges markedly from the recent increase in terrestrial carbon uptake at the global scale1, 2, and is contrary to expectations based on models6.

While 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 and 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

1. The analysis of species distribution patterns along environmental gradients is important for understanding the diversity and ecology of plants and species responses to climate change, but detailed data are surprisingly scarce for the tropics. 2. Here, we analyse the distribution of 100 woody species over 220 1-ha forest plots distributed over an area of c. 160 000 km2, across large environmental gradients in lowland Bolivia and evaluate the relative importance of climate and soils in shaping species distribution addressing four multivariate environmental axes (rainfall amount and distribution, temperature, soil fertility and soil texture). 3. Although species abundance was positively related to species frequency (the number of plots in which the species is found), this relationship was rather weak, which challenges the view that most tropical forests are dominated at large scales by a few common species. 4. Species responded clearly to environmental gradients, and for most of the species (65%), climatic and soil conditions could explain most of the variation in occurrence (R2 > 0.50), which challenges the idea that most tropical tree species are habitat generalists. 5. Climate was a stronger driver of species distribution than soils; 91% of the species were affected by rainfall (distribution), 72% by temperature, 47% by soil fertility and 44% by soil texture. In contrast to our expectation, few species showed a typical unimodal response to the environmental gradients.6. Synthesis. Tropical tree species specialize for different parts of the environmental gradients, and climate is a stronger driver of species distribution than soils. Because climate change scenarios predict increases in annual temperature and a stronger dry season for tropical forests, we may expect potentially large shifts in the distribution of tropical trees

Growth ring variations were used to provide the rates in diameter growth for seven tree species in the Bolivian Cerrado biogeographical province. Ten to 50 trees were measured per species. Ring width measurements provided accurate data on the rates of tree growth. Variations in growth rates were determined among species and among sites for the same species over a common period of 100 years. Diametric increases range from 0.43 to 0.56 cm year-1 in Chiquitano biogeographical district. For species in Guarayos district, diametric increments range from 0.51 to 1.06 cm year-1. For Centrolobium microchaete growing in both districts, the annual diametric increments oscillate between 0.35 to 0.40 cm year-1 and 0.55 to 0.65 cm year-1 in Chiquitano and Guarayos districts, respectively. Diametric increases in Chiquitano district were not significantly different among sites, whereas in Guarayos district, annual increases differ among species and from the same species growing in Chiquitano district. Observed diameter growth rates indicate that diametrical increments are generally slower than commonly assumed, with considerable variation among species and between districts. Therefore, the idea of applying similar rules for the management of different species across different sites without considering actual growth rates is not recommended, with long-term consequences for the sustainability of forests at the tropical dry Bolivian Cerrado., La información obtenida a partir de los anillos de crecimiento fue utilizada para proveer los ritmos de crecimiento diamétrico de siete especies forestales de la provincia biogeográfica del Cerrado Boliviano. En este análisis dendrocronológico se emplearon 10 a 50 árboles por especies. La medición del ancho de los anillos de crecimiento brindó datos precisos, con los cuales se determinó la variabilidad del incremento entre especies y entre sitios para un periodo común de 100 años. Los incrementos diamétricos variaron de 0,43 a 0,56 cm año-1 en especies correspondientes al distrito Chiquitano. Para especies del distrito de Guarayos, los valores fueron de 0,51 a 1,06 cm año-1. Para Centrolobium microchaete que crece en ambos distritos, los valores medios de crecimiento por rodal oscilaron entre 0,35 y 0,40 cm año-1 en el distrito Chiquitano y de 0,55 a 0,65 cm año-1 en el de Guarayos. Los incrementos diamétricos en sitios del distrito Chiquitano no presentaron diferencias significativas, en cambio en Guarayos los incrementos fueron diferentes entre especies y, a su vez, diferentes a los del distrito Chiquitano. Las tasas de crecimiento diamétrico indican que el crecimiento diamétrico, en general, es más lento de lo comúnmente asumido, con variaciones importantes entre especies y entre sitios de crecimiento. Por ello, la idea de establecer pautas fijas de manejo similares para todas las especies y sitios, sin considerar las tasas reales de crecimiento, no sería la recomendada, poniendo en algunos casos en riesgo la sostenibilidad de los bosques "manejados" del cerrado boliviano.

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 1 ha 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.

Total income and income from forest resources among rural dwellers in tropical forest regions are influenced not only by market access, prices, but also organizational, institutional, and social factors. These factors influence the diversity of resources to which the poor have access and result in specializations in livelihood strategies. We analyzed the relation between forest dependence and livelihood strategies in the Bolivian Amazon, applying the SLF. We tested for the differences across strategies with respect to financial, human, physical, social, and natural livelihood assets. Results show that forest income is highly related to cash income from Brazil nut, while income from agriculture and timber exploitation is associated with higher levels of education. Brazil nuts serve as a safety net and start-up capital for certain livelihood strategies in our study region. Livelihood strategies that are based on the commercialization of multiple products from forests and agriculture and services inside and outside communities depend less on forests. Livelihoods can be supported by investing in sustainable livelihood asset endowments. Our results demonstrate that activities that aim to support community forest management and to enhance household income should explicitly consider a differentiated support for different strategies. This will result in a more effective outcome of development efforts from which the poorest people would benefit most.

1. In a recent paper, we analysed the effects of climate, soil and logging disturbance on tree and forest growth (Toledo et al. 2011a). We took advantage of one of the largest data sets in the Neotropics, consisting of 165 1-ha plots and over 62 000 trees distributed over an area of c. 160 000 km2, across large environmental gradients in lowland Bolivia. The main findings were that climate was the strongest driver of spatial variation in tree growth, whereas soils had only a modest effect on growth and that the effect of logging disappeared after a few years. 2. Ferry (2012) suggest that we underestimated the disturbance effects on growth because of a supposedly wrong coding of Time After Logging (TAL) for unlogged plots. Although we have good biological reasons why we coded TAL like we did, we checked Ferry et al.s suggestions for recoding and found no differences in variables that significantly explained tree and forest growth. We agree, however, that for future research, it is important to go beyond simple descriptors such as time after logging and basal area logged, to better describe the variation in logging impact found in areas under forest management. 3. Ferry et al. claim that we did not define basal area growth properly. We believe this is a semantic issue, as we clearly defined basal area growth as the net change in basal area. This net basal area change in Bolivian forests is indeed relatively high compared to other studies, which may be attributed to the higher soil fertility and biogeographic differences in species composition and their traits. 4. Synthesis. Many apparent discrepancies in the ecological literature arise because tropical forest ecologists tend to see the world from the perspective of their own forest (despite clear biogeographic differences) and try to capture the same ecological processes using different variables and measurement protocols. To advance our understanding and go beyond single-case studies, we need to assemble large databases, quantify forest dynamics and disturbances in similar ways, be aware of differences among forests and analyse environmental doseresponse curves.

Floristic variation is high in the Neotropics, but little is known about the factors shaping this variation at the mesoscale. We examined floristic composition and its relationship with environmental factors across 220 1-ha permanent plots in tropical lowland Bolivia. For each plot, abundance of 100 species (93 tree and 7 palm species =10 cm diam) was obtained. Climatic data, related to rainfall seasonality and temperature, were interpolated from all available weather stations in the region, and soil properties, related to texture and fertility, were obtained for each plot. Floristic variation was strongly associated with differences in water availability and temperature, and therefore the climatic gradient shaped floristic variation more strongly than the edaphic gradient. Detrended correspondence analysis ordination divided lowland Bolivia primarily into two major groups (Southern Chiquitano region vs. the Amazon region) and a multiple response permutation procedure distinguished five floristic regions. Overall, the tested environmental variables differed significantly among the five regions. Using indicator species analysis, we distinguished 82 strong indicator species, which had significant environmental preferences for one floristic region. These species can be used as indicators of environmental conditions or to determine which floristic region a certain forest belongs. Given the predicted decreases in rainfall and increases in temperature for tropical lowland forests, our gradient approach suggests that species composition may shift drastically with climate change

Bolivia started to implement the Forestry Law (# 1700) in 1996. Since then the Bolivian forestry sector has changed significantly from an unplanned and exploitative logging regime to an organized system based on reduced impact logging techniques and management plans elaborated by trained forestry technicians and professionals. It has also expanded access to forest harvesting by allowing rural and indigenous communities the right to manage forest resources along with private companies. The law also provided a suite of technical tools to ensure the sustainable use of the forest resource. The 1996 forestry law and its implementation has resulted in a diversification of species being used for timber production, an increase in the amount of finished forest product exports, and improvements towards forest sustainability. This latter aspect is most evident in the approximately two million hectares of tropical forests that have been certified as sustainably managed under the Principles and Criteria defined by the Forest Stewardship Council (FSC) (Certificación Forestal Voluntaria 2008). Despite Bolivia’s status as a sustainable forestry leader, there are political, socioeconomic, and ecological challenges to sustainable forest management. Most of these challenges have their origins outside the forestry sector and are related to the development vision being used in the country. These limitations are of concern to the sustainability of Bolivia’s forestry sector and their recognition is important in order to be able to mitigate their effects in the future. The rest of this chapter will expand upon the successes and challenges to sustainable forest management in Bolivia.

To both celebrate and reflect upon this International Year of Biodiversity, Biotropica has invited opinion articles from a number of scientists across the globe. As lightly edited personal opinions, the commentaries reflect the diversity of passionate and often controversial views expressed across the scientific community. Thus, these commentaries should provide much food for thought, and hopefully some inspiration, on how we perceive biodiversity on our currently human-dominated planet and how we should respond to its loss

The complexity of factors driving tropical deforestation demand integrated approaches from concerned researchers and policy makers. Strict protection is sometimes the most appropriate mode of conservation, but conservation through management is often the better option. In either case, this essay highlights the importance of considering the social/cultural, economic, and political contexts in which these forests are threatened. By attempting to understand the cultural settings, institutional architectures and dynamics, and local expectations, and then by combining the concepts and tools of a range of disciplines, researchers will be more likely to forge lasting partnerships and increase their potential for sustained improvement in resource management and overall forest conservation

Many harvested timber species of tropical forests have not been regenerating sufficiently for future cutting cycles, which can demand the application of post-harvesting silvicultural treatments. This study analyzed the profitability of sawnwood produced through four treatments applied on seedlings and saplings naturally present or planted in logging gaps as follows: (1) the standard procedures of reduced-impact logging or control; (2) the tending of the naturally established regeneration; (3) enrichment planting 1 (EP-1); and (4) enrichment planting 2 (EP-2). In EP-1 commercial species were planted in 2-year-old gaps with no logging residuals removal from the gap while in EP-2 seedlings were planted in 1-year-old gaps with logging residuals removal from the gap. The planted timber species in EP-2 had higher financial value and higher growth rates than the timber species planted in EP-1. The experiment was carried out in a certified managed forest in the Eastern Amazon, Brazil. The growth rates of the treated seedlings and saplings were projected in 30 and 60 years from the treatment establishment to simulate sawnwood production. The simulations indicated that, increases of 25 and 50% in growth rates and increases up to 500% in timber prices under annual interest rates of 4 and 6%, the treatments of tending and enrichment planting can be profitable at year 60. These silvicultural treatments, under technological improvements, tend to become financially more profitable, meaning higher financial returns to forest managers and investors.

The carbon sink capacity of tropical forests is substantially affected by tree mortality. However, the main drivers of tropical tree death remain largely unknown. Here we present a pan-Amazonian assessment of how and why trees die, analysing over 120,000 trees representing > 3800 species from 189 long-term RAINFOR forest plots. While tree mortality rates vary greatly Amazon-wide, on average trees are as likely to die standing as they are broken or uprooted—modes of death with different ecological consequences. Species-level growth rate is the single most important predictor of tree death in Amazonia, with faster-growing species being at higher risk. Within species, however, the slowest-growing trees are at greatest risk while the effect of tree size varies across the basin. In the driest Amazonian region species-level bioclimatic distributional patterns also predict the risk of death, suggesting that these forests are experiencing climatic conditions beyond their adaptative limits. These results provide not only a holistic pan-Amazonian picture of tree death but large-scale evidence for the overarching importance of the growth–survival trade-off in driving tropical tree mortality., Tree mortality has been shown to be the dominant control on carbon storage in Amazon forests, but little is known of how and why Amazon forest trees die. Here the authors analyse a large Amazon-wide dataset, finding that fast-growing species face greater mortality risk, but that slower-growing individuals within a species are more likely to die, regardless of size.