Forest succession after shifting cultivation in eastern Amazonia

Succession following shifting cultivation was studied in secondary forests (5 to 40 years old) and a primary forest in Bragantina region, Para, Brazil. Secondary forests covered 62% of the study area (89 km² ) and crops and pasture 18%. Soil analyses showed an increase in pH, exchangeable calcium, magnesium and potassium and a decrease of organic matter and exchangeable aluminium, immediately after burning. Organic matter and extractable phosphorus increased with forest age, exchangeable aluminium and potassium were the same in both secondary and primary forests and exchangeable calcium and magnesium remained higher in the secondary forests. The highest densities of individuals and the least basal area and height were found in the younger secondary forests. The number of woody species (≥5 cm dbh) 250-m2 plot ranged from 8 to 17 in the secondary forests and 17 to 27 in the primary forest. Ordination and classification of floristic data suggested four successional communities. The forests regenerated readily and studies showed: the largest seed bank (0-5 cm) in the 5-years-old forest (1190 ± 284 seeds m-2) and a decrease with age to 137 ±19 seeds m-2 in the primary forest; the highest seed rain in the 5-years-old forest (883 ± 230 seeds m-2) and least in the primary forest (220 ± 80); 46% of the smaller plants (≥1 m tall, < 5 cm dbh) were seedlings and 54% were sprouts in the 5-years-old forest but in the 10-years and 20-years-old forests, seedlings (81%) predominated; adult plants (≥5 cm db h) in 5 to 20-years-old plots regenerated mainly from sprouts. Even after about 90 years of shifting cultivation the region has the potential for forest regeneration and the soil nutrients are able to recover to values similar to those in the primary forest. This raises the hope that, if a land use plan for Bragantina could be implemented, then it would be successful

Nitrogen and phosphorus additions negatively affect tree species diversity in tropical forest regrowth trajectories

Nutrient enrichment is increasingly affecting many tropical ecosystems, but there is no information on how this affects tree biodiversity. To examine dynamics in vegetation structure and tree species biomass and diversity, we annually remeasured tree species before and for six years after repeated additions of nitrogen (N) and phosphorus (P) in permanent plots of abandoned pasture in Amazonia. Nitrogen and, to a lesser extent, phosphorus addition shifted growth among woody species. Nitrogen stimulated growth of two common pioneer tree species and one common tree species adaptable to both high-and low-light environments, while P stimulated growth only of the dominant pioneer tree Rollinia exsucca (Annonaceae). Overall, N or P addition reduced tree assemblage evenness and delayed tree species accrual over time, likely due to competitive monopolization of other resources by the few tree species responding to nutrient enrichment with enhanced establishment and/or growth rates. Absolute tree growth rates were elevated for two years after nutrient addition. However, nutrient-induced shifts in relative tree species growth and reduced assemblage evenness persisted for more than three years after nutrient addition, favoring two nutrient-responsive pioneers and one early-secondary tree species. Surprisingly, N + P effects on tree biomass and species diversity were consistently weaker than N-only and P-only effects, because grass biomass increased dramatically in response to N + P addition. The resulting intensified competition probably prevented an expected positive N + P synergy in the tree assemblage. Thus, N or P enrichment may favor unknown tree functional response types, reduce the diversity of coexisting species, and delay species accrual during structurally and functionally complex tropical rainforest secondary succession

Developing cost-effective field assessments of carbon stocks in human-modified tropical forests

Across the tropics, there is a growing financial investment in activities that aim to reduce emissions from deforestation and forest degradation, such as REDD+. However, most tropical countries lack on-the-ground capacity to conduct reliable and replicable assessments of forest carbon stocks, undermining their ability to secure long-term carbon finance for forest conservation programs. Clear guidance on how to reduce the monetary and time costs of field assessments of forest carbon can help tropical countries to overcome this capacity gap. Here we provide such guidance for cost-effective one-off field assessments of forest carbon stocks. We sampled a total of eight components from four different carbon pools (i.e. aboveground, dead wood, litter and soil) in 224 study plots distributed across two regions of eastern Amazon. For each component we estimated survey costs, contribution to total forest carbon stocks and sensitivity to disturbance. Sampling costs varied thirty-one-fold between the most expensive component, soil, and the least, leaf litter. Large live stems (≥10 cm DBH), which represented only 15% of the overall sampling costs, was by far the most important component to be assessed, as it stores the largest amount of carbon and is highly sensitive to disturbance. If large stems are not taxonomically identified, costs can be reduced by a further 51%, while incurring an error in aboveground carbon estimates of only 5% in primary forests, but 31% in secondary forests. For rapid assessments, necessary to help prioritize locations for carbon- conservation activities, sampling of stems ≥20cm DBH without taxonomic identification can predict with confidence (R2 = 0.85) whether an area is relatively carbon-rich or carbon-poor—an approach that is 74% cheaper than sampling and identifying all the stems ≥10cm DBH. We use these results to evaluate the reliability of forest carbon stock estimates provided by the IPCC and FAO when applied to human-modified forests, and to highlight areas where cost savings in carbon stock assessments could be most easily made

Variation in stem mortality rates determines patterns of above-ground biomass in Amazonian forests: implications for dynamic global vegetation models

This is the final version of the article. Available from Wiley via the DOI in this record.Understanding the processes that determine above-ground biomass (AGB) in Amazonian forests is important for predicting the sensitivity of these ecosystems to environmental change and for designing and evaluating dynamic global vegetation models (DGVMs). AGB is determined by inputs from woody productivity [woody net primary productivity (NPP)] and the rate at which carbon is lost through tree mortality. Here, we test whether two direct metrics of tree mortality (the absolute rate of woody biomass loss and the rate of stem mortality) and/or woody NPP, control variation in AGB among 167 plots in intact forest across Amazonia. We then compare these relationships and the observed variation in AGB and woody NPP with the predictions of four DGVMs. The observations show that stem mortality rates, rather than absolute rates of woody biomass loss, are the most important predictor of AGB, which is consistent with the importance of stand size structure for determining spatial variation in AGB. The relationship between stem mortality rates and AGB varies among different regions of Amazonia, indicating that variation in wood density and height/diameter relationships also influences AGB. In contrast to previous findings, we find that woody NPP is not correlated with stem mortality rates and is weakly positively correlated with AGB. Across the four models, basin-wide average AGB is similar to the mean of the observations. However, the models consistently overestimate woody NPP and poorly represent the spatial patterns of both AGB and woody NPP estimated using plot data. In marked contrast to the observations, DGVMs typically show strong positive relationships between woody NPP and AGB. Resolving these differences will require incorporating forest size structure, mechanistic models of stem mortality and variation in functional composition in DGVMs.This paper is a product of the European Union's Seventh Framework Programme AMAZALERT project (282664). The field data used in this study have been generated by the RAINFOR network, which has been supported by a Gordon and Betty Moore Foundation grant, the European Union's Seventh Framework Programme projects 283080, ‘GEOCARBON’; and 282664, ‘AMAZALERT’; ERC grant ‘Tropical Forests in the Changing Earth System’), and Natural Environment Research Council (NERC) Urgency, Consortium and Standard Grants ‘AMAZONICA’ (NE/F005806/1), ‘TROBIT’ (NE/D005590/1) and ‘Niche Evolution of South American Trees’ (NE/I028122/1). Additional data were included from the Tropical Ecology Assessment and Monitoring (TEAM) Network – a collaboration between Conservation International, the Missouri Botanical Garden, the Smithsonian Institution and the Wildlife Conservation Society, and partly funded by these institutions, the Gordon and Betty Moore Foundation, and other donors. Fieldwork was also partially supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico of Brazil (CNPq), project Programa de Pesquisas Ecológicas de Longa Duração (PELD-403725/2012-7). A.R. acknowledges funding from the Helmholtz Alliance ‘Remote Sensing and Earth System Dynamics’; L.P., M.P.C. E.A. and M.T. are partially funded by the EU FP7 project ‘ROBIN’ (283093), with co-funding for E.A. from the Dutch Ministry of Economic Affairs (KB-14-003-030); B.C. [was supported in part by the US DOE (BER) NGEE-Tropics project (subcontract to LANL). O.L.P. is supported by an ERC Advanced Grant and is a Royal Society-Wolfson Research Merit Award holder. P.M. acknowledges support from ARC grant FT110100457 and NERC grants NE/J011002/1, and T.R.B. acknowledges support from a Leverhulme Trust Research Fellowship

Hyperdominance in Amazonian Forest Carbon Cycling

While Amazonian forests are extraordinarily diverse, the abundance of trees is skewed strongly towards relatively few ‘hyperdominant’ species. In addition to their diversity, Amazonian trees are a key component of the global carbon cycle, assimilating and storing more carbon than any other ecosystem on Earth. Here we ask, using a unique data set of 530 forest plots, if the functions of storing and producing woody carbon are concentrated in a small number of tree species, whether the most abundant species also dominate carbon cycling, and whether dominant species are characterized by specific functional traits. We find that dominance of forest function is even more concentrated in a few species than is dominance of tree abundance, with only ≈1% of Amazon tree species responsible for 50% of carbon storage and productivity. Although those species that contribute most to biomass and productivity are often abundant, species maximum size is also influential, while the identity and ranking of dominant species varies by function and by region

Resource allocation and seed biology of Stylosanthes angustifolia Vog. (Leguminosae - Papilionoideae)

No presente trabalho, foram estudadas três populações de Stylosanthes angustifólia Vog. coletadas em áreas de campina amazônica na Ilha do Marajó, Estado do Pará, tendo em vista determinar o padrão de distribuição fracionária de energia e estudar a biologia da semente. Após a coleta de sementes em condições naturais e sua multiplicação, foram desenvolvidos ensaios em vasos e em laboratório, ambos no Departamento de Genética da Escola Superior de Agricultura "Luiz de Queiroz", da Universidade de São Paulo em Piracicaba, São Paulo. O ensaio em vasos teve como finalidade avaliar a distribuição fracionária de energia, a produção de flores e de sementes dos artículos apical e basal e a caracterização morfológica do lomento e da semente. Em condições controladas de laboratório, foram realizados diversos ensaios de germinação com os objetivos de avaliar o efeito do dimorfismo do lomento sobre a germinação, a influência de temperaturas constantes e alternadas na germinação e analisar a variabilidade intra e inter populacional com relação à dormência de sementes. Os resultados foram discutidos levando em consideração parâmetros como: esforço reprodutivo, "seed-set", capacidade germinativa, velocidade de germinação, coeficiente de variação genética (CVg) e coeficiente de determinação genotípica (b)Three populations of Stylosanthes angustifolia collected in areas of "campina amazônica", Marajó Island State of Pará, Brazil, were evaluated in order to determine the pattern of resource allocation and to study the seed biology. After the sampling of seeds in natural condiction and its multiplication, pot and laboratory trials were installed at The Department of Genetics, Superior School of Agriculture "Luiz de Queiroz", University of São Paulo, in Piracicaba. A pot trial was conducted, with the aim of evaluating resource allocation, seed production of lower and upper article, flower production and the morphological characterization of the loment and seed. Several germination trials were conducted in laboratory controlled conditions, with the objectives of evaluating the effect of the loment's dimorphism on seed germination, the influence of constant and alternating temperatures on the germination of non-scarified seeds and analysing the intra and inter populational variability related to seed dormancy. The results were discussed based on the following parameters: reproductive effort, seed-set, germination capacity, germination rate, degree of uniformity of germination, genetic coefficient of variation (GVC) and genotipic coefficient of determination (b

Resource allocation and seed biology of Stylosanthes angustifolia Vog. (Leguminosae - Papilionoideae)

No presente trabalho, foram estudadas três populações de Stylosanthes angustifólia Vog. coletadas em áreas de campina amazônica na Ilha do Marajó, Estado do Pará, tendo em vista determinar o padrão de distribuição fracionária de energia e estudar a biologia da semente. Após a coleta de sementes em condições naturais e sua multiplicação, foram desenvolvidos ensaios em vasos e em laboratório, ambos no Departamento de Genética da Escola Superior de Agricultura "Luiz de Queiroz", da Universidade de São Paulo em Piracicaba, São Paulo. O ensaio em vasos teve como finalidade avaliar a distribuição fracionária de energia, a produção de flores e de sementes dos artículos apical e basal e a caracterização morfológica do lomento e da semente. Em condições controladas de laboratório, foram realizados diversos ensaios de germinação com os objetivos de avaliar o efeito do dimorfismo do lomento sobre a germinação, a influência de temperaturas constantes e alternadas na germinação e analisar a variabilidade intra e inter populacional com relação à dormência de sementes. Os resultados foram discutidos levando em consideração parâmetros como: esforço reprodutivo, "seed-set", capacidade germinativa, velocidade de germinação, coeficiente de variação genética (CVg) e coeficiente de determinação genotípica (b)Three populations of Stylosanthes angustifolia collected in areas of "campina amazônica", Marajó Island State of Pará, Brazil, were evaluated in order to determine the pattern of resource allocation and to study the seed biology. After the sampling of seeds in natural condiction and its multiplication, pot and laboratory trials were installed at The Department of Genetics, Superior School of Agriculture "Luiz de Queiroz", University of São Paulo, in Piracicaba. A pot trial was conducted, with the aim of evaluating resource allocation, seed production of lower and upper article, flower production and the morphological characterization of the loment and seed. Several germination trials were conducted in laboratory controlled conditions, with the objectives of evaluating the effect of the loment's dimorphism on seed germination, the influence of constant and alternating temperatures on the germination of non-scarified seeds and analysing the intra and inter populational variability related to seed dormancy. The results were discussed based on the following parameters: reproductive effort, seed-set, germination capacity, germination rate, degree of uniformity of germination, genetic coefficient of variation (GVC) and genotipic coefficient of determination (b

Seeing the woods through the saplings:Using wood density to assess the recovery of human-modified Amazonian forests

Most of the world's remaining tropical forests have been affected by either selective logging, understorey fires, fragmentation or are regrowing in areas that were previously deforested. Despite the ubiquity of these human‐modified forests, we have a limited knowledge of their potential to recover key traits linked to ecosystem processes and consequent services. Here we present data from 31,095 trees and saplings distributed across 121 plots of undisturbed and disturbed primary forests as well as secondary forests in the eastern Amazon. We examined the post‐disturbance recovery trajectory of an important plant functional trait, wood density. We tested whether human‐modified Amazonian forests are experiencing a rapid or a slow, or even impeded, recovery of this trait, which is associated with the provision of a fundamental ecosystem service—carbon storage. As expected, we found that the plot‐level wood density of trees and saplings in disturbed primary and secondary forests was significantly lower than in undisturbed forests. However, there was no significant difference in the average wood density of saplings between disturbed primary and secondary forests, possibly indicating a process of secondarization. We also found evidence that the recovery of wood density in human‐modified forests is being severely disrupted due to edge effects (in the case of disturbed primary forests) and high liana densities (in the case of both disturbed primary and secondary forests). Surprisingly, these two factors were more important predictors of wood density recovery than the time elapsed since the disturbance event. Synthesis. Plant communities in human‐modified Amazonian forests appear to not be recovering a key functional property—wood density, which in turn may affect their ability to store carbon in the future. If the aim of conservation programs in tropical forests is to maintain existing rates of ecosystem functions, processes and services, then they must concentrate efforts on avoiding anthropogenic disturbance in areas of currently undisturbed forests. It is also vital to prevent further disturbance in human‐modified forests to avoid disrupting even more their recovery

Marked non-compliance with deforestation embargoes in the Brazilian Amazon

Advances in monitoring capacity and strengthened law enforcement have helped to reduce deforestation in the Brazilian Amazon since the early 2000s. Embargoes imposed on the use of deforested land are important instruments for deterring deforestation and enabling forest recovery. However, the extent to which landowners respect embargoes in the Brazilian Amazon is unknown. In this study, we evaluated the current recovery status of embargoes due to deforestation imposed between 2008 and 2017 to conduct the first large-scale assessment of compliance with embargo regulations. We observed forest recovery in only 13.1% (±1.1%) of embargoed polygons, while agriculture and pasture activities were maintained in 86.9% (±1.8%) of embargoed polygons. Thus, landowners openly continue to disrespect environmental legislation in the majority of embargoed areas. We attribute the marked non-compliance observed to limited monitoring of embargoed areas, as environmental agents seldom return to verify the status of embargoed lands after they have been imposed. Recent advances in remote sensing provide low-cost ways to monitor compliance and should form the basis of concerted efforts to ensure that the law is observed and that those responsible for illegal deforestation do not benefit from it

A social and ecological assessment of tropical land uses at multiple scales:the Sustainable Amazon Network

Science has a critical role to play in guiding more sustainable development trajectories. Here, we present the Sustainable Amazon Network (Rede Amazonia Sustentavel, RAS): a multidisciplinary research initiative involving more than 30 partner organizations working to assess both social and ecological dimensions of land-use sustainability in eastern Brazilian Amazonia. The research approach adopted by RAS offers three advantages for addressing land-use sustainability problems: (i) the collection of synchronized and co-located ecological and socioeconomic data across broad gradients of past and present human use; (ii) a nested sampling design to aid comparison of ecological and socioeconomic conditions associated with different land uses across local, landscape and regional scales; and (iii) a strong engagement with a wide variety of actors and non-research institutions. Here, we elaborate on these key features, and identify the ways in which RAS can help in highlighting those problems in most urgent need of attention, and in guiding improvements in land-use sustainability in Amazonia and elsewhere in the tropics. We also discuss some of the practical lessons, limitations and realities faced during the development of the RAS initiative so far