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Funding: This work was part of the PhD thesis of the first author, developed at the Graduate Program in Ecology of the National Institute of Amazonian Research (INPA), with a fellowship funded by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES), Finance Code 001, (88887.141433/2017-00). The authors are also grateful for the financial and research support of the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Amazonas State Research Foundation (FAPEAM), the Newton Fund via the Natural Environment Research Council (NE/M022021/1 to O.L.P. and F.R.C.C.), PPBio Manaus, Centro de Estudos Integrados da Biodiversidade Amazônica and RAINFOR. We also thank Karina Melgaço, Aurora Levesley and Gabriela Lopez-Gonzalez for curating and managing ForestPlots.net. This was ForestPlots.net Project 26 led by Thaiane Sousa. This is publication number 832 of the Technical Series of the Biological Dynamics of Forest Fragments Project (BDFFP, INPA/STRI). Aim : Water availability is the major driver of tropical forest structure and dynamics. Most research has focused on the impacts of climatic water availability, whereas remarkably little is known about the influence of water table depth and excess soil water on forest processes. Nevertheless, given that plants take up water from the soil, the impacts of climatic water supply on plants are likely to be modulated by soil water conditions. Location : Lowland Amazonian forests. Time period : 1971–2019. Methods : We used 344 long-term inventory plots distributed across Amazonia to analyse the effects of long-term climatic and edaphic water supply on forest functioning. We modelled forest structure and dynamics as a function of climatic, soil-water and edaphic properties. Results : Water supplied by both precipitation and groundwater affects forest structure and dynamics, but in different ways. Forests with a shallow water table (depth

With current observations and future projections of more intense and frequent droughts in the tropics, understanding the impact that extensive dry periods may have on tree and ecosystem-level transpiration and concurrent carbon uptake has become increasingly important. Here, we investigate paired soil and tree water extraction dynamics in an old-growth upland forest in central Amazonia during the 2018 dry season. Tree water use was assessed via radial patterns of sap flow in eight dominant canopy trees, each a different species with a range in diameter, height, and wood density. Paired multi-sensor soil moisture probes used to quantify volumetric water content dynamics and soil water extraction within the upper 100 cm were installed adjacent to six of those trees. To link depth-specific water extraction patterns to root distribution, fine root biomass was assessed through the soil profile to 235 cm. To scale tree water use to the plot level (stand transpiration), basal area was measured for all trees within a 5 m radius around each soil moisture probe. The sensitivity of tree transpiration to reduced precipitation varied by tree, with some increasing and some decreasing in water use during the dry period. Tree-level water use scaled with sapwood area, from 11 to 190 L per day. Stand level water use, based on multiple plots encompassing sap flow and adjacent trees, varied from ∼1.7 to 3.3 mm per day, increasing linearly with plot basal area. Soil water extraction was dependent on root biomass, which was dense at the surface (i.e., 45% in the upper 5 cm) and declined dramatically with depth. As the dry season progressed and the upper soil dried, soil water extraction shifted to deeper levels and model projections suggest that much of the water used during the month-long dry-down could be extracted from the upper 2–3 m. Results indicate variation in rates of soil water extraction across the research area and, temporally, through the soil profile. These results provide key information on whole-tree contributions to transpiration by canopy trees as water availability changes. In addition, information on simultaneous stand level dynamics of soil water extraction that can inform mechanistic models that project tropical forest response to drought.

Windthrows change forest structure and species composition in central Amazon forests. However, the effects of widespread tree mortality associated with wind disturbances on soil properties have not yet been described in this vast region. We investigated short-term effects (7 years after disturbance) of widespread tree mortality caused by a squall line event from mid-January of 2005 on soil carbon stocks and concentrations in a central Amazon terra firme forest. The soil carbon stock (averaged over a 0–30 cm depth profile) in disturbed plots (61.4 ± 8.2 Mg ha−1, mean ±95 % confidence interval) was marginally higher (p = 0.09) than that from undisturbed plots (47.7 ± 13.6 Mg ha−1). The soil organic carbon concentration in disturbed plots (2.0 ± 0.17 %) was significantly higher (p r2 = 0.332, r = 0.575 and p = 0.019) and with tree mortality intensity (r2 = 0.257, r = 0.506 and p = 0.045). Our results indicate that large inputs of plant litter associated with large windthrow events cause a short-term increase in soil carbon content, and the degree of increase is related to soil clay content and tree mortality intensity. The higher carbon content and potentially higher nutrient availability in soils from areas recovering from windthrows may favor forest regrowth and increase vegetation resilience.

In the Brazilian Amazon Area there is no long-term research reporting on the forest structural response to thinning by girdling. This study was conducted in the Tropical Forestry Experimental Station of the National Institute of Amazonian Research. The objective was to evaluate the structure of an upland forest which had a reduction of basal area by annealing by different intensities. The study was conducted 28 years after the girdling intervention. The experiment was installed in 1985 on 15 hectares. The statistical design was randomized blocks with three replications and four treatments (T1, T2, T3 and T4) and one control (T0). As for the number of trees per hectare (trees.ha-1), the ringed area showed a high capacity for resilience, even when subjected to high levels of intervention. In treatments T1, T2 and T3 the annealing benefited both commercial and non-commercial species. In T4, there was a reversal of this trend, an increase in the proportion of commercial species was detected when compared with T0. The diameter distribution of T1 (χ2 = 16.1) and T2 treatments (χ2 = 15.4) were statistically equal to T0 and the treatments T3 (χ2 = 29.9) and T4 (χ2 = 55.3) were different. The results suggest that the forest structure still has signs of the different interventions. The silvicultural treatment used in T4 has great potential to increase the forest dynamics and tree growth without compromising the forest structure and ecological processes.

Influence of plot size in Weibull's diameter distribution function precision in a primary forest in Central Amazon. This research aimed to evaluate how the observed data of Amazonian forest can be fitted to Weibull's probabilistic function and the influence of plot size to the fitness as well. The Weibull probabilistic function is an important tool for forest management. In this study it was used 15 different plot sizes, installed in the INPA's Experimental Site ZF2 in Manaus, replicated 5 times for the larger sizes and 10 times for the smaller ones. It was collected the diameter of adult trees (DBH > 10 cm), and distributed into 11 diameter classes, with 10 cm interval. Weibull parameters were estimated by Maximum Likelihood method, and the probability of the expected frequency was estimated for each diameter class. The difference between observed and expected frequency generated a set of Chi-squared (χ2) for a 5% critical level (α = 0.05). The main results were: (i) the observed data were fitted by Weibull function appropriately; (ii) the precision obtained by the Weibull function was not influenced by plot size; and (iii) only one function is good enough for Manaus forests, independently of plot size.

The article "The Amazon Forest and the rain" shows that the average annual rainfall is the main weather variable for the forestry sector in the Amazon. The average annual temperature has little variation in the Amazon; only 8%. The average annual rainfall has a greater variation, almost 100%. The growth and increment of Amazonian trees show significant correlations with precipitation. The interannual precipitation presents stronger signals than the intraannual one to explain these correlations. Only the growth and increment of trees are not enought to determine whether the forest is sequestering or emitting carbon. Mortality and recruitment rates play an important role to estimate this balance. These rates have intrinsic relationships with rainfall. The lack or excess of rain influence, mainly, mortality rates. On a regional scale, the lack of rain has contributed to the increased mortality of tropical rainforest trees; in the range of communities is the heavy rainfall that contributes to increased mortality. This article presents the results of two occurrences of weather phenomena in the same year, which reached the Amazon region. In community scale, using three permanent plots (1 ha), results are analyzed to gauge the effects of both phenomena in the forest.

Este trabalho é base do sistema de inventário florestal contínuo (IFC) para o Estado do Amazonas, para ser utilizado na definição e implementação pelo Poder Público de políticas públicas para manejo florestal e projetos de mudanças climáticas . Foram executados estudos sobre estoque de madeira e carbono; dinâmica florestal de áreas não perturbadas, manejadas experimentalmente e empresarialmente; alometria para determinação dos estoques de volume; determinação da altura dominante a partir do inventário de madeira caída e por último determinação de custos de instalação, medição e monitoramento de IFC. Foram utilizados os dados dos inventários florestais em áreas manejadas e não manejadas dos seguintes sítios: Embrapa, MIL Madeireira, ST Manejo de Florestas Ltda, as Resex´s Auati-Paraná, do rio Jutaí, do Baixo Juruá, do Lago do Capanã Grande e do rio Unini; Flona do Pau Rosa e Floresta Estadual de Maués e por último a RDS do Juma. Em cada sítio inventariado, a madeira caída foi utilizada para desenvolver equação local de volume e para estimar a altura dominante que foi utilizada para corrigir a equação de biomassa desenvolvida na região central de Manaus (Estação ZF-2). No sítio MIL Madeireira foi analisado a dinâmica da floresta manejada desde 1995, escala empresarial, tanto do ponto de vista do volume de madeira como de carbono. A Estação ZF-2 do INPA foi utilizada como referência para dinâmica de carbono. Para o Estado do Amazonas, a estimativa do número de indivíduos, área basal, volume de madeira, biomassa total e carbono total, respectivamente foram: 505 ± 52 ind.ha-1; 25,63 ± 1,84 m2.ha-1; 306,50 ± 34,23 m3.ha-1; 563,56 ± 38,66 e 160,34 ± 11,25 (IC 95%). As florestas da Estação ZF-2 e da Comunidade do São José do Inambé (Resex Auati-Paraná, Fonte Boa) têm apresentado incrementos positivos de carbono de 0,03 ± 0,47 t.ha-1 (IC 95%) e 0,91 ± 0,94 t.ha-1 (IC 95%), respectivamente. Onze anos depois da primeira exploração seletiva de madeira na MIL Madeireira o estoque de volume comercial foi de 129,3 ± 28,0 m3.ha-1 e carbono de 153,6 ± 24,5 t.ha-1 (IC 95%), mostrando que passados 11 anos os serviços ambientais são recuperados. As equações não lineares foram as escolhidas para estimar o volume de madeira de cada sítio estudado, com R2 acima de 80% e Syx% abaixo de 10%. Para fins de planejamento de inventário florestal, o custo estimado para instalação e medição foi de R$ 554, 66 ± 120,09 (IC 95%) e para o monitoramento de R$ 452,19 ± 360,20 (IC 95%). O estudo conclui que o Estado do Amazonas tem uma rede de inventário florestal contínuo com metodologia confiável, auditável e replicável. This work is the foundation for the Continuous Forestry Inventory (FCI) system of The State of Amazonas, which can be used in the definition and implementation of public politics for sustainable forest management and climate change projects. There were made studies about timber and carbon stocks; forest dynamics of undisturbed areas that were experimentally and entrepreneurially managed; allometry for determining the volume of stocks; determination of dominant height from the inventory of fallen timber; and finally the determination of inventory costs of installation, measurement and monitoring of IFC. There were used data from forestry inventories in managed and unmanaged areas of the following sites: Embrapa, Mil Madeireira (logging company) , ST Manejo de Florestas Ltda (logging company) , Resex of Auati-Paraná, Resex of Jutai River, Resex of Baixo Juruá, Resex of Lago do Capanã Grande, Resex of Unini River, Flona do Pau Rosa and State Forest of Maués, and also the RDS from Juma. In each site, the fallen trees were used to develop local volume equations and to estimate the dominant height (Hdom). The Hdom were used to correct the biomass equation developed in the ZF-2 Experimental Site, in Manaus City. In the site at MIL Madeireira logging company, it was analyzed the dynamics of the managed forest, since 1995, in a business scale, for timber volume and carbon stock. The ZF-2 site was used as reference for carbon dynamics. The cost of one single sampling plot for FCI in The State of Amazonas were estimated in US$ 278,44 ± 19,10 (IC 95%). The average carbon stock of The State of Amazonas is 160,34 ± 11,25 t.ha-1 (IC 95%). The forests of ZF-2 site and of the local community of São José do Inambé (Resex do Auati-Paraná, Fonte Boa) presented positive carbon increments of 0,03 ± 0,47 t.ha-1 (IC 95%) and 0,91 ± 0,94 t.ha-1 (IC 95%), respectively. Eleven years after the first selective logging at MIL Madeireira the commercial volume stock were estimated in 129,3 ± 28 m3.ha-1 and the carbon stock was 153,6 ± 24,5 t. ha-1 (IC 95%), showing that the environmental services of the forest were recovered. The nonlinear equations were chosen to estimate the volume of wood from each site studied, with R² over 80% and Syx% below 10%. For planning purposes of forest inventory, the estimated cost for installation and measurement was R$ 554 ± 120.09 (95%) and for monitoring of R$ 452.19 ± 360.20 (95%). The study concludes that the State of Amazonas has a network of continuous forest inventory with reliable, repeatable and auditable methodology.

Na Amazônia o fogo é ainda o principal trato cultural utilizado no preparo do solo para agricultura e pecuária, tanto pelos pequenos como pelos grandes fazendeiros. Combinando a baixa fertilidade do solo e o baixo preço da terra, assim que as fontes naturais de nutrientes são exauridas, as áreas são abandonadas e novas florestas primárias são derrubadas e queimadas. Por conta disso, grandes extensões de área da Amazõnia são cobertas por florestas secundárias originadas de áreas abandonadas pela agricultura ou pastagem. Este estudo foi conduzido na Estação Experimental de Silvicultura Tropical (EESTINPA) localizada, aproximadamente, no km 45 da BR-174 em capoeiras com diferentes idades (6, 10 e 25 anos) onde sofreram derruba seguida de queima. Foram mensurados todos os indivíduos com diâmetro à altura do peito maior ou igual a cinco centímetros (DAP = 5 cm) em uma área de 0,4 ha para cada tratamento. Seis, dez e vinte e cinco anos após a queimada, a floresta secundária ainda é muito diferente da floresta original, considerando todos os parâmetros da estrutura da vegetação, como a composição florística, abundância, freqüência, dominância, índice de valor de importância (IVI) e a distribuição diamétrica. As espécies dominantes são, principalmente, das famílias botânicas Annonaceae, Arecaceae, Burseraceae, Cecropiaceae, Euphorbiaceae, Fabaceae, Lecythidaceae, Melastomataceae, Mimosaceae, Sapindaceae e Sterculiaceae. As estimativas de área basal, volume e fitomassa seca das capoeiras com, aproximadamente, 6, 10 e 25 anos de idade foram, respectivamente: 7,5 m².ha-¹, 12,8 m².ha-¹ e 19,2 m².ha-¹; 82,9 m³.ha-¹, 146 m³.ha-¹ e 225,9 m³.ha-¹; 26,3 t.ha-¹, 56,2 t.ha-¹ e 110,1 t.ha-¹. A conversão da floresta primária em secundária, através de derruba e queima, com aproximadamente, seis, dez anos e vinte e cinco anos de idade, já recuperaram 7,5%, 16,5%¨e 32,4% do estoque inicial em fitomassa seca, respectivamente.

Estudos de biomassa em florestas tropicais têm sido utilizados para avaliação ecológica da vegetação e atualmente tem um papel muito importante no processo de assimilação do carbono atmosférico, principalmente devido a mudança no uso da terra na Amazônia. Assim, é necessário saber a quantidade de carbono absorvido na floresta após a exploração florestal. Dessa forma, este trabalho teve como objetivo estudar o efeito do manejo florestal na dinâmica da vegetação e estimar o potencial de créditos de carbono das espécies arbóreas após a exploração na Floresta Nacional do Tapajós (FNT). A pesquisa foi realizada na FNT, ao longo da rodovia Cuiabá-Santarém (BR-163), localizada no estado do Pará, na porção central da floresta amazônica. Para a análise da vegetação foi empregada amostragem em conglomerados alocados aleatoriamente em 37 unidades amostrais com 4 subunidades (parcelas) de 5 m x 50 m, representando uma área amostral de 3,7 ha. Em cada subunidade de conglomerado, antes e após a exploração, foram mensurados todas as árvores com diâmetro a 1,30 m do solo (DAP) ≥ 5 cm e altura total em metros com o aparelho Truepulse 360. Para o sítio controle foram utilizadas 9 parcelas, medindo 50 m x 50 m, totalizando uma área de 2,25 ha. A análise de variância (ANOVA) para o incremento de carbono obteve diferença para as áreas de estudos (F=707,6; p=1,86E-07) e foi significativa de acordo com o teste Tukey (p=3E-07). Em uma análise temporal da área de manejo, o estoque de carbono foi restabelecido após sete anos da atividade florestal, algo que evidencia o serviço ambiental superior (incremento anual 2,13±0,10 MgC.ha -1 ) ao de uma floresta sem intervenção madeireira (incremento 0,85 MgC.ha -1 ). Na análise do potencial de créditos de carbono, o cenário com manejo e queimada, a floresta teve uma perda de 46,73 MgCO 2 eq.ha -1 no manejo e após 5 anos recuperou 31,99 MgCO 2 eq.ha -1 do estoque perdido durante a atividade. Com a queimada, emitiu 156,01 MgCO 2 eq.ha -1 . Quando realizada a projeção de crescimento no segundo cenário, a floresta recuperou o estoque em sete anos e ao longo do ciclo de corte, poderia estocar 218,65 MgCO 2 eq.ha -1 . Isso demonstra resiliência da vegetação diante do sistema de manejo, o que pode ser o diferencial para agregar maior valor a floresta Amazônica, considerando o serviço ambiental carbono. Biomass studies in tropical forests have been used for ecological evaluation of vegetation and currently play a very important role in the assimilation process of atmospheric carbon, mainly due to the change in land use in the Amazon. It is therefore necessary to know the amount of carbon absorbed in the forest after logging. The objective of this study was to study the effect of forest management on vegetation dynamics and to estimate the carbon credits potential of tree species after logging in the Tapajós National Forest (FNT). The research was carried out at the FNT, along the Cuiabá-Santarém highway (BR-163), located in the state of Pará, in the central portion of the Amazon forest. For vegetation analysis, sampling was carried out in conglomerates randomly assigned to 37 sample units with 4 subunits (plots) of 5 m x 50 m, representing a sample area of 3.7 ha. In each conglomerate subunit, before and after the exploration, all trees with a diameter of 1,30 m (DAP) ≥ 5 cm and total height in meters were measured with the Truepulse 360 apparatus. For the control site, 9 plots, measuring 50 mx 50 m, totaling an area of 2.25 ha. The analysis of variance (ANOVA) for the carbon increment obtained a difference for the study areas (F = 707.6, p = 1.86E-07) and was significant according to the Tukey test (p = 3E-07) . In a temporal analysis of the management area, the carbon stock was reestablished after seven years of forestry activity, evidencing the superior environmental service (annual increase 2.13 ± 0.10 MgC.ha -1 ) to that of a forest without timber intervention (increment 0.85 MgC.ha -1 ). In the analysis of the potential carbon credits, the scenario with management and burning, the forest had a loss of 46.73 MgCO 2 eq.ha -1 in the management and after 5 years recovered 31.99 MgCO 2 eq.ha -1 from the lost stock during the activity. With the burning, it emitted 156.01 MgCO 2 eq.ha -1 . When the growth projection was performed in the second scenario, the forest recovered the stock in seven years and during the cutting cycle, could store 218.65 MgCO 2 eq.ha -1 . This shows the resilience of the vegetation before the management system, which can be the differential to add greater value to the Amazon forest, considering the environmental service carbon.