30 research outputs found

    Biomassa de árvores na Amazônia central :

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    Este estudo foi realizado numa área de floresta densa de terra firme na Amazônia central sobre platô com latossolo argiloso. Foram amostradas 310 árvores, com diâmetro na altura do peito (DAP) entre 5 e 122 cm, representando 186 espécies e morfo-espécies. Os objetivos principais foram: (i) determinar a densidade média de madeira das árvores (peso seco a 103°C dividido pelo volume fresco) e as variações radiais e em altura; (ii) verificar as influências da forma não-circular de seções do fuste e da ocorrência de ocos nas estimativas de volume; (iii) discutir as incertezas existentes nas estimativas de biomassa realizadas apartir de inventário florestal comercial. A densidade média de madeira dos fustes foi de 0,67 g.cm-³ (n=307); 4,3% menor que a densidade ao nível do peito (0,70 g.cm-³). Na altura final do fuste a densidade foi de 0,64 g.cm-³ (n=307). A densidade básica do cerne ao nível do peito foi 5,3% maior que a densidade de todo o disco no mesmo nível (n=149). A densidade do cerne obtida por meio de reidratação durante 14 dias, de amostra previamente seca a 103°C, foi 2,5% maior que a densidade da mesma amostra utilizando seu volume verde. Cálculos convencionais de diâmetro, área basal e volume presumem que os perímetros do fuste representem círculos e que o fuste seja um sólido de revolução. Ajustando para a distribuição diamétrica de um inventário de 72 hectares na Amazônia central, tais presunções resultam em superestimativa de 30% na soma da área basal das árvores grandes (DAP2 maior ou igual a 50 cm; n=18) e 11,2% para as árvores estudadas (n=296). O volume dos fustes, somado para todas as árvores acima de 5 cm de DAP, seria superestimado em 12,3% (a maior parte desta correção foi atribuída à forma não­circular das seções; o efeito de ocos foi apenas 0,6% de redução no volume total). Entretando a superestimativa de volume não influencia as estimativas de biomassa realizadas a partir de volume inventariado. Considerando o diâmetro mínimo inventariado pelo Projeto RADAMBRASIL (31,8 cm), a superestimativa volumétrica (soma de 77 fustes) seria de 17,4%. No entanto, a superestimativa de volume associada com os métodos convencionais não significa que as estimativas de biomassa realizadas apartir dos inventários do RADAMBRASIL estejam superestimadas. Utilizando DAP convencional e volume convencional do fuste, o fator de forma médio, utilizando altura total, para todas as árvores estudadas seria de 0,766 ± 0,087 (n=297). Relacionando DAP convencional com volume corrigido pela forma não-circular das seções e pela presença de ocos, o fator de forma médio foi 0,718 maior ou igual a 0,102 para todas as árvores. Para as 76 árvores com DAP maior ou giual a 31,8 cm (diâmetro mínimo nos inventários do RADAMBRASIL) este tipo de fator de forma foi 0,709 ± 0,126; semelhante ao valor de 0,70 adotado pelo RADAMBRASIL

    Maintaining carbon stocks in extractive reserves in Brazilian Amazonia

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    Extractive reserves in the Amazon Forest maintain carbon stocks out of the atmosphere, thereby avoiding greenhouse-gas emissions that provoke global warming. This and other environmental services, such as recycling water and maintaining biodiversity, provide major reasons for creating these reserves and for according them priority in government programs. The importance of reducing carbon emissions from deforestation has been the principal motivation for international funding, which has been key to creating and supporting extractive reserves, notably in the cases of Germany through the PPG7 program and Norway through the Amazon Fund. Estimating the amount of carbon in these reserves and the losses that have occurred from deforestation is essential as an input to making decisions that affect current and potential future extractive reserves. By 2014, there were 47 federal extractive reserves in Brazil’s Legal Amazonia region, of which 45 were in the Amazonian Tropical Forest Biome and 26 extractive reserves belonged to states, all of which were in the Amazonia Biome. This study provides data for each of the 73 extractive reserves in Legal Amazonia, based on biomass information by forest type calculated from RadamBrasil survey data, and deforestation from PRODES monitoring by LANDSAT or equivalent satellites (30-m resolution). The stocks represent carbon in the “pre-modern” biomass, that is, the biomass present in approximately 1970, or before substantial deforestation or logging activity in the region. The carbon losses reflect only deforestation, not degradation of forest by logging and/or fire. The total area of extractive reserves in Legal Amazonia amounted to 126,709 km2, of which 4301 km2 (3.4%) had been cleared by 2014. Those extractive reserves had a remaining carbon stock in forest vegetation (above and below-ground) of 2.1 billion tons. The carbon lost to deforestation totaled 74.9 million tons. Avoiding further carbon loss to both deforestation and degradation needs to be a high priority for the extractivists, as it is the value of the forest’s environmental services that has the greatest potential for providing a means of support that is increasing in value and is inherently sustainable

    Carbon stocks and losses to deforestation in protected areas in Brazilian Amazonia

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    By 2014 approximately 2.2 million km2 (~43%) of Brazil’s Legal Amazonia region had been incorporated into an extensive network of 718 protected areas, which are comprised by 372 indigenous lands, 313 federal, state and municipal (county) conservation units, and 33 Maroon territories (Quilombos). Although protected areas occupy vast expanses in Amazonia, their importance as carbon reserves needs to be better understood. In this study, we estimate the total carbon in 2014 held in protected areas in Brazil’s “Legal Amazonia” and “Amazonia biome” regions, and the carbon loss in the portions of these protected areas that were cleared by 2014. In 2014, a total of 33.4 Pg C or 57.0% of all carbon stored in Legal Amazonia was held in protected areas and 32.7 Pg C or 58.5% of all the carbon stored in the Amazonia biome was held in protected areas. By 2014, carbon lost due to clearing in protected areas in Legal Amazonia and the Amazonia biome totaled, respectively, 0.787 (or 2.3%) and 0.702 (or 2.1%) Pg C if one assumes that previously each protected area was entirely covered by native vegetation. If the protection of these areas is effective, about half of the carbon in Brazilian Amazonia will be maintained. Carbon in protected areas has strategic value for environmental conservation and for mitigation of climate change because these areas are under lower risk of being emitted to the atmosphere than carbon stored in vegetation located outside of protected areas, although the effectiveness of protected areas varies. © 2017, The Author(s)

    Deforestation and Carbon Stock Loss in Brazil’s Amazonian Settlements

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    We estimate deforestation and the carbon stock in 2740 (82 %) of the 3325 settlements in Brazil’s Legal Amazonia region. Estimates are made both using available satellite data and a carbon map for the “pre-modern” period (prior to 1970). We used data from Brazil’s Project for Monitoring Deforestation in Amazonia updated through 2013 and from the Brazilian Biomes Deforestation Monitoring Project (PMDBBS) updated through 2010. To obtain the pre-modern and recent carbon stocks we performed an intersection between a carbon map and a map derived from settlement boundaries and deforestation data. Although the settlements analyzed occupied only 8 % of Legal Amazonia, our results indicate that these settlements contributed 17 % (160,410 km2) of total clearing (forest + non-forest) in Legal Amazonia (967,003 km2). This represents a clear-cutting of 41 % of the original vegetation in the settlements. Out of this total, 72 % (115,634 km2) was in the “Federal Settlement Project” (PA) category. Deforestation in settlements represents 20 % (2.6 Pg C) of the total carbon loss in Legal Amazonia (13.1 Pg C). The carbon stock in remaining vegetation represents 3.8 Pg C, or 6 % of the total remaining carbon stock in Legal Amazonia (58.6 Pg C) in the periods analyzed. The carbon reductions in settlements are caused both by the settlers and by external actors. Our findings suggest that agrarian reform policies contributed directly to carbon loss. Thus, the implementation of new settlements should consider potential carbon stock losses, especially if settlements are created in areas with high carbon stocks. © 2016, The Author(s)

    Height-diameter allometry of tropical forest trees

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    Tropical tree height-diameter (H:D) relationships may vary by forest type and region making large-scale estimates of above-ground biomass subject to bias if they ignore these differences in stem allometry. We have therefore developed a new global tropical forest database consisting of 39 955 concurrent H and D measurements encompassing 283 sites in 22 tropical countries. Utilising this database, our objectives were: 1. to determine if H:D relationships differ by geographic region and forest type (wet to dry forests, including zones of tension where forest and savanna overlap). 2. to ascertain if the H:D relationship is modulated by climate and/or forest structural characteristics (e.g. stand-level basal area, A). 3. to develop H:D allometric equations and evaluate biases to reduce error in future local-to-global estimates of tropical forest biomass. Annual precipitation coefficient of variation (PV), dry season length (SD), and mean annual air temperature (TA) emerged as key drivers of variation in H:D relationships at the pantropical and region scales. Vegetation structure also played a role with trees in forests of a high A being, on average, taller at any given D. After the effects of environment and forest structure are taken into account, two main regional groups can be identified. Forests in Asia, Africa and the Guyana Shield all have, on average, similar H:D relationships, but with trees in the forests of much of the Amazon Basin and tropical Australia typically being shorter at any given D than their counterparts elsewhere. The region-environment-structure model with the lowest Akaike's information criterion and lowest deviation estimated stand-level H across all plots to within amedian −2.7 to 0.9% of the true value. Some of the plot-to-plot variability in H:D relationships not accounted for by this model could be attributed to variations in soil physical conditions. Other things being equal, trees tend to be more slender in the absence of soil physical constraints, especially at smaller D. Pantropical and continental-level models provided less robust estimates of H, especially when the roles of climate and stand structure in modulating H:D allometry were not simultaneously taken into account. © 2011 Author(s)

    Densidade de madeira e alometria de árvores em florestas do arco do desmatamento: implicações para biomassa e emissão de carbono a partir de mudanças de uso da terra na Amazônia brasileira

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    Uncertainties in biomass estimates are the main source of uncertainty in estimates of greenhouse-gas emissions in Amazonia. The results presented in this study reduce the uncertainties in estimates of above-ground biomass, particularly in the southern and southwestern portions of the Brazilian Amazon (SSWA), which are in the arc of deforestation. In Chapter I new data on wood density obtained in the forests of the SSWA area (403 trees identified to species or genus) are combined with the inventories of wood volume produced by Projeto RadamBrasil (1973-1983). The area of each vegetation unit, defined as the intersection among forest types and the boundaries of the nine states in Brazilian Amazonia, was used to calculate a mean wood density of 0.583 g.cm-3 for the SSWA as a whole. This average is 13.6% lower than the value used for this area in previous estimates. An average of 0.642 g.cm-3 was obtained for the Brazilian Amazon as a whole, starting from the new estimates for the forests of the SSWA together with estimates for the other areas of Amazonia, corrected for radial variation (-5.3%). The new density average is 7% lower than the average previously used for the Brazilian Amazon (0.69 g.cm-3). The impact on estimates of biomass and carbon emission is substantial because the reduction is largest in the forest types experiencing the most rapid deforestation. For 1990, with 13.8 × 103 km2 of deforestation, the estimated emission for the Brazilian Amazon would be reduced by 23.4-24.4 × 106 CO2-equivalent Mg C/year (for high and low trace-gas scenarios), or 9.4- 9.5% of the gross emission and 10.7% of the net committed emission, both excluding the soil. In Chapter II linear relationships were appraised that describe the radial variation of density for trees in dense forest in the central Amazon (CA) and new relationships are developed for trees in open forest in the southern Amazon (SA). The linear relationship described in CA for the variation of density along the bole is similar for trees in SA (p = 0.144). It is also demonstrated that the trees in the southern Amazon have significantly higher humidity content in their boles (0.416 ± 0.068 SD; n = 223) than do trees in CA (0.38; n = 50). Moisture content of the bole had a strong inverse relationship with basic wood density and explains the lower moisture content in the trees in CA relative to SA. In Chapter III CA trees are shown to be taller for any given diameter than they are in bamboo-dominated dense forests, bamboo-free dense forests and open forests in the southwestern Amazon (SW), as well as in the open forests of the southern Amazon (SA). The impact on biomass estimates is - 11.0%, -6.2% and -3.6%, respectively. This suggests that the estimate of the Brazilian National Communication to the United Nations Framework Convention on Climate Change requires revision. The relationships observed between diameter and height were inconsistent with the assumptions of metabolic ecological theory and the findings reinforce the argument that the scalar allometric exponent varies among forests growing on different substrata or with different levels of natural disturbance. In Chapter IV new allometric equations for biomass are derived starting from trees weighed directly in SA and from equations for estimates of volume of the bole in CA and in SA. These equations were used to improve the biomass model historically applied in Amazonia, which is based on large-scale inventories of wood volume. A new biomass estimate is produced for the Brazilian Amazon incorporating new values of wood density, corrections for uncertainties in estimates of wood volume and new values for factors used to add the volume of the boles of small trees and the biomass of the crowns. Considering all adjustments the biomass map indicates average biomass of 125.4 Pg (=1015 g) dry weight (above-ground + below-ground) for originally forested areas in the Brazilian Legal Amazon as a whole (104.2 Pg for above-ground only) at the time of the RadamBrasil inventories, which was before intensive deforestation had occurred in the region. If areas deforested through 2006 are eliminated, excluding agriculture, pasture and secondary forest vegetation, the estimation of dry biomass storage was reduced to 113.3 and 94.2 Pg (aboveground + below-ground and only above ground).Incertezas nas estimativas de biomassa são a principal causa de incertezas nas estimativas de emissão de gases de efeito estufa na Amazônia. Os resultados apresentados neste estudo reduzem as incertezas nas estimativas de biomassa acima do solo, particularmente no sul e sudoeste da Amazônia brasileira (SSWA), regiões inseridas no arco do desmatamento . No Capítulo I novos dados de densidade de madeira obtidos nas florestas da região SSWA (403 árvores identificadas em nível de espécie e gênero) foram combinados com os inventários de volume de madeira produzidos pelo Projeto RadamBrasil (1973-1983). A área de cada unidade de vegetação, definidas pela intersecção entre tipos de florestas mapeados e divisão geopolítica dos estados, foi utilizada para obter a densidade de madeira média (0,583 g cm-3) para toda a região SSWA. Esta média é 13,6% menor do que o valor utilizado para esta região em estimativas prévias. A média de 0,642 g cm-3 foi obtida para a Amazônia brasileira como um todo, a partir das novas estimativas para as florestas da porção SSWA juntamente com estimativas para as outras regiões da Amazônia, corrigidas para a variação radial (-5,3%). A nova média de densidade é 7% menor que a média anteriormente estimada para a Amazônia brasileira: 0,69 g cm-3. O impacto sobre as estimativas de biomassa e emissão de carbono é substancial porque a redução é maior em tipos de floresta sob maior desmatamento. Para 1990, com 13,8 × 103 km2 de desmatamento, as emissões para a Amazônia brasileira seriam reduzidas por 23,4-24,4 × 106 Mg CO2-equivalente C/ano (para cenários de gás-traço alto e baixo), ou 9,4-9,5% da emissão grossa e 10,7% da emissão líquida comprometida, ambas excluindo o solo. No Capítulo II foram avaliadas relações lineares que descrevem a variação radial da densidade para árvores em floresta densa na Amazônia central (CA) e desenvolvidas novas relações para árvores em floresta aberta no sul da Amazônia (SA). A relação linear descrita na CA para a variação da densidade ao longo do fuste é similar para árvores no SA (p = 0,144). Também é demonstrado que as árvores no sul da Amazônia possuem conteúdo de umidade no fuste significativamente maior (0,416 ± 0,068 SD; n = 223) do que em árvores na CA (0,38; n = 50). O conteúdo de umidade tem uma forte relação inversa com a densidade básica da madeira, o que explica o menor conteúdo de umidade nas árvores na CA comparado ao SA. No Capítulo III é demonstrado que na CA as árvores são mais altas para um dado diâmetro que em florestas abertas dominadas por bambu e densas livres de bambu, no sudoeste da Amazônia (SW), bem como em florestas abertas no sul da Amazônia (SA). O impacto sobre as estimativas de biomassa foram respectivamente -11,0%, -6,2% e -3,6%. Isto sugere que a estimativa da Comunicação Nacional Brasileira no âmbito da Convenção Quadro das Nações Unidas para Mudanças Climáticas requer redução. As relações observadas entre diâmetro e altura foram inconsistentes com a suposição da teoria de ecologia metabólica e reforça o argumento que o expoente escalar alométrico varia em florestas sobre diferentes substratos ou com diferentes níveis de distúrbios naturais. No Capítulo IV é apresentada nova equação alométrica para estimativa de biomassa desenvolvida a partir de árvores diretamente pesadas no SA e equações para estimativas do volume do fuste na CA e no SA. Estas equações foram utilizadas para aperfeiçoar o modelo de biomassa historicamente aplicado na Amazônia, que se baseia em inventários de volume de madeira em larga-escala. Nova estimativa de biomassa foi produzida para a Amazônia brasileira incorporando novos valores de densidade de madeira, correções para incertezas em estimativa de volume de madeira e fatores utilizados para adicionar o volume dos fustes de pequenas árvores e biomassa das copas. Considerando todos os ajustes, o mapa indica estoque de 125,4 Pg (=1015 g) de biomassa seca (acima e abaixo do solo) para áreas originalmente florestadas na Amazônia Legal Brazileira (104,2 Pg somente acima do solo) no período dos inventários do RadamBrasil, portanto antes que intensivos desmatamentos tivessem ocorrido na região. Se as áreas desmatadas até 2006 forem eliminadas do cálculo, excluindo agricultura, pastagens e vegetação de floresta secundária, a estimativa de biomassa seca estocada é reduzida para 113,3 e 94,2 Pg (acima e abaixo do solo, e somente acima do solo)

    Ocorrência de árvores ocadas em floresta densa na Amazônia central

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    Volume and biomass of trees in central Amazonia: influence of irregularly shaped and hollow trunks

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    Conventional measurements of diameter, basal area and volume of the bole assume that any cross section of the bole is circular and that the bole is a solid of revolution. These assumptions lead to error when the bole is irregularly shaped and/or hollow. These errors were quantified for trees in central Amazonia after adjusting the number of trees sampled in each class based on the diameter distribution of a large inventory. For large trees (DBH ≥50 cm) total basal area was overestimated by 30%, while the overestimate was 11% for all trees with DBH ≥5 cm. The total bole volume per hectare was overestimated by 11.2% (∼40 m3/ha). Most of this volume correction is attributed to the non-circular form of the cross section; the effect of hollow areas on the volume of the bole was only 0.7%. For trees above 31.8 cm DBH, which is the minimum diameter in the Projeto RADAMBRASIL inventories, the volume per hectare was overestimated by 4.4% using conventional measurements. Because of compensating errors in commonly used formulas, however, the volume overestimate associated with conventional methods does not imply biomass overestimation in studies that have used the RADAMBRASIL dataset. © 2006 Elsevier B.V. All rights reserved
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