By 2014 approximately 2.2 million km 2 (~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 BLegal Amazoniaâ nd BAmazonia 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.
RESUMOUtilizando um modelo estocástico, foi projetada a distribuição diamétrica futura de uma floresta submetida à exploração seletiva de madeira na Amazônia Ocidental. Foram utilizados dados de cinco parcelas permanentes localizadas no PC Pedro Peixoto, no Acre. A primeira medição das parcelas ocorreu em 1996, a exploração florestal em 1997 e as re-medições em 1999 e 2001. A principal variável utilizada foi o diâmetro à altura do peito (DAP). A matriz de transição probabilística (Cadeia de Markov) foi utilizada para fazer a projeção da distribuição diamétrica do número de árvores sobreviventes nas classes diamétricas. O modelo foi primeiramente testado para fazer a projeção para 2001, tendo como base as observações de 1999 e seu passado imediato (1997). Quando comparadas às projeções feitas para 2001 e as medições de campo (2001), o teste Qui-quadrado mostrou que não houve diferença significativa entre freqüências esperadas e observadas na distribuição diamétrica (p=0,05). A projeção para 2005 indica que a taxa de mortalidade será próxima a de 2001, e se repetida a taxa de recrutamento em 2005 o total de árvores será maior que o observado em 2001. Esse comportamento da floresta indica que não existe um padrão definido para a dinâmica nas classes diamétricas em termos de mortalidade ou crescimento, apresentando um comportamento aleatório ou probabilístico, justificando a eficiência da Cadeia de Markov para projetar a dinâmica da floresta estudada, podendo auxiliar na determinação do ciclo de corte ou mostrando as tendências que a floresta de hoje apresentará em um futuro próximo.
PALAVRAS-CHAVE:Exploração seletiva, Distribuição diamétrica, Cadeia de Markov, Amazônia.
Projection of the diameter distribution in a selective logging forest in the western Amazon
ABSTRACTThe diameter distribution of an experimental forest stand in the Western Amazon was projected using a stochastic model after selective logging. The study was developed using data from five permanent plots located in the colonization project Pedro Peixoto, in the state of Acre. Initial measurements of diameter at breast height (DBH) were taken in 1996. The forest was selectively logged in 1997 and DBHs were re-measured in two different occasions, 1999 and 2001. A probabilistic transition matrix (Markov Chain) was used to project the diameter distribution of the number of surviving trees in each diameter class. The model was first tested to project the diameter distribution in 2001, based on DBH measurements from 1997 and 1999. When the projected diameter distribution for 2001 was compared with the field data from the same year, a Chi-squared test (α = 0.05) showed that there was not significant difference between the expected and observed diameter distribution. After that, a projection for 2005 (four years in the future) was run using DBH measurements from 1997 to 2001, indicating that mortality rate was similar to 2001. If repeated the rate of recruitment of 2005, the total number of trees will be higher than observed in 2001. The dynamics of the stud...
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