Forest structure and carbon dynamics in Amazonian tropical rain forests

Abstract

Living trees constitute one of the major stocks of carbon in tropical forests. A better understanding of variations in the dynamics and structure of tropical forests is necessary for predicting the potential for these ecosystems to lose or store carbon, and for understanding how they recover from disturbance. Amazonian tropical forests occur over a vast area that encompasses differences in topography, climate, and geologic substrate. We observed large differences in forest structure, biomass, and tree growth rates in permanent plots situated in the eastern (near Santarém, Pará), central (near Manaus, Amazonas) and southwestern (near Rio Branco, Acre) Amazon, which differed in dry season length, as well as other factors. Forests at the two sites experiencing longer dry seasons, near Rio Branco and Santarém, had lower stem frequencies (460 and 466 ha −1 respectively), less biodiversity (Shannon-Wiener diversity index), and smaller aboveground C stocks (140.6 and 122.1 Mg C ha ), which had less seasonal variation in rainfall. The forests experiencing longer dry seasons also stored a greater proportion of the total biomass in trees with >50 cm diameter (41-45 vs 30% in Manaus). Rates of annual addition of C to living trees calculated from monthly dendrometer band measurements were 1.9 (Manaus), 2.8 (Santarém), and 2.6 (Rio Branco) Mg C ha. At all sites, trees in the 10-30 cm diameter class accounted for the highest proportion of annual growth (38, 55 and 56% in Manaus, Rio Branco and Santarém, respectively). Growth showed marked seasonality, with largest stem diameter increment in the wet season and smallest in the dry season, though this may be confounded by seasonal variation in wood water content. Year-to-year variations in C allocated to stem growth ranged from nearly zero in Rio Branco, to 0.8 Mg C ha −1 year −1 in Manaus (40% of annual mean) and 0.9 Mg C ha −1 year −1 (33% of annual mean) in Santarém, though this variability showed no significant relation with precipitation among years. Initial estimates of the C balance of live wood including recruitment and mortality as well as growth suggests that live wood biomass is at near steady-state in Manaus, but accumulating at about 1.5 Mg C ha −1 at the other two sites. The causes of C imbalance in living wood pools in Santarém and Rio Branco sites are unknown, but may be related to previous disturbance at these sites. Based on size distribution and growth rate differences in the three sites, we predict that trees in the Manaus forest have greater mean age (~240 years) than those of the other two forests (~140 years).

Tree Community Composition and Aboveground Biomass in a Secondary Atlantic Forest, Serra Do Mar State Park, São Paulo, Brazil

“…ha -1 ). Medeiros and Aidar (2011) researching a plot at Montane Ombrophilous Dense Forest found that diameters of up to 13 cm comprised 60% of the individuals and 7.4% of the total biomass, similarly to the results found by Vieira et al (2004) in a Central Amazon forest, where trees with diameters between 10 and 29.9 cm corresponded to approximately 80% of the individuals sampled, and contributed only with 26.4 to 32.9% of the total estimated biomass. …”

“…Mandal and Joshi (2014) suggested that these characteristics could change in response to climate, topography, soil and disturbances. The aboveground live biomass varies widely in neotropical forests due to regional differences in the individual size, wood density, species composition, soil fertility, topography and disturbance (VIEIRA et al, 2004;CHAVE et al, 2005;MALHI et al, 2006;VIEIRA et al, 2008). The general trends for forests from high altitudes are the decline in stature and reduction in the aboveground biomass, while there is an increase in wood density (Aiba and Kitayama, 1999;Moser et al, 2007).…”

Systematic assessment of terrestrial biogeochemistry in coupled climate–carbon models

“…To further assess the causes of this model bias in the tropical forest aboveground live biomass pool, we compared the models with carbon budget observations from Amazonia (Miller et al, 2004;Vieira et al, 2004;Figueira et al, 2008;Malhi et al, 2009). GPP in both CASA 0 (3220 g C m À2 yr À1 ) and CN (2900 gC m À2 yr À1 ) was similar to observed levels (3330 AE 420 g C m À2 yr À1 ) (Figueira et al, 2008;Malhi et al, 2009).…”

Qualitative evaluation of Permanent Preservation Areas Stream of Antas, in the city of Morrinhos, Goiás

“…No Cerrado, espécies de plantas da macrofamília das L eguminosas (Caesalpinaceae, Fabaceae e Mimosaceae) são as de maior abundância (VIEIRA et al, 2004;NARDOTO, 2005 Para Formoso (2007, p.13), em plantios feitos para recuperação, em domínio do Cerrado "[...] o uso de espécies leguminosas deve ser intenso, assegurando o aporte de nitrogênio, essencial para equilibrar a relação carbono: nitrogênio do sistema, fator essencial para que ocorram elevações efetivas e estáveis de carbono no solo". Dessa forma, a grande quantidade de leguminosas na área mostra-se muito favorável para o restabelecimento ambiental.…”