The regional variation of aboveground live biomass in old‐growth Amazonian forests

Abstract

The biomass of tropical forests plays an important role in the global carbon cycle, both as a dynamic reservoir of carbon, and as a source of carbon dioxide to the atmosphere in areas undergoing deforestation. However, the absolute magnitude and environmental determinants of tropical forest biomass are still poorly understood. Here, we present a new synthesis and interpolation of the basal area and aboveground live biomass of old-growth lowland tropical forests across South America, based on data from 227 forest plots, many previously unpublished. Forest biomass was analyzed in terms of two uncorrelated factors: basal area and mean wood density. Basal area is strongly affected by local landscape factors, but is relatively invariant at regional scale in moist tropical forests, and declines significantly at the dry periphery of the forest zone. Mean wood density is inversely correlated with forest dynamics, being lower in the dynamic forests of western Amazonia and high in the slow-growing forests of eastern Amazonia. The combination of these two factors results in biomass being highest in the moderately seasonal, slow growing forests of central Amazonia and the Guyanas (up to 350 Mg dry weight ha À1) and declining to 200-250 Mg dry weight ha À1 at the western, southern and eastern margins. Overall, we estimate the total aboveground live biomass of intact Amazonian rainforests (area 5.76 Â 10 6 km 2 in 2000) to be 93 AE 23 Pg C, taking into account lianas and small trees. Including dead biomass and belowground biomass would increase this value by approximately 10% and 21%, respectively, but the spatial variation of these additional terms still needs to be quantified.

Soil-induced impacts on forest structure drive coarse woody debris stocks across central Amazonia

“…Amazonia holds a great diversity of tree species (ter Steege et al 2000), and its forests vary substantially in both vegetation dynamics Quesada et al 2012), and structure Malhi et al 2006;Nogueira et al 2008;Feldpausch et al 2011). Our current understanding suggests that CWD stocks generally decrease from north-eastern to south-western Amazonia (Baker et al 2007;Chao et al 2009a).…”

“…Spatial variation in CWD stocks across the landscape may respond both to short-term climatic disturbances (e.g. Phillips et al 2009;Negrón-Juárez et al 2010) and to long-term differences in forest dynamics in response to environmental characteristics (Keller et al 2004;Malhi et al 2006;Chao et al 2009a). Soils represent an important environmental gradient in Amazonia, with a wide variety of soil types across the Basin and with diverse chemical and physical conditions (Quesada et al 2010;.…”

Tree Species Composition, Structure, and Aboveground Wood Biomass of a Riparian Forest of the Lower Miranda River, Southern Pantanal, Brazil

“…However, the biomass of tropical forests plays an important role in the global carbon cycle, both as a reservoir of carbon and as a source of greenhouse gas emissions from deforestation (Fearnside 1997;Mahli et al 2006). Nunes da Cunha and Junk (2001) investigated the distribution of woody plant communities in the northern part of the Pantanal near the city of Poconé in terms of habitat preference and found approximately 40 flood-resistant tree species, most of them showing a wide distribution range on the topographic gradient, from areas with prolonged flooding to dry habitats that become flooded only during extreme flood events.…”

Brazil’s Amazonian forest carbon: the key to Southern Amazonia’s significance for global climate

“…All of these studies represent advances in interpretation of remote sensing data, but remain limited by their datasets for ground truth. Mitchard et al (2014) contrasted the spatial results of the Saatchi et al (2011) and Baccini et al (2012) remote sensing studies, as well as the geographical information system (GIS) analyses derived directly from plot data by Houghton et al (2001), Malhi et al (2006) and their own analysis of RAINFOR (Amazon Forest Inventory Network) plots (e.g., Phillips et al 2009). The results show major differences between all of the resulting maps, including those with largely overlapping ground-based datasets.…”

“…Standardization for non-tree components, together with trees \10 cm DBH, removes almost all of the difference between aboveground live biomass estimates by Fearnside (1997a), Houghton et al (2001) and Malhi et al (2006) (see review in: Malhi et al 2006Malhi et al , pp. 1120Malhi et al -1121.…”