Amazonian forests play a key role in the global carbon cycle, thus increases their significance, but there is much uncertainty about the quantity and distribution of carbon stored in these forests.

The rapid conversion of tropical forests is a major source of greenhouse gases such as carbon dioxide, methane, and nitrous oxide, which are the principle causes of global warming (Houghton and Fearnside). Nowhere is
deforestation occurring more rapidly than in Brazilian Amazonia, which contains about 40% of the world's remaining tropical rainforests ( Laurance et al., 2001a). From 1995 to 1999, deforestation rates in the Brazilian
Amazon averaged nearly 2 million hectares per year ( INPE, 2000), not including extensive forest areas degraded by logging, ground fires, forest fragmentation, illegal gold-mining, and overhunting ( Skole; Laurance;
Cochrane and Nepstad).

Despite the important role of Amazonian forests in the global carbon cycle (Fearnside, 1997a), data on biomass and carbon storage in the region are clearly inadequate (e.g. Brown; Brown and Brown). Biomass estimates
for Amazonian forests have been the subject of considerable debate (e.g. Brown; Brown; Fearnside; Fearnside and Fearnside) because of limited data, methodological differences among investigators, and small or
incomplete measurements of biomass in some studies (cf. Houghton et al., in press). Current estimates of total carbon storage in Brazilian Amazonia vary by more than a factor of 2, from 39 to 93 Pg C, largely as a result of
uncertainty in the quantity and spatial distribution of forest biomass ( Houghton et al., in press). Houghton et al. (2000) concluded that 60% of the uncertainty in their estimates of annual carbon flux from Brazilian
Amazonia resulted from varying estimates of forest biomass. Clearly, there is a need for additional measurements of biomass across large expanses of the Amazon basin.

In a recent study, Laurance et al. (1999) assessed the relationship between soil features and aboveground biomass of live trees for 65 1 ha plots arrayed across an extensive (ca. 1000 km2) central Amazonian landscape.

Biomass estimates in this study were generated by measuring diameters of all large (10 cm diameter-at-breast-height (DBH)) trees and then using a correction factor to approximate biomass of small (<10 cm DBH)
trees. Here we provide a much more comprehensive estimate of aboveground biomass for the same study area, based on 20 randomly selected 1 ha plots in which biomass of all live and dead material (large trees, small
trees, seedlings, palms, lianas, downed wood debris, snags, litter, aboveground root mat) was quantified.

And.. the results after various testing methods.. whcih ill probably put up later.
 
 

A key conclusion is that biomass in these forests is very high, averaging nearly 400 Mg ha-1

Collectively, these studies illustrate the high capacity of intact Amazonian forests for carbon storage. Assuming that 50% of biomass is carbon, aboveground carbon storage in our study area is nearly 200 Mg ha-1, with
perhaps another 35¯40 Mg ha-1 as belowground biomass and roughly 300 Mg ha-1 as soil organic matter. Forest conversion is unlikely to have major effects on deep soil organic matter, but it can dramatically reduce
carbon storage aboveground and in the roots and upper soil layers

Amazon forests contain a very large stock of terrestrial carbon (Fearnside and Houghton) and are probably an important carbon sink ( Grace; Phillips; Malhi and Chambers). Thus, understanding the spatial distribution of
biomass in these forests is an urgent priority. Carbon storage in undisturbed forests is very high, suggesting that forest conversion is likely to be an even larger source of greenhouse gas emissions than previously anticipated. This is important because plans are well underway to expand networks of highways, railroads, gas lines, and other major infrastructure projects in the Brazilian Amazon. By opening large expanses of the basin's remote interior to exploitative activities, these projects are predicted to sharply accelerate the pace of forest conversion and degradation ( Carvalho and Laurance). Agricultural practices in the Amazon are limited by very low soil fertility ( Kauffman and Fearnside), and the economic value of intact forests for carbon storage, biodiversity conservation, and other natural ecosystem services may ultimately be far greater than that provided by forest conversion.