From treehugger
A report released today by The Wilderness Society emphasizes the enormous carbon reserves held by forests in the contiguous states - roughly equivalent to more than 20 years of current United States greenhouse gas emissions from industrial and other sources. Across the U.S., public and protected forests generally store the most carbon. The analysis also cautions that existing carbon measurement tools have significant limitations due to gaps in the underlying data: old growth forests, in particular, may be undervalued.
The executive summary of "Measuring Forest Carbon: Strengths and Weaknesses of Available Tools" is available here, and the full report may be downloaded as a pdf file here.
"Analysis Shows American Forests Contain Enormous Carbon Reserves, But Available Measuring Tools Reflect Gaps in Underlying Data" Image credit::The Wilderness Society, Full Report here