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QUANTIFYING THE ORGANIC CARBON HELD IN FORESTED SOILS OF THE UNITED STATES AND PUERTO RICO
Citation:
Johnson, M G. AND J. S. Kern. QUANTIFYING THE ORGANIC CARBON HELD IN FORESTED SOILS OF THE UNITED STATES AND PUERTO RICO. Chapter 14, Kimble, JS (ed.), The Potential of U.S. Forest Soils to Sequester Carbon and Mitigate the Greenhouse Effect. CRC Press LLC, Boca Raton, FL, , 47-72, (2003).
Description:
It is well known that soils are an important global reservoir of organic carbon (C). In fact, it has been estimated that at 1500 Pg (1Pg = 1015 g) world soils hold approximately three times the amount of C held in vegetation (~560 Pg) and two times that in the atmosphere (~735 Pg). One of the important characteristics of soil C is that it is a relatively stable reservoir with long C residence times. This feature makes soils a valuable tool for storing C for long periods of time. With the intense focus on increasing atmospheric CO2 and the potential for global climate change, there is an urgent need to assess the feasibility of managing ecosystems to sequester and store C. Forested ecosystems are one of several ecosystems under consideration for storing additional C. On a global basis forests are estimated to cover approximately 4.1 billion hectares and hold about 1150 Pg of C in vegetation and soil combined. Of the different types of vegetation, forests have the unique situation of large above- and belowground stocks of C. We use current map and laboratory data to develop an inventory of the organic C held in forested soils of the U.S. and Puerto Rico (PR). Further, we distinguish between the contribution of organic soils and mineral soils to the total amount of soil C. We estimate that the forested soils of the U.S. and Puerto Rico hold 35.5 Pg of C to a depth of 100 cm. Of this 35.5 Pg, 7.9 Pg, or 22%, of the C is from organic soils. The Oak-Hickory forest holds the most soil C of the 25 forest type groups in the U.S. and Puerto Rico. At 309 Mg C ha-1 (Mg = 106 g), the Hemlock-Sitka forest of Alaska has the most soil C on a C per unit area basis. This inventory of soil C held U.S. and Puerto Rican forests can be used as an aid in identifying those forest types that can be managed for additional C sequestration.