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Land Use Change Effects on Forest Carbon Cycling Throughout the Southern United States

USDA Forest Service-NE, P.O. Box 640, Durham, NH 03824. P.B. Woodbury, current address: Department of Crop and Soil Sciences, Cornell University, Ithaca, NY 14853

View larger version (56K): [in a new window]   Fig. 1. The study region includes the eight-state South-Central and five-state Southeast regions of the United States. Gray shading shows forested areas (Smith et al., 2001).

View larger version (20K): [in a new window]   Fig. 2. Transitions among different types of land use. Black arrows show transitions included by the model. Dashed arrows show transitions not included in the model. The arrows have heads in both directions to indicate that transitions in each direction are included in the model.

View larger version (19K): [in a new window]   Fig. 3. Example of afforestation and deforestation effects on carbon in the forest floor of pine plantations in the Southeast region. Negative values indicate C sequestration and are afforestation. Positive values indicate carbon emission and are deforestation. The equations for pine (and other forest types, not shown) are based on those of Smith and Heath (2002), modified not to exceed average forest floor C accumulation.

View larger version (23K): [in a new window]   Fig. 4. Change in soil carbon after deforestation: our model equation compared to data from North America and to selected models from the literature. Literature data are from Coote and Ramsey (1983), Ellert and Gregorich (1996), Franzluebbers et al. (2000), Giddens (1957), Gregorich et al. (1995), Martel and Mackenzie (1980), and Pennock and van Kessel (1997).

View larger version (28K): [in a new window]   Fig. 5. Change in soil carbon after afforestation: comparison of our model equation to data for pine forest types in the Southeast and South-Central regions of the United States and to selected equations from the literature. Published data are shown as points and models are shown as lines; data are from Garten (2002), Post and Kwon (2000), Van Lear et al. (1995), Houghton and Hackler (2000, 2001), and West et al. (2004). Data from Post and Kwon (2000) are a published literature review covering many studies, other citations are data not included in that review.

View larger version (26K): [in a new window]   Fig. 6. For the Southeast region, cumulative effect of land use change on forest carbon from 1900 to 2050 (positive values are emission to the atmosphere, negative values are sequestration).

View larger version (26K): [in a new window]   Fig. 7. For the South-Central region, cumulative effect of land use change on forest carbon from 1900 to 2050 (positive values are emission to the atmosphere, negative values are sequestration).

View larger version (27K): [in a new window]   Fig. 8. For Southeast region, annual area afforested and annual effect of afforestation on carbon in the soil and forest floor from 1900 to 2050. Area change is shown as negative values for comparison with afforestation, for which negative values show carbon sequestration.

View larger version (27K): [in a new window]   Fig. 9. For the South-Central region, annual area afforested and annual effect of afforestation on carbon in the soil and forest floor from 1900 to 2050. Area change is shown as negative values for comparison with afforestation, for which negative values show carbon sequestration.

View larger version (25K): [in a new window]   Fig. 10. For Southeast region, annual area deforested and annual effect of deforestation on carbon in the soil and forest floor from 1900 to 2050.

View larger version (28K): [in a new window]   Fig. 11. For the South-Central region, annual area deforested and annual effect of deforestation on carbon in the soil and forest floor from 1900 to 2050.

View larger version (24K): [in a new window]   Fig. 12. For Southeast region, comparison of our model estimates of land use change effects on soil and forest floor carbon flux to previous estimates and to an estimate for other forest carbon pools. Afforestation effects are negative values and deforestation effects are positive values. The total effect is shown by the numbers above the bars. Symbol colors are: black = soil; gray = forest floor; white = tree carbon (live trees only for "Affor. only" estimate); diagonal stripes = dead tree, coarse woody debris, and understory. "Heath and others" estimates are from Heath et al. (2002), "Tree C net" estimates were contributed by us to USEPA (2004), and the "Affor. Only." estimate is for all pools except soil and forest floor on afforested lands only and was derived as described in the text.

View larger version (23K): [in a new window]   Fig. 13. For the Southeast region, cumulative predicted effect of land use change on forest carbon stocks from 2000 to 2050: comparison of our model with FORCARB model. Note that positive values are emission to the atmosphere and negative values are sequestration. Numbers in the graph are the total change from 2000 to 2050.

View larger version (22K): [in a new window]   Fig. 14. For the South-Central region, cumulative predicted effect of land use change on forest carbon stocks from 2000 to 2050: comparison of our model with the FORCARB model. Note that positive values are emission to the atmosphere and negative values are sequestration. Numbers in the graph are the total change from 2000 to 2050.