ESTIMATION OF CHANGES IN SOIL ORGANIC CARBON IN HILLSIDE SYSTEMS ON A REGIONAL SCALE

Estimation of soil organic carbon (SOC) stocks at the regional scale, and of the changes that occur over time, is needed to conduct more realistic carbon (C) inventories. This study compares changes in estimated SOC in three regions of the Sierra Norte of Oaxaca (Mazatec, Cuicatec, and Mixe) with the method proposed by the Intergovernmental Panel on Climate Change (IPCC) and the RothC model fed with spatial information from the IPCC method. Changes were estimated for the periods 1980-2000 and 1990-2000. The SOC balance in the study regions resulting from the two methods indicates losses in the range of 342-1509 Gg in the first period and 29-1052 Gg in the second. Changes in SOC estimated with both methods, in general, exhibited the same trend for the two periods. The correlation coefficients varied between 0.86 and 0.99. This study shows that the RothC model used with partial information from the IPCC method is a useful tool for predicting changes in estimated SOC on a regional scale in the hillside systems studied.