the accumulation of organic carbon in mineral soils by afforestation of abandoned farmland在矿质土壤有机碳的积累造林废弃的农田.pdfVIP

The Accumulation of Organic Carbon in Mineral Soils by Afforestation of Abandoned Farmland 1 1 1 1 2 Xiaorong Wei *, Liping Qiu , Mingan Shao , Xingchang Zhang , William J. Gale 1 State Key Laboratory of Soil Erosion and Dryland Farming in the Loess Plateau, Northwest A F University, Yangling, China, 2 College of Resources and Environment, Northwest A F University, Yangling, China Abstract The afforestation of abandoned farmland significantly influences soil organic carbon (OC). However, the dynamics between OC inputs after afforestation and the original OC are not well understood. To learn more about soil OC dynamics after afforestation of farmland, we measured the soil OC content in paired forest and farmland plots in Shaanxi Province, China. The forest plots had been established on farmland 18, 24, 48, 100, and 200 yr previously. The natural 13C abundance of soil organic matter was also analyzed to distinguish between crop- and forest-derived C in the afforested soils. We observed a nonlinear accumulation of total OC in the 0–80 cm depth of the mineral soil across time. Total soil OC accumulated more rapidly under forest stands aged 18 to 48 yr than under forest stands aged 100 or 200 yrs. The rate of OC accumulation was also greater in the 0–10 cm depth than in the 10–80 cm depth. Forest-derived OC in afforested soils also accumulated nonlinearly across time, with the greatest increase in the 0–20 cm depth. Forest-derived OC in afforest soils accounted for 52–86% of the total OC in the 0–10 cm depth, 36–61% of the total OC in the 10–20 cm depth, and 11–50% of the total OC in the 20–80 cm depth. Crop-derived OC concentrations in the 0–20 cm depth decreased slightly after afforestation, but there was no change in crop-derive