|Soil properties and organic carbon sequestration in the long-term afforested stands of plain areas
|Taiwanese Journal of Agricultural Chemistry and Food Science
Afforestation in the marginal cultivated lands of plain areas is positively implemented in Taiwan. However, the information of long-term afforestation effects on soil properties and soil organic carbon (C) sequestration is still scarce, and no field data exists. In this study, the long-term abandoned orchards and afforested sites were examined as the proxies to assess the long-term afforestation effects on soil properties and soil organic C sequestration. Soil organic C size fractionation and clay mineral identification were also conducted to elucidate the mechanisms of soil organic C sequestration. Our results showed that afforestation could result in lower pH and bulk density and higher soil organic C and nitrogen content and storages compared to the adjacent cultivated stands. However, this general trend can be deflected by the specific management of the individual cultivated stand. For example, afforestation on the paddy rice soil could have opposite results due to the lower bulk density and higher C and N content and storages in the paddy rice soil. Fertilization in the adjacent cultivated stands may also increase exchangeable cations, cation exchange capacity and available phosphorus and abate the effect of afforestation. Average soil organic C storages at 0-20 cm depth in the afforested stands was 7.8 ton C ha-1 higher than that in the cultivated stands, while most of these sequestrated C storages belonged to the labile C pools and only a few amount of sequestrated C storages can be stored in the recalcitrant C pools. Annual soil organic C accumulation was 0.34 ton Cha-1, y-1 which was close to the mean value of global afforestation (0.3 ton C ha-1y-1). We estimate that present afforestation policy over 25,000 ha afforested areas can then sequestrate 1.9 × 105ton C in soils.
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