土地利用变化对土壤有机碳贮量的影响

Impact of land-use change on soil carbon storage.

通过对比分析六盘山林区典型天然次生林 (杂灌林、山杨和辽东栎林 )与农田、草地及农田、草地与人工林 (13、18和 2 5年生华北落叶松 )邻近样地土壤有机碳含量和密度及其在土壤剖面上分布的差异 ,研究了天然次生林变成农田或草地及农田或草地造林后对土壤有机碳贮量的影响 .结果表明 ,土壤有机碳含量方面 ,农田和草地比天然次生林分别低 5 4 %和 2 7% ,差异主要在 0～ 5 0cm土层 ;农田和草地比人工林分别低 4 2 %和 2 6 % ,差异主要在 0～ 4 0cm土层 .土壤有机碳密度方面 ,农田和草地比天然次生林分别低35 %和 14 % ,差异主要在 0～ 5 0cm土层 ;农田比人工林低 2 3% ,草地比人工林高 4 % ,差异主要在 0～ 30cm土层 .天然次生林和人工林土壤有机碳含量和密度随土层加深而递减的幅度比农田或草地大 .这些差异主要由土地利用变化引起的土壤有机碳输入与输出及根系分布的变化所致 .结果说明六盘山林区天然次生林破坏变成草地或农田后土壤有机碳含量和密度 (主要是 0～ 5 0cm土层 )将下降 ,而农田中造林后土壤有机碳含量和密度 (主要是 0～ 30cm土层 )又将增加 ,草地上造林后土壤有机碳含量增加而密度变化不大 .另外 。

Through comparing the concentration and inventory of soil organic carbon (SOC) and its distribution in soil profiles under cropland,rangeland,natural secondary forest (brushwood,natural secondary forest dominated by Querces liaotungensis or Populus davidiana) and larch plantations (13,18 and 25 years old Larix principis-rupprechtil),this paper studied the effect of land use change from natural secondary forest to cropland or rangeland as well as from cropland or rangeland to plantation on SOC storage in the Liupan mountain forest zone.The results showed that the concentration of SOC in 0～110 cm soil layer under cropland and rangeland was 54% and 27% lower than that under natural secondary forest,respectively.The difference of SOC concentration between natural secondary forest and cropland or rangeland was greater in 0～50 cm than in 50～110 cm soil layer,while that between larch plantations and cropland or rangeland was greater in 0～40 cm than in 40～110 cm soil layer.The inventory of SOC in 0～110 cm soil layer under cropland and rangeland was respectively 35% and 14% lower than that under natural secondary forest,while 23% lower under cropland and 4% higher under rangeland than that under larch plantations.The difference of SOC inventory between natural secondary forest and cropland or rangeland was greater in 0～50 cm than in 50～110 cm soil layer,while that between plantations and cropland or rangeland was greater in 0～30 cm than in 30～110 cm soil layer.The decreasing magnitude of SOC storage with soil profile depth under natural secondary forest or larch plantations was greater than that under cropland or rangeland.The above-mentioned facts resulted from the changes of SOC input or output and the distribution of roots in soil.The results indicated that the SOC concentration and inventory would decline (mainly in 0～50 cm soil layer) after converting from natural secondary forest to cropland or rangeland,but increase (mainly in 0～30 cm soil layer) following afforestation on cropland.The SOC concentration would increase but its inventory would not change following afforestation on rangeland,and the distribution of the SOC concentration or inventory in soil profile would change with the change of land use in Liupan mountain forest zone.