黄土丘陵区土地利用变化对深层土壤有机碳储量的影响

通过研究黄土丘陵子午岭林区5种典型土地利用类型土壤剖面有机碳分布特征,分析了天然乔木林转变为人工乔木林、天然乔木林转变为农田、天然灌木林转变为农田及撂荒后土壤有机碳变化特征.同时,以浅层(0~100 cm)土壤为对照,探讨了土地利用变化对深层(100~200cm)土壤有机碳储量的影响.结果表明,在0~200 cm剖面上,天然乔木林、天然灌木林、人工乔木林、撂荒地、农田土壤有机碳含量分别为5.85、3.96、4.98、3.09、3.20 g·kg-1,天然乔木林、人工乔木林土壤有机碳含量显著高于天然灌木林、撂荒地和农田(p0.05).各土地利用类型下浅层和深层土壤有机碳含量分别占0~200 cm土壤有机碳含量的58%~73%和27%~42%,不同土地利用类型间浅层土壤有机碳含量差异显著,但深层土壤有机碳含量差异不大.土地利用变化对土壤有机碳储量影响显著.天然乔木林转变为人工乔木林、天然乔木林转变为农田、天然灌木林转变为撂荒地、天然灌木林转变为农田4种土地利用转变方式0~200 cm土壤有机碳储量分别减少了9.68、52.90、20.20、12.49 t·hm-2,减幅为7%、39%、21%、13%,其中,浅层土壤减少了2%~48%,深层土壤减少了12%~22%.相对于林地开垦为农田而言,农田退耕还林后土壤有机碳的恢复要慢得多.研究结果揭示了浅层和深层土壤有机碳对土地利用变化的敏感性,反映了深层土壤有机碳具有较大的稳定性.

Effects of land use change on storage of soil organic carbon in deep soil layers in the hilly Loess Plateau region,China

In order to determine the effects of land use changes on the storage of soil organic carbon (SOC) in deep soil layers (100~200 cm), SOC content and the distribution characteristics of five typical land use types in Ziwuling forest zone on the hilly Loess Plateau were studied in the paper. Response of SOC storage in deep soil to the land use changes was analyzed under four kinds of land use changes, including from natural woodland to artificial woodland, from natural woodland to cropland, from natural shrubland to cropland and from natural shrubland to revegetated grassland. The results showed that SOC content of natural woodland, natural shrubland, artificial woodland, revegetated grassland and cropland was 5.85, 3.96, 4.98, 3.09 and 3.20 g · kg^-1, respectively. SOC content of natural woodland and artificial woodland was significantly higher than those of natural shrubland, revegetated grassland and cropland (p<0.05).SOC in upper and deep soil layers contributed 58%~73% and 27%~42% to total SOC in the whole profile (0~200cm) under all investigated land use types.SOC content in upper soil layer varied significantly between different land use types, however no obvious difference in SOC content was observed in all investigated land use types. Land use changes showed significant effect on SOC storages. SOC storages in 0~200cm profile were reduced by 9.68, 52.90, 20.20 and 12.49 t · hm^-2 under the four aforementioned types of land use changes.SOC storages in 0~100cm profile decreased by 2%~48% while the deep layer decreased by 12%~22%.Compared with conversion from woodland to cropland, SOC recovered slowly when land use changed from cropland to woodland. The results suggested different sensitivity of SOC to land use changes in the upper (0~100 cm) and deep (100~200 cm) soil, and SOC in deep soil layers were more stable than that in upper soil layers.