Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, China.
University of Chinese Academy of Sciences, Beijing, China.
PLoS One. 2018 May 17;13(5):e0197451. doi: 10.1371/journal.pone.0197451. eCollection 2018.
The spatial pattern of soil organic carbon (SOC) and total nitrogen (TN) densities plays a profound important role in estimating carbon and nitrogen budgets. Naiman Banner located in northern China was chosen as research site, a total of 332 soil samples were taken in a depth of 100 cm from the low hilly land in the southern part, sandy land in the middle part and an alluvial plain in the northern part of the county. The results showed that SOC and TN density initially decreased and then increased from the north to the south, The highest densities, were generally in the south, with the lowest generally in the middle part. The SOC and TN densities in cropland were significantly greater than those in woodland and grassland in the alluvial plains and for Naiman as a whole. The woodland SOC and TN density were higher than those of grassland in the low hilly land, and higher densities of SOC and TN in grassland than woodland in the sandy land and low hilly land. There were significant differences in SOC and TN densities among the five soil types of Cambisols, Arenosols, Gleysols, Argosols, and Kastanozems. In addition, SOC and TN contents generally decreased with increasing soil depth, but increased below a depth of 40 cm in the Cambisols and became roughly constant at this depth in the Kastanozems. There is considerable potential to sequester carbon and nitrogen in the soil via the conversion of degraded sandy land into woodland and grassland in alluvial plain, and more grassland should be established in sandy land and low hilly land.
土壤有机碳（SOC）和总氮（TN）密度的空间格局对估算碳氮收支具有深远的重要意义。选择位于中国北方的奈曼旗作为研究地点，从该县南部的低丘地、中部的沙地和北部的冲积平原，共采集了 332 个深度为 100 厘米的土壤样本。结果表明，SOC 和 TN 密度从北到南先降低后升高，密度最高的一般在南部，最低的一般在中部。在冲积平原，农田的 SOC 和 TN 密度明显大于林地和草地，而奈曼旗整体上也是如此。在低丘地，林地的 SOC 和 TN 密度高于草地，而在沙地和低丘地，草地的 SOC 和 TN 密度高于林地。在 5 种土壤类型（均腐土、粗骨土、潜育土、弱淋溶土和黑钙土）中，SOC 和 TN 密度存在显著差异。此外，SOC 和 TN 含量通常随土壤深度的增加而降低，但在均腐土中，在 40 厘米以下深度增加，而在黑钙土中，在该深度大致保持稳定。通过将退化的沙地转化为冲积平原的林地和草地，可以在很大程度上固存碳和氮，同时应在沙地和低丘地建立更多的草地。
