西藏林芝不同土地利用方式的土壤团聚体及其有机碳分布

为揭示西藏林芝地区不同土地利用方式对土壤团聚体及其有机碳含量的影响,以八一镇耕地(FL)、蔬菜大棚(VG)、撂荒地(AL)、草地(GL)、次生林地(SF)为研究对象,采用干筛法对土壤团聚体进行分级,分析团聚体及其有机碳、易氧化有机碳的含量和分布。结果表明:在0~20 cm土层,各土地利用方式下基本以≥2 mm团聚体为主,其含量大致表现为GL、AL高于VG和FL,表明与农用地(FL、VG)相比,自然生态系统的土壤结构较好。土壤团聚体有机碳和易氧化有机碳的含量在不同土地利用方式下整体表现为0~10 cm>10~20 cm,大团聚体(≥0.25 mm)高于微团聚体(<0.25 mm),并以≥2 mm团聚体的贡献率最高,碳汇能力较强。结果说明,自然生态系统的土壤结构较好,草地、林地的开垦行为将导致土壤结构变差。实施保护性耕作措施,减少草地、林地的人为干扰有利于提高土壤有机碳库的稳定性,发挥土壤"碳汇"功能。

Distribution of soil aggregate and organic carbon under different land use types in Linzhi,Tibet

In order to reveal the impact of land use types on soil aggregates and soil organic carbon in Linzhi, farm land (FL), vegetable greenhouse (VG), abandoned land (AL), grass land (GL) and secondary forestland (SF) of Bayi Town were selected as the research objects, dry sieving method was introduced to classify soil aggregates, and the aggregates as well as the content and distribution of soil organic carbon and labile organic carbon were explored. It was shown that soil aggregate with the size ≥2 mm constituted the majority at 0-20 cm, and its content was higher in GL and AL than that of VG and FL, indicating that the soil structure of natural ecosystem was better than agriculture land (FL and VG). The content of organic carbon and labile organic carbon in soil aggregate was higher in 0-10 cm layer than that in 10-20 cm layer, and was higher in macroaggregate (≥0.25 mm) than that in microaggregate (<0.25 mm). The aggregate with size ≥2 mm showed the highest contribution rate to organic carbon and labile organic carbon in soil aggregate, and possessed strong capacity of carbon sink. The soil structure of natural ecosystems was good, and the reclamation of GL and SF would lead to deterioration of soil structure. Protective farming measures or reducing artificial interruption to forest lands and grass lands should be carried out, to enhance the stability of soil organic carbon storage, and ensure its role as soil carbon sink.