不同土地利用方式对土壤惰性碳的影响

Effects of different land use methods on inert soil carbon

摘要:

【目的】研究不同土地利用方式对草地土壤惰性碳的影响，对于客观认识草地在减少大气 CO2排放中的作用，制定草地碳增汇策略，合理利用草地资源具有重要意义。【方法】在中国科学院海北高寒草甸生态系统研究站 3 种不同利用方式土地（冬季自由放牧—冬牧、围封禁牧—禁牧、开垦播种燕麦—燕麦），采用梅花形 5 点采样法采集野外样品，结合室内酸水解等分析方法，对 0~30 cm 土层的土壤总有机碳和惰性碳进行分层研究 。【结果】1）0~10 cm 土层土壤有机碳含量以冬牧最高（95. 15 g/kg），禁牧次之（70. 56 g/kg），开垦播种燕麦最小（54. 44 g/kg）。 冬牧土壤惰性碳含量比禁牧高 27. 77%，冬牧比燕麦高 32. 54%。2）与冬牧相比，禁牧 16 年土壤 0~10 cm 土层有机碳下降了 25. 84%， 开垦 30 年 0~10 cm 土层土壤有机碳下降了 42. 79%。禁牧 16 年土壤 0~30 cm 土层有机碳下降了 10. 89%，开垦 30 年 0~30 cm 土层土壤有机碳下降了 9. 48%。0~30 cm 土层惰性碳平均含量冬牧比禁牧高 22. 67%，冬牧比燕麦高 3. 60%；与开垦相比，禁牧使惰性碳降低了 19. 78%。3）不同土地利用方式土壤理化性质与土壤碳库组成存在显著相关，土壤理化性质的改变是引起不同草地类型土壤碳库组成变化的重要原因。【结论】禁牧后土壤惰性碳含量降低的幅度大于开垦，冬牧有利于土壤惰性碳的积累；健康草地禁牧之后降低了土壤惰性碳的含量，减弱了土壤有机碳的稳定性。不同土地利用方式主要通过影响土壤理化性质及养分含量影响土壤有机碳和惰性碳含量。因此，通过改善放牧管理，可以维持或进一步增加有机碳存储以及土壤有机碳的稳定性，健康草地禁牧不利于土壤有机碳的积累。

Abstract:

【Objective】 Investigating the effects of different land uses on soil inert carbon in grassland is of great significance for objectively understanding the role of grassland in mitigating atmospheric carbon dioxide emissions，developing strategies for carbon sequestration in grassland，and rational utilization of grassland resources.【Method】 The total organic carbon and inert carbon of soil at Haibei Alpine Meadow Ecosystem Research Station of the Chinese Academy of Sciences were studied under three different land use methods （i. e. ，free grazing in winter （winter grazing），grazing exclosure （grazing exclosure），and cultivated annual oats （oats））.【Result】1） Soil organic carbon content in the 0~10 cm soil layer was the highest under winter grazing （95. 15 g/kg），followed by grazing exclosure （70. 56 g/kg），and cultivated annual oats （54. 44 g/kg），The content of soil inert carbon under winter grazing was 27. 77% higher than that under grazing exclosure，and 32. 54% higher than that under cultivated annual oats. 2） Compared with winter grazing，soil organic carbon in the 0~10 cm layer decreased by 25. 84% after 16 years of grazing exclosure，and soil organic carbon in the 0~10 cm layer decreased by 42. 79% after 30 years of cultivation，Compared to free grazing，the organic carbon in the 0~30 cm soil layer decreased by 10. 89% after 16 years of grazing exclosure， and by 9. 48% in the 0~30 cm soil layer after 30 years of cultivation， The average inert carbon content in the 0~30 cm soil layer was 22. 67% higher under winter grazing than under grazing exclosure，and 3. 60% higher under winter grazing than under annual oats，Compared with cultivation，grazing exclosure reduced the inert carbon by 19. 78%. 3） There was a significant correlation between soil physical and chemical properties and soil carbon pool composition under different land use methods，and the change in soil physical and chemical properties was an important reason for the change in soil carbon pool composition under different grassland use methods.【Conclusion】 The decrease of soil inert carbon content after grazing prohibition is greater than that after reclamation，and winter grazing is beneficial to the accumulation of soil inert carbon； after prohibition of soil grazing，soil inert carbon content is reduced and the stability of soil organic carbon is weakened，Different land use methods mainly affect soil organic carbon and inert carbon content by affecting soil physical and chemical properties and nutrient content，Therefore，by improving grazing management， the organic carbon storage and the stability of soil organic carbon can be maintained or further increased，and the prohibition of grazing in healthy grassland is not conducive to the accumulation of soil organic carbon.