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采用土壤有机碳(SOC)物理分组与13C自然丰度相结合技术,研究了稻田长期(19 a)转换为旱地(玉米地)后土壤有机碳及其组分的响应特征,以及不同有机碳组分的周转和更新速率.结果表明,长期种植旱地作物后,农田土壤有机碳和总氮含量显著下降.相同历史背景下,稻田土壤总有机碳(TOC)和总氮(TN)的浓度分别比玉米田高76.7%和47.6%.水稻土包裹态颗粒有机质(oPOM)和矿物结合有机质(MOM)在土壤中的浓度均是玉米田的2倍,但游离态颗粒有机质(fPOM)差异不显著.稻田土壤oPOM和MOM自身碳的浓度均显著高于玉米地,fPOM则相反.特别是oPOM组分,稻田是玉米地的近6倍.表明水稻土团聚体保护碳的能力高于旱地.稻田转换为玉米地19 a后,各组分δ13C值显著升高.fPOM、oPOM和MOM中来自玉米新碳的比例分别达到了54.6%、24.7%和19.0%,平均驻留时间(MRT)依次增大,分别达到24、67和90 a.上述结果进一步证明了稻田土壤比旱地更具固碳潜力,其优势主要体现在土壤中oPOM和MOM组分碳的富积.
The response characteristics of soil organic carbon and its components after long-term (19 years) conversion to dry land (corn land) were studied using the combination of physical grouping of soil organic carbon (SOC) and natural abundance of 13C, The results showed that soil organic carbon and total nitrogen in farmland decreased significantly after long-term cultivation of dry land crops.Under the same historical background, total organic carbon (TOC) and total nitrogen (TN) The corn fields were 76.7% and 47.6% higher, respectively.The concentrations of oPOM and MOM in soils were twice as that in maize fields, but there was no significant difference in fPOM between paddy soils oPOM and MOM own carbon concentrations were significantly higher than corn, fPOM is the opposite.Especially the oPOM component, paddy field is nearly 6 times the corn field, suggesting that paddy soil aggregates to protect carbon than dry land .Field conversion to corn After 19 years, the δ13C value of each component increased significantly, the proportions of new carbon from maize in fPOM, oPOM and MOM reached 54.6%, 24.7% and 19.0%, respectively, and the average residence time (MRT) increased respectively Reaching 24, 67 and 90 a. The above results further evidence More than upland paddy soil carbon sequestration potential, its main advantage plot soil oPOM MOM components and carbon-rich.