典型稻田红壤发生层团聚体稳定性及有机碳的含量变化

Soil Aggregate Stability and the Variation in Organic Carbon Content of Pedogenic Horizons in Typical Paddy Red Earth

    摘要
  • 摘要:
      目的  探究土壤团聚体组成及其稳定性对土壤有机碳(SOC)的储存与周转的影响机制。
      方法  以江西鹰潭孙家典型红壤小流域内不同坡位稻田红壤发生层土壤为研究对象，分析了机械稳定性团聚体（MSA）、水稳定性团聚体（WSA）比例及其有机碳含量、团聚体破碎率（PAD）、平均重量直径（MWD）、几何平均重量直径（GMD）及分形维数（D）等指标的剖面变化差异，并借助于结构方程模型（SEM）探讨了各指标间的相关关系。
      结果  不同坡位稻田红壤各发生层的MSA比例以10 ~ 5 mm所占比例最高（27.6% ~ 87.6%），而< 0.25 mm所占比例最低（1.59% ~ 15.3%）；以< 0.25 mm WSA所占比例最高（3.06% ~ 70.1%），5 ~ 2 mm WSA所占比例最低（0.17% ~ 20.4%）。稻田红壤发生层中团聚体碳（SOCa）均随着土壤发生层深度的增加先迅速降低后缓慢降低；其中，2 ~ 0.25 mm SOCa对SOC的贡献率（7.53% ~ 76.7%）显著高于其它粒级团聚体。PAD、MWD、GMD及D均随发生层深度增加先降低后缓慢增加，但随坡位降低显著增加。SEM分析结果表明，土壤pH、游离铁铝氧化物含量及WSA比例是影响稻田红壤SOC的重要因子。
      结论  孙家小流域内典型稻田各发生层团聚体稳定性及有机碳含量主要受土层深度及坡位的共同影响，即发生层深度的增加使团聚体稳定性及有机碳含量显著降低，这一结果可以为坡耕地稻田剖面有机碳库管理提供科学依据。

     

    Abstract:
      Objective  The paper aimed to explore the influence mechanism of soil aggregate composition and stability on soil organic carbon storage and turnover.
      Methods  The soil of red earth generation layer in paddy fields with different slope sites in the typical red earth watershed of Sunjia in Yingtan, Jiangxi Province, was taken as the research object. The profile variation differences of mechanical stability aggregates (MSA), water stability aggregates (WSA) and soil organic carbon (SOC) content, percentage of aggregate disruption (PAD), mean weight diameter (MWD), geometric mean weight diameter (GMD) and fractal dimension (D) were analyzed. The correlations among those indices were discussed by means of structural equation model (SEM).
      Result  The proportion of MSA in each horizon of red earth in different slope sites was the highest in 10-5 mm (27.6%-87.6%), and the lowest in < 0.25 mm (1.59%-15.3%). The proportion of < 0.25 mm WSA was the highest (3.06%-70.1%), and the proportion of 5-2 mm WSA was the lowest (0.17%-20.4%). The SOC content of aggregate (SOCa) in pedogenic horizons of red paddy field decreased rapidly at first and then slowly with the increase of soil horizons depth. Among them, the contribution rate (7.53%-76.7%) of 2-0.25 mm SOCa to SOC is significantly higher than those of other size aggregates. The PAD, MWD, GMD and D all decreased first and then increased slowly with the increase of formation depth, but increased significantly with the decrease of slope site. The analysis of SEM showed that soil pH, free Fe/Al oxide content and WSA proportion were the important factors affecting SOC in paddy red earth.
      Conclusion  The aggregate stability and SOC content of each horizon in the typical paddy field in Sunjia small watershed are mainly affected by soil depth and slope site, that is, the increase of horizon depth significantly reduces the aggregate stability and SOC content. This result can provide a scientific basis for the management of soil organic carbon pool in the profile of sloping paddy field.

     

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