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    马尾松阔叶化改造土壤团聚体稳定性对胶结剂的响应

    Response of soil aggregate stability to cementing agents in broadleaf transformation of Pinus massoniana forests

      摘要
    • 摘要:
      目的 针叶人工林土壤结构退化，阔叶化改造可实现其土壤结构恢复，但对阔叶化改造如何调节胶结剂以增强土壤团聚体稳定性仍缺乏认识。
      方法 以贵州省龙里林场马尾松纯林（PM）及针−阔混交林为研究对象，通过湿筛法和平均质量直径（MWD）、几何平均直径（GMD）和 > 0.250 mm粒径团聚体质量分数（R0.25）评估团聚体稳定性，采用相关性分析、冗余分析（redundancy analysis，RDA）及随机森林模型评估土壤有机碳（SOC）及铁铝（Fe/Al）氧化物对团聚体稳定性的贡献。
      结果 1）0～20 cm和20～40 cm土层，针−阔混交林较PM普遍增加 > 1.000 mm团聚体质量分数），但0～20 cm土层团聚体稳定性提升比20～40 cm土层更明显。2）除团聚体络合态铝氧化物（Alp）质量分数显著低于PM外，团聚体有机碳（SAOC）和其它Fe/Al氧化物普遍较PM增加。3）0～20 cm土层，游离态铁氧化物（Fed）、SOC和非晶形铁氧化物（Feo）与 > 1.000 mm团聚体显著正相关，且Fed对团聚体稳定性贡献率最大；20～40 cm土层，游离态铝氧化物（Ald）与 > 0.500～1.000 mm团聚体极显著正相关（P < 0.01）且对团聚体稳定性的贡献占主导。4）Fed、Feo、Ald和SOC质量分数受pH调节显著。
      结论 阔叶化改造可提高SOC和Fe/Al氧化物质量分数增强团聚体稳定性，其中Fed/Ald比SOC的贡献更强。研究结果可为针叶人工林土壤结构修复提供依据。

       

      Abstract:
      Objective Soil structure degradation occurs in coniferous plantations, and broadleaf transformation can facilitate its restoration. However, how broadleaf transformation regulates cementing agents to enhance soil aggregate stability remains unclear.
      Methods This study was conducted in pure Pinus massoniana forest (PM) and coniferous-broadleaf mixed forests at Longli Forest Farm in Guizhou province. Aggregate stability was assessed using the wet-sieving method, with mean weight diameter (MWD), geometric mean diameter (GMD), and the content of aggregates with a diameter > 0.250 mm（R0.25） employed as evaluation indicators. The contributions of soil organic carbon (SOC) and iron/aluminum (Fe/Al) oxides to aggregate stability were evaluated using correlation analysis, redundancy analysis (RDA), and random forest modeling.
      Results 1) In both 0−20 cm and 20−40 cm soil layers, the mass fraction of aggregates > 1.000 mm generally increased in coniferous-broadleaf mixed forests compared with PM (P < 0.05 or P > 0.05), but the improvement of aggregate stability was more pronounced in the 0−20 cm layer. 2) Except for complexed aluminum oxides (Alp), which were significantly lower in coniferous-broadleaf mixed forests than in PM (P < 0.05), soil aggregate organic carbon (SAOC) and other Fe/Al oxides generally increased compared with PM. 3) In the 0−20 cm layer, free iron oxides (Fed), SOC, and amorphous iron oxides (Feo) showed significant positive correlations with aggregates > 1.000 mm, with Fed contributing the most to aggregate stability. In the 20−40 cm layer, free aluminum oxides (Ald) exhibited a highly significant positive correlation with aggregates > 0.500−1.000 mm (P < 0.01) and played a dominant role in stabilizing aggregates. 4) The contents of Fed, Feo, Ald, and SOC were significantly regulated by soil pH.
      Conclusions Broadleaf transformation can enhance aggregate stability by increasing SOC and Fe/Al oxide contents, among which Fed and Ald contribute more strongly than SOC. These findings provide a basis for soil structure restoration in coniferous plantations.

       

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