Aims

We investigated morphological variations in podzols caused by changes in soil porosity and permeability upon the growth of large tree-roots in a tropical barrier island (Ilha Comprida, Brazil).

Methods

Soil morphology was described in a continuous lateral sequence of podzols on a 35 m-long cliff. A soil thin section was used to characterize organic matter (OM) accumulation and to estimate soil porosity, permeability, and saturated hydraulic conductivity (Ksat). Soil texture and the contents of organic carbon, Al, and Fe were determined for each pedogenic horizon containing large tree-roots. The evolution of podzol morphology was interpreted in the context of age determinations by optically stimulated luminescence and ¹⁴C.

Results

Taproots of cashew trees (Anacardium occidentale) penetrated the cemented Bhm horizon and the massive-clayey 2Cgj horizon. Aligned with the taproot, we found a vertical OM-band with lower porosity, permeability, and Ksat than the adjacent Bh and E horizons. Irregular or broken boundaries between the E and Bh horizons were caused by large tree-roots. While the maximum age of these podzols is 3390 ± 530 years, significant and rapid changes in the Bh-horizon morphology occurred within the lifetime of the cashew trees (~ 50 years).

Conclusions

The interplay between reduction in flow adjacent to large taproots and the enhanced vertical infiltration at depth has resulted into the development of irregular and broken boundaries between the E and Bh horizons. Because tree-roots alter both local soil porosity and water flow paths, they simultaneously cause the formation and degradation of podzol Bh-horizon.

中文翻译：

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在热带沿海雨林中，树根改变土壤孔隙度和水文学后，podzol形态发生了实质性变化

目的

我们调查了由热带屏障岛（巴西伊利亚·康普达岛）上的大树根生长引起的土壤孔隙度和渗透率变化所引起的足动物的形态学变化。

方法

在35 m长的悬崖上，以连续的侧足序列描述了土壤形态。使用土壤薄片来表征有机物（OM）的积累，并估算土壤的孔隙率，渗透率和饱和水力传导率（Ksat）。确定每个包含大树根的成土层的土壤质地以及有机碳，铝和铁的含量。在年龄确定的背景下，通过光学激发的发光和¹⁴ C解释了Podzol形态的演变。

结果

腰果树（Anacardium occidentale）的主根穿透水泥化的Bhm层和块状粘土2Cgj层。与主根对准，我们发现了一个垂直的OM带，其孔隙度，渗透率和Ksat低于相邻的Bh和E层。E和Bh层之间的边界不规则或断裂是由大的树根引起的。虽然这些豆足动物的最大年龄为3390±530岁，但在腰果树的生命周期内（约50年），Bh水平形态发生了显着且快速的变化。

结论

靠近大根部的水流减少与深部垂直渗透的增强之间的相互作用，导致了E和Bh层之间边界的不规则和破碎。由于树根同时改变了当地的土壤孔隙度和水流路径，因此它们同时导致了Podzol Bh地平线的形成和退化。