Wildfires are natural phenomena for most ecosystems on Earth. Many soil properties are impacted by fire, including soil hydraulic properties. We used a laboratory experiment to replicate the temperatures reached by a natural wildfire and documented the effects on soil hydraulic properties. This study hypothesizes that the impact of heating on soil hydrological properties can be explained by the interaction of a number of variables especially organic matter content (OM), cation exchange capacity (CEC), texture, pH, and electrical conductivity (EC). The main objective of this study is to explore the interconnections between soil hydraulic, chemical, and physical properties, focusing on understanding how these relationships change across different ecoregions and temperatures. Sixteen soils were collected across 16 sites susceptible to forest fires in the Central Zone of Chile and heated to 100 °C and 300 °C for two hours. These sites were representative of two distinct ecoregions: the Chilean Matorral (CM) and the Valdivian Temperate Forests (VTF). Chemical, physical, and hydraulic soil properties were measured before and after heating. At 100 °C, there were no significant changes in chemical, physical, or hydraulic soil properties. At 300 °C, significant changes were observed in most soil properties in soils from both ecoregions. The OM content and CEC decreased, whereas pH and electrical conductivity increased. In addition, clay content and water aggregate stability (WSA) decreased, while all hydraulic properties increased their values. The aforementioned results demonstrate that infiltration increased after the soil was heated. This can be attributed primarily to decreases in clay content. At the same time, the water repellency (R) index decreased, allowing water to more easily wet the soil particles. Correlations revealed that CEC and clay are the main factors ruling soil hydraulic properties at all temperatures. Clay mineralogy also contributes to the soil hydraulic behavior observed. Nonlinear models were developed to estimate hydraulic properties at 100 °C and 300 °C, using the main soil properties. The models illustrated that the soils of the CM ecoregion, which are characterized by lower OM and influence of clay/CEC ratio, would be less affected by fire compared to the soils of VTF. The water holding capacity would decrease in both ecoregions. However, due to the greater changes in OM and clay in VTF, the impact would be greater than in CM.11Ca2+ = Calcium cations (meq/ 100g); CEC = Cation exchange capacity (meq/ 100g); CM = Chilean Matorral; EC = Electrical conductivity (μS/cm); I = Cumulative infiltration (cm); K = Unsaturated hydraulic conductivity (mm/h); K+ = Potassium cations (meq/ 100g); Ks = Saturated hydraulic conductivity (mm/h); Mg2+ = Magnesium cations (meq/100g); Na+ = Sodium cations (meq/100g); OM = Organic matter (g/100g); R index = Water repellency index; Se = Ethanol sorptivity (cm/s05); Sw = Water sorptivity (cm/s05); VTF = Valdivian Temperate Forest; WSA = Water-stable aggregates (%).

中文翻译：

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土壤加热变化对智利中部土壤水力特性的影响


野火是地球上大多数生态系统的自然现象。许多土壤特性都会受到火灾的影响，包括土壤水力特性。我们使用实验室实验来复制自然野火所达到的温度，并记录了对土壤水力特性的影响。本研究假设加热对土壤水文特性的影响可以通过许多变量的相互作用来解释，特别是有机物含量 （OM）、阳离子交换能力 （CEC）、质地、pH 值和电导率 （EC）。本研究的主要目的是探索土壤水力、化学和物理特性之间的相互联系，重点是了解这些关系在不同生态区和温度下如何变化。在智利中部地区易受森林火灾影响的 16 个地点收集了 16 种土壤，并加热至 100 °C 和 300 °C 两个小时。这些地点代表了两个不同的生态区：智利马托拉尔 （CM） 和瓦尔迪夫温带森林 （VTF）。在加热前后测量化学、物理和水力土壤特性。在 100 °C 时，土壤的化学、物理或水力特性没有显著变化。在 300 °C 时，两个生态区土壤的大多数土壤特性都发生了显著变化。OM 含量和 CEC 降低，而 pH 和电导率增加。此外，粘土含量和水团聚体稳定性 （WSA） 降低，而所有水力特性的值均增加。上述结果表明，土壤加热后渗透增加。这主要归因于粘土含量的降低。 同时，拒水性 （R） 指数降低，使水更容易润湿土壤颗粒。相关性表明，CEC 和粘土是在所有温度下支配土壤水力特性的主要因素。粘土矿物学也有助于观察到的土壤水力行为。开发了非线性模型，以使用主要土壤特性来估计 100 °C 和 300 °C 下的水力特性。模型表明，与 VTF 的土壤相比，CM 生态区的土壤具有较低的 OM 和粘土/CEC 比率的影响，受火灾的影响较小。两个生态区的持水能力都会下降。然而，由于 VTF 中 OM 和粘土的变化更大，影响会大于 CM.11Ca2+ = 钙阳离子 （meq/ 100g）;CEC = 阳离子交换容量 （meq/ 100g）;CM = 智利马托拉尔;EC = 电导率 （μS/cm）;I = 累积浸润 （cm）;K = 非饱和水力传导率 （mm/h）;K+ = 钾阳离子 （meq/ 100g）;Ks = 饱和水力传导率 （mm/h）;Mg2+ = 镁阳离子 （meq/100g）;Na+ = 钠阳离子 （meq/100g）;OM = 有机物 （g/100g）;R 指数 = 防水指数;Se = 乙醇吸附率 （cm/s05）;Sw = 水的吸附率 （cm/s05）;VTF = 瓦尔迪夫温带森林;WSA = 水稳定骨料 （%）。