Post-fire Soil Hydrophobicity Degradation

This resource includes code and data used within manuscript titled \"Freeze-Thaw Processes Degrade Post-fire Water Repellency in Wet Soils\" submitted to the Hydrological Processes Journal. Wildfires can cause heightened soil water repellency (hydrophobicity), which reduces infiltration while increasing erosion and flooding from post-fire rainfall. Post-fire soil water repellency degrades over time, often in response to repeated wetting and drying of the soil. This study characterized the changes in hydrophobicity of Sierra Nevada mountain soils exposed to different combinations of wet-dry and freeze-thaw cycling. There are five treatments total consisted of 11 cycles and replicated 6 times. These treatments are: 1) WD -> wet/dry. 2) WDFT -> wet/dry/freeze/thaw 3) WFTD -> wet/freeze/thaw/dry 4) WFT -> wet/freeze/thaw (soil is wetted once but never dried) 5) DFT -> dry/freeze/thaw (soil is never wetted) After each, cycle molarity of ethanol test (MED) was used to assess soil hydrophobicity. MED results are recorded in \"MED.xlsx\" under \"MED and SOM Data\" collection. Soil Organic Matter (SOM) is often associated with soil hydrophobicity, thus we also measured SOM content of each cycle and treatment with 3 replicas for each using Walkley-Black test. SOM results are recorded in \"SOM.xlsx\" under \"MED and SOM Data\" collection. Furthermore, soils of different hydrophobicities and one opportunistic sample of the 7th cycle of wet/dry/freeze/thaw treatment were imaged using scanning electron microscopy (SEM) in a BSE mode at 100 times resolution. Sizes of each individual aggregate were measured using ImageJ software and their area was recorded. SEM images along with recorded grain sizes can be found in the \"SEM\" collection.本资源包含投稿至《水文过程（Hydrological Processes）》期刊的论文《冻融过程削弱火烧后湿润土壤斥水性（Freeze-Thaw Processes Degrade Post-fire Water Repellency in Wet Soils）》中所使用的代码与数据集。 野火可增强土壤斥水性（soil water repellency，又称疏水性hydrophobicity），该效应会降低土壤水分入渗率，同时加剧火烧后降雨引发的土壤侵蚀与洪涝灾害。火烧后土壤斥水性会随时间逐渐衰减，这一过程通常与土壤反复经历干湿循环密切相关。 本研究针对内华达山脉（Sierra Nevada）的山地土壤，表征了其在不同干湿与冻融循环组合处理下的疏水性变化。本研究共设置5种处理方式，每种处理开展11轮循环，并设置6次生物学重复，具体处理如下： 1) WD：干湿循环（wet/dry） 2) WDFT：干湿-冻融循环（wet/dry/freeze/thaw） 3) WFTD：湿-冻融-干循环（wet/freeze/thaw/dry） 4) WFT：湿-冻融循环（wet/freeze/thaw，土壤仅单次湿润，全程未进行干燥处理） 5) DFT：干-冻融循环（dry/freeze/thaw，土壤全程未被湿润） 每轮循环结束后，均采用乙醇摩尔浓度测试（molarity of ethanol test，简称MED）评估土壤疏水性。MED测试结果存储于"MED and SOM Data"数据集下的"MED.xlsx"文件中。 土壤有机质（Soil Organic Matter，简称SOM）通常与土壤斥水性存在显著关联，因此本研究采用沃克利-布莱克（Walkley-Black）法，对每种处理的每轮循环的土壤有机质含量进行3次重复测定。土壤有机质测试结果存储于"MED and SOM Data"数据集下的"SOM.xlsx"文件中。 此外，本研究采用背散射电子模式（BSE mode）、100倍分辨率的扫描电子显微镜（scanning electron microscopy，简称SEM），对不同斥水性的土壤样本以及1份干湿-冻融循环第7轮的机遇性样本进行了成像。采用ImageJ软件对每个土壤团聚体的尺寸进行测量，并记录其面积。扫描电子显微镜图像与测得的颗粒尺寸数据均可在"SEM"数据集下获取。