Area of Ecology, Department of Biodiversity and Environmental Management, Faculty of Biological and Environmental Sciences, University of León, 24071 León, Spain.
Area of Ecology, Department of Biodiversity and Environmental Management, Faculty of Biological and Environmental Sciences, University of León, 24071 León, Spain.
Sci Total Environ. 2022 Oct 10;842:156852. doi: 10.1016/j.scitotenv.2022.156852. Epub 2022 Jun 22.
Remote sensing techniques are of particular interest for monitoring wildfire effects on soil properties, which may be highly context-dependent in large and heterogeneous burned landscapes. Despite the physical sense of synthetic aperture radar (SAR) backscatter data for characterizing soil spatial variability in burned areas, this approach remains completely unexplored. This study aimed to evaluate the performance of SAR backscatter data in C-band (Sentinel-1) and L-band (ALOS-2) for monitoring fire effects on soil organic carbon and nutrients (total nitrogen and available phosphorous) at short term in a heterogeneous Mediterranean landscape mosaic made of shrublands and forests that was affected by a large wildfire. The ability of SAR backscatter coefficients and several band transformations of both sensors for retrieving soil properties measured in the field in immediate post-fire situation (one month after fire) was tested through a model averaging approach. The temporal transferability of SAR-based models from one month to one year after wildfire was also evaluated, which allowed to assess short-term changes in soil properties at large scale as a function of pre-fire plant community type. The retrieval of soil properties in immediate post-fire conditions featured a higher overall fit and predictive capacity from ALOS-2 L-band SAR backscatter data than from Sentinel-1 C-band SAR data, with the absence of noticeable under and overestimation effects. The transferability of the ALOS-2 based model to one year after wildfire exhibited similar performance to that of the model calibration scenario (immediate post-fire conditions). Soil organic carbon and available phosphorous content was significantly higher one year after wildfire than immediately after the fire disturbance. Conversely, the short-term change in soil total nitrogen was ecosystem-dependent. Our results support the applicability of L-band SAR backscatter data for monitoring short-term variability of fire effects on soil properties, reducing data gathering costs within large and heterogeneous burned landscapes.
遥感技术对于监测野火对土壤特性的影响特别感兴趣，而在大型和异质燃烧景观中，这些影响可能高度依赖于背景。尽管合成孔径雷达（SAR）后向散射数据在感知上有助于描述燃烧区土壤空间变异性，但这种方法仍未得到充分探索。本研究旨在评估 C 波段（Sentinel-1）和 L 波段（ALOS-2）SAR 后向散射数据在监测异质地中海景观镶嵌体中土壤有机碳和养分（总氮和有效磷）短期野火影响方面的性能，该景观由灌木林和森林组成，受到一场大型野火的影响。通过模型平均方法，测试了两种传感器的 SAR 后向散射系数和几种波段变换在现场测量的土壤特性的反演能力，这些特性是在火灾后一个月的即时情况（火灾后一个月）下进行的。还评估了基于 SAR 的模型从火灾后一个月到一年的时间转移能力，这使得可以根据火灾前的植物群落类型评估大尺度土壤特性的短期变化。在即时火灾条件下对土壤特性的反演，ALOS-2 L 波段 SAR 后向散射数据的整体拟合度和预测能力均高于 Sentinel-1 C 波段 SAR 数据，不存在明显的低估和高估效应。ALOS-2 基于模型向火灾后一年的转移能力与模型校准情景（即时火灾条件）相似。火灾后一年土壤有机碳和有效磷含量明显高于火灾后立即。相反，土壤总氮的短期变化则依赖于生态系统。我们的研究结果支持 L 波段 SAR 后向散射数据在监测土壤特性短期变化方面的适用性，从而降低了在大型和异质燃烧景观中收集数据的成本。
