Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI 48824, USA.
USDA Forest Service Northern Research Station, Grand Rapids, MN 55744, USA.
Sci Total Environ. 2021 May 1;767:144258. doi: 10.1016/j.scitotenv.2020.144258. Epub 2020 Dec 24.
Prescribed fire is widely used for ecosystem restoration, yet the mechanisms that determine its effectiveness remain poorly characterized. Because soil hydrology influences ecosystem processes like erosion, runoff, and plant competition, it is important to understand how fire affects soil hydrology. A systematic approach to understanding relationships among vegetation, topography, and fire is needed to advance knowledge of how fire influences soil properties that in turn affect restoration success. Our objective was to characterize relationships among burn severity, vegetation, and soil hydrology in a heterogenous landscape under restoration management. Our study took place in a barrens-forest mosaic with recent prescribed fire history ranging from 0 to 10 burns since 1960, and additional variation in fuel loading, burn severity, vegetation cover, topography, and soils. We measured soil hydraulic conductivity (SHC) during two consecutive years, which represented control, prefire, postfire, and 1-year postfire conditions. Regression tree analysis identified an important threshold effect of antecedent soil moisture on SHC; soils with initial moisture < 13% had lower SHC than soils with initial moisture > 13%. Furthermore, above this threshold, sites with intermediate to high recent burn frequency (4-10 burns) had significantly greater SHC than unburned control sites. High fuel loads associated with brush cutting and piling increased SHC at barrens sites but not brush or pine sites, suggesting an interaction between vegetation cover and fire effects on SHC. At the local hillslope scale, toe-slopes had greater SHC than summits. Our results suggest that repeated prescribed fires of moderate to high frequency may enhance SHC, thereby reducing soil water retention and potentially restoring functional pine barren processes that limit woody plant growth. Prescribed fire may therefore be an important management tool for reversing mesophication and restoring a global array of open canopy ecosystems.
计划火烧广泛用于生态系统恢复，但决定其有效性的机制仍未得到很好的描述。由于土壤水文学会影响侵蚀、径流和植物竞争等生态系统过程，因此了解火烧如何影响土壤水文学非常重要。为了深入了解植被、地形和火烧之间的关系，需要采用系统的方法来推进对火烧如何影响土壤特性的认识，而这些特性反过来又会影响恢复的成功。我们的目标是在恢复管理下的异质景观中，描述火烧严重程度、植被和土壤水文学之间的关系。我们的研究在一个荒地-森林镶嵌体中进行，该地区最近的计划火烧历史可追溯到 1960 年以来的 0 到 10 次火烧，此外，燃料负荷、火烧严重程度、植被覆盖、地形和土壤等方面也存在差异。我们在连续两年内测量了土壤水力传导度（SHC），代表了对照、火灾前、火灾后和火灾后 1 年的条件。回归树分析确定了土壤初始湿度对 SHC 的重要阈值效应；初始湿度<13%的土壤比初始湿度>13%的土壤具有更低的 SHC。此外，在这个阈值以上，最近火烧频率（4-10 次）处于中等至高水平的地点的 SHC明显大于未火烧的对照地点。与灌木砍伐和堆积相关的高燃料负荷增加了荒地地区的 SHC，但在灌木或松树地区没有增加，这表明植被覆盖与火烧对 SHC 的影响之间存在相互作用。在局部山坡尺度上，趾坡的 SHC 大于山顶。我们的研究结果表明，重复进行中度到高强度的计划火烧可能会提高 SHC，从而减少土壤水分保持能力，并可能恢复限制木本植物生长的功能松荒地过程。因此，计划火烧可能是一种重要的管理工具，可以逆转中生演替并恢复全球一系列开阔树冠生态系统。
