Prairie–forest ecotones are ecologically important for biodiversity and ecological processes. While these ecotones cover small areas, their sharp gradients in land cover promote rich ecological interaction and high conservation value. Our objective was to understand how historical and current fire occurrences and human development influenced the Palouse Prairie–forest ecotone. We used General Land Office survey field notes about the occurrence of bearing trees to locate historical (1870s to 1880s) prairie, pine savanna, and forest at the eastern edge of the bioregion. We combined LANDFIRE Existing Vegetation classes to contrast historical land cover with current land cover. We reconstructed historical fire occurrence (1650 to 1900) from fire-scarred trees. We used fire and lightning records from 1992 to 2015 to interpret the role of people and lightning. Historically, the ecotone was a matrix of prairie with extensive savanna and some forest. More than half of the ecotone area was prairie, which is now dominated by agriculture, with some residential development. The 16% of the landscape that was pine savanna is now forest or shrubs, agriculture, perennial vegetation under the Conservation Reserve Program, or developed; no savanna now exists. Forests covered 12% of the ecotone and these are still mostly forest. Fires were historically frequent, occurring on average every 5 to 8 years at most sites. Lightning was not frequent but could likely have been sufficient to ignite fires that could spread readily given the rolling terrain and long fire season. Fire was far more frequent historically than currently. Conservation, restoration, and other ongoing land-use changes will likely result in more continuous vegetation and hence fuel for fires. Lightning and people may ignite fires that therefore spread readily in the future. Understanding the past and potential future of fire in the Palouse Prairie bioregion may help us live with fire while conserving ecological values here and in similar prairie–forest ecotones.

中文翻译：

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美国华盛顿和爱达荷州Palouse草原-森林交错带的火灾和土地覆盖变化

草原－森林过渡带对生物多样性和生态过程具有重要的生态意义。这些生态交错带虽然覆盖面积很小，但它们在土地覆盖物中的陡峭梯度却促进了丰富的生态互动和高保护价值。我们的目标是了解历史和当前的火灾事件以及人类发展如何影响Palouse草原-森林过渡带。我们使用了国土资源部的调查实地记录，关于承压树木的发生，以将历史（1870年代至1880年代）的大草原，松树大草原和森林定位在生物区东部边缘。我们结合了LANDFIRE现有植被类别，以对比历史土地覆盖率和当前土地覆盖率。我们从烧焦的树木中重建了历史性的火灾事件（1650年至1900年）。我们使用1992年至2015年的火灾和闪电记录来解释人与闪电的作用。从历史上看，过渡过渡带是草原的矩阵，有大量的稀树草原和一些森林。过渡带地区的一半以上是草原，现在以农业为主，并有一些住宅开发。松树稀树草原的16％的景观现在是森林或灌木，农业，在自然保护区计划下的多年生植被或已开发；现在没有大草原。森林覆盖了过渡带的12％，其中大部分仍然是森林。从历史上看，火灾频发，大多数地点平均每5至8年发生一次。闪电并不常见，但由于起伏的地形和漫长的火灾季节，可能足以点燃容易蔓延的火灾。从历史上讲，火灾远比现在频繁。保护，恢复和其他正在进行的土地利用变化可能会导致植被更加连续，从而引发火灾。闪电和人可能会点燃火种，因此将来很容易蔓延。了解帕卢斯草原生物区火灾的过去和潜在的未来，可能会帮助我们着火，同时在这里和类似的草原-森林交错带中保持生态价值。