NOAA/WDS Paleoclimatology - Heyerdahl fire data from Lytle Creek, central Oregon - IMPD USLYT001

Dry mixed-conifer forests are widespread in the interior west of North America, but their historical fire regimes are poorly understood. We reconstructed a multicentury history of the spatial complexity in forest fire regimes (frequency, severity, and extent) in dry mixed-conifer forests in central Oregon. We sampled four 30-plot grids over 3,222 ha, one in the eastern Cascade Range and three in the Ochoco Mountains. All four sites are currently dominated by grand fir, Douglas-fir, and ponderosa pine with varying, but minor, amounts of western larch, incense cedar, or western juniper growing fine-grained mosaics. We sampled 4,065 trees to determine their recruitment dates and/or the dates of surface fires and used these to reconstruct remarkably similar historical fire regimes at all four sites. These regimes were dominated by frequent and often extensive surface fires, but included occasional patches of severe fire. Although forest types varied within sites, historical fire regimes did not vary substantially among these types.

干旱混交针叶林广泛分布于北美内陆西部，但学界对其历史火制度（fire regime）的认知仍较为匮乏。本研究针对俄勒冈州中部的干旱混交针叶林，重建了其历史火制度（包括火频率、火烈度与过火范围）空间复杂性的百年演化历史。我们在总面积3222公顷的区域内布设了4个各含30个样地的样方网格，其中1个位于喀斯喀特山脉东段，其余3个分布于奥乔科山脉。当前四个样地均以大冷杉、花旗松、美国黄松为优势树种，伴生少量西部落叶松、香雪松或西加圆柏，形成细粒度的植被镶嵌格局。我们共采样4065株树木，以确定其定植年代和/或地表火发生年份，并以此重建了四个样地间极为相似的历史火制度。这些火制度以高频且多为大面积的地表火为主，但偶有重度火烧斑块出现。尽管样地内部的森林类型存在差异，但不同森林类型间的历史火制度并未出现显著差异。