NOAA/WDS Paleoclimatology - Iniguez fire data from Rincon Peak RP05 - IMPD USRPK_05

Spatial and temporal patterns of fire history are affected by factors such as topography, vegetation, and climate. It is unclear, however, how these factors influenced fire history patterns in small isolated forests, such as that found on Rincon Peak, a “sky island” mountain range in southern Arizona, USA. We reconstructed the fire history of Rincon Peak to evaluate the influences of broad-scale (i.e., climate) versus local-scale (i.e., topographic) factors on fire occurrence and extent. We evaluated both fire scars and tree demography (natality and mortality) to investigate surface fire and crown fire events. The fire history of a 310 ha study area surrounding the top of Rincon Peak was reconstructed by tree-ring sampling in 21 plots. Between 1648 and 1763, spreading fires on Rincon Peak were controlled primarily by regional climate. Widespread surface fires occurred during drought years, and were generally synchronized with regional fire events known from an extensive network of other fire history studies. After 1763, fire extent was apparently limited by local factors (i.e., fuels) as frequent fires continued to burn, but were limited to the southern part of the study area until a widespread fire occurred in 1819. Landscape fires (i.e., fires that scarred ≥2 plots) were absent from the entire study area between 1819 and 1867 despite continued burning in adjacent mountain ranges. Multiple lines of evidence indicate that the 1867 fire was both a surface and a stand-replacing event that killed most trees within a 60 ha patch. Our findings suggest that past climatic variations had important effects on fire regimes and age structures of small, fragmented ponderosa pine (Pinus ponderosa) landscapes like Rincon Peak. Given anticipated climate changes, the rich biodiversity harbored in these steep, isolated landscapes will be critical habitat in the migration of species and should therefore be considered high conservation priority.

火灾历史的时空格局受地形、植被与气候等因素调控。然而目前尚不清楚，此类因素如何影响小型孤立森林的火灾历史格局——例如美国亚利桑那州南部的“天空岛（sky island）”山脉林孔峰（Rincon Peak）所辖的孤立林区。本研究通过重建林孔峰的火灾历史，以评估大尺度（即气候）与局地尺度（即地形）因素对火灾发生及过火范围的影响。本研究同时结合火疤（fire scars）与树木种群动态（更新与死亡）数据，探究地表火（surface fire）与树冠火（crown fire）事件。本研究以林孔峰周边310公顷的研究区域为对象，通过21个样地的树轮采样（tree-ring sampling）重建其火灾历史。1648年至1763年间，林孔峰的蔓延火灾主要受区域气候调控：干旱年份多发大范围地表火，且通常与其他大量火灾历史研究揭示的区域火灾事件同步。1763年后，尽管火灾频发，但过火范围明显受局地因素（即可燃物）限制，仅在研究区南部蔓延，直至1819年发生大范围火灾。1819年至1867年间，尽管邻近山脉持续发生火灾，但整个研究区域未出现景观尺度火灾（即过火覆盖≥2个样地的火灾）。多项证据表明，1867年的火灾兼具地表火与林分更替型火灾特征，造成60公顷斑块内的绝大多数树木死亡。本研究结果显示，过往气候波动对林孔峰这类小型破碎化黄松（Pinus ponderosa）景观的火灾制度（fire regimes）与年龄结构具有显著影响。鉴于未来气候变化的预期趋势，这类陡峭且孤立的景观所承载的丰富生物多样性，将成为物种迁移过程中的关键栖息地，因此应将其列为高优先级保护对象。