NOAA/WDS Paleoclimatology - Iniguez fire data from Rincon Peak RP01 - IMPD USRPK_01

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.

火烧历史的时空格局受地形、植被与气候等因素调控。然而，目前尚不清楚这些因素如何作用于小型孤立森林的火烧历史格局——例如美国亚利桑那州南部的“天空之岛（sky island）”山脉林孔峰（Rincon Peak）所在的森林。本研究重建了林孔峰的火烧历史，以评估大尺度（即气候）与局地尺度（即地形）因素对火烧发生与过火范围的影响。我们同时评估了火疤（fire scars）与树木种群动态（出生率与死亡率），以探究地表火（surface fire）与冠层火（crown fire）事件。通过在21个样地开展树木年轮采样（tree-ring sampling），我们重建了林孔峰周边310公顷研究区域的火烧历史。1648年至1763年间，林孔峰的蔓延型火烧主要受区域气候控制：干旱年份频发大范围地表火，且通常与其他大量火烧历史研究中记录的区域火烧事件同步发生。1763年之后，尽管仍有频繁火烧活动，但过火范围明显受局地因素（即可燃物）限制，且仅局限于研究区域南部，直至1819年发生一场大范围火烧。1819年至1867年间，尽管相邻山脉持续有火烧活动，但整个研究区域未发生景观尺度火烧（即过火覆盖≥2个样地的火烧）。多方面证据表明，1867年的火烧兼具地表火与林分毁灭性火灾特征，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美国黄松（Pinus ponderosa）景观的火动态格局与林分年龄结构具有重要影响。鉴于未来预期的气候变化，这类陡峭且孤立的景观所孕育的丰富生物多样性，将成为物种迁移的关键栖息地，因此应被列为高优先级保护对象。