NOAA/WDS Paleoclimatology - Iniguez fire data from Catalina Rose Canyon CRC19 - IMPD USCRC_19

Fire histories contribute important information to contemporary fire planning, however, our knowledge is not comprehensive geographically. We evaluated the influence of topography on fire history patterns in two contrasting landscapes within the Santa Catalina Mountains of southeastern Arizona. Multiple fire-scarred trees from randomly selected 2-ha plots were used to develop plot composite mean fire intervals (PCMFIs) within the Butterfly Peak (BP) and Rose Canyon (RC) landscapes. BP is dominated by steep, northerly aspects and presence of potential fire spread barriers (exposed rock bluffs and scree slopes). RC is dominated by more gentle and southerly aspects with relatively few fire barriers. Within each landscape, PCMFIs did not differ significantly between aspect classes from A.D. 1748 to 1910 (BP: p = 0.73 and RC: p = 0.57). Pooled PCMFIs in the gentler RC landscape were, however, significantly shorter (p < 0.001) than in the steeper BP landscape. The frequency of relatively widespread fires (i.e., number of fire years when ≥2 plots scarred) was similar between landscapes, but fires in the gentler RC landscape were significantly larger (p = 0.033). The higher frequency of large fires (i.e., fires that burned >75% of the landscape) in RC resulted in more area burned over time and shorter fire intervals at individual plots. Conversely, smaller fires in the dissected BP landscape resulted in less area burned and longer periods between fires at individual plots. The different topographies in the two landscapes likely result in different wind intensities, fuel moistures, and fuel/vegetation types—and consequently, different historical fire spread patterns. Our conclusion is that fire history patterns are not influenced primarily by stand-scale topography, but rather by the topographic characteristics of the broader, surrounding landscape.

火灾历史记录可为当代火灾规划提供关键信息，但目前我们的相关认知在地理覆盖范围上仍存在不足。本研究针对美国亚利桑那州东南部圣卡塔利娜山脉（Santa Catalina Mountains）内两处具有显著差异的景观，评估了地形对火灾历史格局的影响。我们从随机选取的2公顷样地中采集多株带火疤的树木，以此构建蝴蝶峰（Butterfly Peak, BP）与玫瑰谷（Rose Canyon, RC）景观内的样地综合平均火灾间隔期（plot composite mean fire intervals, PCMFIs）。蝴蝶峰景观以陡峭的北向坡面为主，且存在潜在的火灾蔓延阻隔物（裸露岩崖及碎石坡）；玫瑰谷景观则以坡度较缓的南向坡面为主，火灾阻隔物相对稀少。在两处景观内部，公元1748年至1910年间，不同坡向等级的样地综合平均火灾间隔期均无显著差异（蝴蝶峰：p=0.73；玫瑰谷：p=0.57）。但坡度较缓的玫瑰谷景观的合并样地综合平均火灾间隔期显著短于陡峭的蝴蝶峰景观（p<0.001）。两处景观的相对大范围火灾发生频率（即当年至少有2个样地出现火疤的火灾年份数）较为相似，但坡度较缓的玫瑰谷景观的火灾规模显著更大（p=0.033）。玫瑰谷景观中大尺度火灾（即过火范围覆盖景观75%以上区域的火灾）发生频率更高，这使得该景观随时间推移的总过火面积更大，且单个样地的火灾间隔期更短。与之相反，地形破碎的蝴蝶峰景观内的火灾规模更小，总过火面积更少，单个样地的火灾间隔期也更长。两处景观的地形差异可能导致风速、可燃物湿度以及可燃物/植被类型的不同，进而形成不同的历史火灾蔓延格局。本研究得出结论：火灾历史格局主要不受林分尺度地形的影响，而是受更大范围周边景观的地形特征调控。