Fire scars are the primary source of physical evidence used to date past fires around the world, and to estimate parameters of historical fire regimes and fire-climate relationships. Despite an increase in studies about historical fire regimes and the relationship between fire and climate, these studies are still limited for Mexican forests. Our goal was to characterize the historical fire regime in two sites with different elevations, to assess changes in fire frequency, and to determine the relationship between fire regimes and climate patterns in a conifer-dominated forest in the Upper Nazas watershed of the Sierra Madre Occidental, Mexico. We were able to cross-date 50 fire-scarred samples of Pinus arizonica Engelm., P. strobiformis Engelm., P. teocote Schlecht. & Cham., P. durangensis Martínez, and Pseudotsuga menziesii (Mirb.) Franco and identify a total of 596 fire scars. Evidences are compelling evidences on forest fires occurred frequently in the study area, starting in the mid eighteenth century and through the mid twentieth century. The season of fire occurrence was determined for 560 (94%) fire scars. Most fire scars at both of our sampling locations, found at low and high elevation sites, occurred in the spring (525, 93.8%) and only 6.2% occurred in the summer. The mean fire interval and Weibull median fire interval values were < 10 years for all fire-scar filter (all samples, ≥10% and ≥ 25%), and the average per-sample fire interval was < 25 years. Our results suggest fire frequency has changed over time at our study site, becoming less common and less extensive since the 1950s. In addition, extensive fires occurred in dry years as indicated by low precipitation, negative NIÑO 3 Sea Surface Temperature (SST) values, and negative Palmer Drought Severity Index (PDSI) values. Fire frequencies must be maintained within the amplitude of their historical regime, with the objective of reducing the risk of severe fires and preserving ecological and hydrological benefits in the watershed.

中文翻译：

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气候对墨西哥杜兰戈纳萨斯流域火灾状况的影响（1700年至2008年）

火灾疤痕是用于确定世界各地以往火灾历史，估算历史火灾状况和火灾与气候关系参数的主要物理证据。尽管有关历史火灾状况以及火灾与气候之间关系的研究有所增加，但这些研究仍仅限于墨西哥森林。我们的目标是表征两个海拔不同地点的历史火灾状况，评估火灾频率的变化，并确定西马德雷河上游纳扎斯流域的针叶林为主的森林中火灾状况与气候模式之间的关系。 ，墨西哥。我们能够对50个亚利桑那州松树，P。strobiformis Engelm，P。teocote Schlecht的火烧痕迹样品进行约会。＆Cham。，P。durangensisMartínez和Pseudotsuga menziesii（Mirb。）并找出总共596处火伤痕迹。证据是令人信服的证据，表明该研究区域始于18世纪中叶直至20世纪中叶频繁发生森林火灾。确定了560（94％）起火伤痕的起火季节。在我们两个采样点上，在低海拔和高海拔地区发现的大多数火疤都发生在春季（525，93.8％），而在夏季仅发生6.2％。所有防火疤痕过滤器（所有样品，≥10％和≥25％）的平均燃烧间隔和韦布尔中值燃烧间隔值均<10年，且每个样本的平均燃烧间隔<25年。我们的研究结果表明，自1950年代以来，火灾发生的频率在我们的研究地点已经随着时间的推移而改变，变得越来越少见，传播范围也越来越小。此外，低降水，NIÑO3海面温度（SST）负值和帕尔默干旱严重指数（PDSI）负值表明，干旱年份发生了大火。火灾频率必须保持在其历史范围内，目的是减少严重火灾的风险，并保持流域的生态和水文效益。