Seasonal dry tropical forest (STDF) is a widespread vegetation type in western Mexico. Generally, this type of forest develops in semihumid habitats where lacustrine basins are scarce, preventing documentation of the vegetation history and forest dynamics using a paleoecological approach. Here, we present a palynological record from the Santa Maria del Oro crater lake, located within the distribution area of the STDF and the adjacent dry oak forest which gives insight into the changes in diversity and human impact at this tropical site. Pollen data, in combination with geochemical analysis and microcharcoal data from a lacustrine sequence, are used to discuss vegetation change and diversity in the plant assemblages related to drought or anthropogenic activity over the last 5000 years. Our results show three distinct periods of drought in the basin, from 4200 to 3850, 3100 to 2300, 1570 to 1100 and 300 cal year BP, with changes in vegetation composition mainly related to a decrease in taxa diversity during these periods. Based on the presence of maize pollen, two periods of human activity (3790–2160 and 280 cal year BP to present) were detected with an increase in herbaceous pollen used as a surrogate for deforestation. These two disturbance periods, pre-Columbian and postcolonial, occurred during wet conditions in the basin. Our results highlight the correlation between El Niño events, drought and fire with changes in the composition and diversity of STDF.

季节性干热带森林（STDF）是墨西哥西部的一种普遍的植被类型。通常，这种类型的森林生长在湖盆稀少的半湿润地区，从而无法使用古生态方法来记录植被历史和森林动态。在这里，我们介绍了来自STDF分布区和邻近的干燥橡树林的Santa Maria del Oro火山口湖的古生物学记录，这使人深入了解了这个热带地区的多样性变化和人类影响。花粉数据与地球化学分析和湖泊序列中的微炭数据相结合，用于讨论过去5000年与干旱或人为活动相关的植物群落中的植被变化和多样性。我们的结果显示了该盆地三个不同的干旱时期，从4200到3850、3100到2300、1570到1100和300 cal年BP，植被组成的变化主要与这些时期的分类单元多样性的减少有关。根据玉米花粉的存在情况，检测到人类活动有两个时期（目前为3790-2160年和BP 280 cal年），而用作草场替代品的草本花粉有所增加。这两个扰动期是前哥伦布时期和后殖民时期，发生在盆地潮湿的条件下。我们的结果强调了厄尔尼诺事件，干旱和火灾与STDF组成和多样性的变化之间的相关性。发现有两个人类活动时期（目前为3790–2160和BP 280 cal年），而用作破坏森林的替代品的花粉却增加了。这两个扰动期是前哥伦布时期和后殖民时期，发生在盆地潮湿的条件下。我们的结果强调了厄尔尼诺事件，干旱和火灾与STDF组成和多样性的变化之间的相关性。发现有两个人类活动时期（目前为3790–2160和BP 280 cal年），而用作破坏森林的替代品的花粉却增加了。这两个扰动期是前哥伦布时期和后殖民时期，发生在盆地潮湿的条件下。我们的结果强调了厄尔尼诺事件，干旱和火灾与STDF组成和多样性的变化之间的相关性。