Fire is an important disturbance that influences species composition, community structure, and ecosystem function in forests. Disturbances such as hurricanes and landslides are critical determinants of community structure to Caribbean forests, but few studies have addressed the effect of paleofire disturbance on forests in Puerto Rico, USA. Soil charcoal is widely used to reconstruct fire history. However, the occurrence and frequency of paleofire can be underestimated due to charcoal decay. We reconstructed the fire history of subtropical dry forests of Puerto Rico based on the analysis of soil macrocharcoal numbers adjusted by the negative exponential decay function of charcoal. Twenty-one fire events occurred over the last 1300 yr in the subtropical dry forest of northeastern Puerto Rico, and 10 fire events occurred over the last 4900 yr in the subtropical dry forest of southeastern Puerto Rico. The average turnover time of charcoal in these subtropical dry forest soils of Puerto Rico was 1000 to 1250 yr. Soil charcoal decay leads to an underestimation of one to two undetected fire events during the Late Holocene in the subtropical dry forests of Puerto Rico. The peak of paleofire events for subtropical dry forests in northeastern and southeastern Puerto Rico was broadly similar, occurring between 500 to 1300 calibrated years before present (cal yr BP; before present is understood to mean before 1950 AD). Fire frequency of the subtropical dry forests in Puerto Rico decreased after the immigration of Europeans in the past 500 yr. The fire that occurred between 4822 and 4854 cal yr BP can be interpreted as either a natural fire or a new record of a native peoples settlement in southeastern Puerto Rico. Fire became a frequent disturbance in the subtropical dry forest of Puerto Rico after the development of cultigens by native peoples. Our data suggested that fire was a frequent disturbance and human activity was likely a dominant cause of these paleofires in the subtropical dry forests of Puerto Rico.

中文翻译：

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波多黎各亚热带干旱森林晚新世火史和木炭腐烂

火灾是影响森林中物种组成，群落结构和生态系统功能的重要干扰。飓风和滑坡等干扰是加勒比森林群落结构的关键决定因素，但在美国波多黎各，很少有研究探讨古火干扰对森林的影响。土壤木炭被广泛用于重建火灾历史。然而，由于木炭的腐烂，古火的发生和频率可能被低估。我们根据对木炭的负指数衰减函数调整的土壤大型木炭数量的分析，重建了波多黎各亚热带干旱森林的火灾历史。在过去的1300年中，波多黎各东北部的亚热带干旱森林发生了21次火灾 在过去的4900年中，波多黎各东南部的亚热带干旱森林发生了10起火灾。波多黎各这些亚热带干林土壤中木炭的平均周转时间为1000至1250年。在波多黎各亚热带干旱森林的全新世晚期，土壤木炭的腐烂导致低估了一到两个未发现的火灾。波多黎各东北部和东南部的亚热带干旱森林古火事件的高峰大致相似，发生在距今约500至1300个校准年之间（cal BP；距今已知是指1950年之前）。在过去的500年中，欧洲人移民后，波多黎各亚热带干旱森林的火灾频率降低。BP发生在4822年和4854年之间的大火可以解释为自然大火，也可以解释为波多黎各东南部一个土著居民定居点的新记录。在当地人培育出栽培品种后，波多黎各亚热带干旱森林的火灾频发。我们的数据表明，在波多黎各的亚热带干旱森林中，火灾是频繁发生的干扰，人类活动可能是造成这些古火灾的主要原因。