Over the last century, northern coastal scrub has encroached into open grasslands along the central California coast, increasing fire risk in coastal wildland–urban interfaces. Understanding prehistoric ecological conditions is crucial for fire mitigation projects. Current estimates of these conditions in coastal California grasslands and shrublands are largely speculative because tree ring data, lake sediment evidence and ethnographic information are sparse. Phytolith analysis is an alternative palaeoecological tool that has been successfully used to reconstruct the extent of prehistoric grass cover in California. Our study uses phytolith analysis of soil samples from the East Bay hills of the San Francisco Bay region as a novel approach to estimate prehistoric grassland distribution and infer fire frequency in central coastal California. Our data strongly indicate that many areas in the region were dominated by perennial bunchgrasses for at least several hundred years before European contact. Because grass-dominated grasslands in the East Bay hills are disturbance-dependent, our data suggest prehistoric fire frequency was of the order of 5 years or less in the region. Phytolith analysis is a useful technique for prehistoric fire regime reconstruction for grasslands and shrublands worldwide, leading to improved, data-based land management.

中文翻译：

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使用植硅体分析重建加利福尼亚中部沿海地区的史前火灾状况

在上个世纪，北部沿海灌木已经侵入加利福尼亚中部海岸的开阔草原，增加了沿海荒地-城市交界处的火灾风险。了解史前生态条件对于减轻火灾的项目至关重要。目前对加利福尼亚沿海草原和灌木地这些条件的估计主要是推测性的，因为树木年轮数据、湖泊沉积物证据和人种学信息很少。植硅体分析是另一种古生态工具，已成功用于重建加利福尼亚史前草覆盖的范围。我们的研究使用来自旧金山湾地区东湾山的土壤样品的植硅体分析作为估计史前草原分布和推断加利福尼亚中部沿海火灾频率的新方法。我们的数据有力地表明，在欧洲人接触之前，该地区的许多地区至少在数百年中以多年生丛草为主。由于东湾丘陵以草为主的草原依赖于干扰，我们的数据表明该地区的史前火灾频率约为 5 年或更短。植硅体分析是一种有用的技术，可用于重建全球草原和灌木地的史前火灾状况，从而改进基于数据的土地管理。