Fire, Vegetation Change, and Human Settlement

该项目将研究美洲原住民在多大程度上利用火改变了森林，以增加可用作食物资源的树木数量，如橡树的橡子，并创造开放的林地，这比自然密集的森林更受欢迎。 欧洲人到达后，灭火变得普遍，森林封闭，比早期欧洲探险家所描述的开放森林更密集。 许多研究人员认为，欧洲人发现的开阔森林是闪电引起的火灾的结果，通常不归因于美洲原住民对景观的操纵。 很长一段时间以来，区分美洲原住民引起的森林变化和闪电火灾一直是科学家的挑战。 许多美国国家森林现在正在经历更大，更具破坏性的森林火灾，影响许多物种并威胁到家园和财产。 这些火灾增加的原因之一是灭火后森林密度增加。 制定新的政策，使用规定的火来创造一个更开放的森林，需要土地管理者了解火灾前的森林是什么样子，是什么导致森林树冠保持开放。 了解第一批欧洲探险家遇到的开阔森林是自然火灾还是人为纵火的结果，为森林管理人员提供了关于哪些过程创造了这些森林条件的信息。 这些信息可以用来管理现代森林，更好地保护它们。 这项研究将与当地的美洲原住民部落合作进行，并将为来自科学领域代表性不足的群体的本科生提供服务。雷击野火是任何生态系统的自然组成部分，一般认为这类火灾是森林结构的主要决定因素。 然而，有重要的证据表明，尽管存在自然火灾，美洲原住民经常进行有控制的景观燃烧，以提高某些陆地资源的生产力，作为维持高人口密度的一种手段。 该项目的研究人员将使用花粉和木炭分析来重建过去2,000年的森林历史，并将其与根据树木年轮研究重建的独立气候历史进行比较，以确定森林结构的变化是否与气候模式一致。 研究人员假设，如果发现美洲原住民用于食物资源但需要干燥条件和开放栖息地的树木类型在凉爽潮湿时期增加，那么最可能的原因是美洲原住民通过传统的资源管理实践增加了火灾。 研究人员将使用生态模型来测试闪电引起的火灾是否会导致特定的森林变化，或者是否也需要人为纵火。 研究人员将把森林变化的时间与美洲原住民的考古记录进行比较，以确认森林结构的变化是否与更密集的资源使用相吻合。 本项目将通过加州的Sierra内华达州的案例研究来调查这些问题，但研究的见解将适用于整个美国的国家林地，那里的森林火灾管理是一个公众关注的问题。

This project will study the extent to which forests were altered by Native Americans using fire to increase the number of trees available for food resources, such as acorns from oak trees, and to create open woodlands, which were preferred over the naturally denser forests. After the arrival of Europeans, fire suppression became common and forests closed-up and became denser than the open forests described at contact by early European explorers. Many researchers have suggested that the open forests found by Europeans were the result of fires started due to lightning and are generally not ascribed to Native American landscape manipulation. Distinguishing forest change caused by Native Americans from lightning fires has challenged scientists for a long time. Many U.S. national forests now are experiencing larger and more destructive forest fires that impact many species and threaten homes and property. One cause of these increased fires is the increased density of forests following fire suppression. Creating new policies that use prescribed fire to create a more open forest requires land managers to understand what pre-fire suppression forests looked like and what caused the forest canopy to remain open. Knowing whether the open forests encountered by the first European explorers were the result of natural fire or human set fire provides forest managers with information regarding which processes created those forest conditions. This information can then be used to manage modern forests and better protect them. This study will be conducted in collaboration with local Native American tribes and will serve undergraduate students from groups underrepresented in the sciences. Lightning-strike wildfires are a natural part of any ecosystem, and it is generally assumed that such fires are the primary determinant of forest structure. There is significant evidence, however, that despite the presence of natural fires, Native Americans regularly conducted controlled burns of the landscape to increase productivity of certain terrestrial resources as a means of sustaining high population densities. The investigators of this project will use pollen and charcoal analysis to reconstruct the last 2,000 years of forest history and compare it with independent climate history reconstructed from tree-ring studies to determine whether forest structure changes in a manner consistent with patterns of climate. The investigators hypothesize that if the abundance of tree types that Native Americans used for food resources but which required drier conditions and open habitat are found to have increased during cool wet periods, then the most likely cause would be increased fires set by Native Americans through traditional resource-management practices. The investigators will use ecological models to test whether fires caused by lightning alone could have produced specific forest changes or whether human-set fires also were needed. The investigators will compare the timing of forest changes with the archaeological record of Native Americans to confirm whether the changes in forest structure coincide with more intense use of resources. This project will investigate these questions through a case study in the Sierra Nevada of California, but the research insights will be applicable to national forest lands throughout the United States where forest fire management is a public concern.