Ecosystem Resilience to Human Impacts: Ecological Consequences of Early Human-Set Fires in New Zealand

几千年来，人类通过对着火率、燃料和土地覆盖的影响来影响火灾制度。火灾制度的变化通过改变植物群落、为新物种的吸收创造机会、重建陆地表面过程和营养循环，极大地改变了生态系统的动态。古生态和考古数据表明，大约700年前，新西兰大面积的森林砍伐与已知的第一个毛利人（波利尼西亚人）的存在有关。在没有气候变化的情况下，少数短暂的毛利人通过使用火突然砍伐森林，这种情况与其他温带雨林地区相反，在这些地区，森林砍伐与定居人口和重大气候变化有关。新西兰是人类故意使用火造成森林砍伐的最引人注目的例子之一，它的植被和火灾历史为理解大规模燃烧热带雨林的后果提供了一个重要的案例研究。早期的研究使用高分辨率的木炭和花粉数据来记录毛利人到达新西兰南岛后的一个独特的燃烧时期。这个事件现在被称为初始燃烧期（IBP）。本研究项目将解决以下问题：在IBP期间，火灾的空间和时间模式是什么？它们是否暗示了燃烧的动机？IBP的环境后果主要是由燃烧的性质、新扰动的引入，还是由特定地点的物理特征决定的？是什么限制了IBP之后新西兰本土森林的恢复？调查人员将使用最近恢复的记录来密切比较南岛和北岛的火灾制度，南岛的农业相对不成功，人口流动，北岛的定居点建立得很好，规模很大。他们将从南岛东部沿海平原和北岛肥沃的火山地区获取新的湖泊沉积物岩心。他们将开发高分辨率的宏观木炭和花粉记录，这些记录跨越过去2000年，并研究IBP期间的火灾状况和植被变化。他们将重建每个地点的详细植被历史，并开发高分辨率年表，以同步多个流域的古环境代理。他们将检查来自多个地点的高分辨率地球化学、湖泊生物和磁化率数据，以记录IBP期间分水岭事件的顺序，他们将使用GIS数据库进行多地点火灾模式与考古、物理和环境特征的比较。他们将把独立的古气候代用物与过去2000年的火灾变化进行比较，并使用景观模拟模型来了解IBP期间和之后的事件顺序。在卡尔顿学院科学教育资源中心的协调下，调查人员将开发和传播教育材料，以便在美国和新西兰广泛推广。该项目将为关于前欧洲景观是原始的还是人性化的程度的辩论提供新的信息。新工具的应用和改进，如分子生物标志物（用于识别和表征沉积物中的木炭），以及记录和理解过去火灾的方法，有可能将火灾历史科学转变为一个真正的跨学科领域。该项目还将为自然资源管理者提供有关火灾变异性的历史范围和火灾后后果的信息，以及关于人与环境相互作用、可持续性和科学发现等主题的教育材料。该项目应用景观模拟模型来研究火灾行为和蔓延，将允许对火灾、燃料和景观条件的不同组合进行情景测试，以解释过去人类活动的后果及其对生态系统的影响。

Humans have influenced fire regimes for thousands of years through their impact on ignition rates, fuels, and land cover. Changes in fire-regimes have dramatically altered ecosystem dynamics by shifting plant communities, creating opportunities for recruitment of new species, and restructuring land-surface processes and nutrient cycles. Paleoecological and archeological data indicate widespread deforestation in New Zealand about 700 years ago associated with the first known Maori (Polynesian) presence. Abrupt deforestation through the use of fire was achieved by small transient Maori populations in the absence of climate change, a situation that is contrary to other temperate rainforest regions where deforestation was associated with sedentary populations and significant climate change. New Zealand offers one of the most dramatic examples of human-caused deforestation through the deliberate use of fire, and its vegetation and fire history provides an important case study for understanding the consequences of wholesale burning of rainforests. Earlier research used high-resolution charcoal and pollen data to document a distinct period of burning following Maori arrival on the South Island of New Zealand. This event now is termed the Initial Burning Period (IBP). This research project will address the following questions: What spatial and temporal patterns of fire are evident during the IBP, and do they suggest the motivation for burning? Were the environmental consequences of the IBP largely shaped by the nature of the burning, the introduction of a novel disturbance, or by site-specific physical characteristics? What limited the recovery of native New Zealand forests after the IBP? The investigators will use recently recovered records to closely compare fire regimes on the South Island, where agriculture was relatively unsuccessful and populations were transient, with those on the North Island, where settlements were well established and large. They will acquire new lake-sediment cores from the eastern coastal plain on the South Island and the fertile volcanic regions of the North Island. They will develop high-resolution macroscopic charcoal and pollen records that span the last 2,000 years and examine changes in fire regime and vegetation during the IBP. They will reconstruct detailed vegetation histories for each site and develop high-resolution chronologies to synchronize paleoenvironmental proxy from multiple watersheds. They will examine high-resolution geochemical, limnobiotic, and magnetic susceptibility data from multiple sites to document the sequence of watershed events during the IBP, and they will use a GIS database for multiple-site comparisons of patterns of fire with archeological, physical, and environmental characteristics. They will compare independent paleoclimate proxies with variations in fires during the past 2,000 years and use landscape simulation models to understand the sequence of events during and after the IBP. In coordination with the Science Education Resource Center at Carleton College, the investigators will develop and disseminate educational materials for broad outreach in the U.S. and New Zealand.This project will contribute new information to debates about the extent to which pre-European landscapes were pristine or humanized. The application and refinement of new tools, such as molecular biomarkers (used to identify and characterize charcoal in sediments), and approaches to document and understand past fires have the potential to transform fire-history science into a truly interdisciplinary field. The project also will provide information about the historical range of variability of fire and post-fire consequences for natural resource managers and educational materials on the topics of human-environmental interactions, sustainability, and scientific discovery. The project's application of landscape simulation models to study fire behavior and spread will allow scenario testing of different combinations of fire, fuels, and landscape conditions to explain the past consequences of human action and its effects on ecosystems.