一项研究提示，波利尼西亚人（毛利人）和之后到来的欧洲定居者在新西兰点燃的火启动了一直持续到今天的地貌转变。此前的研究已经证明，在700-800年前波利尼西亚人到来之前，树木覆盖了新西兰的85%到90%，但是到了19世纪中期欧洲人在这里定居的时候，新西兰南岛40%以上的森林已经被草和灌木取代。David McWethy及其同事使用木炭和花粉记录、放射性碳测年测定的沉积物岩芯以及藻类和蚊虫的残骸从而理解导致这个岛的森林迅速减少的事件先后顺序。这组作者重建了新西兰南岛的16个不同的湖的流域历史，结果发现在大多数地点，在已知的毛利人到达时间的2个世纪内发生了几次高烈度的火，以及随着燃烧而来的植被、侵蚀和湖泊化学成分的变化。这组作者报告说，在19世纪，欧洲人引发了进一步的流域变化，把灌木变成了草原。包括树木年轮和洞穴构造等历史气候代用指标向这组作者提示，人类活动而非异乎寻常的干燥或温暖的环境导致了这些火。这组作者说，该研究可能有助于科研人员改善森林火灾管理和自然保护策略。（生物谷Bioon.com）
生物谷推荐原文出处：
PNAS doi: 10.1073/pnas.1011801107
Rapid landscape transformation in South Island, New Zealand, following initial Polynesian settlement
David B. McWethya,1, Cathy Whitlocka, Janet M. Wilmshurstb, Matt S. McGloneb, Mairie Fromontb, Xun Lic, Ann Dieffenbacher-Kralld, William O. Hobbse, Sherilyn C. Fritze, and Edward R. Cookf
Abstract
Humans have altered natural patterns of fire for millennia, but the impact of human-set fires is thought to have been slight in wet closed-canopy forests. In the South Island of New Zealand, Polynesians (Māori), who arrived 700–800 calibrated years (cal y) ago, and then Europeans, who settled ～150 cal y ago, used fire as a tool for forest clearance, but the structure and environmental consequences of these fires are poorly understood. High-resolution charcoal and pollen records from 16 lakes were analyzed to reconstruct the fire and vegetation history of the last 1,000 y. Diatom, chironomid, and element concentration data were examined to identify disturbance-related limnobiotic and biogeochemical changes within burned watersheds. At most sites, several high-severity fire events occurred within the first two centuries of Māori arrival and were often accompanied by a transformation in vegetation, slope stability, and lake chemistry. Proxies of past climate suggest that human activity alone, rather than unusually dry or warm conditions, was responsible for this increased fire activity. The transformation of scrub to grassland by Europeans in the mid-19th century triggered further, sometimes severe, watershed change, through additional fires, erosion, and the introduction of nonnative plant species. Alteration of natural disturbance regimes had lasting impacts, primarily because native forests had little or no previous history of fire and little resilience to the severity of burning. Anthropogenic burning in New Zealand highlights the vulnerability of closed-canopy forests to novel disturbance regimes and suggests that similar settings may be less resilient to climate-induced changes in the future.
