一項(xiàng)研究提示,，波利尼西亞人（毛利人）和之后到來(lái)的歐洲定居者在新西蘭點(diǎn)燃的火啟動(dòng)了一直持續(xù)到今天的地貌轉(zhuǎn)變。此前的研究已經(jīng)證明,，在700-800年前波利尼西亞人到來(lái)之前，樹(shù)木覆蓋了新西蘭的85%到90%,，但是到了19世紀(jì)中期歐洲人在這里定居的時(shí)候，新西蘭南島40%以上的森林已經(jīng)被草和灌木取代,。David McWethy及其同事使用木炭和花粉記錄、放射性碳測(cè)年測(cè)定的沉積物巖芯以及藻類和蚊蟲(chóng)的殘骸從而理解導(dǎo)致這個(gè)島的森林迅速減少的事件先后順序,。這組作者重建了新西蘭南島的16個(gè)不同的湖的流域歷史,，結(jié)果發(fā)現(xiàn)在大多數(shù)地點(diǎn),，在已知的毛利人到達(dá)時(shí)間的2個(gè)世紀(jì)內(nèi)發(fā)生了幾次高烈度的火，以及隨著燃燒而來(lái)的植被,、侵蝕和湖泊化學(xué)成分的變化。這組作者報(bào)告說(shuō),，在19世紀(jì),，歐洲人引發(fā)了進(jìn)一步的流域變化,，把灌木變成了草原,。包括樹(shù)木年輪和洞穴構(gòu)造等歷史氣候代用指標(biāo)向這組作者提示,，人類活動(dòng)而非異乎尋常的干燥或溫暖的環(huán)境導(dǎo)致了這些火,。這組作者說(shuō),，該研究可能有助于科研人員改善森林火災(zāi)管理和自然保護(hù)策略。（生物谷Bioon.com）
生物谷推薦原文出處：
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.
