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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Ecological consequences of early Late Pleistocene megadroughts in tropical Africa
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Ecological consequences of early Late Pleistocene megadroughts in tropical Africa

机译：热带非洲晚更新世早期大干旱的生态后果

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Extremely arid conditions in tropical Africa occurred in several discrete episodes between 135 and 90 ka, as demonstrated by lake core and seismic records from multiple basins [Scholz CA, Johnson TC, Cohen AS, King JW, Peck J, Overpeck JT, Talbot MR, Brown ET, Kalindekafe L, Amoako PYO,et al. (2007) Proc Natl Acad Sci USA 104:16416-16421]. This resulted in extraordinarily low lake levels, even in Africa's deepest lakes. On the basis of well dated paleoecological records from Lake Malawi, which reflect both local and regional conditions, we show that this aridity had severe consequences for terrestrial and aquatic ecosystems. During the most arid phase, there was extremely low pollen production and limited charred-particle deposition, indicating insufficient vegetation to maintain substantial fires, and the Lake Malawi watershed experienced cool, semidesert conditions (< 400 mm/yr precipitation). Fossil and sedimentological data show that Lake Malawi itself, currently 706 m deep, was reduced to ≈ 125 m deep saline, alkaline, well mixed lake. This episode of aridity was far more extreme than any experienced in the Afrotropics during the Last Glacial Maximum (≈35-15 ka). Aridity diminished after 95 ka, lake levels rose erratically, and salinity/alkalinity declined, reaching near-modern conditions after 60 ka. This record of lake levels and changing limnological conditions provides a framework for interpreting the evolution of the Lake Malawi fish and invertebrate species flocks. Moreover, this record, coupled with other regional records of early Late Pleistocene aridity, places new constraints on models of Afrotropical biogeographic refugia and early modern human population expansion into and out of tropical Africa.
机译：热带非洲的极端干旱条件发生在135至90 ka之间的几个离散事件中，如湖心和多个盆地的地震记录所证明的[Scholz CA，Johnson TC，Cohen AS，King JW，Peck J，Overpeck JT，Talbot MR， Brown ET，Kalindekafe L，Amoako PYO等。 （2007）Proc Natl Acad Sci USA 104：16416-16421]。即使在非洲最深的湖泊中，这也导致了极低的湖泊水位。根据马拉维湖最新的古生态记录（反映了当地和区域情况），我们表明这种干旱对陆地和水生生态系统造成了严重后果。在最干旱的阶段，花粉产量极低，烧焦的颗粒沉积有限，表明植被不足以维持大量的火势，马拉维湖流域经历了凉爽，半沙漠化的条件（降水量<400毫米/年）。化石和沉积学数据表明，马拉维湖本身（目前为706 m深）已被减少至≈125 m深的盐水，碱性，混合良好的湖泊。干旱的发作远比最后一次冰期末期（≈35-15ka）发生在非洲黑人中的经历更为极端。 95 ka之后，干旱减弱，湖泊水位上升，盐度/碱度下降，在60 ka之后达到近现代水平。湖泊水位和变化的湖泊条件的记录为解释马拉维湖鱼类和无脊椎动物种群的演变提供了框架。此外，这一记录，再加上晚更新世早期干旱的其他区域记录，对非热带生物地理避难所和现代人类早期向热带非洲的扩张和扩张提供了新的限制。

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