Hydroclimate variability was the main control on fire activity in northern Africa over the last 50,000 years: dataset

North Africa features some of the most frequently burnt biomes on Earth, including the semi-arid grasslands of the Sahel and wetter savannas immediately to the south. Natural fires are fuelled by rapid biomass production during the wet season, its desiccation during the dry season and ignition by frequent dry lightning strikes. Today, fire activity decreases markedly both to the north of the Sahel, where rainfall is extremely low, almost eliminating biomass over the Sahara, and to the south where forest biomes are too wet to burn. Over the last glacial cycle, rainfall and vegetation cover over northern Africa varied dramatically in response to gradual astronomically-forced insolation change, changes in atmospheric carbon dioxide levels, and abrupt cooling events over the North Atlantic Ocean associated with the reorganisation of Meridional Overturning Circulation (MOC). Here we report the results of a study into the impact of these climate changes on fire activity in northern African over the last 50,000 years (50 kyr). Our reconstructions come from marine sediments with strong age control that provide an uninterrupted record of charcoal particles exported from the African continent. We studied three sites on a latitudinal transect along the northwest African margin between 21 and 9°N. Our sites exhibit a distinct latitudinal relationship between past changes in rainfall and fire activity. At the southernmost site (GeoB9528-3, 9°N), fire activity decreased during intervals of increasing humidity, while our northernmost site (ODP Site 658, 21°N) clearly demonstrates the opposite relationship. The site in the middle of our transect, offshore of the present day southern Sahel today (GeoB9508-5, 15°N), exhibits a “Goldilocks” relationship between fire activity and hydroclimate, wherein charcoal fluxes peak under intermediate rainfall climate conditions and are supressed by transition to more arid or more humid conditions. Our results are remarkably consistent with the predictions of the intermediate fire-productivity hypothesis developed in conceptual macroecological models and supported by empirical evidence of modern day fire activity. Feedback processes operating between fire, climate and vegetation are undoubtedly complex but, based on composite records, temperature is suggested to be the main driver of temporal change in fire activity globally, with the precipitation-evaporation balance perhaps a secondary influence in the Holocene tropics. Yet there is only sparse coverage of Africa in the composite record. We conclude that hydroclimate exerted the dominant control on burning in the tropics of northern Africa well before the Holocene (from at least 50 ka). This datasheet contains: Charcoal concentration and flux data from 0-50ka measured at ocean drill cores ODP Site 658, GeoB9508-5 and GeoB9528-3 Sediment Total Organic Carbon data (TOC%) from ODP Site 658北非拥有地球上野火发生最频繁的生物群系之一，包括萨赫勒（Sahel）半干旱草原以及其南侧更湿润的稀树草原。自然野火的发生有赖于湿季快速生成的生物量、干季生物量的干燥脱水，以及频发的干雷电引发的点火。如今，野火活动在萨赫勒北侧显著减弱——这里降雨量极低，撒哈拉地区几乎无生物量留存；南侧的森林生物群系则因过于湿润而无法发生野火。 在过去的冰期旋回中，北非的降雨量与植被覆盖度随一系列因素发生剧烈变化：受天文强迫的日射量缓慢改变、大气二氧化碳水平变化，以及与经向翻转环流（Meridional Overturning Circulation, MOC）重组相关的北大西洋突发性降温事件。本文报道了一项针对过去5万年（50 kyr）内北非气候变化对野火活动影响的研究成果。 我们的古气候重建数据源自定年控制可靠的海洋沉积物，该序列完整记录了从非洲大陆输运而来的木炭颗粒。本研究沿西北非洲大陆边缘选取了三个位于北纬21°至9°的纬度断面采样站点。各站点均呈现出降雨量变化与古野火活动间清晰的纬度相关性：最南侧站点（GeoB9528-3，9°N）的野火活动在湿度升高时段显著降低；而最北侧站点（大洋钻探计划（Ocean Drilling Program, ODP）658站位，21°N）则呈现出完全相反的关系。位于断面中部、对应现今南萨赫勒近海的站点（GeoB9508-5，15°N），则呈现出野火活动与水文气候间的“金发姑娘（Goldilocks）”型关系：即木炭通量在中等降雨气候条件下达到峰值，当气候向更干旱或更湿润方向转变时，木炭通量会受到抑制。 我们的研究结果与基于概念性宏观生态模型提出的中间火生产力（intermediate fire-productivity）假说的预测高度一致，该假说也得到了现代野火活动的实证证据支持。野火、气候与植被之间的反馈过程无疑极为复杂，但综合现有记录来看，全球野火活动的时间变化主要由温度驱动，而降水-蒸发平衡可能在全新世热带区域起到次要调控作用。然而，综合记录中非洲地区的采样点分布极为稀少。我们得出结论：早在全新世之前（至少始于5万年前），水文气候就对北非热带区域的野火活动起到了主导调控作用。 本数据集包含： 1. 0-5万年时间段内，大洋钻探计划（Ocean Drilling Program, ODP）658站位、GeoB9508-5与GeoB9528-3海洋钻探岩芯的木炭浓度与通量数据； 2. ODP 658站位的沉积物总有机碳（Total Organic Carbon, TOC）占比数据。