Solar irradiance and vegetation dynamics at the K/Pg boundary.

1980年，路易斯·阿尔瓦雷斯和他的同事发表了他们的开创性论文，将白垩纪古近纪界线上恐龙和许多其他物种的死亡与一颗大型陨石对地球表面的影响联系起来。研究小组提出，最有可能的致死机制是全球尘埃云的发展，它减少了到达地球表面的太阳光的数量，导致全球变冷，光合作用减少。这将最终导致净初级生产力的下降，从而在食物链上连锁，导致物种灭绝。然而，尽管这一优雅的假说在35年前就已经发表，但从未被直接检验过。为了测试这一想法，我们需要一些技术，使我们能够直接从化石记录中推断出这一信息。花粉和孢子记录是古生物学家可以研究的最完整的时空记录之一。我们的提案提出了一个创新的框架，将利用这一记录来测试这些想法。在过去的十年里，我们的研究计划已经证明，花粉和孢子壁的化学成分受到亲本植物接收的光量的调节。这使我们能够利用孢子和花粉颗粒中的化学变化来追踪阳光在时间上的变化。在本应用程序中，我们将使用此技术来了解碰撞后光环境是如何变化的。通过在广泛的纬度范围内收集高分辨率样本，我们将能够限制尘埃云的时间和空间动力学，首次测试Alvarez团队提出的主要杀死机制。同时，将产生花粉和孢子记录中所代表的K/PG植被的新记录，以产生关于植被如何应对这一标志性的全球物种灭绝事件的广泛预测。我们将使用这一新记录来测试灭绝程度是否与影响冬季的严重程度有关，这是通过孢子化学的变化来衡量的。这一高分辨率的记录还将被用来通过物种灭绝事件推断植被动态的变化，并确定这种变化是如何随纬度变化的。具体地说，我们将能够测试关键的植物性状，如基因组大小或授粉策略(授粉昆虫的风)是否与北美K/PG地区的灭绝和/或生存有关。

In 1980 Luis Alvarez and colleagues published their ground breaking paper which linked the death of the dinosaurs along with numerous other species at the Cretaceous Palaeogene boundary to the impact of a large meteorite on the Earth's surface. The team proposed that the most likely kill mechanism was the development of a global dust cloud that reduced the amount of sun light reaching the Earth's surface causing global cooling and a reduction in photosynthesis. This would have culminated in a reduction in net primary productivity that would have cascaded up the food chain driving extinction. However, despite being published over 35 years ago this elegant hypothesis has never been directly tested. To test this idea we require techniques that allow us to directly infer this information from the fossil record. The pollen and spore record is one of the most complete temporal and spatial records available to palaeontologists to study. Our proposal sets outs an innovative framework that will use this record to test these ideas. Over the past decade our research programme has demonstrated that the chemical composition of the pollen and spore wall is regulated by the amount of light the parent plant receives. This allows us to use the chemical changes in spores and pollen grains to track sunshine through time. In this application we will use this technique to deliver an understanding of how post impact light environment changed. By collecting high resolution samples across a broad latitudinal range we will be able to constrain the temporal and spatial dynamics of the dust cloud, testing for the first time the major kill mechanism proposed by the Alvarez team. In parallel will generate new records of K/Pg vegetation as represented in the pollen and spore record to generate broad predictions about how vegetation responded to this iconic global extinction event. We will use this new record to test if the level of extinction is linked to the severity of the Impact winter as measured by changes in spore chemistry. This high resolution record will also then be used to infer changes in vegetation dynamics through the extinction event and determine how this changes with latitude. Specifically we will be able to test if key plant traits such as genome size or pollination strategy (wind of insect pollinated) were associated with extinction and/ or survivorship across the K/Pg in North America.