RUI/Collaborative Research: The Rise of C4 Grasses in South America: Linking Grassland Transitions to the South American Summer Monsoon

草覆盖了地球的大部分地区，为人类提供了许多主食。然而，关于草原将如何应对环境变化存在相当大的分歧，作物生产力、物种入侵和生物多样性的潜在戏剧性变化仍然未知。如果不确切了解过去导致暖季草传播的气候条件，很难预测它们未来将如何反应。数百万年前中新世草的地理范围的显著扩大是本研究的重点。该项目是第一个收集南美洲中新世降水和植被数据并用它来模拟这一重要生态变化期间的古代气候的项目。这一结果使人们对暖季牧草的丰富度如何随着未来的环境变化而变化有了新的理解。C4牧草的扩张是过去6500万年来最戏剧性的生态变化之一。为了预测这些经济上重要的牧草将如何对未来的环境变化做出反应，必须了解控制它们过去分布的因素。在南美洲，C4草的扩张与南美夏季风的加强和区域构造变化相一致。该项目将多代理古植被重建与基于代理的古气候重建和古气候建模技术相结合，以了解南美洲构造、气候和环境变化之间的联系。这些结果使人们对C4草生长的条件有了新的理解。这项研究的社会效益包括能够更好地预测自然和管理景观中C4草的丰度如何随着未来的环境变化而变化。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Grasses cover a large portion of the Earth and provide many staple foods for humanity. However, there is considerable disagreement on how grasslands will respond to environmental change, and the potentially dramatic changes to crop productivity, species invasions, and biodiversity remain unknown. Without a firm understanding of the climatic conditions that caused the spreading of warm-season grasses in the deep past, it is difficult to predict how they will respond in the future. The significant enlargement of grasses' geographic range millions of years ago during the Miocene is the focus of this study. This project is the first to collect data on precipitation and vegetation during the Miocene in South America and to use it to make simulations of ancient climate during this important ecological change. Results are leading to new understanding about how the abundance of warm-season grasses may change in natural and managed landscapes in response to future environmental changes.The Late Miocene expansion of C4 grasses is one of the most dramatic ecological changes in the past 65 million years. In order to predict how these economically important grasses will respond to future enviornmental change, the factors controlling their past distributions must be understood. In South America, C4 grass expansion was coincident with a strengthening of the South American Summer Monsoon and regional tectonic changes. This project is combining multi-proxy paleovegetation reconstructions with proxy-based paleoclimatic reconstructions and paleoclimatic modeling techniques to understand the linkages between tectonics, climate, and environmental change in South America. Results are leading to new understanding of the conditions under which C4 grasses expanded. A societal benefit of this research includes the ability to make better predictions for how the abundance of C4 grasses may vary in natural and managed landscapes in response to future environmental changes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.