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

草覆盖了地球的很大一部分，为人类提供了许多主食。然而，关于草原如何应对环境变化，以及对作物生产力、物种入侵和生物多样性的潜在巨大变化，人们仍存在相当大的分歧。如果对导致暖季草在过去蔓延的气候条件没有明确的了解，就很难预测它们在未来的反应。数百万年前中新世期间草类地理范围的显著扩大是本研究的重点。该项目首次收集了南美洲中新世降水和植被数据，并利用这些数据模拟了这一重要生态变化期间的古代气候。研究结果使人们对自然和人工管理景观中暖季草的丰度如何随着未来环境变化而变化有了新的认识。中新世晚期C4草的扩张是过去6500万年中最引人注目的生态变化之一。为了预测这些具有重要经济意义的禾草将如何应对未来的环境变化，必须了解控制它们过去分布的因素。在南美洲，C4草的扩张与南美洲夏季风的增强和区域构造变化是一致的。本项目将多代古植被重建与代古气候重建和古气候模拟技术相结合，以了解南美洲构造、气候和环境变化之间的联系。研究结果对C4禾本科植物生长的条件有了新的认识。这项研究的一个社会效益包括能够更好地预测C4草的丰度在自然和管理景观中如何因应未来的环境变化而变化。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.