Fire, Atmospheric pCO2, and Climate as Alternative Primary Controls of C4-Grass Abundance: The Late-Quaternary Perspective

草占主导地位的生态系统覆盖了地球陆地表面的三分之一，影响着全球生物地球化学过程（例如水，碳和营养循环），并作为人类和食草动物的主要食物来源。 这些生态系统对未来气候和大气化学变化最为敏感。 这种敏感性可以部分归因于两个主要功能组，C3和C4植物的不同反应。 C4植物在某些环境条件下（如火、热、干旱和低pCO 2）获得竞争优势。 C3和C4植物反过来对主要的生物地球化学过程有不同的影响;例如，C4植物在全球净初级生产中的作用大得不成比例。 尽管有这些众所周知的差异，它仍然是有争议的环境因素直接控制C3和C4植物的相对丰度。 古生态学研究可以帮助解释C3和C4植物对各种环境条件的反应，从而为预测未来的变化提供信息。 该项目将评估过去25，000年来东非和澳大利亚火灾，气候和大气CO2浓度对C4草丰度变化的影响。 研究人员将分析一套生态代用指标的沉积物岩心，并开发一种新技术来估计地质记录中C4植物的丰度。该项目为教育公众了解气候变化和草原生态提供了极好的背景。研究人员将组织针对初中和高中教师以及土地管理人员的暑期课程。

Grass-dominated ecosystems cover about one-third of Earth's land surface, influence global biogeochemical processes (e.g. water, carbon, and nutrient cycling), and serve as major food sources for humans and herbivores. These ecosystems are among the most sensitive to future changes in climate and atmospheric chemistry. This sensitivity can be partially attributed to the differential responses of two major functional groups, C3 and C4 plants. C4 plants gain competitive advantages under certain environmental conditions (e.g. fire, heat, drought, and low pCO2). C3 and C4 plants in turn have distinct influences on major biogeochemical processes; for example, the role of C4 plants in global net primary production is disproportionately large. Despite these well-known differences, it remains controversial what environmental factors directly control the relative abundances of C3 and C4 plants. Paleoecological studies can help decipher the responses of C3 and C4 plants to a wide range of environmental conditions, thereby offering information for anticipating future changes. This project will evaluate the effects of fire, climate, and atmospheric CO2 concentration on the variation of C4-grass abundance over the past 25,000 years in East Africa and Australia. The researchers will analyze sediment cores for a suite of ecological proxy indicators and develop a novel technique to estimate the abundance of C4 plants in geological records. This project provides an excellent context for educating the general public on climate change and grassland ecology. The researchers will organize summer courses targeting middle and high school teachers as well as land managers.