Impacts of air pollution on productivity of natural and cultivated tropical C4 grasses: implications in the face of land use change in Brazil

在低层大气中，臭氧（O3）是一种重要的人为温室气体，是一种空气污染物，每年造成数十亿磅的植物生产力损失。自1850年以来，由于车辆、工业过程和森林燃烧的化学排放，地表O3增加了一倍。热带生态系统负责全球近一半的植物生产力，正是在这些热带地区，我们可能会看到本世纪人类人口的最大扩张。随着人口的增长，我们看到城市化和高密度农业地区的O3前体排放量增加。甘蔗是一种重要的热带和生物能源作物，为糖，乙醇（生物燃料）和能源生产提供原料，并为圣保罗州（SP）和巴西的生物经济做出贡献。虽然圣保罗州负责巴西一半以上的甘蔗生产，但甘蔗衍生产品占巴西能源矩阵的17%。在全球范围内，生物燃料生产是一种主要的陆地碳中和方法，可以减少我们对化石燃料的依赖，从而帮助社会实现具有挑战性的巴黎雅阁，将气候变化限制在2 ℃以下。在过去的二十年中，SP州经历了大规模的牧场（天然C4草）转化为甘蔗田。与此同时，空气质量测量表明，在大部分的SP以上的O3浓度是已知的对plants.This项目将使第一个全面的测量O3对植物功能和生长的热带草，无论是栽培（如甘蔗）和自然（如用作牧场）使用我们独特的热带实验设施在澳大利亚凯恩斯。在这里，我们将热带草暴露在不同水平的臭氧中，以获得O3剂量和生产力损失之间的关系。最后，我们将利用这些信息来评估区域O3浓度和巴西南部土地覆盖变化（从天然C4牧场到甘蔗）的影响，并与政策和学术界的相关利益相关者进行接触。

In the lower atmosphere ozone (O3) is an important anthropogenic greenhouse gas and is an air pollutant responsible for several billion pounds in lost plant productivity each year. Surface O3 has doubled since 1850 due to chemical emissions from vehicles, industrial processes, and the burning of forests. Tropical ecosystems are responsible for nearly half of global plant productivity and it is in these tropical regions that we are likely to see the greatest expansion of human populations this century. Alongside this growing population, we see the expansion of O3 precursor emissions from urbanization and high-intensity agricultural areas. Sugarcane is an important tropical and bioenergy crop, supplying raw material for sugar, ethanol (biofuel) and energy production and contributes to the bioeconomy of both São Paulo state (SP) and Brazil. While the São Paulo state is responsible for over half of Brazilian sugarcane production, sugarcane-derived products account for 17% of the Brazilian energy matrix. In a global context, biofuel production is one major land-based carbon-neutral approach to reduce our reliance on fossil fuels, and thus help society to achieve the challenging Paris accord of limiting climate change to below 2oC.Over the two last decades, SP state has experienced large-scale conversion of pasture (natural C4 grass) to sugarcane fields. At the same time air quality measurements demonstrate O3 concentrations across much of SP above those known to be harmful to plants.This project will make the first comprehensive set of measurements of O3 effects on plant functioning and growth in tropical grasses, both cultivated (e.g. sugarcane) and natural (e.g. used as pasture) using our unique tropical experimental facility in Cairns, Australia. Here we expose tropical grasses to different levels of ozone, to derive relationships between O3 dose and productivity loss. In addition, we investigate the role of drought on the O3 sensitivity of tropical grasses.Finally, we will use this information to assess the impact of regional O3 concentrations and changing land-cover (from natural C4 pasture to sugarcane) for southern Brazil and engage with relevant stakeholders from both policy and academia.