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，臭氧是一种重要的人为温室气体，也是一种空气污染物，每年造成数十亿英镑的植物生产力损失。自1850年以来，由于车辆、工业过程和森林燃烧产生的化学物质排放，地表臭氧翻了一番。热带生态系统占全球植物生产力的近一半，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。在人口不断增长的同时，我们看到城市化和高强度农业区的臭氧前体排放也在扩大。甘蔗是一种重要的热带和生物能源作物，为制糖、乙醇(生物燃料)和能源生产提供原料，为S和巴西的生物经济做出了贡献。虽然巴西甘蔗产量的一半以上来自S保罗州，但甘蔗衍生产品占巴西能源总量的17%。在全球范围内，生物燃料生产是一种主要的陆基碳中和方法，可以减少我们对化石燃料的依赖，从而帮助社会实现将气候变化限制在20摄氏度以下的具有挑战性的巴黎协议。在过去的20年里，SP州经历了将牧场(天然C4草)大规模转变为甘蔗田。同时，空气质素量度显示大部分悬浮粒子的臭氧浓度高于已知对植物有害的水平。这项计划将利用我们位于澳大利亚凯恩斯的独特热带实验设施，首次全面测量臭氧对热带草本植物功能和生长的影响，这些热带草本植物包括栽培的(例如甘蔗)和天然的(例如用作牧场)。在这里，我们将热带牧草暴露在不同水平的臭氧中，以得出臭氧剂量和生产力损失之间的关系。此外，我们还将调查干旱对热带草地臭氧敏感性的影响。最后，我们将利用这些信息来评估巴西南部地区臭氧浓度和土地覆盖变化(从天然C4牧场到甘蔗)的影响，并与来自政策和学术界的相关利益攸关方进行接触。

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.