On mature reflection: Ozone damage can be detected in oak trees by hyperspectral reflectance

At the near-surface, ozone (O₃) is a toxic pollutant which has reached dangerously high concentrations across the world and is predicted to continue to rise. O₃ reduces the growth, productivity and resilience of trees but the extent of O₃ damage to forests is uncertain. To develop a high throughput method of monitoring O₃ damage to forests, we pioneer hyperspectral monitoring of O₃ damage in adult oak trees across a range of naturally occurring O₃ concentrations. Using a machine learning approach, we demonstrate accurate prediction of O₃ exposure of trees from hyperspectral leaf reflectance alone. This method could be used for forest level assessments of O₃ damage. Vegetation indices characterising green reflectance and red-edge track O₃ induced changes in leaf reflectance. Vegetation indices have the potential to scale up O₃ damage monitoring across spatial scales. As O₃ concentrations continue to rise globally, understanding the extent of O₃ damage to forests is crucial to effectively harness the carbon sequestration potential of forests. We demonstrate the exciting potential of spectral monitoring of O₃ damage in mature trees under natural conditions.