Lee Jones Anna, Gardner Anna, Hayes Felicity, Pfrang Christian, Jeffers Elizabeth S
Department of Biology, University of Oxford, South Parks Road, Oxford, OX1 3SZ UK.
Department of Plant Sciences, University of Cambridge, Cambridge, UK.
Trees (Berl West). 2025;39(4):69. doi: 10.1007/s00468-025-02650-w. Epub 2025 Jul 10.
Experimentally elevated CO does not significantly alter the overall leaf reflectance of mature , but increases Plant Senescence Reflectance Index (PSRI) suggesting a change in the ratio of chlorophyll to carotene content. Rising atmospheric CO concentrations, driven by anthropogenic emissions, are projected to reach 550 ppm by 2050. Elevated CO (eCO) is expected to have a fertilisation effect on forests, influencing productivity, water relations, and phenology. However, the impact of eCO on leaf reflectance in mature forests remains poorly understood, despite its critical role in radiative transfer processes and remote sensing of forest health. Utilising the Birmingham Institute of Forest Research (BIFoR) Free-Air CO Enrichment (FACE) experiment, we investigated the hyperspectral leaf reflectance of 180-year-old L. trees exposed to eCO for 7 years. Our results demonstrate that overall leaf reflectance under eCO is similar to that of leaves exposed to ambient CO, but the Plant Senescence Reflectance Index (PSRI) is significantly higher under eCO. This index relates to the ratio of foliar chlorophyll and carotene pigments. These findings suggest that reflectance will not significantly shift under future CO conditions, but the relative content of pigments will change, altering the reflectance of specific wavelengths and providing insights into the leaf level physiological and phenological responses of mature trees to eCO.
实验性升高的二氧化碳浓度并不会显著改变成熟叶片的整体反射率，但会增加植物衰老反射指数（PSRI），这表明叶绿素与类胡萝卜素含量的比例发生了变化。由人为排放驱动的大气二氧化碳浓度预计到2050年将达到550 ppm。预计升高的二氧化碳（eCO）会对森林产生施肥效应，影响生产力、水分关系和物候。然而，尽管eCO在辐射传输过程和森林健康遥感中起着关键作用，但人们对其对成熟森林叶片反射率的影响仍知之甚少。利用伯明翰森林研究所（BIFoR）的自由空气二氧化碳富集（FACE）实验，我们研究了暴露于eCO 7年的180年树龄的L.树的高光谱叶片反射率。我们的结果表明，eCO条件下的整体叶片反射率与暴露于环境二氧化碳的叶片相似，但eCO条件下的植物衰老反射指数（PSRI）显著更高。该指数与叶片叶绿素和类胡萝卜素色素的比例有关。这些发现表明，在未来的二氧化碳条件下，反射率不会显著变化，但色素的相对含量会改变，从而改变特定波长的反射率，并为成熟树木对eCO的叶片水平生理和物候反应提供见解。
