DataSheet1_Modulating effects of temperature on CO2-inhibited isoprene emissions in Eucalyptus urophylla.pdf

Terrestrial vegetation emits substantial amounts of highly reactive isoprene, significantly impacting atmospheric chemistry and climate change. Both atmospheric carbon dioxide (CO2) concentration and temperature can influence plant isoprene emissions; however, whether these factors have a synergistic effect remains unclear, particularly for tropical/subtropical plants. In this study, we conducted in-situ controlled experiments on Eucalyptus urophylla, a representative tropical/subtropical species, to investigate the seasonal variation in the response of isoprene emissions to CO2 concentrations (ISOP-CO2 response) and to identify potential controlling factors. The results showed that high CO2 exerts a nearly linear inhibitory effect on isoprene emissions, as indicated by the slope of the ISOP-CO2 response curve. This inhibitory effect exhibited evident seasonal changes, with stronger suppression during cooler seasons and weaker suppression during warmer seasons. This finding contrasts with the default ISOP-CO2 response in the MEGAN model, which ignored seasonal variation. Further analysis showed a significant correlation between the slope of the ISOP-CO2 response curve and growth temperature from the past 10 days, indicating that these metrics are effective indicators for predicting seasonal changes. Our findings reveal a synergistic mechanism between temperature and CO2 concentration effects on isoprene emissions. By coupling the effects of growth temperature with the ISOP-CO2 response, this mechanism can be integrated into models to provide more accurate predictions of future isoprene emissions, reducing prediction biases, especially during cooler seasons.

陆地植被可释放大量高反应性异戊二烯（isoprene），对大气化学与气候变化产生显著影响。大气二氧化碳（CO₂）浓度与温度均可影响植物异戊二烯排放，但二者是否存在协同效应仍不明确，针对热带/亚热带植物的相关研究尤其不足。本研究以典型热带/亚热带物种尾叶桉（Eucalyptus urophylla）为研究对象，开展原位控制实验，旨在探究异戊二烯排放对CO₂浓度的响应（ISOP-CO2 response）的季节变化特征，并识别潜在调控因子。研究结果表明，高CO₂浓度对异戊二烯排放几乎呈现线性抑制效应，该效应可通过ISOP-CO2响应曲线的斜率得以表征。该抑制效应表现出显著的季节变化：低温季节的抑制作用更强，温暖季节的抑制作用则较弱。该发现与MEGAN模型中默认的ISOP-CO2响应方案相悖，该方案未考虑季节变化因素。进一步分析显示，ISOP-CO2响应曲线的斜率与过去10日的生长温度存在显著相关性，表明这两项指标可作为预测季节变化的有效指标。本研究结果揭示了温度与CO₂浓度对异戊二烯排放的协同影响机制。通过将生长温度效应与ISOP-CO2响应进行耦合，该机制可被整合至现有模型中，从而更精准地预测未来异戊二烯排放量，降低预测偏差，尤其在低温季节效果更为显著。