Separating direct and indirect effects of rising temperatures on biogenic volatile emissions in the Arctic

Volatile organic compounds (VOCs) are released from biogenic sources in a
temperature-dependent manner. Consequently, Arctic ecosystems are expected
to greatly increase their VOC emissions with ongoing climate warming,
which is proceeding at twice the rate of global temperature rise. Here, we
show that ongoing warming has strong, increasing effects on Arctic VOC
emissions. Using a combination of statistical modelling on data from
several warming experiments in the Arctic tundra and dynamic ecosystem
modelling, we separate the impacts of temperature and soil moisture into
direct effects and indirect effects through vegetation composition and
biomass alterations. The indirect effects of warming on VOC emissions were
significant, but smaller than the direct effects. Furthermore, vegetation
changes also cause shifts in the chemical speciation of the emissions.
Both direct and indirect effects result in large geographic differences in
VOC emission responses in the warming Arctic, depending on the local
vegetation cover and the climate dynamics. Our results outline complex
links between local climate, vegetation, and ecosystem-atmosphere
interactions, with likely local-to-regional impacts on the atmospheric
composition.

挥发性有机物（Volatile organic compounds，VOCs）通过生物源排放，且排放过程具有温度依赖性。因此，在当前气候变暖（增速为全球平均气温上升速率的两倍）的背景下，北极生态系统的VOC排放量预计将大幅提升。本研究证实，持续变暖对北极VOC排放具有显著且持续增强的影响。研究结合北极苔原多项增温实验的统计建模数据与动态生态系统模型，将温度与土壤湿度的影响拆解为直接效应，以及通过植被组成和生物量改变介导的间接效应。变暖对VOC排放的间接效应虽显著，但强度低于直接效应。此外，植被变化还会引发排放物化学形态的改变。直接与间接效应共同使得变暖北极地区的VOC排放响应存在显著地理差异，该差异取决于当地的植被覆盖状况与气候动态。本研究结果揭示了局地气候、植被与生态系统-大气相互作用之间的复杂关联，其对大气组成的影响可能覆盖从局地到区域的多个尺度。