Volatile organic compound emission in tundra shrubs - Dependence on species characteristics and the near-surface...

Temperature is one of the key abiotic factors during the life of plants, especially in the Arctic region which is currently experiencing rapid climate change. We evaluated plant traits and environmental variables determining leaf temperature in tundra shrubs and volatile organic compound (VOC) emissions with field measurements on deciduous tundra shrubs, Salix myrsinites and Betula nana, and evergreen Cassiope tetragona and Rhododendron lapponicum. Higher leaf-to-air temperature difference was observed in evergreen, compared to deciduous shrubs. Evergreen shrubs also showed continuously increasing photosynthesis with increasing temperature, suggesting high thermal tolerance. For the deciduous species, the optimum temperature for net photosynthesis was between our measurement temperatures of 24 °C and 38 °C. Air temperature and vapor pressure deficit were the most important variables influencing leaf temperature and VOC emissions in all the studied plants, along with stomatal density and specific leaf area in the deciduous shrubs. Using climate data and emission factors from our measurements, we modelled total seasonal tundra shrub VOC emissions of 0.3-2.3 g m^-2 over the main growing season. Our results showed higher-than-expected temperature optima for photosynthesis and VOC emission and demonstrated the relative importance of plant traits and local environments in determining leaf temperature and VOC emissions in a subarctic tundra.