Wildfire Smoke Directly Changes Biogenic Volatile Organic Emissions and Photosynthesis of Ponderosa Pines

Wildfires are increasing across the USA. While smoke events affect human exposure and air quality, wildfire smoke effects on ecosystem-atmosphere interactions are poorly understood. We investigate smoke effects on biogenic volatile organic compound (VOC) emissions and photosynthesis for ponderosa pines. During several wildfire smoke events, we observed photosynthetic reduction with evidence for stomatal plugging and changes in leaf-level uptake and emission of both biogenic and wildfire VOCs. During intense smoke events, photosynthesis and VOC emissions were almost entirely suppressed, but increased dramatically upon stomatal opening. We propose four types of VOC responses to this burst in stomatal opening: post-burst emissions, pulsed emissions, surge emissions, and post-burst uptake. Our observations suggest that wildfire smoke can affect plant physiology and leaf-atmosphere gas exchange. Wildfires are becoming more prevalent in the United States. Wildfire smoke affects human health and air quality, but we know little about how smoke interacts with plants, or the subsequent feedback with the atmosphere. We present results from a field experiment during which smoke repeatedly spread across a pine forest. We measured smoke-induced changes in plant physiology (namely photosynthesis) and a suite of chemical emissions. During prolonged periods of intense smoke, we found that both photosynthesis and leaf emissions of chemical compounds decreased. When we induced photosynthesis, we observed a burst of different chemicals and identified several different pathways for these chemical releases. Further analyses suggest that smoke intensity and exposure may change the known relationship between emissions and temperature. Wildfire smoke interacts with stomates and leaf surfaces, suppressing photosynthesis and stomatal conductance Intense smoke can alter emissions and uptake of biogenic and other volatile organic compounds through three mechanisms The effects of wildfires on photosynthetic capacity and leaf emissions appear proportional to the intensity and duration of smoke events