Enhanced Photosynthesis and Transpiration in an Old Growth Forest Due To Wildfire Smoke

Abstract

AbstractWe document the response of a 2 day wildfire smoke event on a moist temperate coniferous old‐growth forest in the western U.S. Wildfire smoke increased air temperature and suppressed relative humidity and total incoming radiation. Despite these conditions a ∼10% increase in ecosystem photosynthesis was observed. This was explained by a large increase (41%) in ecosystem‐scale stomatal conductance, inferred from measurements of carbonyl sulfide. Increased stomatal conductance contradicts expected stomatal closure at high vapor pressure deficit and was likely caused by an increase in diffuse light and thus shade leaf insolation. Higher ecosystem productivity and transpiration were linked to a greater drawdown of soil moisture. Ecosystem‐scale measurements across a diverse range of ecosystems are needed to better understand the canopy response to wildfire smoke, which is an increasingly common phenomenon across large parts of the world, including the forests of western North America.