Final Report Summary - SIP-VOL+ (Stress-Induced Plant Volatiles in Biosphere-Atmosphere System)
The overall impact of plant-emitted trace gas (BVOC) emissions on large-scale Earth processes is poorly understood. Particularly limited is the understanding of how plant stress-elicited volatiles contribute to the formation of ozone, secondary organic aerosols (SOA) and cloud condensation nuclei (CCN) and what is the effect of these emissions on air quality and Earth radiative balance and climate. The current project had the overall objective to evaluate the effect of plant-generated BVOC emissions on air composition and environment under global change, with particular emphasis on the role of BVOC induced upon environmental and biological stresses. The study first time quantified the BVOC production vs. stress severity relationships across species with differing stress tolerance and demonstrated that stress responsiveness is a novel key driver of plant physiological performance that drives the response of vegetation trace gas release to environmental stresses and to biotic impacts. A novel quantitative model to simulate induction and release of BVOC under different stresses was developed and scaled up to regional and global scales to assess the contribution of induced emissions to overall BVOC budget, and ozone, SOA, and CCN formation. The analysis demonstrates that plant BVOC emission capacity has been significantly underestimated so far and that consideration of induced emissions profoundly alters current estimates of vegetation BVOC production, often several-fold for compounds most potent in SOA and CCN formation. The analysis demonstrated that in many Earth regions, existing SOA and CCN formation and growth rates cannot be explained without stress-induced emissions. Ultimately, the analysis demonstrates existence of key novel feedbacks between stress, SOA and CCN formation and the Earth climate, indicating that the role of plants in Earth system has been much underestimated.