Biodiversity matters in feedbacks between climate change and air quality: a study using an individual‐based model

Abstract

Air quality is closely associated with climate change via the biosphere because plants release large quantities of volatile organic compounds (VOC) that mediate both gaseous pollutants and aerosol dynamics. Earlier studies, which considered only leaf physiology and simply scale up from leaf-level enhancements of emissions, suggest that climate warming enhances whole forest VOC emissions, and these increased VOC emissions aggravate ozone pollution and secondary organic aerosol formation. Using an individual-based forest VOC emissions model, UVAFME-VOC, that simulates system-level emissions by explicitly simulating forest community dynamics to the individual tree level, ecological competition among the individuals of differing size and age, and radiative transfer and leaf function through the canopy, we find that climate warming only sometimes stimulates isoprene emissions (the single largest source of non-methane hydrocarbon) in a southeastern U.S. forest. These complex patterns result from the combination of higher temperatures' stimulating emissions at the leaf level but decreasing the abundance of isoprene-emitting taxa at the community level by causing a decline in the abundance of isoprene-emitting species (Quercus spp.). This ecological effect eventually outweighs the physiological one, thus reducing overall emissions. Such reduced emissions have far-reaching implications for the climate-air-quality relationships that have been established on the paradigm of warming-enhancement VOC emissions from vegetation. This local scale modeling study suggests that community ecology rather than only individual physiology should be integrated into future studies of biosphere-climate-chemistry interactions.

Gap models across micro- to mega-scales of time and space: examples of Tansley’s ecosystem concept

“…3e). These results strongly support the role of forest community in mediating the forest ecosystem responses to global change agents, pointing to the deficiency of PFT-based models in scaling up physiology directly and to the advantage of forest gap model in incorporating community processes (Wang et al 2016(Wang et al , 2018.…”

“…3) with this new micro-scale gap model. These studies clearly indicate the considerable roles of community-level processes in mediating ecosystem responses to environmental pressures (Wang et al 2016(Wang et al , 2018. For example, ozone, a secondary air pollutant that is harmful to both human health and plant activity, is assumed responsible for global-vegetationproductivity decline and land-carbon-sink reduction (Sitch et al 2007;Wang et al 2017b).…”

“…Current state-of-the-art gap models, e.g. UVAFME, are better positioned to tackle these problems of complexity (Wang et al 2016(Wang et al , 2017a(Wang et al , 2018. In contrast to models based on plant-functional types, a gap modelbased VOCs emission simulator is explicit in considering inter-specific emission variation and variation associated with vertical light change within canopy and tree crown (Fig.…”

“…Prior to and beyond the threshold, distinctive feedback mechanisms between climate and atmospheric chemistry mediated by forests may occur. Figures reproduced from Wang et al (2016Wang et al ( , 2017aWang et al ( , 2018 vegetation-disturbance dynamics but experiencing similar climate conditions.…”

Effects of a Detailed Vegetation Database on Simulated Meteorological Fields, Biogenic VOC Emissions, and Ambient Pollutant Concentrations over Japan

“…Moreover, vegetation is changing over time due to various factors including climate change. Such a dynamic change in vegetation should affect BVOC emissions [51]. It is necessary to gather more information and data to more precisely represent vegetation and resulting BVOC emissions in order to further improve model performance on meteorological fields and ambient pollutant concentrations.…”