Estimates of biomass reductions of ozone sensitive herbaceous plants in California
Citation:
Kaylor, S. Douglas, S. Snell Taylor, AND J. Herrick. Estimates of biomass reductions of ozone sensitive herbaceous plants in California. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, Netherlands, 878:163134, (2023). https://doi.org/10.1016/j.scitotenv.2023.163134
Impact/Purpose:
In order to evaluate ozone effects on herbaceous plants, we asked the following questions: given a set of known ozone-sensitive plant species which are found within California, what are the likely growth declines at recent ozone levels? Are there substantial risks to nonwoody plants from recent levels of ozone exposure in California? Based on these projections, what areas of the state have the greatest risk of biomass loss? We combined EPA ozone monitoring data from 2016 with published exposure-response relationships from controlled exposure experiments for twenty herbaceous plant species occurring in California. County-wide ozone exposure estimations were then combined with published exposure response functions for focal plants, and maps were created to estimate ozone-induced growth losses in the counties where the plants occur. The herbaceous species had estimated annual growth losses from < 1% to > 20% based on exposure levels and sensitivity. Of the 20 plant species, 17 had predicted biomass loss greater than 5% in at least one county, emphasizing the vulnerability of herbaceous species at recent ozone concentrations. Areas with greatest risk are determined by the occurrence of sensitive species, and these are mapped within the paper. Risk could be of particular concern for annuals damaged by a single year of ozone exposure. Regional partners as well as other government agencies like NPS could use this work to inform monitoring and protection efforts.
Description:
Exposure to tropospheric ozone pollution impairs photosynthesis and growth in plants and this can have consequences for ecosystems. However, exposure-response research in the United States (U.S.) has historically focused on trees and crops, and less attention has been given to non-crop herbaceous species. We combined U.S. Environmental Protection Agency ozone monitoring data from the entirety of 2016 with published exposure-response relationships from controlled exposure experiments for twenty herbaceous plant species occurring in California. The U.S. Department of Agriculture PLANTS database was used to identify county-level occurrence data of these plant species. A kriged ozone exposure surface for 2016 was generated using data from monitoring stations in California and surrounding states, using Accumulated Ozone exposure over a Threshold of 40 ppb (AOT40) as an exposure metric. County-wide ozone exposure estimations were then combined with published exposure response functions for focal plants, and maps were created to estimate ozone-induced growth losses in the counties where the plants occur. Plant species had estimated annual growth losses from <1 % to >20 % based on exposure levels and sensitivity. Of the 20 species, 17 had predicted biomass loss >5 % in at least one county, emphasizing the vulnerability of herbaceous species at recent ozone concentrations. Butte, Nevada, Plumas, San Luis Obispo, and Shasta Counties, an area of about 31,652 km2, had the highest number of species (6) with >10 % estimated biomass loss, the loss threshold for European critical levels. White clover (Trifolium repens L.) was one of the most affected species with more than an estimated 10% annual estimated growth loss over 59% of the state. Overall, these estimated growth losses demonstrate potential for shifts in plant communities and negative effects on ecosystems. This study addresses critical policy needs for risk assessments on herbaceous species in a single year of ozone exposure.
URLs/Downloads:
DOI: Estimates of biomass reductions of ozone sensitive herbaceous plants in California