Ozone affects plant, insect, and soil microbial communities: A threat to terrestrial ecosystems and biodiversity

Elevated tropospheric ozone concentrations induce adverse effects in plants. We reviewed how ozone affects (i) the composition and diversity of plant communities by affecting key physiological traits; (ii) foliar chemistry and the emission of volatiles, thereby affecting plant-plant competition, plant-insect interactions, and the composition of insect communities; and (iii) plant-soil-microbe interactions and the composition of soil communities by disrupting plant litterfall and altering root exudation, soil enzymatic activities, decomposition, and nutrient cycling. The community composition of soil microbes is consequently changed, and alpha diversity is often reduced. The effects depend on the environment and vary across space and time. We suggest that Atlantic islands in the Northern Hemisphere, the Mediterranean Basin, equatorial Africa, Ethiopia, the Indian coastline, the Himalayan region, southern Asia, and Japan have high endemic richness at high ozone risk by 2100

Ozone affects plant, insect, and soil microbial communities: a threat to terrestrial ecosystems and biodiversity

Elevated tropospheric ozone concentrations induce adverse effects in plants. We reviewed how ozone affects (i) the composition and diversity of plant communities by affecting key physiological traits; (ii) foliar chemistry and the emission of volatiles, thereby affecting plant-plant competition, plant-insect interactions, and the composition of insect communities; and (iii) plant-soil-microbe interactions and the composition of soil communities by disrupting plant litterfall and altering root exudation, soil enzymatic activities, decomposition, and nutrient cycling. The community composition of soil microbes is consequently changed, and alpha diversity is often reduced. The effects depend on the environment and vary across space and time. We suggest that Atlantic islands in the Northern Hemisphere, the Mediterranean Basin, equatorial Africa, Ethiopia, the Indian coastline, the Himalayan region, southern Asia, and Japan have high endemic richness at high ozone risk by 2100

The fingerprint of tropospheric ozone on broadleaved forest vegetation in Europe

Tropospheric ozone (O3) increased globally in the 20th century, contributes to climate change and can have adverse effects on terrestrial ecosystems. The response of forest vegetation to ozone is modulated by species- and site-specific factors and visible foliar symptoms (VFS) are the only direct evidence of ozone effects on vegetation. VFS have been observed and reproduced under (semi-) controlled conditions and their field assessment has been largely harmonized in Europe. We analyzed ozone concentration and VFS data as measured at (respectively) 118 and 91 intensive monitoring sites of the International Co-Operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) spanning over five European biogeographic regions from 2005 to 2018. Average values for VFS were calculated accounting for the number of species present and their observed frequency. Spatial and temporal variation of ozone concentrations, VFS, and their relationships across Europe were then investigated by applying Generalized Linear Mixed Models (GLMMs) and combined GLMMs. Ozone concentrations exceeded 40 ppb on 37.3 % of the sites and were significantly higher (p < 0.05) in the Alpine and the Mediterranean regions. Over the 2005–2018 period there was a substantial stagnation of ozone concentrations with a tendency towards decreasing values in the Alpine-Boreal sites and increasing values in the Atlantic sites. Ozone left a “fingerprint” in terms of VFS on 38 % of the observed broadleaved woody species across Europe, with no significant difference among biogeographic regions. Overall, and again with the exception of an increase at the Atlantic sites, the frequency of VFS remained unchanged or has been slightly declining over the investigated period. We found positive relationship between ozone concentrations and VFS across Europe (p < 0.05), while their temporal trends (both insignificant) were not related. The species with the highest frequency of VFS were those classified as sensitive species under controlled/semi-controlled experimental conditions. Frequency of VFS tends to be modulated by vegetation traits such as specific leaf area and leaf thickness (p < 0.10). Our results showed that, although ozone levels suggested a North-to-South gradient of increasing potential risk to vegetation with hot spots in the Alps and in the Mediterranean, VFS observed on the actual species assemblage at the sites modifies this picture. According to frequency of VFS, ozone risk for vegetation may be higher in parts of the Alpine and Continental Europe than in the Mediterranean regio

Strategic roadmap to assess forest vulnerability under air pollution and climate change

Although it is an integral part of global change, most of the research addressing the effects of climate change on forests have overlooked the role of environmental pollution. Similarly, most studies investigating the effects of air pollutants on forests have generally neglected the impacts of climate change. We review the current knowledge on combined air pollution and climate change effects on global forest ecosystems and identify several key research priorities as a roadmap for the future. Specifically, we recommend (1) the establishment of much denser array of monitoring sites, particularly in the South Hemisphere; (2) further integration of ground and satellite monitoring; (3) generation of flux-based standards and critical levels taking into account the sensitivity of dominant forest tree species; (4) long-term monitoring of N, S, P cycles and base cations deposition together at global scale; (5) intensification of experimental studies, addressing the combined effects of different abiotic factors on forests by assuring a better representation of taxonomic and functional diversity across the similar to 73,000 tree species on Earth; (6) more experimental focus on phenomics and genomics; (7) improved knowledge on key processes regulating the dynamics of radionuclides in forest systems; and (8) development of models integrating air pollution and climate change data from long-term monitoring programs.</p

Commentary: EPA's proposed expansion of dose-response analysis is a positive step towards improving its ecological risk assessment

The United States Environmental Protection Agency (US EPA) has recently proposed changes to strengthen the transparency of its pivotal regulatory science policy and procedures. In this context, the US EPA aims to enhance the transparency of dose-response data and models, proposing to consider for the first time non-linear biphasic dose-response models. While the proposed changes have the potential to lead to markedly improved ecological risk assessment compared to past and current approaches, we believe there remain open issues for improving the quality of ecological risk assessment, such as the consideration of adaptive, dynamic and interactive effects. Improved risk assessment including adaptive and dynamic non-linear models (beyond classic threshold models) can enhance the quality of regulatory decisions and the protection of ecological health. We suggest that other countries consider adopting a similar scientific-regulatory posture with respect to dose-response modeling via the inclusion of non-linear biphasic models, that incorporate the dynamic potential of biological systems to adapt (i.e., enhancing positive biological endpoints) or maladapt to low levels of stressor agents