**Contents**

#### **About the Editors**

**Evgenios Agathokleous** graduated from Agricultural University of Athens (AUA), Greece, in February 2013 with a Diploma in Agriculture (equivalent to the Anglo-Saxon MSc in Agricultural Science). As a scholar of the Government of Japan, he continued his studies at Hokkaido University in Sapporo, Japan. From April to September 2014, he was a Research Student at the Research Faculty of Agriculture. From October 2014, he was a PhD student at the same School. He graduated from the Special Postgraduate Program in Biosphere Sustainability Science with a PhD in Environmental Resources in March 2017. During the period April 2017–March 2019, he was an International Research Fellow of the Japan Society for the Promotion of Science, hosted by Forestry and Forest Products Research Institute. At the same time, he was a Researcher at the Research Faculty of Agriculture of Hokkaido University. Since April 2019, he has served as Full Professor at the School of Applied Meteorology at Nanjing University of Information Science and Technology in Nanjing, China. His research concerns the dose–response relationship and its mechanisms. He has so far published around 90 articles in prestigious international scientific journals, including about 50 as first author. Some of his papers are published in journals with an impact factor in the range 12–20 (e.g., Nano Today, Science Advances, Trends in Plant Science, Trends in Pharmacology), and including invited papers in several journals. He has also authored 10 book chapters, of which 9 are international. His resume includes 34 oral and 49 poster presentations; almost all delivered at international conferences. He has been honored with the Outstanding New Investigator 2018 award of the International Dose–Response Society for his research on hormesis. He has been involved in large-scale research funding, with a significant portion of it ensured either as a fellow or as a Principal Investigator of projects. He has reviewed 390 papers for 62 SCI journals. He is Associate Editor-in-Chief of the Journal of Forestry Research (Springer) and Editor of Science of the Total Environment (Elsevier), Plant Stress (Elsevier), Climate (MDPI), Frontiers in Forests and Global Change (Frontiers), and Sci (MDPI).

**Elisa Carrari** started her academic studies at the Agriculture faculty of the University of Florence (Italy) where she graduated in 2012 in Science and Technology of Forest Systems. In 2016, she received her PhD in Plant, Microbiology, and Genetic Science and Technology, with the certification of Doctor Europaeus from the same university in co-supervision with the University of Ghent (Belgium). She was declared expert in "Biodiversity of Forest Vegetation" by the University of Florence for the Academic year 2015–2016. She is now contract Professor in Applied Botany at the University of Florence. Currently, she is also working in the managemen<sup>t</sup> and protection of historic gardens using innovative approaches (remote sensing) to face stresses deriving from climate change. She was project manager of the LIFE MOTTLES project on ozone effect on forest ecosystems and responsible of the MOTTLES European network for the protection of forests from ozone. From 2014 to 2018, she was External Research Associate at the ForNaLab of Ghent University. She has completed numerous Postdoctoral Fellowships at various research institutes, e.g., for the "Monitoring the Ozone injuries on Forests" at the Institute of Sustainable Plant Protection, National Research Council of Italy (CNR) from 2016 to 2020, for the "Analyses of the Forest Biodiversity Related to Biotic and Abiotic Factors" from 2015 to 2016 and for the "Phytosanitary Monitoring of Sporadic Species under Biotic Threats" in 2013 at the Department of Agricultural and Environmental Production of Unifi. She is author of 29 articles published in SCI journals, 19 oral contributions, and 31 posters at national and

international conferences.

**Pierre Sicard** PhD in Atmospheric Chemistry, is working on air pollution and climate change impacts on forests ecosystems to reduce the risk for plant ecosystems by using integrated assessment modeling, deposition model, epidemiological studies, and statistical and multivariate analysis. He is involved in numerous national and EU-funded projects as coordinator (e.g., FO3REST, AIRFRESH) or as Principal Investigator or on the steering committee (e.g., MOTTLES). He also has experience in assessment of air pollution impacts on human health (AirQ model) and developed the Aggregate Risk Index. He is very active in communication serving as Deputy Coordinator of the RG 8.04.00 "Air Pollution & Climate Change" under the International Union of Forest Research Organizations (IUFRO); involved as UNECE Expert Panel on Clean Air in Cities and active in the EU Clean Air Forum; member of the Editorial Board of journals (Environmental Research, Climate, Frontiers in Forests and Global Change); member of the scientific committee of meetings; and has published >60 papers and has a h-index of 26. He is also involved as Regional Expert Group on Climate in "Provence-Alpes-Cote d'Azur" region. ˆ

#### *Editorial* **SI: Air Pollution and Plant Ecosystems**

#### **Evgenios Agathokleous 1,\*, Elisa Carrari 2 and Pierre Sicard 3**


Received: 30 July 2020; Accepted: 4 August 2020; Published: 9 August 2020

**Abstract:** Air pollution continues to be a serious issue for plant health and terrestrial ecosystems. In this issue of climate, some papers relevant to air pollution and its potential impacts on plant health and terrestrial ecosystems are collated. The papers provide some new insights and offer the opportunity to further advance the current understandings of air pollution and its linked impacts at different levels.

**Keywords:** air pollution; carbon dioxide; ethylenediurea; gross primary production; plant protection; tropospheric ozone; plant ecosystems

#### **1. Introduction**

Air pollution, and especially ground-level ozone (O3) pollution, is a major issue for vegetation, challenging scientific and regulatory communities in a continuing effort to better understand air pollution and its impacts on vegetation [1–3]. Notable research progress has been observed over recent decades, highly advancing our understandings of air pollution spatiotemporal characteristics and trends [4–6] as well as air pollution effects on plants, from the molecular level to communities and ecosystems [1–3,7–9]. While air pollution spatiotemporal patterns and trends became clearer and air pollution impacts better understood, a vast array of these research programs suggests that there is still much to accomplish. Recognizing the need for more research in these topics, a Special Issue on "Air Pollution and Plant Ecosystems" is published in *Climate*. This Editorial presents the collective findings in the papers published in the *Climate* Special Issue "Air Pollution and Plant Ecosystems".

#### **2. Special Issue Content**

A total of 11 papers were submitted for potential publication within the Special Issue. Finally, six papers have been accepted for publication [10–15], translating to an acceptance rate of about 55%.

Fumagalli et al. [10] exposed grapevine (*Vitis vinifera*) to different O3 levels over two growing seasons and revealed that high O3 levels affected grapevine weight and yields. Their study suggests that wine quality can be affected by reduced polyphenols that can decrease the nutritional value of the agricultural product and induce a more aggressive taste to wine. This project provides evidence of potential O3 impacts on the quality of grapes and wine, encouraging the implementation of further studies to examine the potential effects on animals consuming such products altered by O3.

Tobita et al. [11] exposed *Fagus crenata* plants to ambient air, elevated CO2 (550 μmol mol−<sup>1</sup> CO2), elevated O3 (2 × ambient O3), and elevated CO2 combined with elevated O3 during two growing seasons. They found that the total plant biomass and elongation of second-flush shoots were increased more by elevated CO2 combined with elevated O3, and less by elevated CO2 alone. Both elevated O3 and elevated CO2, as single stresses, decreased biomass allocation to the roots. This research suggests that elevated concentrations of CO2 mitigate the negative impacts of O3 on net CO2 assimilation.

Kitao et al. [12] analyzed the fate of absorbed light energy, including photosynthesis, photorespiration, and regulated and nonregulated nonphotochemical quenching, by using data from experiments studying the effects of nitrogen limitation and drought on Japanese white birch (*Betula platyphylla* var. *japonica*), as well as the effect of elevated O3 on Japanese oak (*Quercus mongolica* var. *crispula*) and Konara oak (*Q. serrata*) under elevated CO2 concentrations. The rate of regulated nonphotochemical quenching (JNPQ) could compensate for decreases in the photosynthetic electron transport rate (JPSII) under the different stresses. It was also found that even decreases in nonregulated nonphotochemical quenching (JNO) occurred under limited nitrogen and elevated O3, irrespective of CO2 conditions. These may indicate a preconditioning adaptive response preparing plants to cope with predicted environmental challenges. The results of this study can be used as a platform upon which to base new studies directed at revealing whether elevated CO2 may not affect the plant responses to environmental stresses in terms of susceptibility to photodamage occurring in different experimental systems.

Proietti et al. [13], considering the importance of soil water availability as a driver of vegetation productivity, analyzed the spatiotemporal variation of a proposed temperature vegetation wetness index as a proxy of soil moisture and evaluated its effect on gross primary production using 19 representative tree species in Europe over the time period 2000–2010. The Modified Temperature Vegetation Wetness Index (mTVWI) displayed minimum soil water availability in Southern Europe and maximum soil water availability in Northeastern Europe. Furthermore, gross primary productivity decreased from 20% to 80% by mTVWI, depending on the site, tree species, and meteorological conditions. This wetness index adds a new dimension in understanding the impacts of water deficit stress which often occurs in tandem with air pollution.

Pandey et al. [14] treated 11 Indian wheat (*Triticum aestivum*) cultivars grown in high ambient O3 (twice the critical threshold for wheat yield) with the antiozonant chemical ethylenediurea (300 mg L-1), and found a high variation in resource allocation strategies among cultivars. They found that plants treated with ethylenediurea (EDU) produced more grain yields and had a higher photosynthetic rate and stomatal conductance as well as lower lipid peroxidation. They also observed varied responses of superoxide dismutase activity, catalase activity, and oxidized and reduced glutathione content. Responses to EDU (or O3 assuming the differences were due to ambient O3) varied across cultivars and plant developmental stages and sites. Authors grouped cultivars into four groups according to their response strategies. This research provides useful information to better understand the determinants of tolerance/susceptibility of Indian wheat to ambient O3.

El-Tahan [15] used data of the Total Ozone Column (TOC), yielded from the Atmospheric Infrared Sounder (AIRS) and the modelModern-Era Retrospective analysis for Research and Applications (MERRA). The long-term trend and the spatial distribution over Egypt are studied, and a comparison between both sources of TOC is made. According to the results, the spatial maps from AIRS could identify the location of both high and low concentrations of O3. Conversely, spatial maps from MERRA-2 underestimated TOC and were not effective in capturing the variability identified by AIRS. The study concludes that the MERRA-2 dataset also underestimated the temporal TOC over Egypt compared to the AIRS dataset. Among others, this study indicates the need to construct TOC from numerical models, such as, for example, numerical weather research and forecasting models coupled with chemistry.

#### **3. Conclusions**

A total of six papers on a variety of topics related to air pollution and its impacts were published in this special issue, constituting an orchestrated collection for researchers, environmentalists, educators, and local or regional regulators interested in air pollution and its impacts on plant ecosystems. We wish you an enjoyable and informative reading.

**Author Contributions:** Conceptualization, writing—original draft preparation, writing—review and editing: E.A., E.C., and P.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding. **Acknowledgments:** The Editors are grateful to all those who have submitted their works to this Special Issue. E.A. acknowledges multi-year financial support from The Startup Foundation for Introducing Talent of Nanjing University of Information Science & Technology (NUIST), Nanjing, China (No. 003080 to E.A.).

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
