Terpene-emitting plants may risk air quality and agricultural yields by increasing tropospheric ozone with nitrogen oxides. However, the number of non- or low-terpene-emitting species is limited, leading to a potential trade-off in species diversity when air quality considerations are prioritized for afforestation and urban greening. To expand the available choices, developing non- or extremely low-terpene-emitting cultivars from species with high-terpene emissions could be a feasible solution. In this study, we observed terpene emissions from multiple individuals of a common afforestation tree in Asia with high monoterpene emission rates, Quercus myrsinifolia, to identify natural low-monoterpene-emitting variants. A screening result showed that the total monoterpene emission rate at temperature of 30 °C and photosynthetic photon flux density of 1000 μmol m-2 s-1 among the 47 individuals ranged from no detection to 8.8 nmol m-2 s-1 in summer, where two out of them showed no detectable monoterpene emissions. With additional validation over months using the leaf cuvette method, extremely low monoterpene emissions which were solely composed of β-ocimene were detected for the two candidates during a warm month, and no monoterpenes were detected in the later months. Concurrently, net photosynthetic rates of the two candidate individuals were comparable to those of other individuals. Subsequent observations of the clones propagated from these variants detected no monoterpene emissions. These findings indicated that their extremely low-monoterpene-emitting trait is reproducible and attributed to their genotype. These variants are expected to be the foundation for establishing a low-air-quality-impacting cultivar for afforestation and urban greening.

Monoterpene (MT) emissions may contribute greatly to air pollution. The presence of non-storage-type MT emitters was thought to be rare but has been increasingly detected in recent years. The seasonality in non-storage-type MT emissions remains unclear, and estimation models for this type have not yet been developed. This study measured the MT basal emission rates (MT-BERs) of Japanese non-storage-type MT emitting evergreen oaks (Castanopsis cuspidata var. sieboldii and Quercus myrsinifolia) throughout a year. The MT-BERs of both species were low in May (<0.6 nmol m-2 s-1) and thereafter increased and peaked in summer, corresponding to increased net photosynthetic rates (NPRs). The MT-BERs gradually decreased in fall and reached zero in winter, while the NPRs remained high. The Model of Emissions of Gases and Aerosols from Nature (MEGAN) could not adequately explain the MT-BER seasonality of these evergreen oaks. Multiple regression analyses were also applied to estimate the MT-BERs (objective variables), using the history of environmental factors (explanatory variables: accumulated values of the hourly air temperature and global solar radiation). Air temperature had significant positive effects on the seasonality of the MT-BERs, whereas light intensity did not. In temperature-based simple regression analyses, setting temperature thresholds (20-25 °C) with accumulation period of 32-37 days remarkably improved the MT-BER estimations, compared to those without a temperature threshold and the other models mentioned above (MEGAN and multiple regression analyses). Our study has also proposed a new estimation model using temperature thresholds to explain the seasonality of MT-BERs of non-storage-type MT emitters.

Oil palm (Elaeis guineensis) is known for its substantial isoprene emissions, which can contribute to air pollution and climate change. As oil palm plantations expand across Southeast Asia, developing effective mitigation strategies such as propagating low-isoprene-emitting variants of this species is essential. To this end, we measured the isoprene emissions from oil palm saplings grown from seeds and clonally propagated under controlled environmental conditions in an E. guineensis nursery in Sessang, Malaysia. The effects of the leaf position, time of day, root conditions, and growth stage were examined for further data quality control. The first set of results showed that isoprene emissions varied more widely in seed-derived saplings (mean: 13.6 +/- 5.2 nmol m_ 2 s_ 1) than in clonal saplings (mean: 18.6 +/- 2.9 nmol m_ 2 s_ 1), with the latter exhibiting consistently higher emissions. Further investigation of the potential influencing factors revealed that isoprene emission rates varied with leaf position, with the upper and middle fronds producing more isoprene than lower fronds. Additionally, the emissions exhibited clear peaks in the morning or midday. Older trees exhibited significantly higher isoprene emission rates (26.32 +/- 6.49 nmol m_ 2 s_ 1) than saplings, suggesting that the emissions change with growth stage. Based on these findings, we recommended that isoprene emission measurements be taken from the middle or upper leaves in the morning or at midday to ensure a reliable comparison. The substantial intraspecific variability in isoprene emission among E. guineensis saplings from crossbreeding highlights the potential for identifying and selecting low-emission variants.

An international workshop on “Adapting Agriculture to Climate Change and Air Pollution” took place at Nanjing University of Information Science and Technology, Nanjing, China, during 23–27 October, 2023. Experts working in various multi-disciplinary areas of agroecosystem and environmental research gathered for academic communication and discussions. Two discussion groups focused on “agriculture under air pollution and climate change: current challenges and priorities for the future” and “adapting agriculture to air pollution and climate change: current status and next steps.” Insights derived from the discussions are summarized in this article and include opinions about current issues, knowledge gaps' identification, and potential priorities and actions that could be taken. The first discussion mainly addresses ozone impact estimates; ozone metrics for impact and risk assessments; ozone monitoring; air pollution impacts and policy; and the pivotal role of agriculture and consumer choices. The second discussion covers adaptation and mitigation; greenhouse gases and energy efficiency; concerns about the link between adaptation and mitigation; local food, planetary-health diets and carbon footprint; irrigation and climate change adaptation; scientific evidence and policy-making; air pollution and crop adaptation; machine learning and crop modeling; and challenges faced by smallholder farmers and large-scale enterprises. Hence, this report could be useful for reseach, educational, and policy purposes, collating opinions of experts working in diverse research areas.

To investigate effects of CO2 concentration, light intensity, and nutrient solution strength on the growth of wasabi (Eutrema japonicum (Miq.) Koidz.) seedlings, they were grown in environmentally controlled chambers. In the first experiment, single effect of CO2 concentration on growth of wasabi cultivar 'Izuma' was investigated. The dry weight of the whole seedling was increased more under enriched CO2 concentrations (1000 and 2000 ppm (v/v)) than under ambient CO2 concentration (400 ppm). However, the CO2 effect to raise photosynthesis was weakened in the latter half of the experiment. To sustain the effect of the enriched CO2 throughout the whole seedling cultivation period and maximize the wasabi seedling growth, the wasabi seedlings were grown under different light intensities and different nutrient solution strengths in the second experiment. Two wasabi cultivars 'Izuma' and 'Fujimidori' were used. 'Fujimidori' is a newly developed cultivar that is more tolerant to high temperatures. The results revealed that 'Fujimidori' had the highest whole dry weight under enriched CO2 concentration (1000 ppm), higher light intensity (200 mu mol m(-2 )s(-1)), and higher concentration of the nutrient solution. Contrary, the whole dry weight of 'Izuma' under such environmental conditions was almost the same as that of 'Izuma' grown under a lower concentration of nutrient solution but enriched CO2 concentration and higher light intensity, and under lower light intensity but enriched CO2 concentration and higher concentration of nutrient solution. This suggests that a combination of a higher concentration of the nutrient solution and higher light intensity cannot amplify the CO2 effect on 'Izuma' growth. The difference in the environmental response between the two cultivars seemed to be partially caused by the different temperature tolerances.

Quercus phillyraeoides, a strong monoterpene-emitting species, is widely planted in urban and suburban areas in Japan. Urban-greening plants with terpenoid emission may affect air quality by increasing photochemical oxidants through the reaction between their terpenoid emissions and urban gases. In mitigating this issue, replacing the original plants with low-emitting variants can be a workable approach without substantially altering the original landscapes and ecotopes. This study aimed to identify the low- or non-emitting variants among Q. phillyraeoides. To deal with a large number of Q. phillyraeoides samples, a method using detached leaves was adopted and optimized for observation of terpenoid emission rates from Q. phillyraeoides. The testing showed that the emission rate would be relatively stable at approximately 40 min of incubation under a photosynthetic photon flux density of similar to 1000 mu mol m(-2) s(-1) and a surrounding temperature of 30 degrees C. Although the emission rates were different from those derived using the conventional method (i.e., the leaf cuvette method), they were well calibrated, with a regression line between the datasets of the two methods. We used this method to inspect the monoterpene emission rate from Q. phillyraeoides in multiple locations in Shizuoka Prefecture and detected a variability in the monoterpene emission rate (no detection to 14.8 nmol m(-2) s(-1)), which were independent of environmental effects for each location. The Q. phillyraeoides individuals with no emission of monoterpenes are expected to be suitable for propagation as non-terpenoid-emitting greening materials.

The effects of elevated CO2 concentration on the defensive ability of two Alnus species (A. maximowiczii, A. hirsuta) against herbivory attacks (alder leaf beetle; Agelastica coerulea) were investigated using a free-air CO2 enrichment. Elevated CO2 significantly affected consumed leaf area index (CLI) of A. maximowiczii but soil fertility did not, while more significant effects on CLI of A. hirsuta were found in both CO2 and soil fertility. As found in natural conditions, A. hirsuta was grazed five times more than A. maximowiczii in both CO2 levels, which was explained with the low condensed tannin (CT) concentration of the leaves. The value of leaf mass per area in fertile soil was 10 g m(-2) lower than that in infertile soil under ambient CO2 in July. Leaf C/N ratio was not affected by elevated CO2 for both species but that of A. hirsuta was little higher in infertile soil when compared to fertile soil in July. CT of A. maximowiczii tended to increase in September under elevated CO2. CT of A. hirsuta was higher in infertile soil than in fertile soil in July and showed an overall decrease in September compared to July. Nitrogen-fixing activity by a nodule of Frankia sp. on A. maximowiczii was higher in elevated CO(2)treatments than in ambient CO(2)independent of soil fertility. As a result of changes in these parameters, except for fertile soil, the peak of the herbivorous damage was later in elevated CO2 for the Alnus species than in the control.

Uncontrolled terpenoid emissions from forest trees in Japan may have contributed to high O3 concentrations observed in urban and suburban areas. To estimate ozone formation via a series of reactions between NOx and terpenoids using atmospheric chemistry models, it is important to produce terpenoid emission inventories by collecting all reported emission data for the major tree species in Japan and examining their reliability. In this review, we first describe three different plant terpenoid emission types, i.e., isoprene-emitting type, monoterpene-emitting type with storage tissues and organs, and monoterpene-emitting type without storage tissues and organs. Second, we describe various methods for measuring plant terpenoid emissions, including a recently developed simplified method, and explain their reliability. We emphasized that applicable measurement methods depend on the terpenoid emission types. Data obtained using static chamber methods should not be considered because they have the highest uncertainty resulting from normal chamber materials that are not specific to terpenoid measurements and lack humidity control. Finally, we show the absolute values of the collected emission rates and describe their variability. The deciduous oak species, Quercus serrata and Quercus mongolica var. crispula, and bamboo species, Phyllostachys pubescens and Phyllostachys bambusoides, are strong isoprene emitters. Among the monoterpene emitters, four evergreen broadleaf trees, including three Quercus species, had the highest basal emission rate (BER). The monoterpene storage type conifers Larix kaempferi and Pinus densiflora have relatively lower BERs. Emission data are not available for Castanopsis cuspidata, and seasonal changes in emission rates have not been reported for several major tree species in the top 20 rankings. Within species, the reported emission rates of some tree species differed by threefold. These differences may be attributed to the reliability of the measurement and analytical systems, tree age, leaf morphology, environmental conditions, and genetic diversity. We emphasize the need for reliable measurements to achieve a more precise terpenoid emission inventory for major tree species in Japan.

To investigate effects of environmental factors in nurseries on growth of Wasabi (Eutrema japonicum (Miq.) Koidz.) seedlings, they were grown in four different sites in Shizuoka and one site in Yamanashi during summer season in 2021 and 2022. At the end of experiment, ratio of shippable seedlings among the seedlings used for experiment was highest (= 80%) at Yamanashi site, followed by Fujinomiya highland site. At the site of Fujinomiya lowland, no shippable seedlings were obtained. Environmental factors affecting the shippable ratio at individual sites seemed to be different, i.e. air temperature, vapor pressure deficit, or light intensity. A multiple regression analysis was applied to clarify the significant factors affecting the shippable ratio. Accumulated air temperature over 30 degrees C, diurnal range of air temperature, light intensity, and yearly-different growing setup have been revealed to be affecting factors. Using the relationship, suitable sites for Wasabi seedling cultivation during summer season were estimated among 55 sites where meteorological data were provided by Japan Meteorological Agency. The number of the suitable sites were 1, 3, and 20 in Shizuoka, Yamanashi, and Nagano prefectures, respectively. Assuming that air temperature was 1 degrees C higher than average of those during 2021 and 2022, the number of the suitable sites was decreased, but Yamanakako village was left, to which our experimental site in Yamanashi was adjacent.

An increasing number of studies have reported stimulation of various organisms in the presence of environmental contaminants. This has created a need to critically evaluate sublethal stimulation and hormetic responses of arthropod parasitoids and parasites following exposure to pesticides and other contaminants. Examining this phenomenon with a focus on arthropods of agricultural and environmental importance serves as the framework for this literature review. This review shows that several pesticides, with diverse chemical structures and different modes of action, applied individually or in combination at sublethal doses, commonly stimulate an array of arthropod parasitoids and parasites. Exposure at sublethal doses can enhance responses related to physiology (e.g., respiration, total lipid content, and total protein content), behavior (e.g., locomotor activity, antennal drumming frequency, host location, and parasitization), and fitness (longevity, growth, fecundity, population net and gross reproduction). Concordantly, the parasitic potential (e.g., infestation efficacy, parasitization rate, and parasitoid/parasite emergence) can be increased, and as a result host activities inhibited. There is some evidence illustrating hormetic dose-responses, but the relevant literature commonly included a limited number and range of doses, precluding a robust differentiation between sub-and superNOAEL (no observed-adverse-effect level) stimulation. These results reveal a potentially significant threat to ecological health, through stimulation of harmful parasitic organisms by environmental contaminants, and highlight the need to include sublethal stimulation and hormetic responses in relevant ecological pesticide risk assessments. Curiously, considering a more utilitarian view, hormesis may also assist in optimizing mass rearing of biological control agents for field use, a possibility that also remains neglected.

Long-chain fatty acids (LCFAs) in leaves have attracted attention as nutritious phytochemicals and olfactory signals that influence the behavior and growth of herbivorous insects. In recognition of the negative effects of increasing tropospheric ozone ( O-3) levels on plants, LCFAs can be altered through peroxidation by O-3. However, how elevated O-3 changes the amount and composition of LCFAs in field-grown plants is still unknown. We investigated palmitic, stearic, oleic, linoleic, linolenic LCFAs in the two leaf types (spring and summer) and two stages ( early and late stage after expansion) of Japanese white birch (Betula platyphylla var. japonica) after a multi-year O-3 exposure on the field. Summer leaves exhibited a distinct composition of LCFAs under elevated O-3 at the early stage, whereas both stages of spring leaves did not exhibit significant changes in LCFAs composition by elevated O-3. In the spring leaves, the amounts of saturated LCFAs significantly increased at the early stage, however, the amount of total, palmitic, and linoleic acids at the late stage were significantly decreased by elevated O-3. Summer leaves had a lower amount of all LCFAs at both leaf stages. Regarding the early stage of summer leaves, the lower amount of LCFAs under elevated O-3 was possibly due to O-3- suppressed photosynthesis in the current spring leaves. Furthermore, the decrease ratio of spring leaves over time was significantly increased by elevated O-3 in all LCFAs, whereas summer leaves did not exhibit such an effect. These findings suggest that further studies should be conducted to reveal the biological functions of LCFAs under elevated O-3, considering the leaf type- and stage-dependent changes of LCFAs.

Plant volatiles, particularly biogenic volatile organic compounds (BVOCs), emitted in urban areas have attracted attention as olfactory signals between plants and other organisms, including insects. However, in urban areas, elevated ozone (O-3) levels inhibit plant growth and degrade olfactory signals, including both insect pheromones and BVOCs, resulting in disrupted biological communication. In this article, we review recent findings on how O-3 modifies olfactory interactions, focusing on both the emitters and receivers of these signals. The influence of O-3 on herbivorous insects and their enemies alters the pressure caused by herbivorous damage in the field, which can affect the development of the defensive capacities of plants at the hereditary level. To address the challenges posed by O-3 in biological interactions, BVOC characteristics (e.g., emission rate and species, blend composition, O-3 reactivity, and oxidative products) and O-3 effects on insects (e.g., preference and antennal detectivity) should be clarified. At the same time, BVOC emissions are expected to increase with rising temperatures, which will likely increase the impact of BVOCs on O-3 formation in the future. Therefore, it is necessary to devise strategies, such as selecting non- or low BVOC emitters, to regulate BVOC emissions from urban greening plants and mitigate O-3 risks to olfactory interactions and plant health.

In broad-leaved trees, growth and plant defense chemicals have originated from photosynthates. Therefore, defense chemicals should be efficiently distributed in a leaf against herbivory, especially when the leaves are exposed to long-term biotic and abiotic stresses. To reveal this phenomenon, we examined the distribution of phenolic compounds, in particular tannins in the leaves of juvenile and adult Siebold’s beech ( Fagus crenata Blume) under various light conditions by both chemical and histochemical analyses. The cotyledons and first true leaves of seedlings mainly included tannins in the upper and lower epidermis. By contrast, tannins were distributed in all tissues of the sun leaves of saplings (except in spongy tissue) and adult trees under higher light intensity, whereas phenolic compounds, but not tannins, were mainly present in palisade parenchyma cells and bundle sheath cells of the sun leaves of adult trees under lower light intensity. Furthermore, in adult trees, there were no changes in the distribution of phenolic compounds irrespective of the increase in the concentration of condensed tannins from June to September. These findings showed that the distribution of phenolic compounds in beech leaves changes from juvenile to adult trees and is also strongly affected by light conditions.

Ground-level ozone (O 3 ) is a widespread air pollutant causing extensive injuries in plants. However, its effects on perennial energy crops remain poorly understood due to technical difficulties in cultivating fast-growing shrubs for biomass production under O 3 treatment on the field. Here we present the results of a two-year evaluation in the framework of which willow ( Salix sachalinensis F. Schmid) shrubs were exposed to ambient (AOZ) or elevated (EOZ) O 3 in two successive growing seasons (2014, 2015) and treated with 0 (EDU0) or 400 mg L −1 (EDU400) ethylenediurea spray in the second growing season. In 2014, EOZ altered the chemical composition of both top young and fallen leaves, and a novel mechanism of decreasing Mg in fallen leaves while highly enriching it in young top leaves was revealed in shrubs exposed to EOZ. In 2015, EDU400 alleviated EOZ-induced decreases in leaf fresh mass to dry mass ratio (FM/DM) and leaf mass per area (LMA). While EDU400 protected against EOZ-induced suppression of the maximum rate at which leaves can fix carbon ( A max ) in O 3 -asymptomatic leaves, it did not alleviate EOZ-induced suppression of the maximum rates of carboxylation ( V Cmax ) and electron transport ( J max ) and chlorophylls a , b , and a + b in the same type of leaves. In O 3 -symptomatic leaves, however, EDU400 alleviated EOZ-induced suppression of chlorophylls a and a + b , indicating different mode of action of EDU between O 3 -asymptomatic and O 3 -symptomatic leaves. Extensive herbivory occurred only in AOZ-exposed plants, leading to suppressed biomass production, while EOZ also led to a similar suppression of biomass production (EDU0 × EOZ vs. EDU400 × EOZ). In 2016, carry-over effects were also evaluated following cropping and transplantation into new ambient plots. Effects of EOZ in the preceding growing seasons extended to the third growing season in the form of suppressed ratoon biomass production, indicating carry-over effect of EOZ. Although EDU400 protected against EOZ-induced suppression of biomass production when applied in 2015, there was no carry-over effect of EDU in the absence of EDU treatment in 2016. The results of this study provide novel mechanistic understandings of O 3 and EDU modes of action and can enlighten cultivation of willow as energy crop.

Conservation of urban greens is an essential action for city residents, however, declining symptoms and/or traces in the annual ring of trees grown are found in parks and forest stands in a city as well as its suburb with a high level of ozone (O3). Urban greens, including roof-green, provide comfortable conditions for the people and a moderate environment in a city. They are exposed to severe environments; heat, drought, air-pollutions, etc. even with intensive management of the people. How can we proceed with the conservation and wise use of urban greens? We should know the ecophysiological responses of urban trees to such a global environment as well as a local one. Defensive capacities of urban greens should be analyzed in terms of damages caused by biotic and abiotic stresses, and it is important to understand their interactions from the viewpoint of plant-insect/disease. There is a concern that some green areas are suffering from an outbreak of insects and diseases, reducing the vigor and health of urban greens. We discuss these based on specific examples, such as man-made forests, in cities in far east Asia for considering our approach to how to keep urban green resources.

Behavior of insects, such as pollination and grazing, is usually determined by biogenic volatile organic compounds (BVOCs). However, particularly in O3-polluted urban forests, the BVOCs-based plant-insect communication can be disrupted by the reaction of O3 with leaf-emitted BVOCs, such as between Japanese white birch (Betula platyphylla var. japonica) and a leaf beetle (Agelastica coerulea). To understand plant-insect communication in O3-polluted environments, it is necessary to identify chemical species of BVOCs that contribute to attractiveness toward insects but are diminished by elevated O3. In this study, we conducted olfactory response tests and gas chromatography mass spectrometry (GC-MS) analyses to clarify whether there is a similarity of BVOC components among Betulaceae host trees that can explain the attraction of the stenophagous insect A. coerulea. The olfactory response tests indicated that Betulaceae host trees attract A. coerulea via leaf-emitted BVOCs, while there was no preference of the leaf beetles to non-host trees (Sorbus commixta and Morus bombycis). However, GC-MS analyses indicated that the composition of BVOC blends considerably differed among Betulaceae host trees, although alders (Alnus hirsuta and A. japonica) had a similar composition of BVOC blend in each season (June and September) during which the adult leaf beetle is active. A distinct characteristic of the emission from B. platyphylla was that 2-carene and limonene, which are O3-reactive species, were emitted with a high monoterpene ratio irrespective of the season. Thus, these volatiles and the blend could be expected to lead the disrupted communication found between B. platyphylla and A. coerulea under elevated O3 in previous field studies. In addition, our results indicated that A. coerulea is attracted to more than one blend within Betulaceae host trees, suggesting that grazing damages can be affected by different host preferences and O3 reactivity with specific BVOCs in the field. BVOCs-based plant-insect interactions should be further studied in multi-species communities to better understand plant-insect communication in O3-polluted environments.

Plant–insect interactions are basic components of biodiversity conservation. To attain the international Sustainable Development Goals (SDGs), the interactions in urban and in suburban systems should be better understood to maintain the health of green infrastructure. The role of ground-level ozone (O 3 ) as an environmental stress disrupting interaction webs is presented. Ozone mixing ratios in suburbs are usually higher than in the center of cities and may reduce photosynthetic productivity at a relatively higher degree. Consequently, carbon-based defense capacities of plants may be suppressed by elevated O 3 more in the suburbs. However, contrary to this expectation, grazing damages by leaf beetles have been severe in some urban centers in comparison with the suburbs. To explain differences in grazing damages between urban areas and suburbs, the disruption of atmospheric communication signals by elevated O 3 via changes in plant-regulated biogenic volatile organic compounds and long-chain fatty acids are considered. The ecological roles of plant volatiles and the effects of O 3 from both a chemical and a biological perspective are presented. Ozone-disrupted plant volatiles should be considered to explain herbivory phenomena in urban and suburban systems.

Elevated ground-level ozone (O3) reduced C-based defense chemicals; however, severe grazing damages were found in leaves grown in the low O3 condition of a free air O3-concentration enrichment (O3-FACE) system. To explain this phenomenon, this study investigates the role of BVOCs (biogenic volatile organic compounds) as signaling compounds for insect herbivores. BVOCs act as scents for herbivore insects to locate host plants, while some BVOCs show high reactivity to O3, inducing changes in the composition of BVOCs in atmospheres with elevated O3. To assess the aforementioned phenomenon, profiles of BVOCs emitted from birch (Betula platyphylla var. japonica Hara) leaves were analyzed ex situ, and Y-tube insect preference tests were conducted in vitro to study the insect olfactory response. The assays were conducted in June and August or September, according to the life cycle of the adult alder leaf beetle Agelastica coerulea Baly (Coleoptera: Chrysomelidae). The Y-tube tests revealed that the leaf beetles were attracted to BVOCs, and O3 per se had neither an attractant nor a repellent effect. BVOCs became less attractant when mixed with highly concentrated O3 (>80 ppb). About 20% of the total BVOCs emitted were highly O3-reactive compounds, such as β-ocimene. The results suggest that BVOCs emitted from the birch leaves can be altered by elevated O3, thus potentially reducing the attractiveness of leaves to herbivorous insects searching for food.

Japanese elm (Ulmus davidiana var. japonica) is a native species in cool-temperate forests in Japan. We investigated growth, physiological reactions, and leaf defense capacity of Japanese elm seedlings under nitrogen (N) loading (45.3 kg N ha-1 year-1) and seasonal insect dynamics in a free-air ozone (O3)-enriched environment (about 54.5 nmol O3 mol-1) over a growing season. Higher leaf N content and lower condensed tannin content in the presence of N loading and lower condensed tannin content in elevated O3 were observed, suggesting that both N loading and elevated O3 decreased the leaf defense capacity and that N loading further enhanced the leaf quality as food resource of insect herbivores. Two major herbivores were observed on the plants, elm leaf beetle (Pyrrhalta maculicollis) and elm sawfly (Arge captiva). The peak number of observed insects was decreased by N loading. Visible foliar injury caused by N loading might directly induce the reduction of number of the observed elm sawfly individuals. While elevated O3 slightly suppressed the chemical defense capacity, significantly lower number of elm leaf beetle was observed in elevated O3. We conclude that N loading and elevated O3 can alter not only the leaf defense capacity of Japanese elm seedlings but also the dynamics of elm leaf beetle and sawfly herbivores.