Seedling insensitivity to ozone for three conifer species native to Great Smoky Mountains National Park

Field symptoms typical of ozone injury have been observed on several conifer species in Great Smoky Mountains National Park, and tropospheric ozone levels in the Park can be high, suggesting that ozone may be causing growth impairment of these plants. The objective of this research was to test the ozone sensitivity of selected conifer species under controlled exposure conditions. Seedlings of three species of conifers, Table Mountain pine (Pinus pungens), Virginia pine (Pinus virginiana), and eastern hemlock (Tsuga canadensis), were exposed to various levels of ozone in open-top chambers for one to three seasons in Great Smoky Mountains National Park in Tennessee, USA. A combination of episodic profiles (1988) and modified ambient exposure regimes (1989-92) were used. Episodic profiles simulated an average 7-day period from a monitoring station in the Park. Treatments used in 1988 were: charcoal-filtered (CF), 1.0x ambient, 2.0x ambient, and ambient air-no chamber (AA). In 1989 a 1.5x ambient treatment was added, and in 1990, additional chambers were made available, allowing a 0.5x ambient treatment to be added. Height, diameter, and foliar injury were measured most years. Exposures were 3 years for Table Mountain pine (1988-90), 3 years for hemlock (1989-91), and 1 and 2 years for three different sets of Virginia pine (1990, 1990-91, and 1992). There were no significant (p<0.05) effects of ozone on any biomass fraction for any of the species, except for older needles in Table Mountain and Virginia pine, which decreased with ozone exposure. There were also no changes in biomass allocation patterns among species due to ozone exposure, except for Virginia pine in 1990, which showed an increase in the root:shoot ratio. There was foliar injury (chlorotic mottling) in the higher two treatments (1.0x and 2.0x for Table Mountain and 2.0x for Virginia pine), but high plant-to-plant variability obscured formal statistical significance in many cases. We conclude, at least for growth in the short-term, that seedlings of these three conifer species are insensitive to ambient and elevated levels of ozone, and that current levels of ozone in the Park are probably having minimal impacts on these particular species.     

Seasonal development of ozone-induced foliar injury on tall milkweed (Asclepias exaltata) in Great Smoky Mountains National Park

The goals of this study were to document the development of ozone-induced foliar injury, on a leaf-by-leaf basis, and to develop ozone exposure relationships for leaf cohorts and individual tall milkweeds (Asclepias exaltata L.) in Great Smoky Mountains National Park. Plants were classified as either ozone-sensitive or insensitive based on the amount of foliar injury. Sensitive plants developed injury earlier in the season and to a greater extent than insensitive plants. Older leaf cohorts were more likely to belong to high injury classes by the end of each of the two growing seasons. In addition, leaf loss was more likely for older cohorts (2000) and lower leaf positions (2001) than younger cohorts and upper leaves, respectively. Most leaves abscised without prior ozone-like stippling or chlorosis. Failure to take this into account can result in underestimation of the effects of ozone on these plants.     

Surface ozone in Yosemite National Park

During the summers of 2003 and 2005, surface ozone concentrations were measured with portable ozone monitors at multiple locations in and around Yosemite National Park. The goal of these measurements was to obtain a comprehensive survey of ozone within Yosemite, which will help modelers predict and interpolate ozone concentrations in remote locations and complex terrain. The data from the portable monitors were combined with concurrent and historical data from two long-term monitoring stations located within the park (Turtleback Dome and Merced River) and previous investigations with passive samplers. The results indicate that most sites in Yosemite experience roughly similar ozone concentrations during well-mixed daytime periods, but dissimilar concentrations at night. Locations that are well exposed to the free troposphere during evening hours tend to experience higher (and more variable) nocturnal ozone concentrations, resulting in smaller diurnal variations and higher overall ozone exposures. Locations that are poorly exposed to the free troposphere during nocturnal periods tend to experience very low evening ozone, yielding larger diurnal variations and smaller overall exposures. Ozone concentrations are typically highest for the western and southern portions of the park and lower for the eastern and northern regions, with substantial spatial and temporal variability. Back-trajectory analyses suggest that air with high ozone concentrations at Yosemite often originates in the San Francisco Bay Area and progresses through the Central California Valley before entering the park.     

Ozone Regimes in or near Forests of the Western United States: Part 2. Factors Influencing Regional Patterns

Abstract

Ozone levels in or near forests of the western United States resulted from transport of ozone from urban areas, photochemical formation of ozone in nonurban areas from either natural or manmade precursors, and downward mixing of ozone from the tropospheric reservoir. Similarities in ozone exposure regimes were clearly associated with ozone characteristics, such as the shape of the diurnal curve in hourly ozone concentrations and the magnitudes of ozone levels. No single site characteristic dominated across the region. Eight classes of ozone regimes were identified: largeurban, medium-urban, small-urban, urban downwind-urban, urban-transport, rural, rural-remote, and remote. Sites in the western United States can be classified according to these classes. Of the sites included in the analysis, Olympic National Park, Colorado National Monument, Redwood National Park, Grand Canyon, and Crook County in Oregon showed the lowest impact from urban-generated ozone. The greatest impact of manmade ozone was found in forests of southern and central California, and to some extent in Rocky Mountain National Park and along the western slopes of the Cascades in Washington.

The eight groups of sites showing similar ozone exposure regimes as identified by Böhm et al.¹ corresponded closely with the eight classes of ozone regimes, indicating that regional similarities in ozone exposure regimes can be linked to ozone formation and transport processes despite a lack of geographic cohesion. Sixty-four percent of variance in ozone exposure regimes can be expressed in a twodimensional space called diurnal-curve space. Group membership is more cohesive in diurnal-curve than geographic space. Applications of diurnal-curve space include (1) a sensitive regional analysis of the nature and magnitudes of ozone exposure regimes in or near western forests; (2) a pro-active means for identifying sites with changing ozone exposure regimes; and (3) guidelines from which biologists can develop realistic experimental fumigation protocols. It is suggested that univariate statistics, such as 7-hour mean, 24-hour mean, SUM06, and SUM08, cannot identify up to 39% of the variance in ozone exposure regimes among sites in or near forests of the western United States.     

Concentrations of mercury in otters (Lutra lutra L.) in Scotland in relation to rainfall

The incidence and severity of visible foliar ozone injury on black cherry (Prunus serotina) seedlings and saplings and tall milkweed (Asclepias exaltata) plants in Great Smoky Mountains National Park (GRSM) were determined by surveys along selected trails conducted during late summer 1992. The incidence (% injured plants) of ozone injury on black cherry was 47% and the percent injured leaves/injured plant and average leaf area injured were 43 and 6%, respectively. Maximum severity (avg. leaf area of the most severely injured leaf) was 12%. Black cherry seedlings and saplings exhibiting ozone injury were taller than non-injured plants. When insect feeding was present, it occurred 96% of the time on plants with ozone injury. Significantly more injury (p=0.007) on black cherry (% injured leaves/injured black cherry) occurred in the NW section of GRSM compared with the other Park sections. Regression analyses showed no relationships in ozone injury with respect to aspect, slope or elevation. Tall milkweed was evaluated twice during August for ozone injury. The incidence (% injured plants) of ozone injury was 74 and 79% for the first and second survey, respectively. The percentage of injured leaves per plant from the first to second survey was 63 to 79%, respectively. Tall milkweeds showing ozone injury were taller than the non-injured plants. The percentage of insect-damaged plants was 50% among plants without ozone injury and 60% among ozone-injured plants. Non-injured tall milkweed had fewer flowers and/or pods than the injured plants. Mean leaf area injured increased over time, and mean maximum leaf area injured increased from 8 to 11% during the same period. Regression analyses showed no differences in ozone injury regarding aspect, slope or elevation. Our findings indicate that ozone injury is widespread throughout the Park on sensitive vegetation.     

Seasonal ozone response of mature beech trees (Fagus sylvatica) at high altitude in the Bavarian forest (Germany) in comparison with young beech grown in the field and in phytotrons

Mature beech trees (Fagus sylvatica) grown at two different altitudes in the Bavarian forest were compared with young beech trees grown at nearby field sites or in phytotrons for their macroscopic and physiological responses to different ozone (O(3)) exposures. Cumulative O(3) exposure expressed as the sum of hourly mean concentrations above the canopy ranged between 100 and 150 microl l(-1) h, with the vertical O(3) profiles at the higher altitude site being enhanced by 30%. O(3) profiles at all sites were reduced by up to 20% with increasing depth within and beneath the canopy. The leaf discoloration that developed in the absence of premature leaf loss was similar in the sun foliage of mature and young trees (including plant grown in the phytotron). Injury became apparent at low O(3) exposures, expressed as accumulated hourly means over a threshold of 40 nl l(-1) (AOT40 <3.5 microl l(-1) h) at the lower site in both the mature trees and the young beech at the field site, but only occurred when AOT40 values reached 7 microl l(-1) h at the upper site, and 6 microl l(-1) h in the phytotrons. However, the association between injury and O(3) exposure was improved when cumulative ozone uptake to sun leaves was the ozone index, used with values of about 3 mmol m(-2) resulting in visible injury in both mature and young beech growing in phytotrons. Under high ozone exposure levels of inositol were lowered, whilst concentrations of lignin-like materials were enhanced in mature beech. Similar responses were observed in young beech grown in phytotrons. As the sun foliage was affected by only a small and variable extent each year, the seasonal O(3) impact at high altitude did not appear to pose an acute risk to mature beech trees.     

Air quality in natural areas: interface between the public, science and regulation

Natural areas are important interfaces between air quality, the public, science and regulation. In the United States and Canada, national parks received over 315million visits during 2004. Many natural areas have been experiencing decreased visibility, increased ozone (O(3)) levels and elevated nitrogen deposition. Ozone is the most pervasive air pollutant in North American natural areas. There is an extensive scientific literature on O(3) exposure-tree response in chambered environments and, lately, free-air exposure systems. Yet, less is known about O(3) impacts on natural terrestrial ecosystems. To advance scientifically defensible O(3) risk assessment for natural forest areas, species-level measurement endpoints must be socially, economically and ecologically relevant. Exposure-based indices, based on appropriate final endpoints, present an underused opportunity to meet this need. Exposure-plant indices should have a high degree of statistical significance, have high goodness of fit, be biologically plausible and include confidence intervals to define uncertainty. They must be supported by exposure-response functions and be easy to use within an air quality regulation context. Ozone exposure-response indices developed within an ambient air context have great potential for improving risk assessment in natural forest areas and enhancing scientific literacy.     

Ozone injury on cutleaf coneflower (Rudbeckia laciniata) and crown-beard (Verbesina occidentalis) in Great Smoky Mountains National Park

Incidence and severity of visible foliar ozone injury on cutleaf coneflower (Rudbeckia laciniata L.) and crown-beard (Verbesina occidentalis Walt.) were determined along selected trails at three locations in Great Smoky Mountains National Park during the summers of 2000 and 2001: Clingmans Dome, Cherokee Orchard Road and Purchase Knob. Cutleaf coneflower exhibited a greater amount of foliar injury than crown-beard each year of the 2-year study. Incidence and severity of injury was significantly greater for cutleaf coneflower growing near the edge of the Clingmans Dome trail than in the interior of the stand. Injury was greater at Clingmans Dome than Purchase Knob (70% vs. 40% ozone-injured plants, respectively), coincident with greater ozone exposures. In contrast to Clingmans Dome, there were no differences in injury between plants growing near- and off-trail at Purchase Knob. Differences in sensitivity to ozone were not observed for crown-beard growing near the edge compared with the interior of the stand adjacent to the Cherokee Orchard Road Loop. Ozone injury was greatest on the lower leaves for both species sampled with over 95% of the injured leaves occurring on the lower 50% of the plant. This is the first report of foliar ozone injury on these plant species in situ, in the Park, illustrating the great variability in symptom expression with time, and within and between populations.     

Using a source–receptor approach to characterize the volatile organic compounds from control device exhaust in a science park

The science parks have helped shape Taiwan as a high-tech island with a good reputation worldwide. But some complaints on air pollution from the science parks have recently risen. To better understand the environmental effects of volatile organic compounds (VOCs) emitted from various high-tech factories in a science park, this study uses a source–receptor approach to characterize the environmental effects of VOCs from control device exhaust in Taichung Science Park. The chemical mass balance model (CMB8.2) of field measurements of 30 stacks and ambient air at nine sites was used to identify the source and relative contribution of ambient VOCs. The exhaust gas of various pollution control devices was also sampled by drawing a stream of the gases from the exhaust duct at its sampling port. The VOC source profile of each control device exhaust was determined using a database of noncharacteristic compounds. Monthly ambient concentrations of 167 VOCs were divided into monsoon datasets to investigate the effect of monsoon conditions on the emission of VOCs in the science park. This study also suggests a method for determining the optimum source profile in source–receptor modeling, and identifies and analyzes the sources of ambient VOCs at nine sites during southwest and northeast monsoons. Results show a direct relationship between the relative contribution of each source and its control device efficiency. The proposed source–receptor approach can characterize the environmental effect of air pollutants from various factories and successfully assess the efficiency of various control devices.     

Response to ambient ozone of two white clover (Trifolium repens L.cv. "Regal") clones, one resistant and one sensitive, grown in a Mediterranean environment

Two clones of white clover (Trifolium repens L.) differing in ozone tolerance were grown in southern Italy during 1997 and 1998 to study the effects of ambient ozone exposure on yield, leaf morphology and water use. Ambient ozone levels were high in both years with values exceeding the threshold for leaf injury reported in the literature. In both years ozone injury was observed on the sensitive clone (NC-S) but not on the resistant one (NC-R), and leaf and stolon dry matter production was significantly lower in NC-S than in NC-R. However, it cannot be excluded that other factors, such as high temperature, interacted with the effect of ozone on biomass production. The clones differed in morphological characteristics. Lower total leaf area in NC-S plants was due to a smaller number of leaves per plant, but the average area per leaf was higher in NC-S. Specific leaf weight and net assimilation rate were higher in the more productive clone (NC-R). Cumulative plant water use was higher in NC-R in each growth period because of the larger leaf area; by contrast, water use per unit leaf area was higher in NC-S, indicating higher leaf conductance to water vapour. The results suggest that ozone significantly reduces the yield of sensitive white clover plants under well-watered conditions, and that the difference in ozone tolerance between clover clones is related to differences in leaf morphology and water use.     

对化工园区标准化管理体系应用实践的认识

随着全球经济一体化步伐的加快,中国的化工企业已呈现各种化工园区集聚发展的态势。化工园区作为地区化工行业集聚区域,也是一个地区工业经济发展的重要载体,已逐渐成为推动区域经济快速增长的重要支撑。本文分析了国内外先进化工园区管理模式及经验,总结了目前国内化工园区管理中存在的问题,通过借鉴国内外先进化工园区管理模式及成功经验,分析提出解决化工园区环境管理问题的建议,以期为改善园区管理现状、促进化工园区科学发展提供理论依据。     

基于DEA模型的太湖流域企业污水治理效率

运用数据包络分析DEA方法,建立了太湖殷村港流域工业园区企业污水治理效率评价体系,并利用该体系对园区内企业污水治理效率进行了实证研究。利用效率评价函数对园区内20家企业进行评价,结果表明,其中4家企业达到环境治理效率相对高效;20家企业的废水排放量、COD和NH3-N排放削减总量分别为3 691 860、217.53和14.64 t/a,削减潜力较大。实证研究结果表明,该环境绩效评价系统可为园区企业污水治理调控提出定量化的调整建议。     

Size-mediated foliar response to ozone in black cherry trees

Local ozone concentration and visible foliar injury were measured over the 1994 growing season on open-grown black cherry (Prunus serotina Ehrh.) trees of varying size (age) within forest stands and adjacent openings at a site in north-central Pennsylvania. Relationships were determined between visible ozone injury and ozone exposure, as well as calculated between injury and ozone uptake expressed as the product of stomatal conductance and ozone concentration. In addition, simultaneous measurements of visible symptoms and leaf gas exchange were also conducted to determine the correlation between visible and physiological injury and ozone exposure. By September, the amount of leaf area affected by visible foliar ozone injury was greatest for seedlings (46%), followed by canopy trees (20%) and saplings (15%). A large amount of variability in foliar ozone symptom expression was observed among trees within a size class. Sum40 and Sum60 (ozone concentration > 40 and > 60 nl liter(-1)) cumulative exposure statistics were the most meaningful indices for interpretation of foliar injury response. Seedlings were apparently more sensitive to ozone injury than larger trees because their higher rates of stomatal conductance resulted in higher rates of ozone uptake. Seedlings also had higher rates of early leaf abscission than larger trees with an average of nearly 30% of the leaves on a shoot abscised by 1 September compared to approximately 5% for larger trees. However, per unit ozone uptake into the leaf, larger trees exhibited larger amounts of foliar injury. The amount of visible foliar injury was negatively correlated (r(2) = 0.82) with net photosynthetic rates, but was not related to stomatal conductance. Net photosynthesis and stomatal conductance thus became uncoupled at high levels of visible foliar injury.     

Integrated assessment modeling of atmospheric pollutants in the Southern Appalachian Mountains. Part I: hourly and seasonal ozone

Recently, a comprehensive air quality modeling system was developed as part of the Southern Appalachians Mountains Initiative (SAMI) with the ability to simulate meteorology, emissions, ozone, size- and composition-resolved particulate matter, and pollutant deposition fluxes. As part of SAMI, the RAMS/EMS-95/URM-1ATM modeling system was used to evaluate potential emission control strategies to reduce atmospheric pollutant levels at Class I areas located in the Southern Appalachians Mountains. This article discusses the details of the ozone model performance and the methodology that was used to scale discrete episodic pollutant levels to seasonal and annual averages. The daily mean normalized bias and error for 1-hr and 8-hr ozone were within U.S. Environment Protection Agency guidance criteria for urban-scale modeling. The model typically showed a systematic overestimation for low ozone levels and an underestimation for high levels. Because SAMI was primarily interested in simulating the growing season ozone levels in Class I areas, daily and seasonal cumulative ozone exposure, as characterized by the W126 index, were also evaluated. The daily ozone W126 performance was not as good as the hourly ozone performance; however, the seasonal ozone W126 scaled up from daily values was within 17% of the observations at two typical Class I areas of the SAMI region. The overall ozone performance of the model was deemed acceptable for the purposes of SAMI's assessment.     

Integrated Assessment Modeling of Atmospheric Pollutants in the Southern Appalachian Mountains. Part I: Hourly and Seasonal Ozone

Abstract

Recently, a comprehensive air quality modeling system was developed as part of the Southern Appalachians Mountains Initiative (SAMI) with the ability to simulate meteorology, emissions, ozone, size- and composition-resolved particulate matter, and pollutant deposition fluxes. As part of SAMI, the RAMS/EMS-95/URM-1ATM modeling system was used to evaluate potential emission control strategies to reduce atmospheric pollutant levels at Class I areas located in the Southern Appalachians Mountains. This article discusses the details of the ozone model performance and the methodology that was used to scale discrete episodic pollutant levels to seasonal and annual averages. The daily mean normalized bias and error for 1-hr and 8-hr ozone were within U.S. Environment Protection Agency guidance criteria for urban-scale modeling. The model typically showed a systematic overestimation for low ozone levels and an underestimation for high levels. Because SAMI was primarily interested in simulating the growing season ozone levels in Class I areas, daily and seasonal cumulative ozone exposure, as characterized by the W126 index, were also evaluated. The daily ozone W126 performance was not as good as the hourly ozone performance; however, the seasonal ozone W126 scaled up from daily values was within 17% of the observations at two typical Class I areas of the SAMI region. The overall ozone performance of the model was deemed acceptable for the purposes of SAMI’s assessment.     

Translating science into policy: using ecosystem thresholds to protect resources in Rocky Mountain National Park

Concern over impacts of atmospheric nitrogen deposition to ecosystems in Rocky Mountain National Park, Colorado, has prompted the National Park Service, the State of Colorado Department of Public Health and Environment, the Environmental Protection Agency, and interested stakeholders to collaborate in the Rocky Mountain National Park Initiative, a process to address these impacts. The development of a nitrogen critical load for park aquatic resources has provided the basis for a deposition goal to achieve resource protection, and parties to the Initiative are now discussing strategies to meet that goal by reducing air pollutant emissions that contribute to nitrogen deposition in the Park. Issues being considered include the types and locations of emissions to be reduced, the timeline for emission reductions, and the impact of emission reductions from programs already in place. These strategies may serve as templates for addressing ecosystem impacts from deposition in other national parks.     

Relations between crown condition and ozone and its dependence on environmental factors

It is now widely accepted that stomatal ozone uptake provides a more reliable indicator for the assessment of risk of ozone damage to forest trees than ozone exposure. Thus, environmental factors influencing stomatal opening strongly affect the sensitivity of forest trees towards high ozone concentrations. In this study the hydrological model WAWAHAMO is used to simulate stomatal opening dependent on air temperature, solar radiation, vapor pressure deficit and soil water potential. Then, a statistical analysis was carried out to investigate relations between crown defoliation and ozone concentrations dependent on stomatal opening. The results support the hypothesis that tropospheric ozone contributes to the observed crown defoliation. However, environmental factors strongly affect tree response to high ozone concentrations.     

Background ozone monitoring and phytodetection in the greater rural area of Corinth--Greece

Natural background ozone levels were monitored in three places within the greater rural area of Corinth, namely Bogdani Hill, Astronomical Observatory of Krionerion, and Kiato, and compared with ambient ozone monitored in the metropolitan area of Athens. Measurements were made sequentially, for a few weeks at each place, during the summer of 2000. In addition, ozone phytodetection, using tobacco (Nicotiana tabacum L.) plants of the Bel-W3 and Zichnomirodata varieties, was conducted in 12 places (the above included). Moreover, stomatal conductance was measured in the Bel-W3 plants, as well as in leaves of cultivated grape-vines (Vitis vinifera L.) and in needles of Aleppo pine (Pinus halepensis Mill.) trees and compared with the diurnal pattern of ozone concentrations.The 24 and 12 (08:00-20:00) hourly averages of ozone concentrations were high in Athens (37; 51 ppb), at Bogdani Hill (53; 56 ppb) and at the Astronomical Observatory (56; 55 ppb), but relatively low in Kiato (30; 34 ppb). Furthermore, the average daily AOT40 (accumulated exposure over 40 ppb for the daylight hours) (ppbh) was 193 in Athens, 212 at Bogdani Hill, 192 at the Astronomical Observatory and 47 in Kiato. Ozone concentrations exhibited the usual diurnal pattern in Athens (altitude 50 m), where they were maximum during midday and early afternoon hours, as well as at Bogdani Hill (300 m) and in Kiato (5 m) where, however, they were maximal 1-3 h later. At the Astronomical Observatory (altitude 920 m) ozone remained constant during both daylight and night hours. The differences in diurnal patterns are consistent with those in places of different elevation, reported elsewhere.The Bel-W3 plants were injured at all 12 places; Zichnomirodata plants exhibited lower injury and only in some of the places; probable ozone symptoms were also observed on vine plants and pine trees. The greatest injury was observed at the high altitude places of Astronomical Observatory and Mougostos. Stomatal conductance, in all three species, peaked during morning and early midday hours when ozone levels were higher in the high altitude, and lower in the low altitude, places.     

A flux-based assessment of the effects of ozone on foliar injury, photosynthesis, and yield of bean (Phaseolus vulgaris L. cv. Borlotto Nano Lingua di Fuoco) in open-top chambers

Stomatal ozone uptake, determined with the Jarvis' approach, was related to photosynthetic efficiency assessed by chlorophyll fluorescence and reflectance measurements in open-top chamber experiments on Phaseolus vulgaris. The effects of O₃ exposure were also evaluated in terms of visible and microscopical leaf injury and plant productivity. Results showed that microscopical leaf symptoms, assessed as cell death and H₂O₂ accumulation, preceded by 3-4 days the appearance of visible symptoms. An effective dose of ozone stomatal flux for visible leaf damages was found around 1.33 mmol O₃ m⁻². Significant linear dose-response relationships were obtained between accumulated fluxes and optical indices (PRI, NDI, ΔF/F_m^′). The negative effects on photosynthesis reduced plant productivity, affecting the number of pods and seeds, but not seed weight. These results, besides contributing to the development of a flux-based ozone risk assessment for crops in Europe, highlight the potentiality of reflectance measurements for the early detection of ozone stress.     

Modelling of stomatal conductance and ozone flux of Norway spruce: comparison with field data

It has been proposed that stomatal flux of ozone would provide a more reliable basis than ozone exposure indices for the assessment of the risk of ozone damage to vegetation across Europe. However, implementation of this approach requires the development of appropriate models which need to be rigorously tested against actual data collected under field conditions. This paper describes such an assessment of the stomatal component of the model described by Emberson et al. (2000. Modelling stomatal ozone flux across Europe. Environmental Pollution 110). Model predictions are compared with field measurements of both stomatal conductance (g(s)) and calculated ozone flux for shoots of mature Norway spruce (Picea abies) growing in the Tyrol Mountains in Austria. The model has been developed to calculate g(s) as a function of leaf phenology and four environmental variables: photosynthetic flux density (PFD), temperature, vapour pressure deficit (VPD) and soil moisture deficit (SMD). The model was run using climate data measured on site, although the SMD component was omitted since the necessary data were not available. The model parameterisation for Norway spruce had previously been collected from the scientific literature and therefore established independently from the measurement study. Overall, strong associations were found between model predictions and measured values of stomatal conductance to ozone (GO(3)) and calculated stomatal ozone flux (FO(3)). Average diurnal profiles of GO(3) and FO(3) showed good agreement between the field data and modelled values except during the morning period of 1990. The diurnal pattern of ozone flux was determined primarily by PFD and VPD, as there was little diurnal variation in ozone concentration. In general, the model predicted instances of high ozone flux satisfactorily, indicating its potential applicability in identifying areas of high ozone risk for this species.