For assessment of ozone risks to forests we used ozone thresholds and air quality guidelines set by several international organizations for protection of vegetation. We also used spatial modelling for estimation of basic ozone characteristics. Calculations of models were performed in the environment of the programme Idrisi 32. The spatial coverage of ozone monitoring network in the Slovak Republic has insufficient density. Ozone data come from two sources; SHMI/EMEP database of ozone concentrations from 4 monitoring stations and ozone database of FRI from 3 monitoring stations

Both CO2 and ozone increased the diseased leaf area of clone V5952 in Exp. 1 in the year 2000. The size of spots increased most under ozone fumigation, and the number of spots under ozone and CO2 + O3 fumigations. In clone K1659 all fumigation treatments decreased or had no effect on the DLA, or the number and size of the leaf spots. Also the number of fallen leaves under fumigation treatments was higher in clone V5952 than in clone K1659. Analysis of the year 2001 monitoring results is currently going on

Global environmental change, including increasing atmospheric CO2 and tropospheric O3 is likely to impact forest growth and wood properties. Increase in CO2 enhances photosynthesis, growth and productivity. On the contrary, O3 is detrimental to forest vitality and yield. At present reports of long-term studies on the effects of combined exposures of CO2 and O3 on stem wood chemistry of deciduous trees are lacking. The aim of this study was to investigate the effects of CO2 and O3, singly or in combination, on stem wood chemistry of four-year old saplings of trembling asspen (Populus tremuloides) clones differing in ozone tolerance, paper birch (Betula papyrifera) and sugar maple (Acer saccharum)

The future productivity of forests will be affected by combinations of anthropogenic stresses including elevated atmospheric CO2 and O3. Because the productivity of forests, will be in part, determined by the growth of young trees, we evaluated the responses of Pinus ponderosa seedlings to ambient or elevated CO2 and/or high O3. Shoot growth and whole plant biomass were evaluated for seedlings growing under the CO2 and O3 treatments for 3 years in sun-lit mesocosms with ambient temperature and humidity. This study indicated the potential for CO2 but not O3 effects on Pinus ponderosa seedlings under realistic field conditions as used in this study

Under elevated CO2 photosynthesis was 15-50% higher than in chamber controls depending on the weather conditions of the growing seasons. When measured at 360 ppm CO2 both elevated CO2 and elevated CO2 + O3 treatments decreased net photosynthesis, stomatal conductance and also transpiration, indicating downregulation of photosynthesis at elevated CO2

Stimulation of photosynthesis by elevated CO2 has been consistently found for aspen but not for maple. Similar responses have been shown for growth. In contrast, O3 causes decreased levels of photosynthesis and growth in aspen but does not appear to impact sugar maple significantly. When the pollutants co-occur, CO2 induced enhancements in photosynthesis and growth are moderated so that trees in CO2 and O3 treatments respond similarly to those in control rings. In this presentation, we will provide a physiological interpretation of our results in modelling growth response under future atmospheric conditions

Passive samplers offer considerable advantages for measuring ozone (O3) concentrations in remote areas. Measurements with passive samplers typically result in data about weekly-to-monthly O3 concentrations, which are not consistent with the definitions of cumulative indices currently being used to estimate the exposure of vegetation to O3. For this reason, attempts were and are being made to develop statistical and empirical methods to estimate exposure indices like the AOT40 adopted in Europe (O3 Accumulated Over Threshold 40 ppb) starting from mean concentrations obtained from passive samplers. This paper describes an empirical method adopted in Italy to estimate 1996-2000 AOT40 values at 20 forest sites of the Italian network of intensive monitoring of forest ecosystems

Ailanthus altissimia Desf. is a non-native species spread throughout the Southern Europe as invasive plant. It demonstrated to be very sensitive to ozone and ozone-polluted environment, develops brownish stipples on the upper leaf surface. In the 2001 summer 12 young plants were placed in a site near the city of Florence (Italy), where high levels of ozone were experienced. Six of them were regularly watered and six were watered only when the wilting of their leaves was evident. Regular assessments were done during the experiment. They concerned growth, production of new leaves, dead and shedding of old leaves, visible symptoms of damage, stomatal conductance and CO2 uptake, chlorophyll fluorescence. The results suggest that the sensitivity to ozone of watered plants is connected to their higher growth ratio and stomatal conductance. Ozone plays a more important role than drought in producing foliar stress conditions

Foliage of three trembling aspen clones differing in O3 tolerance from Rhinelander, Kenosha and Kalamazoo were examined for 24 elements in the year 2001 and they were analyzed by INAA at reactor IBR-2, by AAS Varian 400 and by elemental analyzer LECO SC 132 and SP 228. In the fofliage of trembling aspen we found no statistically significant difference in the concentration of 22 elements except for K and Ni between clones. For the concentrations of elements between localities we found statistically significant difference for Al, Ba, Ca, Cd, Cl, Co, Cu, La, Mo, Na, Ni, Pb, Sm, Sr and Zn

We studied elevated CO2 and ozone effects in single and in combination on crown structure of two Betula pendula clones. Shoot ramification, shoot length, number of metamers, leaves and buds were measured at four heights in every tree. Chamber effect was substantial on sylleptic branching and on shoot length and ramification. However these responses differed between the clones. Ozone treatment affected shoot length and caused slight decrease in shoot ramification. Elevated CO2 affected appearance of long shoots in complex manner, but in lower crown positions CO2 caused increased number of long shoots in both clones