Ozone at the intensive monitoring plots in South-Western European forests: levels, risks, actual and potential effects

Rationale

Visible symptoms arising from ozone-induced injury on Viburnum lantana leaves

Ozone (O₃) is the most important regional air pollutant that may impact forest vegetation in Europe and elsewhere (e.g. Fowler et al., 1999). Current O₃ levels and model predictions, together with a series of field and experimental evidences, seem to support the above concern. Yet, "especially the lack of ozone data is a serious limitation" for the EU Intensive Monitoring (Level II) database (De Vries, 2000, p. 27) and it is a considerable scientific and political shortcoming in a program aimed to investigate air pollution effects on forests. Besides the obvious connections with the potential effects on forests, the same strategy document of the EC and UN/ECE intensive monitoring reports the relevance of O₃ data also in relation to other themes which were subjected to important political agreement, like the tropospheric chemistry changes and the regional ozone formation (see e.g. the CLRTAP multi-pollutant, multi-effect directive; the Un Biodiversity Convention; the EU Habitat Directive; the EU acidification strategy, the UN/ECE CLRTAP, the EU Air Quality directive) (De Vries, 2000, p. 19).

While atmospheric O₃ monitoring is still optional under the EU Level II program, various countries are currently measuring O₃ at their intensive monitoring plots: for example France, Italy, Spain and Switzerland are measuring O₃ concentrations by means of e.g. passive samplers. Passive samplers are useful to get an idea about mean weekly/fortnightly O₃ levels, but they do not provide indication about e.g. AOT40 values, i.e. the exposure indicator currently adopted to estimate the potential risk for forests as well as natural vegetation and crops (Fuhrer et al, 1997), nor about the actual vegetation O₃ uptake.

However, some work has been done to estimate O₃ concentrations under complex terrain condition as function of altitude and daytime (e.g. Loibl et al., 1994) and this provide the basis for calculating AOT40 (Level I) values starting from e.g. weekly mean values obtained by passive samplers. However, it is widely recognised that plant response is actually more closely related to the internal ozone dose i.e. the ozone taken into the plant through the stomata, which in turn depends on a variety of ecological factors. Recently, considerable progresses has been done to estimate AOT40 Level II values (an expression of exposure that incorporates the factors modifying the response of plants to ozone, thus providing an estimation of the actual O₃ uptake by plants) (Emberson et al., 1998, 2000; Simpson et al., 2000) or other exposure indices (e.g. Grünhage et al., 2001) that may provide more reliable estimates of the actual risk due to O₃.

Interpolated Ozone Levels, 1998

Project aims

The project addresses an important ecological, scientific and political issue not yet addressed in the 2000-2005 strategy plan for data evaluation suggested by the Forest Intensive Monitoring Coordinating Institute (FIMCI). The project will concentrate on the objectives listed below:

1. Provide a synoptic view of descriptors of ozone concentration at 62 forest sites in south-western Europe ( a comprehensive dataset about forest sites will provide a considerable input for a better understanding of ozone levels in remote areas).
2. Evaluate the factors associated to ozone concentration, with major emphasis placed on geographical and meteorological factors. The identification of the main driving factors and the relative contribution will provide the basis for future upscaling studies.
3. Estimate AOT40 Level I values and other exposure indices (e.g., mean values on different time basis, Grünhage et al., 2001) for the intensive monitoring plots in France, Italy, Spain and Switzerland starting from the data collected by passive samplers, their validation against continuous O3 monitors (where available ) and/or comparison with available modeled data (e.g. EMEP). This will provide a first estimation of the potential risks in relation to ozone.
4. Estimate actual O3 uptake by taking into account the modifying factors.

Methods

• Passive sampling
• multiple regression models
• Residuals analysis
• Modelling

Work plan

The following working packages have been identified:

The Swiss participants are responsible for WP 3.

Data

Ozone data (WP1, WP2, WP3)

Response indicators data (NFCs):

• BAI of the dominant storey
• Crown transparency and discoloration (plus additional indicators, if any)
• Net throughfall of base cations (Ca, Mg, K)
• Foliar nutrients (N, P, Ca, Mg, K)
• (Foliar symptoms)

Predictors data:

• Site elevation, slope, aspect, coordinates
• Number of trees per ha
• Management practice (high forest; coppice; stored coppice)
• Soil nutrients, BCE, ACE, CEC
• Soil type
• Meteo data (P, T, Stress indices)

Results

This study investigated “Ozone at the intensive monitoring plots in South-Western European Forests – Levels, risk, actual and potential effects”.

Ozone (O₃) concentration was measured by passive sampling at 83 forest monitoring sites in France, Italy, Spain and Switzerland. Distinct latitudinal and altitudinal trends are detected.

On the basis of passive sampling, cumulated exposure AOT40 was estimated and results show that exceedance of the critical level (either the “old” 10 ppm*h and the “new” 5 ppm*h) occur at the majority of the investigated sites.

An attempt to model stomatal O₃ flux was undertaken: the results are realistic and
provide evidence of the possibility of an inconsistency between the outcome of the
AOT40 and the flux analysis. Multivariate analysis identifies O₃ as a significant predictor of crown defoliation although its influence seems less important than site and soil characteristics. Visible O₃-like foliar symptoms are reported for many sites and taxa in France, Italy, Spain and Switzerland. Symptoms occur throughout the exposure range with little relation to exposure levels. Overall, the project provides a number of valuable information about O₃ levels, exposures and effects and many indications to improve the monitoring of O₃ risk in the context of an effect-oriented monitoring program.

Participants

• Norbert Kräuchi (Project leader)
• Marcus Schaub
• Kris Novak
• Marco Ferretti
• José Maria Sanz
• Vicent Calatayud
• Filippo Bussotti
• Enrico Pompei
• Bruno Petriccione
• Erwin Ulrich
• Gerardo Sanchez

Publications

• Schaub, M., Emberson, L., Büker, P. and Kräuchi, N., 2007. Preliminary results of modeled ozone uptake for Fagus sylvatica L. trees at selected EU/UN-ECE intensive monitoring plots. Environmental Pollution, in press. doi:10.1016/j.envpol.2006.02.029
• Ferretti, M., Bussotti, F., Calatayud, V., Schaub, M., Kräuchi, N., Petriccione, B., Sanchez-Peña, G., Sanz, M-J. and Ulrich, E., 2007. Ozone and forests in South-Western Europe – What have we learned? Environmental Pollution, in press. doi:10.1016/j.envpol.2006.02.027
• Ferretti, M., Bussotti, F., Calatayud, V., Schaub, M., Kräuchi, N., Petriccione, B., Sanchez-Peña, G., Sanz, M-J. and Ulrich, E., 2007. Ozone and forests in South-Western Europe. Environmental Pollution, in press. doi:10.1016/j.envpol.2006.02.026
  
• Ferretti, M., Calderisi, M. and Bussotti, F., 2007. Ozone exposure, defoliation of beech (Fagus sylvatica L.) and visible foliar symptoms on native plants in selected plots of South-Western Europe. Environmental Pollution, in press. doi:10.1016/j.envpol.2006.02.028
• Sanz, M.J., Calatayud, V. and Sánchez-Peña, G., 2007. Measures of ozone concentrations using passive sampling in forests of South Western Europe. Environmental Pollution, in press. doi:10.1016/j.envpol.2006.02.031
  
• Gerosa, G., Ferretti, M., Bussotti, F. and Rocchini, D., 2007. Estimates of ozone AOT40 from passive sampling in forest sites in South-Western Europe. Environmental Pollution, in press. doi:10.1016/j.envpol.2006.02.030
  
• Ferretti, M., Bussotti, F., Calatyud, V., Sanz, M.J., Schaub, M., Kräuchi, N., Petriccione, B., Sanchez-Peña, G., Ulrich, E., 2004. O3 SWE - Ozone and the forests of South-Western Europe: an international co-operative initiative. In: Ferretti, M., Sanz, M.J., Schaub, M. (Eds.), O3 SWE - Ozone and the Forests of South-Western Europe. Final Report. Jointly prepared by Corpo Forestale dello Stato, Italia; Ministerio de Medio Ambiente, Dirección General para la Biodiversidad, España; Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft - WSL, Schweiz; Office National des Forêts, France: 149 pps. (pdf-file).
• Ferretti, M., Bussotti, F., Calatyud, V., Sanz, M.J., Schaub, M., Kräuchi, N., Petriccione, B., Sanchez-Peña, G., Ulrich, E., 2004. Ozone and the forests of South-Western Europe: a summary. In: Ferretti, M., Sanz, M.J., Schaub, M. (Eds.), O3 SWE - Ozone and the Forests of South-Western Europe. Final Report. Jointly prepared by Corpo Forestale dello Stato, Italia; Ministerio de Medio Ambiente, Dirección General para la Biodiversidad, España; Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft - WSL, Schweiz; Office National des Forêts, France: 149 pps. (pdf-file).
• Ferretti, M., Sanz, M.J., Schaub, M., (Eds.), 2004. O3 SWE - Ozone and the Forests of South-Western Europe. Final Report. Jointly prepared by Corpo Forestale dello Stato, Italia; Ministerio de Medio Ambiente, Dirección General para la Biodiversidad, España; Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft - WSL, Schweiz; Office National des Forêts, France: 149 pps. (Front cover, Impressum, Chapter 1, Chapter 2, Chapter 3, Chapter 4, Chapter 5, Chapter 6 ).
• Schaub, M., Kräuchi, N., Emberson, L., Büker, P., 2004. Preliminary estimates of ozone uptake for Fagus sylvatica L. canopy stands on selected EU/UN-ECE intensive monitoring plots in South-Western Europe. In: Ferretti, M., Sanz, M.J., Schaub, M. (Eds.), O3 SWE - Ozone and the Forests of South-Western Europe. Final Report. Jointly prepared by Corpo Forestale dello Stato, Italia; Ministerio de Medio Ambiente, Dirección General para la Biodiversidad, España; Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft - WSL, Schweiz; Office National des Forêts, France: 149 pps. (pdf-file)

• Marcus Schaub
  

Link

• Effect- and Risk Assessment of Ozone Air Pollution on Forest Vegetation in Switzerland