ACTION 1: Exposure and visible symptoms - Forest and air quality data supply

Location

The total number of forest plots is 30 in South of France, including 3 RENECOFOR plots, and 49 across Italy including 24 plots in Piedmont region and 23 CONECOFOR plots. The ozone and meteorological measurements (passive samplers, analysers and modelling) and the modelling of the stomatal ozone uptake with the DO3SE model are carried out at every plot.

In parallel, the ozone-induced injury assessment is carried out at the 24 plots in Piedmont region and 28 in South of France. The tree growth analysis is made at 23 CONECOFOR plots across Italy and 3 RENECOFOR in South of France. For the RENECOFOR and CONECOFOR plots, the available data and observations are: foliar (every 2 years) and soil (every 10 years) chemistry, ambient air quality and meteorology (continuously), tree growth (every 5 years), crown condition (annually) and atmospheric deposition chemistry (continuously).


Main objectives

(1) Provide data which allow the assessment of dose-response relationships for a better understanding of the relationships between the condition of forest ecosystems and air pollution.

(2) Promote the collection, analysis and broadcasting of information on forests and interactions between forests and environment.

(3) Highlight relationships between ambient ozone concentrations, stomatal ozone uptake and observed impacts.

We analyse ozone versus leaf injury in order to evaluate present and proposed standards and thresholds for Mediterranean trees (such as Aleppo pine, Arolla pine, beech…) protection against ozone.


Methods employed

  • Passive samplers

  • They are placed in the open air, not under forest cover, and were protected by a metal sheet approximately 1.8m above the ground. The samplers contain a filter soaked in an ozone-absorbing solution. The gas enters the tube through the open end and passes through the filter by molecular diffusion. Each sampler remained in place for one month. Ionic chromatography was used to analyse the ozone (IVL Laboratories - Sweden). These data are used to correlate ambient ozone concentrations recorded and visible impacts on some trees.


  • Meteorological and ozone data by modelling

    The Chemical Transport Model CHIMERE multi-scale model, developed by the Pierre-Simon Laplace Institute (IPSL/CNRS), is designed to produce hourly forecasts and analysis of ozone with a resolution from 2 to 6 Km over the given region. The current version of CHIMERE coupled with the Weather Research and Forecasting (WRF) mesoscale meteorological model.



  • Stomatal ozone flux

    The determination of stomatal ozone fluxes is essential to assess the potential damage to plants due to ozone uptake. The stomatal flux is only a fraction of the total ozone flux between the atmosphere and the earth surface, i.e. the amount of ozone molecules (or moles) which cross the air/surface interface per unit area and time.


    DO3SE (Deposition of Ozone and Stomatal Exchange) has been developed to estimate the risk of O3 damage to European vegetation and is capable of providing flux-modelling estimates according to UNECE LRTAP (Long-Range Transboundary Air Pollution) methodologies for effects-based risk assessment. The DO3SE model is able to estimate O3 dry deposition to both stomatal and non-stomatal components of vegetated surfaces. The DO3SE model as described in Emberson et al. (2000) was applied using observed reference height O3 concentration and meteorological data.


    The stomatal conductance model described in the UNECE Mapping Manual (LRTAP Convention, 2004) is:

    gsto = gmax *[min(fphen, fO3)]* flight * max{fmin, (ftemp * fVPD * fSWC)}


    where gsto (mmolO3.m-2) is the stomatal uptake of O3 and gmax is the maximum stomatal conductance to O3 occurring during the growing season. fmin represents the minimum daytime stomatal conductance observed under field conditions before the onset of permanent wilting point. The factors fphen, flight, ftemp, fVPD and fSWC represent the modification of gmax due to leaf phenology, irradiance, air temperature, vapour pressure deficit (VPD) and soil water content (SWC), respectively. The f functions are expressed in relative terms between 0 and 1. Previous evaluations of the multiplicative gs models have found the identification of an appropriate value for gmax to be crucial in determining the predictive abilities of the model.



  • Ozone-induced injury: observation and notation

    Various studies have indicated the ozone impacts on ecosystems (Contran et al., 2007 ; Dalstein et al., 2001, 2002, 2004, 2005 et 2008; Ferretti et al., 2007 ; Paoletti et al., 2007; Ulrich et al., 2006). In order to identify ozone damages on vegetation, specific observations of ozone symptoms will be led on tree species, chosen according to their economic value in forestry and their sensibility to ozone and climate change. Increments in diameter will be also recorded.


    The ozone injury assessment is based on the ICP-Forests protocol. For every forest experimental plot, specific notations of ozone injury are realized on needles sample and/or branches on five branches of five trees.


    For broad-leaved trees, the ozone symptoms are assessed on thirty leaves of the annual twigs. For conifers, the same protocol is followed for every branch, at least thirty needles of the current year, one-year-old and two-years-old are examined. Observed symptoms on identified species are photographed and sampled for the herbarium realization. Damages are then confirmed by ICP-Forests experts.



  • Change in Growth: increments in volume

    The relationship between the ozone levels and the increments in volume at RENECOFOR and CONECOFOR plots are analysed. The growth data are assessed and available every five years for sensitive trees to ozone exposure.

 

Conclusion

Stepwise multivariate analyses will be carried out to understand the relative contribution of ozone (concentrations and stomatal uptake) and other correlated variables (light, air temperature, soil water content) to visible injury occurrence and tree growth reductions.

The DO3SE model has not been extensively tested under Mediterranean conditions with only one comparative study (Tuovinen et al., 2004) having been conducted to date for wheat growing in Italy. It is imperative that further evaluations should be performed, firstly since the model should be tested under all European climate types.

Finally, most experiments to establish biologically relevant plant responses have been performed under controlled conditions not representative of actual field conditions and the results may not provide realistic results for developing standards for protecting vegetation in natural environments. In comparison to other projects, the FO3REST project is directed toward a specific analysis of ozone symptoms and real damage levels in the field, trying to define more realistic thresholds for vegetation protection against ozone pollution.

FO3REST provides an opportunity to infer an evaluation of the DO3SE model parameterisation under “Mediterranean style” conditions. FO3REST will expand the sets of site-specific biological, climatic, soil and O3 as well as vegetation damage data, so that flux approaches may be validated.