Ozone and particle fluxes in a Mediterranean forest predicted by the AIRTREE model (original) (raw)
Related papers
Atmospheric Environment, 2005
Ozone (O 3) induces deleterious effects on plants by its oxidising capacity. Efforts have aimed at defining O 3 critical loads which are based on O 3 penetrating into the plant through the stomata, being an important mechanism of O 3 removal. Recently, papers have proposed the use of process-based models for estimating the O 3 dose at the community level. These models should define the stomatal O 3 flux (F st) on vegetation, correlating it to O 3-induced injury and hence to improve the database available for decision makers. A process-based model has been utilised for the quantification of O 3 flux (F) toward a Holm oak forest and its repartition in F st and non-stomatal flux (F nost) during daylight. The model outputs have been compared with eddy covariance measurements. Simulation of O 3 fluxes under the climatic limitations of summer 2003 showed that the mean values of F st represented only 28.9% of F, which was similar to eddy covariance (31.5%). The use of LAI effective to link the leaf F st to the canopy scale O 3 stomatal flux (F effectjve ; on ground unit) is shown to be useful not only for the model validation but also for upscaling purposes from leaf to canopy. Forest acts as a LAI ¼ 1; i.e. a ''real'' big leaf for canopy O 3 uptake. Changes in O 3 fluxes were more closely related to the factors that control O 3 deposition than to the factors controlling O 3 concentration. Simulations showed that Holm oak forest was most effective at taking up O 3 under moderate to high irradiance and high physiological activity, but not in limiting environmental conditions. The model used here does not require a great number of input variables and it is based on simple assumptions with respect to other more recognised models. So, the use of this model can have useful applications for the risk assessment of level II for the forests.
Tropospheric ozone (O 3 ) is one of the most toxic compounds for plants in the atmosphere. The large amount of anthropogenic O 3 precursors in the urban areas promote O 3 formation, thus making Mediterranean forests located in periurban areas particularly vulnerable to this pollutant. O 3 fl ux measurements have been carried out using the Eddy Covariance technique over a Holm oak forest located 25 Km from Rome downtown, inside the Presidential Estate of Castelporziano (Italy).Two transition periods -early Spring and late Fall -in two consecutive years were examined. The uncommon low precipitation recorded in both transition periods in 2012 allowed to evaluate the infl uence of water availability on O 3 fl uxes during seasons which are not commonly affected by drought stress. Overall, the forest canopy showed to be a net sink of O 3 , with peak values of mean daily O 3 fl uxes of -8.9 nmol m -2 s -1 at the beginning of fl owering season and -4.6 nmol m -2 s -1 at the end of Fall. O 3 fl uxes were partitioned between stomatal and non stomatal sinks using the evaporative/resistive method based on canopy transpiration in analogy with an Ohm circuit. By comparison of the two years, water availability showed to be an important limiting factor during Spring, since in this season plants are more photosynthetically active and more sensitive to water availability, while in Fall, under conditions of low stomatal conductance, the dependence on water availability was less appreciated.
Modelling ozone fluxes to forests for risk assessment: status and prospects
Annals of Forest Science, 2009
Risk assessment of ozone effects on forests is gradually moving from concentration-based exposure metrics to a more complicated approach that requires modelling of ozone fluxes to trees. • This study reviews the status of the DO 3 SE stomatal flux model employed within the Convention on Long-range Transboundary Air Pollution, describing a range of applications and identifying major research needs, especially in the context of support that could be provided by the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests. • The most urgent development need for DO 3 SE is the modelling of the soil moisture status and its effect on stomatal conductance. Furthermore, the data related to the physical characteristics and the seasonal dynamics of physiological activity of vegetation continue to pose problems. • There is a clear need for more extensive validation of models and risk estimates using more rigorous statistical procedures and comparisons with flux networks and satellites. • The current large-scale forest monitoring activities provide only limited possibilities for flux modelling, but could be enhanced by introducing a new monitoring strategy outlined here.
Environmental Pollution, 2009
Ozone fluxes to a Holm oak coastal forest show inter-annual variations depending on meteorological conditions and water availability. a b s t r a c t Ozone and energy fluxes have been measured using the eddy covariance technique, from June to December 2004 in Castelporziano near Rome (Italy), and compared to similar measurements made in the previous year. The studied ecosystem consisted in a typical Mediterranean Holm oak forest. Stomatal fluxes have been calculated using the resistance analogy and by inverting the Penmann-Monteith equation. Results showed that the average stomatal contribution accounts for 42.6% of the total fluxes. Non-stomatal deposition proved to be enhanced by increasing leaf wetness and air humidity during the autumnal months. From a comparison of the two years, it can be inferred that water supply is the most important limiting factor for ozone uptake and that prolonged droughts alter significantly the stomatal conductance, even 2 months after the soil water content is replenished. Ozone exposure, expressed as AOT40, behaves similarly to the cumulated stomatal flux in dry conditions whereas a different behaviour for the two indices appears in wet autumnal conditions. A difference also occurs between the two years.
Theme 1 : Quantifying ozone impacts on Mediterranean Forests
2012
How well does DO 3 SE perform? Can we predict flux from passive sampler measurements? Can we set new critical levels specific to Mediterranean forests yet? Is there field-based evidence of predicted impacts? 09:00-10:30: session 1 (15 min per presentation, 10 min discussion per paper) 09:00 Mihaela Mircea et al.-Ozone simulations over Italy with the atmospheric modelling system of the Minni project: evaluation and perspectives for vegetation. 09:25 Angelo Finco et al.-When stomatal flux is predictable from AOT40. Results of a 13 years stomatal flux calculation exercise at an Alpine spruce forest with the DO 3 SE model. 09:50 Alessandra De Marco et al.-FO 3 REST project-First application of DO 3 SE model on French and Italian Forests: Comparison of risk indicators for Mediterranean trees. 10:15 General discussion. 10:30-11:00 Coffee/tea 11:00-12:20: session 2 (15 min per presentation, 10 min discussion per paper) 11:00 Silvano Fares et al.-Measured and modelled stomatal and non-stomatal ozone fluxes in a mixed Mediterranean forest. 11:25 Rocio Alonso et al.-Ozone critical levels for Mediterranean forests.
Journal of Geophysical Research, 2012
The effect of air pollution on vegetation and the consequent changes in atmospheric chemistry are largely under-investigated; a new generation of chemical transport models fully coupled with complex land surface models is needed to better represent the feedbacks between vegetation and atmospheric chemistry. In this context, we coupled at high spatial resolution (30 km) the chemistry transport model CHIMERE with the land surface model ORCHIDEE to study the regional impact of tropospheric ozone on Euro-Mediterranean vegetation and the consequent changes in biogenic emission and ozone dry deposition owing to modifications in canopy conductance and LAI due to the ozone stress on vegetation. Results for the year 2002 show that the effect of tropospheric ozone on vegetation leads to a significant reduction of about 23% in the annual gross primary production, followed by a reduction in leaf area index. In addition, results show that CHIMERE does not correctly reproduce the activity of evergreen forests, grassland and crops during winter and fall, and consequently the dry deposition velocity is affected by this wrong pattern. On the other hand, in the coupled model, we have a better representation of vegetation activity during cold months, and the general performance of the model is improved compared to local site observations.
DO3SE modelling of soil moisture to determine ozone flux to forest trees
Atmospheric Chemistry and Physics, 2012
The DO 3 SE (Deposition of O 3 for Stomatal Exchange) model is an established tool for estimating ozone (O 3 ) deposition, stomatal flux and impacts to a variety of vegetation types across Europe. It has been embedded within the EMEP (European Monitoring and Evaluation Programme) photochemical model to provide a policy tool capable of relating the flux-based risk of vegetation damage to O 3 precursor emission scenarios for use in policy formulation.
This report synthesises current knowledge on the effects of ground-level ozone on carbon sequestration in the living biomass of trees. Ground-level ozone is not only an important air pollutant, it is also the third most important greenhouse gas after carbon dioxide and methane. Both carbon dioxide and ozone are taken up through the thousands of microscopic pores on the surfaces of leaves. Whereas carbon dioxide is required for plant growth, ozone inhibits growth in sensitive species. Trees are an important sink for carbon dioxide and ozone, reducing their concentration in the atmosphere and hence the amount of global warming. However, the damaging impact of ozone on vegetation reduces the land carbon sink for these greenhouse gases, resulting in a positive feedback on global warming. For the first time, ozone effects in Europe have been quantified using the flux-based methodology that takes into account the modifying effect of climate, soil and plant factors on the amount of ozone t...
2015
Tropospheric ozone (O3) produces harmful effects to forests and crops, leading to a reduction of carbon assimilation that, consequently, influences land sink and crop yield production. To assess the potential negative O3 impacts to vegetation, the European Union uses the Accumulated Ozone over Threshold of 40 ppb (AOT40). This index has been chosen for its simplicity and flexibility in handling different ecosystems as well as for its linear relationships with yield or biomass loss. However, AOT40 does not give any information on the physiological O3 uptake into the leaves since it does not include any environmental constraints to O3 uptake through stomata. Therefore, an index based on stomatal O3 uptake, which describes the amount of O3 entering into the leaves, would be more appropriate. We compare different potential O3 risk assessments based on two methodologies (i.e. AOT40 and stomatal O3 uptake) using a framework of mesoscale models that produces hourly meteorological and O3 da...