Assessing the role of soil water limitation in determining the Phytotoxic Ozone Dose (PODY) thresholds

Alessandra De Marco, Pierre Sicard, Silvano Fares, Juha-Pekka Tuovinen, Alessandro Anav, Elena Paoletti

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23 Citations (Scopus)

Abstract

Phytotoxic Ozone Dose (PODY), defined as the accumulated stomatal ozone flux over a threshold of Y, is considered an optimal metric to evaluate O3effects on vegetation. PODY is often computed through the DO3SE model, which includes species-specific parameterizations for the environmental response of stomatal conductance. However, the effect of soil water content (SWC) on stomatal aperture is difficult to model on a regional scale and thus often ignored. In this study, we used environmental input data obtained from the WRF-CHIMERE model for 14,546 grid-based forest sites in Southern Europe. SWC was obtained for the upper 10 cm of soil, which resulted in a worst-case risk scenario. PODY was calculated either with or without water limitation for different Y thresholds. Exclusion of the SWC effect on stomatal fluxes caused a serious overestimation of PODY. The difference increased with increasing Y (78%, 128%, 237% and 565% with Y = 0, 1, 2 and 3 nmol O3m−2s−1, respectively). This behaviour was confirmed by applying the same approach to field data measured in a Mediterranean Quercus ilex forest. WRF-CHIMERE overestimated SWC at this field site, so under real-world conditions the SWC effect may be larger than modelled. The differences were lower for temperate species (Pinus cembra 50–340%, P. sylvestris 57–363%, Abies alba 57–371%) than for Mediterranean species (P. pinaster 87–356%, P. halepensis 96–429%, P. pinea 107–532%, Q. suber 104–1602%), although a high difference was recorded also for the temperate species Fagus sylvatica with POD3 (524%). We conclude that SWC should be considered in PODY simulations and a low Y threshold should be used for robustness.
Original languageEnglish
Pages (from-to)88 - 97
Number of pages10
JournalAtmospheric Environment
Volume147
DOIs
Publication statusPublished - 1 Dec 2016
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Environmental Science(all)
  • Atmospheric Science

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