Estimation of ozone concentrations above forests using atmospheric observations at urban air pollution monitoring stations

Abstract

As tropospheric ozone (O 3 ) concentrations over Japan are increasing, there is concern over its potential adverse effects on forest trees induced by stomatal uptake in the daytime. Although atmospheric data, including O 3 levels, have been frequently collected at air pollution monitoring stations in urban areas since the 1970s, continuous recording of O 3 concentration data above forests has been less frequent. Therefore, O 3 concentrations above forests were monitored at three flux towers in Sapporo, Appi, and Yamashiro from 2012 onwards. Furthermore, past daytime O 3 concentrations in the forests were estimated by a multiple regression model using atmospheric and meteorological data of the forests and nearby monitoring stations. The obtained daytime (sunrise to sunset) forest O 3 concentrations were positively correlated with urban O 3 concentrations, although less correlated early in the morning. In the multiple regression analysis, the model with the minimum Akaike information criterion was employed using data from 2012 and validated using data from 2013. To assess past O 3 risk, we estimated O 3 concentrations over the forests from 2000 to 2011 and calculated the cumulative exposure index AOT40 during daylight hours (≥ 50 Wm -2 global radiation). Among the three sites, AOT40 was lowest in the Sapporo forest site and did not exceed the critical level for the dominant canopy species (Betula platyphylla var. japonica and Quercus mongolica var. crispula) from 2000 to 2011. Conversely, since the dominant canopy species of the Appi forest site is Fagus crenata, categorized as a highly O 3 -sensitive species, the forest of Appi was subject to AOT40 above the critical level throughout the period from 2001 to 2011. As AOT40 of Yamashiro has increased and exceeded the critical level of the dominant canopy species, Q. serrata (a moderately O 3 -sensitive species), since 2006, the forest of Yamashiro might have suffered some adverse effects of O 3 exposure.

Seasonal Changes in Interclone Variation Following Ozone Exposure on Three Major Gene Pools: An Analysis of Cryptomeria Japonica Clones

“…In recent years, there has been an increase in the concentration of ozone in Japan due to a decrease in NO titration and an increase in transboundary air pollution [1][2][3]. With long-term ozone exposure effects on plants, changes in the carbon allocation, photosynthetic rate [4], stomatal conductance [5], yield of crops [6], and biogenic volatile organic compound (BVOC) emission characteristics [7] have been reported.…”

Increased phytotoxic O3 dose accelerates autumn senescence in an O3-sensitive beech forest even under the present-level O3

“…Then, we developed a multiple linear regression model for each forest site estimating the daytime tower O 3 concentration, using O 3 and NO 2 concentrations at the air pollution station and air temperatures at both the station and the forest site (details in ref. 42 ). Using the models, we estimated C m at the flux sites (2001 to 2006 at Appi forest site and 2004, 2005, and 2009 at Yamashiro forest site) based on the past meteorological data monitored at the adjacent air pollution stations.…”

FACE-ing the challenges of increasing surface ozone concentration in Asia

“…Ozone concentrations at three forest sites in Japan were analyzed with respect to the calculated O 3 risks for vegetation (Komatsu et al, 2015). The two forests with sensitive species being dominant appear to be at risk of O 3 damages.…”