Trends and inter-relationships of ground-level ozone metrics and forest health in Lithuania.


Hokkaido Research Centre, Forestry and Forest Products Research Institute, Sapporo, Japan; Research Faculty of Agriculture, Hokkaido University, Sapporo, Japan. Electronic address: [Email]


Lithuania is representative of maritime to continental climate, no water limitation, and moderate ground-level ozone (O3) pollution. We investigated the trends of meteorological variables and O3 and how these environmental conditions associate with tree health from 2001 onward. Ozone metrics for forest protection, based on Accumulated O3 exposure Over a Threshold of X ppb (AOTX) or on Phytotoxic O3 Dose over a Y threshold (PODY), were modeled at nine ICP-Forests plots over the time period 2001-2014. Tree-response indicators, i.e. crown defoliation and visible foliar O3 injury, were assessed during annual field surveys carried out at each ICP-Forests plot over the time period 2007-2017. Mann-Kendall and Sen statistical tests were applied to estimate changes over time of meteorological variables, response indicators and O3 metrics. Finally, the O3 metrics were correlated (Spearman test) to the response indicators over the common period 2007-2014. Over this time period, trend analyses revealed an increasingly hotter (+0.27 °C decade-1, on average) and drier climate (rainfall, -48 mm decade-1). A reduction was found for O3 annual mean (-0.28 ppb decade-1, on average) and AOT40 (-2540 ppb·h decade-1, on average) whereas an increase was found for POD0 (+0.40 mmol m-2 decade-1, on average). Visible foliar O3 injury increased (+0.17% decade-1), while an improvement of the crown conditions (-5.0% decade-1) was observed. AOT40 was significantly associated with crown defoliation while PODY and soil water content were correlated with visible foliar O3 injury. As visible foliar O3 injury was negligible in all the studied species, the results suggest that moderate O3 pollution (approximately 30 ppb as annual average) does not induce biologically significant effects on this forest vegetation under the current conditions, however the overall O3 risk (POD0) is expected to increase in the future under a hotter and drier climate.


Crown defoliation,Epidemiology,Ozone,POD,Stomatal flux-based,Visible injury,

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