Ambient Ozone Exposure in Czech Forests: A GIS-Based Approach to Spatial Distribution Assessment

Ambient ozone (O3) is an important phytotoxic pollutant, and detailed knowledge of its spatial distribution is becoming increasingly important. The aim of the paper is to compare different spatial interpolation techniques and to recommend the best approach for producing a reliable map for O3 with respect to its phytotoxic potential. For evaluation we used real-time ambient O3 concentrations measured by UV absorbance from 24 Czech rural sites in the 2007 and 2008 vegetation seasons. We considered eleven approaches for spatial interpolation used for the development of maps for mean vegetation season O3 concentrations and the AOT40F exposure index for forests. The uncertainty of maps was assessed by cross-validation analysis. The root mean square error (RMSE) of the map was used as a criterion. Our results indicate that the optimal interpolation approach is linear regression of O3 data and altitude with subsequent interpolation of its residuals by ordinary kriging. The relative uncertainty of the map of O3 mean for the vegetation season is less than 10%, using the optimal method as for both explored years, and this is a very acceptable value. In the case of AOT40F, however, the relative uncertainty of the map is notably worse, reaching nearly 20% in both examined years

Long-term effect of climate and air pollution on health status and growth of Picea abies (L.) Karst. peaty forests in the Black Triangle region

The Jizerské hory Mts. (the Czech Republic) are part of the Black Triangle region strongly af- fected by a decline and dieback of Norway spruce (Picea abies [L.] Karst.) stands since the 1970s. In the studied peaty spruce stands in the summit parts of the Jizerské hory Mts., the health status, radial growth and foliar nutrient content in relation to air pollution (SO2, NOX and O3) and climate factors (temperature, precipitation) were investigated in 1960–2015. A considerable disturbance of the stand structure induced by an increased mortality was observed in 1981–1983 when more than a half of the tree individuals died. Severe defoliation occurred in 1981 as a consequence of the synergic effects of air pollution, winter des- iccation and spruce bark beetle outbreak, as well as in 2015 due to the drought and high temperatures. Tree ring analyses indicated significant growth depression in 1979–1987, a period of the highest SO2 load, and in 2010–2015. Foliation and diameter increment were significantly influenced by SO2 and NOX con- centrations, the maximum daily concentration being the most negative factor; no significant correlation of the ozone exposure was detected, though. Foliar analyses also document significant negative impacts of air pollutants on the nutrient status of forest stands, mainly in the increase of the sulphur level. Since 1990, a significant increase in calcium and magnesium has been observed, as a result of forest liming. Interaction between radial growth and temperature was stronger compared to precipitation. Low temper- atures and high precipitation in growing season were the limiting factors for radial growth in waterlogged mountain areas

Stand dynamics in natural Scots pine forests as a model for adaptation management?

The paper deals with the dynamics of structure, diversity and growth of natural pine stands without direct human impact during the ten-year period in Nature Reserve (NR) Kostelecké bory, Czech Republic. The objective was to determine the main characteristics of the spontaneous development of Scots pine (Pinus sylvestris L.) forest stands in relation to their naturalness, ecological stability and adaptation to climate change and air pollution stress. Horizontal and vertical structure and species diversity of the tree layer, dead wood and natural regeneration of each permanent research plot (PRP) were evaluated (n = 6, 50 × 50 m /0.25 ha/, Northern Bohemia, 410–425 m above sea level). The average ring series of PRPs were correlated with the climatic data (precip- itation, temperature) according to individual years from the Doksy climatic station, and the air pollution data (SO2 in 1988–2015, NOX and AOT40F – ozone exposure in 1992–2015) from Radimovice station. In 2016, the stand volume increased by 26.0% to 136 m3 ha−1 (108 m3 ha−1 in 2006) and the volume of dead wood increase by 127.2% to 27 m3 ha−1 (12 m3 ha−1 in 2006). The horizontal structure of tree layer and natural regeneration was predominantly aggregated to random. More distinct changes in biodiversity and structural characteristics occurred in the natural regeneration (21.5%) compared to tree layer (2.8%). The precipitation had a significantly higher effect on radial growth compared to temperature. The lack of pre- cipitation in growing season and high temperature in previous autumn and winter were limiting factors for growth. Climatic factors had significant effect on diameter increment in July of the current year (P < 0.01) and June of the current and previous year (P < 0.05). Radial growth was negatively correlated with SO2 con- centrations (P < 0.01) and ozone exposure (P < 0.05). NOX concentrations had low effect on radial growth. The natural stand dynamics had positive effect on biodiversity and functional integrity of natural pine eco- systems

In search for evidence: combining ad hoc survey, monitoring, and modeling to estimate the potential and actual impact of ground level ozone on forests in Trentino (Northern Italy)

A 5-year project was carried out over the period 2007–2011 to estimate the potential and actual ozone effect on forests in Trentino, Northern Italy (6207 km2) (Ozone EFFORT). The objective was to provide explicit answers to three main questions: (i) is there a potential risk placed by ozone to vegetation? (ii) are there specific ozone symptoms on vegetation, and are they related to ozone levels? (iii) are there ozone-related effects on forest health and growth? Different methods and techniques were adopted as follows: monitoring ozone levels, ad hoc field survey for symptoms on vegetation and chlorophyll-related measurements, modeling to upscale ozone measurements, ozone flux estimation, statistical analysis, and modeling to detect whether a significant effect attributable to ozone exists. Ozone effects were assessed on an ad hoc-introduced bioindicator, on spontaneous woody species, and on forest trees. As for question (i), the different ozone-risk critical levels for both exposure and stomatal flux were largely exceeded in Trentino, evidencing a potentially critical situation for vegetation. As for question (ii), specific ozone foliar symptoms related to ozone exposure levels were observed on the introduced supersensitive Nicotiana tabacum L. cv Bel-W3 and on the spontaneous, ozone-sensitive Viburnum lantana L., but not on other 33 species surveyed in the field studies. Regarding question (iii), statistical analyses on forest health (in terms of defoliation) and growth (in terms of basal area increment) measured at 15 forest monitoring plots and tree rings (at one site) revealed no significant relationship with ozone exposure and flux. Instead, a set of factors related to biotic and abiotic causes, foliar nutrients, age, and site were identified as the main drivers of forest health and growth. In conclusion, while ozone levels and fluxes in the investigated region were much higher than current critical levels, evidence of impact on vegetation—and on forest trees in particular—was limited