The impact of industrial SO 2 pollution on north Bohemia conifers Rydval & Wilson (2012) – Water, Air, & Soil Pollution. doi: /s Miloš Rydval – Rob Wilson – School of Geography & Geosciences, University of St Andrews, St Andrews, United Kingdom Paper number: B53B-0665 University of St Andrews Conclusions Background The study region (Fig.1), centrally situated inside the so-called ‘Black Triangle’ in the heavily industrialised border area of the Czech Republic, Poland and Germany, is considered to have had some of the highest levels of atmospheric pollution in Europe in the 1970s and 1980s. The 2100 MW Turów power station, in operation since 1962 is fuelled by locally mined lignite with a high sulphur content and is the dominant source of regional pollution. Modernisation of the power station in the 1990s resulted in an 82% decrease of SO 2 emissions, reduction of NO X by 45% and a 96% reduction of dust pollution (Nordic Investment Bank, 2005). Local stands exhibited clear signs of environmental stress (Fig.2). Methodology Sites with similar attributes (e.g. elevation, aspect) were selected for sampling, with distance from pollution source as the primary modulating variable. Sites included 1 Silver fir and 5 (+1 additional dataset ’KRK’ from ITRDB) Norway spruce sites located SE of the power station. Gridded climate data were used as climate model inputs and a composite of 44 regional SO 2 datasets were used as SO 2 inputs. Fig.1: Regional context and site locations Aim Assessing the spatio-temporal impact of atmospheric SO 2 pollution from a single point source of pollution (a coal-fired power station) on conifer tree- growth in the Jizerské Mts. using dendrochronological methods. Fig.2: Example of Norway spruce ‘telephone poles’ (standing deadwood) at site 3 Comparing Jizerské Mts. and Bavarian Forest Results Tree growth responded mainly to summer temperatures, although precipitation also had an additional minor influence at some sites. Presence of abrupt, decade-long growth suppression in all spruce chronologies was observed (Fig.3). Sites closest to Turów experienced greatest suppression in 1980 and the following decade. Analysis of 268 identified missing rings (Fig.4) revealed increased incidence at sites closest to Turów around 1980, further reflecting stressful growth conditions. Rapid response to high SO 2 concentrations suggested greater significance of direct atmospheric SO 2 rather than an indirect influence through soil acidification (Elling et al. 2009). Unfavourable climatic conditions (e.g. heavy winter frost) likely 'triggered' a period of growth suppression in stands stressed by high pollution levels. Poor performance of the ‘Climate’ model in the prediction period indicates a period of divergence manifested as a weakening of the climate signal (Fig.3). Marked increase in agreement between modelled and actual ring-width when SO 2 data are included in models. The mis-fit between actual and modelled growth post~1992 suggests no return to pre~1980 growth response despite lower pollution levels. Unlike spruce, the lower elevation (FIR) site retained a climate signal, although missing rings suggest increased and longer-term stress at this site (Fig.4). Climate model: Modelling of tree growth based on available temperature (and precipitation data where applicable) using OLS regression was used to predict theoretical growth between based on the relationship established in the calibration period. Climate + SO 2 model: A second model was developed which also included regional SO 2 data in addition to climate data. A comparison of SO 2 emissions / atmospheric concentrations with spruce and fir affected by SO 2 emissions in the Bavarian Forest, Germany reveal differences in the timing of growth suppression coinciding with differing emission regimes (Fig.6). The different response of both species between the two regions reflects influence of regional factors (e.g. distance from pollution source, elevation), resulting in a complex story. Fig.3: Site chronologies together with ‘Climate’ and ‘Climate + SO 2 ’ model results Fig.4: Number and percentage of missing rings in site chronologies Fig.6: Comparison of Czech and German conifer sites, and regional SO 2 index / emissions Fig.5: Scatter plot showing a strong positive relationship between (A) the 1980, and (B) mean of Norway spruce site ring- width indices, and distance from Turów Suppression and Distance References: D’Arrigo, R., Wilson, R., Liepert, B., & Cherubini, P. (2008). On the ‘divergence problem’ in northern forests: a review of the tree-ring evidence and possible causes. Global and Planetary Change, 60, 289–305. Elling, W., Dittmar, C., Pfaffelmoser, K., & Rötzer, T. (2009). Dendroecological assessment of the complex causes of decline and recovery of the growth of silver fir (Abies alba Mill.) in Southern Germany. Forest Ecosystem Management, 257, 1175–1187. Nordic Investment Bank (2005). July Bulletin: cross-border cooperation.URL: 15 Dec Decreasing influence of pollution on growth suppression with increasing distance from pollution source. Growth suppression detected in 1980 and the following decade was most likely caused by a combination of high pollution levels and adverse climatic conditions. Distinct difference in response between Norway spruce and Silver fir. Indication that growth response has not returned to the pre-impact state. Difference in timing of response between Jizerské Mts. and Bavarian Forest. Influence of pollution as a potential contributor to the ‘divergence problem’ (D’Arrigo et al. 2008) has implications for dendroclimatic reconstructions in regions affected by pollution. A strong relationship between growth suppression and distance of sites from Turów was identified (Fig.5).