Sensitivity of unmanaged relict pine forest in the Czech Republic to climate change and air pollution

Abstract

The relict pine forests have a considerable regenerative capacity after the reduction of heavy air pollution load; nevertheless, tree data clearly reflect the climate and air pollution changes in the given stand conditions. The dynamics of “poor relict pine forests” under the long-term influence of climate changes and air pollution stress (SO2, NO X , and O3) was studied in 1958–2015 in northeast Czech Republic, including health status since 1975. The research was focused on permanent research plots in the protected area of sandstone blocks without active forest management for more than 80 years. The analyses of air pollution effects showed a relatively close relation with radial growth and foliation of Scots pine (Pinus sylvestris L.). Diameter increment was significantly negatively correlated with SO2 concentrations in growing season (P < 0.05), especially in June–August (P < 0.01) and on more exposed sites (P < 0.001). Foliation was significantly negatively correlated with SO2 concentrations and ozone exposure (P < 0.01), but a significant effect of NO X was not detected in study plots. The most serious damage can be attributed to the synergism of chemical and climatic stress, especially in combination with severe drought. Correlation between increment and temperature was stronger compared to precipitation. The climate in December and June had the highest effect on radial growth (P < 0.05). In 1975–2015, the foliage increased on average by 20.7% (to 72.5%). The growth structural indicators were, in 2015, mostly higher than in 2000; the standing volume increased by up to 29% (to 331 m3 ha−1). The spatial pattern of tree layer was mostly random, only on extremely rocky sites, it was significantly aggregated (α = 0.05), such as by recruits. Tree layer biodiversity was generally high, but in the last 15 years, its variability was relatively low.