Current issue: 54(2)
Various environmental conditions (heat waves and drought events) strongly affect leaf and xylem phenology. Disentangling the influence of temperature, precipitation and soil moisture content (AWR) on the forest productivity remains an important research area. We analyzed the impact of climate variability on the leaf phenology (10 sample trees) and radial growth (17 sample trees) of European beech (Fagus sylvatica L.). The study was conducted on 130-year-old European beech trees growing in a temperate forest stand in the Czech Republic. Detailed 20-year phenological monitoring was performed at the study site (1992–2011). As expected, leaf phenological events were mainly driven by the growing season temperatures. Leaf unfolding was highly affected positively by spring temperatures and the top-layer (to 40 cm) AWR in March. The correlation of tree-ring width with the interpolated climate data was positive significant for the growing season AWR and precipitation signal. Furthermore, the water availability in the top soil layer was found to be an important predictor of tree growth and extremely low growth occurrence. The extended phenological growing season, which was caused by a temperature increase, was not followed by an increased tree-ring width. The examined relationships point out the significance of the water availability in the top soil layer in European beech stands.
Fast-growing hybrids of Populus L. have an increasing importance as a source of renewable energy and as industrial wood. Nevertheless, the long-term sensitivity of Populus hybrids to weather conditions and hence to possible climatic hazards in Northern Europe have been insufficiently studied, likely due to the limited age of the trees (short rotation). In this study, the climatic sensitivity of ca. 65-year-old hybrid poplars (Populus balsamifera L. × P. laurifolia Ledeb.), growing at two sites in the western part of Latvia, and ca. 55-year-old hybrid aspens (Populus tremuloides Michx. × P. tremula L.), growing in the eastern part of Latvia, have been studied using classical dendrochronological techniques. The high-frequency variation of tree-ring width (TRW) of hybrid poplar from both sites was similar, but it differed from hybrid aspen due to the diverse parental species and geographic location of the stands. Nevertheless, some common tendencies in TRW were observed for both hybrids. Climatic factors influencing TRW were generally similar for both hybrids, but their composition differed. The strength of climate-TRW relationships was similar, but the hybrid poplar was affected by a higher number of climatic factors. Hybrid poplar was sensitive to factors related to water deficit in late summer in the previous and current years. Hybrid aspen was sensitive to conditions in the year of formation of tree-ring. Both hybrids also displayed a reaction to temperature during the dormant period. The observed climate-growth relationships suggest that increasing temperatures might burden the radial growth of the studied hybrids of Populus.
The effect of climatic factors on wood anatomy of the alien red oak (Quercus rubra L.) growing in three experimental plantations in Latvia was assessed by classical dendrochronological techniques. Two tree-ring proxies – tree-ring width (TRW) and mean area of earlywood vessel lumen (VLA) – were studied on 33 trees. Annual variation of TRW amongst trees was similar (mean r = 0.46), but there was more individuality in VLA (mean r = 0.26); nevertheless, chronologies of both proxies had rather synchronous variation amongst the sites. Annual variation of TRW was affected by factors related to water deficit in late summer, as suggested by the negative effect of temperature and positive effect of precipitation that have intensified during the 20th century, likely due to warming. Although weather conditions during the dormant period did not directly affect TRW, temperature during the autumn-spring period has been the main climatic determinant of VLA likely via influence on overwintering and hence vigour of tree. This suggests that conductive properties of wood and hence the susceptibility to water deficit have been affected by weather conditions before the formation of tree rings. During the 20th century, sensitivity of VLA has shifted from temperature in winter to temperature in autumn likely due to climate change. Still, the positive effect of these factors suggests that warming of climate would increase VLA and hence the risk of embolism and xylem disfunction. Therefore, the importance of availability of water for growth of red oak in Latvia is increasing.
Tree-ring width (TRW) and maximum latewood density (MXD) data of Faxon fir (Abies faxoniana Rehd. et Wils.) were analyzed for five timberline sites in the western Qinling Mountains and northeastern Tibetan Plateau, to investigate their relationships to climate change, especially twentieth century warming. The cross-correlations among TRW chronologies at the low-frequency band were higher, while the higher correlations among MXD chronologies were found at the high-frequency band. Response analysis showed that the tree-ring formation of fir trees was significantly and positively affected by temperature variations, while it was also negatively affected by precipitation. The TRW series captured the warming trends and allowed detecting the recent warming in a long-term context, while the MXD series showed no upward trend. We also found the temperature sensitivity of the TRW series is unstable over space and time. The divergent response between TRW and MXD might be caused by the seasonal variations of warming trends.