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The article presents the current state of knowledge on climate change in Poland (Central Europe) in the first half of the last millennium (1001–1500). To this end, it employs all available quantitative climate reconstructions created in the last two decades and four new reconstructions using three dendrochronological series and an extensive database of historical source data on weather conditions. The growth of conifers in lowland and upland Poland depends on the temperature in the cold season, especially in February and March. All available reconstructions based on dendrochronology date represent this time of the year. Summer temperatures were reconstructed using biological proxies and documentary evidence. The latter, however, is limited to the 15th century only. Winter temperature was used as the proxy for annual temperature proxies instead of the more usual use of summer temperature. The Medieval Warm Period (MWP; also called the Medieval Climate Anomaly [MCA]) occurred in Poland probably from the late 12th century to the first halves of the 14th or 15th centuries. All the analysed quantitative reconstructions suggest that the MWP in Poland was comparable to or warmer than the current temperature (1951–2000). The coldest conditions in the entire study period were noted in the first half of the 11th century (both winter and summer) and the second half of the 15th century (only winter). The greatest climate continentality occurred in the 15th century. Good agreement was found between the reconstructions of Poland’s climate and many reconstructions available for Europe.

In the context of global change, the integration of non-native tree (NNT) species into European forestry is increasingly being discussed. The ecological consequences of increasing use or spread of NNTs in European forests are highly uncertain, as the scientific evidence is either constraint to results from case studies with limited spatial extent, or concerns global assessments that lack focus on European NNTs. For either case, generalisations on European NNTs are challenging to draw. Here we compile data on the impacts of seven important NNTs (Acacia dealbata, Ailanthus altissima, Eucalyptus globulus, Prunus serotina, Pseudotsuga menziesii, Quercus rubra, Robinia pseudoacacia) on physical and chemical soil properties and diversity attributes in Europe, and summarise commonalities and differences. From a total of 103 publications considered, studies on diversity attributes were overall more frequent than studies on soil properties. The effects on soil properties varied greatly among tree species and depended on the respective soil property. Overall, increasing (45%) and decreasing (45%) impacts on soil occurred with similar frequency. In contrast, decreasing impacts on biodiversity were much more frequent (66%) than increasing ones (24%). Species phylogenetically distant from European tree species, such as Acacia dealbata, Eucalyptus globulus and Ailanthus altissima, showed the strongest decreasing impacts on biodiversity. Our results suggest that forest managers should be cautious in using NNTs, as a majority of NNT stands host fewer species when compared with native tree species or ecosystems, likely reflected in changes in biotic interactions and ecosystem functions. The high variability of impacts suggests that individual NNTs should be assessed separately, but NNTs that lack European relatives should be used with particular caution.

Tree rings are natural archives of climate and environmental information with a yearly resolution. Indeed, wood anatomical, chemical, and other properties of tree rings are a synthesis of several intrinsic and external factors, and their interaction during tree growth. In particular, Intra-Annual Density Fluctuations (IADFs) can be considered as tree-ring anomalies that can be used to better understand tree growth and to reconstruct past climate conditions with intra-annual resolution. However, the ecophysiological processes behind IADF formation, as well as their functional impact, remain unclear. Are IADFs resulting from a prompt adjustment to fluctuations in environmental conditions to avoid stressful conditions and/or to take advantage from favorable conditions? In this paper we discuss: (1) the influence of climatic factors on the formation of IADFs; (2) the occurrence of IADFs in different species and environments; (3) the potential of new approaches to study IADFs and identify their triggering factors. Our final aim is to underscore the advantages offered by network analyses of data and the importance of high-resolution measurements to gain insight into IADFs formation processes and their relations with climatic conditions, including extreme weather events.

Tree rings are natural archives of climate and environmental information with a yearly resolution. Indeed, wood anatomical, chemical, and other properties of tree rings are a synthesis of several intrinsic and external factors, and their interaction during tree growth. In particular, Intra-Annual Density Fluctuations (IADFs) can be considered as tree-ring anomalies that can be used to better understand tree growth and to reconstruct past climate conditions with intra-annual resolution. However, the ecophysiological processes behind IADF formation, as well as their functional impact, remain unclear. Are IADFs resulting from a prompt adjustment to fluctuations in environmental conditions to avoid stressful conditions and/or to take advantage from favorable conditions? In this paper we discuss: (1) the influence of climatic factors on the formation of IADFs; (2) the occurrence of IADFs in different species and environments; (3) the potential of new approaches to study IADFs and identify their triggering factors. Our final aim is to underscore the advantages offered by network analyses of data and the importance of high-resolution measurements to gain insight into IADFs formation processes and their relations with climatic conditions, including extreme weather events.

Western hemlock (Tsuga heterophylla Sarg.) is an exotic species rarely encountered in Poland. The study site was located in the territory of the Dobrzany Forest District, in the oldest stands of this species in Poland. The research material comprised 20 wood samples from 10 trees aged 78 years. The chronology was built covering the period between 1942 and 2009. Indicator years were determined and dendroclimatological analysis was performed. Thermal conditions in January and February and the amount of precipitation in July and February influenced the tree−rings width. Missing rings were detected in 30% of wood samples in 1982., Sylwan 156 (4): 287-293

The study aimed at dendrochronological and dendroclimatological analysis of radial increments of two Scots pine specimens of atypical stems (fig. 1). Investigated trees grow in the Borne Sulinowo Forest District (tab.). Although the individuals differ with age, the anomaly occurs almost in the same time (fig. 2). Tree−ring widths of analysed pines show greater similarity before the anomaly onset. Atypical stem construction results in variable growth pattern within individual tree. Samples from ‘ridges' are more similar to the master chronology. Climate conditions (temperature in April and June) significantly influence tree ring formation within ‘rows' of tree at site #2 (fig. 3−4). Frost damages originating from extremely low temperature in winter 1956 may be the cause of the observed stem anomaly., Sylwan 155 (8): 555-562

Sylwan 152 (3): 50-57

Sylwan 150 (5): 44-50

Tree rings are natural archives of climate and environmental information with a yearly resolution. Indeed, wood anatomical, chemical, and other properties of tree rings are a synthesis of several intrinsic and external factors, and their interaction during tree growth. In particular, Intra-Annual Density Fluctuations (IADFs) can be considered as tree-ring anomalies that can be used to better understand tree growth and to reconstruct past climate conditions with intra-annual resolution. However, the ecophysiological processes behind IADF formation, as well as their functional impact, remain unclear. Are IADFs resulting from a prompt adjustment to fluctuations in environmental conditions to avoid stressful conditions and/or to take advantage from favorable conditions? In this paper we discuss: (1) the influence of climatic factors on the formation of IADFs; (2) the occurrence of IADFs in different species and environments; (3) the potential of new approaches to study IADFs and identify their triggering factors. Our final aim is to underscore the advantages offered by network analyses of data and the importance of high-resolution measurements to gain insight into IADFs formation processes and their relations with climatic conditions, including extreme weather events. This research is linked to activities conducted within the COST FP1106 “STReESS” network. Collection of datasets used for this work was supported by the projects: – ELENA (CGL2012-31668) and CGL2015-69985-R funded by the Spanish Science and Innovation Ministry (MICINN) and FEDER funds. – PGIDIT06PXIB502262PR funded by Dirección Xeral de Investigación, Desenvolvemento e Innovación, Xunta de Galicia. – Slovenian Research Agency (program P4-0015). – Austrian Science Fund (FWF-TRP 122-B16). – Russian Science Foundation 14-14-00295. – POCI/CLI/58680/2004 and PTDC/AAC-AMB/111675/2009 funded by the Portuguese Foundation for Science and Technology (FCT) and the European Union (POCI 2010) SI