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The article presents updated knowledge on climate change in Poland (central Europe) in the first half of the last millennium (1001–1500). This knowledge is required to delimit the existence, duration, and scale of the Medieval Warm Period (MWP, also called the Medieval Climate Anomaly, MCA, here). To this end, it employs all available quantitative climate reconstructions created for Poland in the last 2 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 data 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 MWP 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 mean temperature in the period 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. [ABSTRACT FROM AUTHOR]

Tradeoffs between intra and interspecific distances of individual plants determine the spatial distributions of local plant communities and small‐scale community assembly. Here we use an individual based approach and null model standardization to compare intra‐ and interspecific nearest neighbour distances of plant ramets as well as mean differences in functional trait expression to nearest heterospecifics within local communities of temperate forest understorey plants in northern Poland. We found a general tendency towards clustered intraspecific and segregated interspecific ramet distributions. Spatial distribution patterns of understorey plants differed considerably between two nearby forest sites that mainly differed in the age structure of trees. Individuals of clonal species tended to have significantly smaller intraspecific and larger interspecific nearest neighbour distances than seed dispersing species. Our results indicate a major influence of dominant plant species on the spatial distributions of subdominants. Trait expressions related to plant growth (specific leaf area and leaf mass) and reproduction (seed mass) were significantly segregated in comparison to the spatial distribution of conspecific individuals and less so in comparison to heterospecific individuals. We argue that spatially explicit analyses of plant community assembly need to consider respective distributions of important traits and that the tradeoffs of contrasting trait distributions trigger small scale plant community composition and species distributions. We present a general framework for the analysis of plant community assembly based on the spatial distributions of individual plants and functional traits. [ABSTRACT FROM AUTHOR]

European beech Fagus sylvatica and Sessile oak Quercus petraea are reaching the north-eastern limits of their natural ranges in northern Poland. According to the projected changes in potential ranges in this region, climatic conditions for both species until 2080 will remain stable. On the other hand, a decrease in the vitality of mature trees and a reduction in their radial growth are currently observed. To understand these contradictory findings, we monitored the cambial activity in both species during two vegetation seasons. 2015 was characterized by a negative water balance, while 2017 was wet. This provided an opportunity to compare how the xylogenesis proceeds in diffuse-porous beech and ring-porous oak during contrasting in the summer precipitation seasons. The forming annual increments were sampled with Presler borer at variable time intervals depending on the leaf phenological phases. The cores were prepared using a sledge microtome and double-stained with safranin and astra blue. Observations of the phases of wood formation and measurements of the width of the forming increments were analysed on the microslide digital images. Differences in the dates of the phenological phases were analysed using Two-Way ANOVA, while the dynamics of the formation of annual increments were fitted to the Single and Double Gompertz function for beech and oak, respectively. The beginning of vessel formation started earlier in both seasons compared to previous studies. Inter-seasonal differences in the duration of spring phenological phases were insignificant for both species, while inter-species differences were significant due to physiological diversity between diffuse-porous beech and ring-porous oak. In dry 2015, cambial activity ceased sooner in both species than in 2017. Differences between oak and beech were insignificant in both years, but statistically significant disparities existed within each species due to varying in precipitation seasons. Rainfall significantly elongated the duration of cambial activity and caused wider tree-rings. According to our study, despite predicted maintaining their climatic niche, both species, situated at the north-eastern cooler range boundary, are expected to produce wood at a lower rate due to the projected warmer central European climate with increased heatwaves and summer droughts. [ABSTRACT FROM AUTHOR]