Bytebier J., De Mil T., Vanhellemont M., Verheyen K., Haneca K., Van den Bulcke J. [2022] Linking wood density records of common beech (Fagus sylvatica L.) with temperature and precipitation variability from a temperate lowland site. Dendrochronologia 76 (2022) 126018

European lowland beech stands are under pressure by current climate change and increased drought spells.
Climate sensitivity of trees is most commonly studied by examining tree-ring width records and wood densitybased time series, yet the potential of the latter is underexplored for hardwoods and beech (Fagus sylvatica L.) in particular. Here, we investigate how variability in radial growth, Maximum Latewood Density (MXD) and intra-annual wood density records in lowland beech are related to monthly and daily temperature (T) and precipitation (P) records, as well as the Standardized Precipitation Evapotranspiration Index (SPEI), during the past 50 years. 45 increment cores were collected from healthy (co-) dominant beech trees in Flanders (northern Belgium). We used X-ray micro Computed Tomography (XμCT) to obtain wood density and tree-ring width series. By dividing every tree-ring into 4 sectors of equal radial width, we also assessed climatic forcings on intraannual wood density variability (meanQi, i = 1:4). Water availability (SPEI) is the most important factor limiting radial growth, whereas MXD is correlated with summer temperature (period May-July, r = 0.334). Scanning resolution (110, 60, 20 μm) proves to be an important parameter when interpreting MXD values. We found that to quantify climate signals at the end of the growing season, density values should be representative for a relatively large part of the latewood. Our results also suggest that a sector approach is useful by showing climatic influences during the entire growing season. Wood density at the beginning of the growing season is mainly influenced by water availability (meanQ1~SPEI, r = 0.416), whereas towards the end of the growing season only significant correlations with temperature were observed (meanQ4~T, r = 0.347). We recommend to further explore MXD values for hardwood trees in lowland Europe.