Environment rather than provenance explains levels of foliar phenolics in European beech (Fagus sylvatica L.) seedlings

With progressive climate change, the chemical defense in European beech ( Fagus sylvatica L.) is likely to change, which might impact its fitness and ability to establish beyond its current northern distribution limit. We studied the phenolic defense in six beech provenances grown in three common gardens in Norway the two first years after planting. We analyzed low molecular weight phenolic compounds by HPLC and condensed tannins by the acid-butanol assay. Sampling year explained most of the variance in phenolic defense, followed by environment (growing location), while the genetic background (provenance) showed the least explanatory power. After the first year in the field, the northernmost growing location had about 70% higher concentration of low molecular weight phenolics than the southern growing locations. The concentrations of condensed tannins, however, were lowest in the north. The mean concentration of total low molecular weight phenolics was twice as high after the first year compared to the second year. After the second year, the differences between the growing locations in many cases disappeared. The differences between the growing locations are probably caused by differences in temperature and soil fertility, while we attribute the decrease in low molecular weight phenols from the first to the second year to decreased water and nutrient stress, as well as aging. Our results suggest that intraspecific variations in concentration and composition of phenolic compounds in beech are caused by differences in the environment to a greater extent than the genetic background, which may indicate fast changes in chemical defense with climate change.