Masting behaviour and dendrochronology of European beech (Fagus sylvatica L.) in southern Sweden

To identify weather controls of beech diameter growth and masting in southern Sweden, we analyze records of monthly weather, regional masting record, and tree-ring chronologies from five beech-dominated stands. The results indicate a strong weather control of temporal pattern of masting events in southern Sweden over the second half of the 20th century. Negative summer temperature anomaly 2 years prior to a mast year, coupled with positive temperature anomaly in the year immediately preceding the same mast year, is a characteristic weather pattern associated with known mast years. Strong dependence of beech masting behaviour on temperature explains the high degree of regional synchronization of masting events. Growth of beech in southern Sweden is strongly and negatively correlated with previous year's summer temperature and positively - with previous year's October temperature. The present study does not provide a conclusive answer in identifying a full set of direct and indirect effects of climatic variables controlling tree-ring growth, since the negative effect of previous year's summer temperature may be a result of a temperature-controlled increase in the beech nut production in the current year. Consistent and significant negative departures of ring-width index during mast years support the hypothesis about a trade-off between investment of bioassimilates into production of beech nuts and tree-ring growth. Alternative explanation of growth anomalies in mast years, relating such anomaly to a negative impact of previous year's growing season, was not supported by the data. We found a limited effect of masting on diameter growth in the following years, indicating that decline in the overall wood production, associated with heavy masting, is short term and typically occurs in the year of actual masting.