Growth partitioning within beech trees (Fagus sylvatica L.) varies in response to summer heat waves and related droughts
2016
Latte, Nicolas | Lebourgeois, François | Claessens, Hugues
KEY MESSAGE : Beech growth variability and climate sensitivity are much higher in the crown top than in the bole. The most notable bole–crown discrepancies occurred in response to extreme climate conditions. To characterize growth partitioning within the tree and its responses to climate, we studied eight dominant beech trees (Fagus sylvatica L.) of a pure, even-aged 98-year-old stand in Belgium. We sampled ten disks along the stem from breast height to treetop and examined the inter-annual patterns of, and discrepancies between, ring-area and volume increments by performing detailed stem analysis and dendroecological investigations. Although the common inter-annual variation among all increment series was high, we observed increasing growth variability and climate sensitivity with height, leading to notable bole–crown discrepancies. Both the common inter-annual variation and bole–crown discrepancies were mainly driven by summer heat waves and related droughts of the previous year, and spring droughts of the current year. Despite these discrepancies, the radial growth at breast height can be considered a good estimate of the tree volume increment but not for the purpose of focusing on climatic effects of isolated years. Extreme climatic conditions increase the risk of inaccurate estimations. The results of the present study are discussed in relation to tree ecophysiology hypotheses.
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