Low pre-death growth rates of oak (Quercus robur L.)-Is oak death a long-term process induced by dry years?

• Background and purpose A complex interplay between biotic and abiotic factors is believed to be responsible for several oak declines in pedunculate oak (Quercus robur L.). This study aims to clarify the temporal process of oak declines, as well as identifying individual tree and environmental variables that affects growth rate and that may increase the risk of mortality. The study was performed in southern Sweden at three sites. Findings Cross-dating revealed that most trees had died during the last decade and that the growth rates of the dead oaks were affected long before death. Averaged growth chronologies of dead and control trees reaching 150 years back in time illustrated an excellent match up until around 1992, when a severe drought occurred after which the dead trees started to express reduced growth. Precipitation the previous year during August-September and during March-June this current year was of significant importance for oak growth. Site-specific results that showed that dead trees: included fewer small-sized trees, grew on non-clay soils, were more likely to have shelf fungus and cavities and were exposed to less sunshine. Conclusion The results support the theories that oak mortality is a long process that may be induced decades before the actual death.

Nyckelord

Dendrochronology

Growth depression

Oak decline

Extreme weather

Pointer year

TECHNOLOGY

TEKNIKVETENSKAP

Publikations- och innehållstyp

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