Oak (Quercus robur L.) mortality in south-eastern Sweden: influence of weather and environmental variables
Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
The complex interplay between biotic and abiotic factors, believed to be responsible for several oak declines in European oak stands during the last three decades, remains poorly understood. Hence, this study aims at clarifying the temporal process of oak declines, as well as identifying individual tree and environmental variables that increase the risk of oak mortality. The study was performed in one of the few areas in northern Europe still holding high densities of old oaks (Quercus robur L.). Cross dating revealed that most trees had died during the last decade. Averaged chronologies and multiple chronological clustering suggested that the onset of the oak decline happened in 1992, when a severe drought took place. Two of the sites showed a rather short time period of heavily reduced growth prior to death, most likely caused by an insect defoliation in combination with a mildew infection of the replacement shoots. Environmental variables presented a rather weak influence on oak mortality. The results support the idea of attributing oak mortality to a combination of long- and short-term stresses, and emphasize the importance of including present as well as past factors when analysing the causes of oak declines.
Place, publisher, year, edition, pages
2009. , 14 p.
Dendrochronology, extreme weather, growth depression, growth pattern, insect defoliation, oak decline, oak mortality, pointer year, tree-ring
IdentifiersURN: urn:nbn:se:liu:diva-19278ISRN: LiTH-IFM- EX--2126--SEOAI: oai:DiVA.org:liu-19278DiVA: diva2:223981
Subject / course
UppsokLife Earth Science
Bergman, Karl-Olof, Universitetslektor
Milberg, Per, Professor