Dendrochronological evidence of cockchafer (Melolontha sp.) outbreaks in subfossil tree-trunks from Tovačov (CZ Moravia)

0391947 - ÚVGZ 2014 RIV IT eng J - Journal Article
Kolář, Tomáš - Rybníček, M. - Tegel, W.
Dendrochronological evidence of cockchafer (Melolontha sp.) outbreaks in subfossil tree-trunks from Tovačov (CZ Moravia).
Dendrochronologia. Roč. 31, č. 1 (2013), s. 29-33. ISSN 1125-7865. E-ISSN 1612-0051
R&D Projects: GA MŽP(CZ) SP/2D1/93/07; GA MŠMT(CZ) ED1.1.00/02.0073; GA MŠMT(CZ) EE2.3.20.0256
Institutional support: RVO:67179843
Keywords : Cockchafer * Oak * Tree-ring * Dendrochronology * Subfossil trunk
Subject RIV: EH - Ecology, Behaviour
Impact factor: 1.697, year: 2013
http://www.sciencedirect.com/science/article/pii/S1125786512000574

In dendrochronological dating, we encounter the trouble that some samples cannot be dated due to the occurrence of anomalies in the tree-ring series. When dating subfossil wood for the extension of existing master chronologies, this may be an especially unwanted circumstance as subfossil wood is scarce and each sample valuable. In Moravia (Czech Republic) outbreaks of the cockchafer (Melolontha sp.) used to appear with a disastrous effect on agricultural crops, and, for a dendrochronologist, on samples of wood to be dated. Oak ring width reduction caused by cockchafer induced defoliation can superimpose climate induced growth variations and may complicate dating of historical or subfossil samples. For this study, 33 samples of sub-fossil trunks were assessed; 19 of which were attacked by cockchafer. For comparison, we analysed a total of nine living oak trees, recently attacked by the cockchafer. Occurrence of the cockchafer was reported there in 1999, 2003 and 2007. We found clear growth patterns with cyclic narrow rings every four years. This allowed us to create an artificial curve expressing the recurring cycles of cockchafer outbreaks which assisted us in the detection of the same pattern in subfossil tree growth. The tree-ring series of the attacked living oak stand as well as the 19 individual tree-ring series from subfossil oak trunks could not be dated using standard chronologies and showed a high resemblance to the cockchafer life cycle. Additionally, we found out that the living oak stand was attacked in 1983, 1987, 1991 and 1995 as well. The results support the hypothesis that the periodical reduction observed in tree-rings at regular increments is caused by cockchafer infestation. A mean tree-ring series was created from the individual tree-ring series of subfossil oaks even though radiocarbon dating showed completely different ages of samples. This means that the affected tree-ring series cannot be used for dendrochronological analyses.
Permanent Link: http://hdl.handle.net/11104/0220904