The main objectives of this investigation were to determine the impact of climate
on mountain birch (Betula pubecens ssp. czerepanovii (Orlova)) growth and to develop a
regional chronology of autumnal moth outbreaks. To accomplish the objective, cores of
mountain birch were taken from 21 sites in Norrbotten, Sweden. Tree-ring chronologies
were developed for each site. Climatic influences were determined by correlating ring
widths to climatic variables (average monthly temperature, average monthly
precipitation and NAO). Outbreaks were recovered from the ring width indices using
the non-host method with Scots pine (Pinus sylvestris (L.)) as the non-host. This method
removes the climatic influence on growth to enhance other factors. Patterns of
synchrony and regional outbreaks were detected using regression and cluster analysis
techniques.
The primary climatic influences on the tree ring growth of mountain birch are
June and July temperatures; precipitation during October is of secondary importance.
Climate explained 46% of yearly tree ring width variation. Outbreaks of the autumnal
moth occur at varying time intervals depending on the scale of study. Intervals between outbreaks on the tree level are twice as long as at the plot level. On the regional scale
plots within the same valley had more similar outbreak intervals and magnitudes of
outbreaks. Elevation is a driver in determining the length of outbreaks and length
between outbreaks. The percent monocormicity of a plot is also a determining factor of
the length between outbreaks.
This study is the first regional scale study on climate and outbreaks of the
autumnal moth on mountain birch. The results complement research being conducted on
autumnal moth larval densities and will help in modeling and assessing the effects of
outbreaks with increasing climatic change.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2008-08-58 |
| Date | 16 January 2010 |
| Creators | Young, Amanda B. |
| Contributors | Cairns, David |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis |
| Format | application/pdf |
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