Young, Amanda B. (2008-08). Climate and the autumnal moth (Epirrita autumnata) at Mountain Birch (Betula pubecens ssp. czerepanovii) Treelines in northern Sweden.. Master's Thesis. Thesis uri icon

abstract

  • 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.
  • 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.

publication date

  • August 2008