Epsilon Archive for Student Projects

Abstract

The mountain birch ecosystem forms the northern treeline in subarctic Europe. Since the treeline is
extremely sensitive to temperature, stress in mountain birch can be used as an indicator of stress on
the ecosystem as a whole, and in predictions of how climate change factors will influence the
subalpine-tundra ecotone and treeline dynamics. Fluctuating asymmetry (FA) is a common
technique for assessing stress in mountain birch. While no previous research has studied withintree
variations of FA in mountain birch, other species have shown significant variation depending
on location of the leaf within the crown, and thus leaf collection location is important to consider
when sampling. The objective of this study is to determine if a relationship exists between leaf FA
and location within the tree crown of mountain birch leaves across three elevation zones in
subarctic Sweden. Leaves were collected from various locations within the crown with regards to
height (bottom, middle, top), direction (north, east, south, west), and position (inner, outer), and at
3 elevation sites (valley, forest-limit, treeline). A nested ANOVA was used to analyze the data.
The treeline site showed a higher amount of FA than the valley or forest-limit sites (P = 0.0228),
but no significant difference was found between any of the within-tree leaf locations. This suggests
that there is no influence from crown location on FA in the leaves of mountain birch, and therefore
future studies involving FA can freely sample leaves from any location within the crown.