A Dendrochronological Study of Climate Influence on Earlywood growth in Scots Pine in the Nature Reserve Halle-Vagnaren in Bohuslän, Sweden
Abstract
There has been a great acceleration of global mean surface temperature increase since the
1950s, where changes in different spheres and more frequent weather and climate extremes
have been observed. To be able to better understand the past, and thereby prepare for the
future, climate proxies are used to reconstruct the climate. Tree rings are one of them and is
considered to be one of the best proxies, with its high resolution and availability. Each year,
an annual tree ring is formed, which consist of earlywood, produced in the early part of the
growing season, and latewood, produced on the late part of the growing season. There are
both internal and external factors that affect the tree ring growth. Two of the external factors
are temperature and precipitation. This report investigates the correlation between the two
climate parameters and earlywood width, as well as the tree ring width. It is also investigated
if the correlation differs between the period before and after the Great Acceleration in 1950.
Lastly it is also investigated if earlywood and tree ring width can be used for climate
reconstructions. A total of 25 Scots pine trees (Pinus Sylvestris) were sampled upon with a 5
mm tree ring bore from the nature reserve Halle-Vagnaren located in Bohuslän, Sweden.
Standardized chronologies were created and compared to normalized mean temperature and
precipitation data. No statistically significant correlation was found between temperature and
earlywood width and ring width, which indicates that temperature is not the limiting factor. A
statistically significant correlation was found in precipitation in May the same year for both
earlywood and ring width for the early period. The similarities can be explained by the high
proportion of earlywood in an annual ring. In the late period, no statistically significant
correlation was found for earlywood, which indicates that the climate parameter influencing
the earlywood have changed. There was almost a statistically significant correlation found for
precipitation in June the same year for ring width during the late period. This raises the
question regarding the influence of latewood in the ring width, where potential changes in
climate only affect the formation of latewood. What is interesting to see is that there are
differences during the studied periods, indicating that there has been a shift regarding what
climate parameters affect the tree ring growth. Earlywood has the potential to be used for a
precipitation reconstruction, but only before 1950. Further investigation is needed to see if the
correlation remains further back in time, as well as extended research in the area, to see if the
climate parameters have the same influence in a wider area. The tree ring width has also a
potential with reconstructing precipitation, however, the shift in correlating months needs to
be further investigated.
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Date
2023-08-18Author
Eskilsson, Linda
Series/Report no.
B1237
Language
eng