Beyond maximum density: multi-parameter insights into Scots pine climate sensitivity

Area of Science:

• Dendrochronology and Climate Science
• Ecology and Evolutionary Biology
• Forestry and Environmental Science

Background:

• Pinus sylvestris L. is a key species for Eurasian dendroclimatological reconstructions.
• Traditional methods rely on tree-ring width (TRW) and maximum latewood density (MXD).
• Climatic signals from earlywood/latewood density (EWD/LWD) and minimum density (MND) are under-explored.

Purpose of the Study:

• To investigate the climate change response of multiple P. sylvestris tree-ring parameters.
• To compare these responses at two contrasting sites in Scotland and Sweden.
• To assess the skill of EWD/LWD and MND in dendroclimatological reconstructions.

Main Methods:

• Analysis of well-replicated tree-ring density data from Scotland and Sweden.
• Correlation analysis between tree-ring parameters (LWD, MXD, MND) and temperature data.
• Investigation of temporal changes in climate-growth relationships.

Main Results:

• LWD and MXD showed strongest correlations with temperature (0.5–0.7) for July, August, and the June-August season.
• A significant negative correlation between MND and July temperatures was found in Swedish data, diminishing since the late 20th century.
• Northern Scotland's site showed no comparable inverse MND-temperature signal, suggesting site-specific physiological changes.

Conclusions:

• Climate sensitivity of P. sylvestris has changed, with shifts in minimum density.
• The stability of MXD contrasts with changes in MND, highlighting the need for additional density parameters.
• Altered tree growth sensitivity may reduce the effectiveness of proxies from northern European sites for climate reconstructions.