Climatic effects on earlywood and latewood density and width in plantation-grown Picea glehnii

This study examined the climatic sensitivity of annual-ring characteristics in plantation-grown Picea glehnii from eight sites in Hokkaido, Japan, with particular emphasis on earlywood density. Earlywood density, earlywood width, latewood density, latewood width, ring density and ring width were measured using soft X-ray densitometry and analyzed using linear mixed-effects models that accounted for site- and tree-level variation. Earlywood density was negatively related to total precipitation during April-June and positively related to sunshine duration, whereas spring temperature had no significant effect. By contrast, earlywood width increased with spring temperature but showed no significant response to precipitation or sunshine duration. Latewood density was positively related to summer temperature and sunshine duration and negatively related to summer precipitation, indicating that warm, sunny, and relatively dry summer conditions promote higher latewood density. Latewood width was positively related only to summer sunshine duration. These findings suggest that trees exposed to particularly high precipitation during the early growing season may produce wood with lower earlywood density, potentially increasing the susceptibility of logs to cracking.