Near-Synchronous Xylem Width Increase and Biomass Production in European Beech Revealed by X-ray Micro-Computed...

Area of Science:

• Forest ecology
• Plant physiology
• Wood science

Background:

• Accurate estimation of forest carbon sequestration requires understanding the seasonal dynamics of wood formation (xylogenesis).
• Environmental variability, especially drought, can significantly impact the timing and rate of carbon allocation into wood.

Purpose of the Study:

• To quantify the seasonal dynamics of xylem width increase and xylem biomass production in European beech (Fagus sylvatica).
• To compare these dynamics during a severe drought year (2020) and a mesic year (2021).
• To assess the coupling between xylem expansion and biomass production and validate measurement techniques.

Main Methods:

• High-resolution X-ray micro-computed tomography (XμCT) was used to measure xylem width, density, and biomass production.
• Point dendrometer and microtomy measurements were employed for validation.
• Seasonal onset and cessation of xylogenesis were tracked.

Main Results:

• Xylem width increase and biomass production followed a sigmoidal trajectory in both years.
• The temporal lag between xylem expansion and biomass production was minimal (< 3 days) and insignificant, indicating near-synchronous development.
• Earlier onset and cessation of xylogenesis were observed in the dry year compared to the mesic year.

Conclusions:

• Xylem expansion and secondary wall formation are tightly coupled in European beech, irrespective of water availability.
• Dendrometer data can serve as a reliable proxy for intra-seasonal wood biomass production at the stand level.
• XμCT is a valuable tool for quantifying xylogenesis and understanding carbon allocation dynamics under environmental variability.