Ecological stress memory in wood architecture of two Neotropical hickory species from central-eastern Mexico

Drought periods are major evolutionary triggers of wood anatomical
adaptive variation in Lower Tropical Montane Cloud Forests tree species.
We tested the influence of historical drought events on the effects of
ecological stress memory on latewood width and xylem vessel traits (vessel
density, vessel grouping index, hydraulic diameter, and percent conductive
area) in two relict hickory species (Carya palmeri and Carya
myristiciformis) from central-eastern Mexico. We hypothesized that
latewood width would decrease during historical drought years, developing
correlations between growth and hydric stress conditions, and that during
past tree growth, moisture stress would imprint on wood anatomical traits
between successive drought events. We analyzed latewood anatomical traits
that developed during historical drought and pre- and post-drought years
in both hickory species. We found that repeated periods of hydric stress
left climatic signatures for annual latewood growth and xylem vessel
traits that are essential for hydric adaptation in tropical moist tree
species. Our results demonstrate the existence of cause‒effect
relationships in wood anatomical architecture and highlight the ecological
stress memory linked with historical drought events. Thus, combined
time-series analysis of latewood width and xylem vessel traits is a
powerful tool for understanding the ecological behavior of hickory
species.