Intraspecific differences in spring leaf phenology in relation to tree size in temperate deciduous trees

Area of Science:

• Ecology
• Forest Science
• Plant Phenology

Background:

• Spring leaf phenology is crucial for temperate deciduous forest productivity.
• Previous studies show conflicting patterns regarding tree size and budburst timing.
• The underlying physiological and environmental factors for these discrepancies are not fully understood.

Purpose of the Study:

• To investigate the relationship between tree size and spring leaf phenology in deciduous species.
• To determine the influence of environmental factors like temperature and snowfall on budburst timing.
• To assess the role of phylogeny in observed phenological differences.

Main Methods:

• Field study of 11 deciduous species in a cool-temperate Japanese forest over two years with varying snowfall.
• Data collection on budburst timing and tree height (<1m, 1-10m, >10m).
• Literature survey of budburst data across multiple studies to analyze relationships with tree size, phylogeny, temperature, and snowfall.

Main Results:

• Non-linear relationships between tree height and budburst/leaf maturation timing were observed, with saplings (<1m) showing larger discrepancies than short (1-10m) and tall (>10m) trees.
• Saplings required fewer cumulative degree-days for budburst, suggesting an adaptation for early establishment.
• Budburst timing varied with snowfall: earlier in saplings at low-snowfall sites and earlier in tall trees at high-snowfall sites.

Conclusions:

• Observed discrepancies in spring phenology between studies may stem from variations in the 'target size' of trees studied (saplings vs. taller trees).
• Microclimatic conditions, particularly snow depth, significantly influence phenology, leading to delayed sapling budburst in heavy snow areas.
• Understanding these size and environment-driven phenological shifts is vital for predicting forest productivity and ecosystem responses to climate change.