Geographic variation in shoot traits and branching intensity in relation to leaf size in Fagus crenata: A common garden experiment.

ABSTRACT

PREMISE OF THE STUDY Differences in leaf size are expected to be coordinated with various shoot traits and branching intensity because these relationships will influence light capture efficiency, water use, and biomechanics. Previous studies have mainly focused on interspecific patterns of these trait relationships, but not on intraspecific patterns at the geographic scale. We investigated intraspecific variation in shoot traits and branching intensity of Fagus crenata in Japan. METHODS: Allometric relationships between the traits of current-year shoots and branching intensity per branch unit of 1-m length on the main axis (BI) and its coordination with latitude were investigated using trees from 10 provenances in a common garden. KEY RESULTS: Individual trees originating from lower latitudes have smaller leaves with greater leaf mass per area and nitrogen content per area, greater Huber value (stem cross-sectional area per total leaf area [ATL]) of current-year shoots, and greater BI. Notably, the slope of the log-log relationship between BI and ATL was close to -1.0 across the trees from different source sites, implying that branching in this species occurs to control leaf area. CONCLUSIONS: Shoot traits and branching intensity were apparently coordinated with leaf size to control leaf area deployment in this species. Such patterns probably reflect differences in competition for hydraulic conductance among nearby shoots within crowns, as a consequence of different meteorological conditions across the source sites.