Canopy accession strategies and climate-growth relationships in Acer rubrum

A pervasive pattern of forest composition change is occurring throughout the Central Hardwood Forest of the eastern US. Acer rubrum has invaded the understory of Quercus stands across a variety of site types. The proliferation of A. rubrum, and that of other shade-tolerant mesophytes, inhibits the regeneration of Quercus. Without alterations in disturbance or climate regimes, composition in invaded stands is expected to shift towards A. rubrum dominance. Canopy accession strategies and climate-growth relationships of A. rubrum are critical factors in this successional shift. We quantified patterns of suppression and release during canopy accession, examined the relationships between climate variables and radial growth, and compared our findings for A. rubrum in an old-growth forest in Tennessee to other studies throughout the region to elucidate broad-scale patterns. The most common mode of A. rubrum canopy recruitment began with a tree originating in a gap followed by accession into the canopy without a period of suppression (61%). The remaining trees experienced a period of suppression before recruiting to the main canopy. A prominent establishment pulse occurred from the 1940s to the 1960s and 93% of trees that recruited to the canopy during this period established in gaps and were never suppressed. The mean age at canopy accession for individuals that experienced suppression was 24 yr. The transition from suppression to release phases in radial growth trends was abrupt. The mean interseries correlation and the average mean sensitivity of the A. rubrum tree-ring chronology were comparatively high for the region. Acer rubrum individuals were most productive during cool, wet springs preceded by wet autumns and warm winters. Our results indicate that A. rubrum will remain competitive in the coming decades without a change in current disturbance regimes and the Quercus component will be difficult for managers to maintain in similar stands of the Central Hardwood Forest.

► We quantified canopy accession and climate-growth relationships for Acer rubrum.
► An establishment pulse occurred from the 1940s to the 1960s.
► Most A. rubrum established in canopy gaps and never experienced suppression.
► Productivity was high with cool wet springs preceded by wet autumns and warm winters.
► Acer rubrum will remain competitive without a change in the disturbance regime.