Determinants of shade tolerance in deciduous forest trees: relationship to leaf phenology, canopy geometry, stature, and species distribution
Givnish TJ. 1992. Determinants of shade tolerance in deciduous forest trees: relationship to leaf phenology, canopy geometry, stature, and species distribution. Bulletin of the Ecological Society of America. 73(2):186-187
Species with early leaf flushing should be more tolerant than late flushers (provided they have appropriate canopy geometries), because their saplings enjoy input from a "window" of intense light in spring before the canopy closes. Taller individuals and species should be less tolerant, given their heavier allocation to support tissue. Species of dry or nutrient-poor sites should also be less tolerant because they allocate heavily to root tissue. Comparative data to test these predictions are presented for the dominant tree species of mid-elevation forests in the Great Smoky Mountains. As expected, early flushing is correlated with shade tolerance provided that it is not coupled with a multilayered canopy (e.g., Populus). Monolayers are shade tolerant and multliayers shade intolerant, but a flaw in Horn's classic model is uncovered. The fraction of shade tolerant species decreases in moving from mesic to xeric sites, and the implications this has for the peak in the abundance of subcanopy tree species (and in overall tree species diversity) in mid-gradient is discussed.
- Type
- Journal Article
- Authors
- Givnish, Thomas
- Units
- GRSM
- Keywords
- Great Smoky Mountains National Park, NC, TN