Foliar temperature-respiration response functions for broad-leaved tree species in the southern Appalachians

We measured leaf respiration in 18 eastern deciduous forest tree species to determine if there were differences in temperature-respiration response fu nctions among species or among canopy positions. Leaf respiration rates wer e measured in situ and on detached branches for Acer pensylvanicum L., A. r ubrum L., Betula spp. (B. alleghaniensis Britt. and B. lenta L.), Carya gla bra (Mill.) Sweet, Cornus florida L., Fraxinus spp. (primarily F. americana L.), Liriodendron tuliptfera L., Magnolia fraseri Walt., Nyssa sylvatica M arsh., Oxydendrum arboreum L., Platanus occidentalis L., Quercus alba L., Q . coccinea Muenchh., Q. prinus L., Q. rubra L., Rhododendron maximum L., Ro binia psuedoacacia L., and Tilia americana L. in the southern Appalachian M ountains, USA. Dark respiration was measured on fully expanded leaves at 10 , 15, 20, 25, and 30 degrees C with an infrared gas analyzer equipped with a temperature-controlled cuvette. Temperature-respiration response function s were fit for each leaf. There were significant differences in response fu nctions among species and by canopy position within species. These differen ces were observed when respiration was expressed on a mass, nitrogen, or ar ea basis. Cumulative nighttime leaf respiration was calculated and averaged over ten randomly selected nights for each leaf. Differences in mean cumul ative nighttime respiration were statistically significant among canopy pos itions and species. We conclude that effects of canopy position and species on temperature-respiration response functions may need to be considered wh en making estimates of whole-tree or canopy respiration.