Interspecific and environmentally induced variation in foliar dark respiration among eighteen southeastern deciduous tree species

We measured variations in leaf dark respiration rate (R(d)) and leaf nitrogen (N) across species, canopy light environment, and elevation for 18 co-occurring deciduous hardwood species in the southern Appalachian mountains of western North Carolina. Our overall objective was to estimate leaf respiration rates under typical conditions and to determine how they varied within and among species. Mean dark respiration rate at 20 °C (R(d,mass), μmol CO₂ (kg leaf dry mass)^-1 s^-1) for all 18 species was 7.31 μmol kg^-1 s^-1. Mean R(d,mass) of individual species varied from 5.17 μmol kg^-1 s^-1 for Quercus coccinea Muenchh. to 8.25 μmol kg^-1 s^-1 for Liriodendron tulipifera L. Dark respiration rate varied by leaf canopy position and was higher in leaves collected from high-light environments. When expressed on an area basis, dark respiration rate (R(d,area), μmol CO₂ (kg leaf dry area)^-1 s^-1) showed a strong linear relationship with the predictor variables leaf nitrogen (N(area), g N (m leaf area)^-2) and leaf structure (LMA, g leaf dry mass (m leaf area)^-2) (r² = 0.62). This covariance was largely a result of changes in leaf structure with canopy position; smaller thicker leaves occur at upper canopy positions in high-light environments. Mass-based expression of leaf nitrogen and dark respiration rate showed that nitrogen concentration (N(mass) mg N (g leaf dry mass)^-1) was only moderately predictive of variation in R(d,mass) for all leaves pooled (r² = 0.11), within species, or among species. We found distinct elevational trends, with both R(d,mass) and N(mass) higher in trees originating from high-elevation, cooler growth environments. Consideration of interspecies differences, vertical gradients in canopy light environment, and elevation, may improve our ability to scale leaf respiration to the canopy in forest process models.