PARENT SESSION
Oral Session #24: Forests: Carbon allocation, carbon budgets. Presiding: C. Reid.
Tuesday, August 7, 2001. 8:00 AM to 11:15 AM. Hall of Ideas F.

Fine root physiology, tissue construction and morphology in tree species of different growth rate.

COMAS, LOUISE¹, TROAST, LAURA¹, REED, SHARON¹, EISSENSTAT, DAVID¹, ¹

ABSTRACT- Despite their important role in plant carbon budgets and carbon cycling, there is little information available on fine root characteristics of tree species. We examined root traits important for modeling root carbon cycling among species differing in growth rate. Specifically, we examined root diameter, specific root length (SRL), specific surface area (SSA), specific tissue density, and phenolic and nitrogen concentrations in nineteen species, and fine root phosphorus uptake and respiration rate in a subset of six of these species. Tree species were grouped into three categories based on shoot qualities and root symbioses formed: deciduous endo-mycorrhizal, deciduous ecto-mycorrhizal, and evergreen ecto-mycorrhizal species. In general, variation in root morphology traits within the groups could not be explained by differences in tree growth rate. Phenolic concentration was negatively correlated with tree growth rate among deciduous and evergreen ecto-mycorrhizal species (R2=0.39 & 0.23). Overall, nitrogen concentration tended to increase as tree growth rate increased (R2=0.34) although no strong relationships were found within each group. Finally, comparing roots of six species, fast-growing species within each group had higher P uptake (P< 0.01) and respiration (P< 0.01) than slow-growing species. In conclusion, forests composed of predominately fast- growing species will likely differ in root physiology and tissue composition from those composed of slow-growing, but root morphology in these forests will depend on specific species composing the forest.

KEY WORDS: fine root physiology, temporate forest trees, root decomposition