Fine-root turnover patterns and their relationship to root diameter and soil depth in a 14C-labeled hardwood forest.
Characterization of turnover times of fine roots is essential to understanding patterns of carbon allocation in plants and describing forest C cycling. We used the rate of decline in the ratio of 14C to 12C in a mature hardwood forest, enriched by an inadvertent 14C pulse, to investigate fine-root turnover and its relationship with fine-root diameter and soil depth. Biomass and Delta14C values were determined for fine roots collected during three consecutive winters from four sites, by depth, diameter size classes (< 0.5 or 0.5-2 mm), and live-or-dead status. Live-root pools retained significant 14C enrichment over 3 yr, demonstrating a mean turnover time on the order of years. However, elevated Delta14C values in dead-root pools within 18 months of the pulse indicated an additional component of live roots with short turnover times (months). Our results challenge assumptions of a single live fine-root pool with a unimodal and normal age distribution. Live fine roots < 0.5 mm and those near the surface, especially those in the O horizon, had more rapid turnover than 0.5-2 mm roots and deeper roots, respectively.
Joslin
J D
JD
Below-ground Forest Research, Apartado 104-5655, Monteverde, Puntarenas, Costa Rica. devjoslin@hotmail.com
Gaudinski
J B
JB
Torn
M S
MS
Riley
W J
WJ
Hanson
P J
PJ
D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D002250:Carbon Radioisotopes / Q000378:metabolism; D017753:Ecosystem; D018517:Plant Roots / Q000033:anatomy & histology* / Q000378:metabolism*; D012987:Soil; D013997:Time Factors; D014197:Trees / Q000378:metabolism*
D002250:Carbon Radioisotopes; D012987:Soil; D002244:Carbon