Contrasting dynamics and trait controls in first-order root compared with leaf litter decomposition

Significance Decomposition of plant roots and associated fungal mutualists is a dominant process in ecosystem carbon cycles, yet is woefully understudied compared with decomposition of leaf litter, particularly for the finest order roots that have the highest turnover. In a field experiment, we compared decomposition of the finest, most distal roots and leaf litter among 35 cooccurring temperate forest species over 6 years. We found that decomposition rates of root tips were considerably lower than those of leaf litter and were controlled by nonlignin carbon compounds in contrast to lignin:nitrogen ratio control over leaf litter decomposition. Our study suggests that models of terrestrial carbon cycling based on aboveground patterns are inadequate to describe decomposition of the finest plant roots.