Relative contributions of leaf litter and fine roots to soil organic matter accumulation in mangrove forests

Mangrove above- and belowground litter contributes greatly to soil carbon (C) especially in systems with limited allochthonous input. This study aims to estimate the relative contributions of mangrove leaf litter vs. fine roots to the annually accumulated plant debris in the soil. Annual production of leaf litter and fine roots in four mono-specific mangrove forests was combined with their mass remaining after one year of decomposition to make the estimation. Annual fine root production was 2.2-5.1 times greater than leaf litter production, which ranged between 266 and 814 g m(-2). After 391 days of decomposition, 0-41% and 75-88% of leaf litter and fine root initial mass respectively remained. Only 5.9-69 months were expected for leaf litter to reach an approximately complete decomposition, in contrast to 111-655 months expected for fine roots. Annual plant detritus accumulation in the soil amounted to 405-2812 g m(-2), with leaf litter and fine roots contributing 2.5-7.6% and 92.4-97.5%, respectively. Fine roots are the dominant contributor to soil organic matter accumulation in mangroves due to high production and low decomposition rates. Management practices that foster fine root production are expected to accelerate soil C accumulation.