Document: ZHI-3-58-41

Earthworm influence on plant litter decomposition in tropical pasture and wet forest.

LIU, Z.* and X.ZOU

University of Puerto Rico, San Juan PR 00936 USA ¹

Abstract:
We initiated this study to examine the influence of earthworms on the decomposition of plant leaf and root materials in tropical pasture and undisturbed wet forest of Puerto Rico in which earthworm populations were reduced by electroshocking as compared with control within enclosures (1 by 2 m, 4 replicates each treatment per site) in field scale experiment. Field sampling at the end of the experiment indicated that earthworm populations in the electroshocked enclosures were markedly reduced by 85.4% and 87.3% compared with those in the control enclosures in the pasture and forest, respectively. Earthworm reduction significantly decreased the annual decay rates of plant leaves, but had no effects on those of plant roots in both pasture and forest sites. The decay rate was greater when organic materials had low ratios of carbon to nitrogen or phosphorus. Soil respiration was also decreased in the enclosures with reduced earthworms. In contrast, soil microbial biomass C was not affected by earthworm reduction. Furthermore, there were no significant differences between the two treatments in soil bulk density, moisture content, pH, and temperature for both sites. Our results suggest that earthworms play a direct role in leaf litter decomposition, through the interaction of earthworm-microbial activities. These results further suggest that converting tropical forests to pastures may contribute to the increases in atmospheric CO ₂ levels by accelerating plant litter decomposition due to earthworms.

Keywords:

This abstract is being presented at: 3:30 PM in session:
MICROBIAL ECOLOGY