Fourteen-year field experiment reveals neutral effects of N and P deposition on abundance and stoichiometric traits of the earthworm Pontoscolex corethrurus in tropical plantations

Abstract

The afforestation of tropical forests plays an important role in mitigating climate change. Exploring the impacts of nitrogen (N) and phosphorus (P) deposition on earthworm communities is significant for understanding the contributions of tropical forests to global change. A 14-year field experiment simulating N and P deposition at a station with 50-year-old tropical plantations was conducted. We found that the pantropical widespread exotic earthworm species Pontoscolex corethrurus was dominant, and it did not respond to exogenous N input. Moreover, P addition only increased the abundance of P. corethrurus after 14 years. Similarly, neither N addition nor P addition changed the stoichiometric traits of P. corethrurus. However, over the past decade, the abundance, biomass, and carbon (C), N, and P concentrations in the tissues of P. corethrurus have increased. A strong positive correlation between P. corethrurus population size and soil gram-negative (G⁻) bacteria biomass was observed, suggesting that P. corethrurus may benefit from the soil bacterial channel. This study ascertained that non-natural tropical lands may be resistant to N and P deposition in terms of earthworm related belowground processes, which would be helpful for fully understanding plant-soil biota feedback and their contributions to tropical plantation development and the mitigation of global climate change.