Recovery of Native Earthworms in Abandoned Tropical Pastures

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Abstract
Regeneration of secondary forests is recognized as an important means for the recovery of native species biodiversity in human‐disturbed tropical lands. Native earthworms are often replaced with exotic species after deforestation. We studied changes in earthworm diversity and community structure along a chronosequence of abandoned tropical pastures in the Cayey Mountains of Puerto Rico. This chronosequence consisted of active pastures, young secondary forests 25–40 years old, and mature secondary forests>77 years old. Earthworm diversity increased along successional stages. The exotic soil‐feeding earthwormPontoscolex corethrurusdominated the pastures and young secondary forests. Five native earthworm species ( litter feedersBorgesia sedecimsetae,Estherellasp.,Onychochaeta borincana,Neotrigaster rufa, andTrigaster longissimus ) were found in the mature forests, together withP. corethrurus. Earthworm density was highest in the active pastures ( 273 individuals/m2 ), decreased as forest regeneration proceeded, and was lowest in the mature forests ( 88 individuals/m2 ). Our results suggest that regeneration of mature secondary forests, and the consequent increase in litter biomass on the forest floor, can promote the recovery of earthworm diversity and native species of earthworms in old tropical pastures.