Effects of post-hurricane fertilization and debris removal on earthworm abundance and biomass in subtropical forests in Puerto Rico
Hurricanes are a common disturbance in the Caribbean, striking the island of Puerto Rico on average every 21 years. Hurricane Hugo (1989) distributed the canopy litter onto the forest floor changing the chemistry and quantity of litter inputs to the soil. In this study, we determined the effect of inorganic fertilization on earthworm abundance, biomass, and species composition in hurricane-damaged subtropical wet (tabonuco) and elfin forests. In addition, the effects of the removal of hurricane-generated litter on earthworm populations were studied in the tabonuco (wet) forest. We found that earthworms were more abundant in tabonuco (El Verde) than in elfin forest. In the tabonuco forest, the density and biomass (fresh and dry) of total and endogeic earthworms was significantly greater in the control than in the fertilization treatments. The removal of hurricane-generated debris significantly increased the density of total endogeic earthworms in the tabonuco forest. The results from the subtropical wet forest (tabonuco) in this study support the contention that earthworm density and biomass can decreased by fertilization via changes in soil acidity. Available N, higher soil PH and reduction of the litter fauna might explain differences in abundance in litter removal treatments as compared to fertilize and control plots at this site.