Document: EST-3-63-30

Distribution and abundance of phosphorus fractions in northern hardwood forest soils invaded by exotic earthworms.

SUÁREZ, E.*, M.FISK and T.FAHEY

Cornell University , Ithaca, NY 14853, USA ¹

Abstract:
Through their burrowing and feeding activities, earthworms can greatly impact the physical structure and nutrient cycling of soils. Their activity can enhance aeration and porosity of the soil, and alter phosphorus and nitrogen availability. These effects should be especially important in forest soils that have developed without native earthworms and are currently being invaded by exotic worms. As a part of a project aimed to understand the effects of the invasion of introduced earthworms in hardwood forests in northeastern New York, we studied the content and vertical distribution of phosphorus in forest soils with and without exotic worms. The different pools of soil P were determined according to their potential availability for plants, using Hedley's fractionation procedure. Our results reveal complex changes in the availability and distribution of soil P. Specifically, we found a two-fold increase in the amount of readily available P, and a decrease in the percentage of labile organic P in the upper layers of the mineral soil of the worm invaded plots. Compared to the no-worm sites, the soil of the worm-invaded sites also showed significantly reduced amounts of non-available P (hydroxide and acid extractable P) throughout the soil profile. Conversely, no differences were found in the content and distribution of highly recalcitrant, unavailable P between the plots with and without earthworms. These results suggest that the activities of earthworms not only enhance the amount of readily available forms of P in the soil, but can also alter the status and distribution of unavailable fractions of this element. The elimination of the forest floor and incorporation of litter residues in the soil, as well as stimulation of organic matter decomposition are potential causes for the changes that we observed in the distribution and availability of P in the earthworm invaded plots. These changes could have important consequences for P losses and productivity in these forests.

Keywords: earthworms, soil phosphorus, phosphorus fractionation, northern harwood forests

This abstract is being presented at: 3:30 PM in session:
Poster Session #15: Nutrient Cycling.