The effects of earthworm (Lumbricus terrestris) activity on phosphorus availability in an Ontario podzol

Porter, Jacqueline Anna
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University of Guelph

Phosphorus availability in hardwood forest ecosystems growing on acidic, weathered soils is thought to rely on the efficient recycling of mineralized phosphorus through the humus layer. I hypothesized that high levels of earthworm activity in such systems would increase the concentrations of iron- and aluminium-associated phosphorus and reduce the proportion of soil phosphorus in labile inorganic forms by exposing phosphate mineralized from decomposing detritus to fixation by the mineral soil. Using a modified Hedley fractionation, I divided the phosphorus into six fractions of differing biological availability: Resin-P, Bicarb-Pi. Bicarb-Po, NaOH-Pi, NaOH-Po, and HCI-P. The introduction of ' L. terrestris' to podzolic soil in an incubation experiment revealed that earthworm activity, contrary to expectations, did not change the concentration of iron- and aluminium-associated phosphorus (NaOH-Pi) and increased the concentrations of the labile inorganic phosphorus fractions (Resin-P and Bicarb-Pi) as well as the proportion of extracted phosphorus found in these fractions. In addition, earthworm activity decreased the concentration of calcium-associated phosphorus (HCI-P). It is possible that earthworm activity reduced the phosphate adsorption capacity of the soil by increasing the formation of organic-mineral complexes. These findings suggest that earthworm activity could increase phosphorus availability in forest ecosystems.

Ontario, podzol, earthworm activity, phosphorus, hardwood forest ecosystems, acidic weathered soils