A Temporal Sequence (Chronosequence) of Soil Carbon and Nitrogen Development after Phosphate Mining on Nauru Island

Abstract

Ten composite soil samples (0-15 cm depth) were collected from abandoned phosphate-mined sites on Nauru Island (Central Pacific) and analyzed for % organic C and % N. The samples represent a temporal sequence (chronosequence) of soil development spanning < 55 yr. The increase of% C and % N was fairly rapid. In recently mined sites « 1 yr) the values of % C were between 0.41 and 0.48, and those for % N were between 0.03 and 0.04. Fifty-five years after mining, the values of % C and % N were 4.56 and 0.33, respectively, and comparable to the amounts found in undisturbed Lithic Haplustolls, Typic Haplustolls, and Lithic Ustorthents epipedons. These changes in soil properties are considered to be a function of time and the accompanying seral development of vegetation (particularly the fern cover of Nephrolepis biserrata and Polypodium scolopendria) , because parent materials, climate, and other factors of soil formation are considered to be constant. Rate of soil development is faster in the unconsolidated sands and limestone rubble of the pit bottoms and slower on the dolomitic limestone pinnacle surfaces.