Carbon and phosphorus transformations during decomposition of pine forest floor with different phosphorus status |
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Authors: | S Saggar R L Parfitt G Salt M F Skinner |
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Institution: | (1) Landcare Research, Private Bag 11052, Palmerston North, New Zealand Tel.: +64-6-3567154; Fax: +64-6-3559230; e-mail: SaggarS@Landcare.cri.nz, NZ;(2) New Zealand Forest Research Institute, Private Bag 3020, Rotorua, New Zealand, NZ |
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Abstract: | Summary Information on the mineralization of inorganic phosphate (Pi) from organically bound P (Po) during decomposition of forest floor and soil organic matter is vital for understanding P
supply in forest ecosystems. Carbon (C) and phosphorus (P) fluxes were determined for forest floor samples from three Pinus radiata plots which had received no P (Control), 62.5 kg P ha–1 (Low P) and 125 kg P ha–1 (High P) 20 years before sampling. The P concentration of the forest floor samples had increased with fertilizer application,
and the C:P ratio ranged between 585 and 1465. During a 9-week laboratory incubation 8.2–19.0% of the forest floor C was evolved
as CO2-C. The amount of CO2 evolved from the forest floor of the Control plot was more than twice the amounts from the Low P and High P plots. There
was little change in net P mineralization in the Control and Low P treatments throughout the incubation, but it increased
slightly for the High P samples, suggesting a critical forest floor C:P ratio of 550 for net P mineralization. Changes in
the 32P-specific activities of the Pi and microbial P pools during incubation, and concurrent changes in microbial-32P and 32Pi, indicated internal P cycling between these pools. The rate of internal P cycling varied with forest floor quality, and was
highest in the High P forest floor. The High P samples had microbial C:P ratios of 22 : 1 which remained constant during the
incubation, suggesting the microorganisms had adequate P levels.
Received: 2 July 1997 |
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Keywords: | Forest floor Microbial phosphorus Microbial carbon C:P ratio Gross phosphorus mineralization and immobilization |
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