STORAGE EFFECTS ON NUTRIENT MINERALIZATION IN CONIFEROUS FOREST FLOOR SAMPLES

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Abstract
Forest floor samples were obtained from three mature, even-aged, naturally regenerated conifer stands which varied with respect to drainage and indigenous soil fertility. Field moist subsamples were stored for 200 days in a refrigerator maintained at 4 °C and in a freezer maintained at − 10 °C; in addition, forest floor samples, dried at 60 °C for 48 h, were stored at room temperature. Subsamples were extracted initially and at predetermined time intervals with 2 N KCl (to determine mineral NH4+-N and NO3−-N), with neutral 1 N ammonium acetate (to determine water-soluble + exchangeable K, Ca, and Mg), and with distilled water (to determine soluble P). At 4 °C, extractable NH4+-N changed little during the first week of storage but increased steadily thereafter at rates which appeared to increase with increasing total N. Nitrification, present only in the sample taken from the most fertile site, commenced after 40 days of refrigerated storage. Concentrations of soluble P decreased initially, but rose thereafter at low, moderate, and high rates depending on total P. Freezing changed mineral NH4+-N to a minor extent, whereas NO3−-N was not affected. Concentrations of soluble P increased steadily during the first 2 mo of storage at − 10 °C. Levels of extractable K, Ca, and Mg were not affected by refrigeration and by length of storage time, but freezing increased extractable K considerably. Drying at 60 °C for 48 h produced abrupt increases in exchangeable + water-soluble nutrient levels. Further changes, however, were not observed during subsequent storage at room temperature.
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