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Soil Science Society of America Journal Abstract -

Nitrogen Mineralization in Soils of a Chaparral Watershed in Arizona


This article in SSSAJ

  1. Vol. 56 No. 5, p. 1629-1634
    Received: Aug 6, 1991

    * Corresponding author(s):
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  1. James O. Klemmedson  and
  2. Brian J. Wienhold
  1. School of Renewable Natural Resources, Univ. of Arizona, Tucson, AZ 85721
    USDA-ARS Hydrology Lab., Beltsville, MD 20705



This study was undertaken to extend our knowledge of nutrient availability in soils of the Arizona chaparral. Our objective was to determine the effect of shrub species and topographic aspect on N mineralization of soils from a watershed in central Arizona and to relate N mineralization to other soil properties. Soil for an incubation study was collected from the 0- to 2- and 2- to 10-cm soil layers beneath the canopy of 32 randomly selected shrubs, eight each of birchleaf mountain mahogany (Cercocarpus betuloides Nutt. ex. Torr. & A. Gray) and shrub live oak (Quercus turbinella Greene) from both north and south aspects. Neither cumulative N mineralization (Nm) nor potentially mineralizable N (No) was influenced by shrub species or aspect. Aspect significantly influenced NH4 released in the 2- to 10-cm layer, with greater amounts released in soils from north and south aspects. Both Nm and No were markedly higher in the 0- to 2-cm soil layer than in the 2- to 10-cm layer; NO3 was the dominant form of mineralized N. Nitrogen-mineralized in both soil layers correlated highly with soil C, N, P, and N/P and C/P ratios. Phosphorus supply (Pav) differed markedly between the two soil layers (3.8 and 0.7% of total P, respectively) and was related to Nm. The association of Pav with N, however, leaves the real effect of Pav on Nm in doubt.

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