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This article in SSSAJ

  1. Vol. 52 No. 4, p. 1155-1162
     
    Received: Mar 11, 1987
    Published: July, 1988


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doi:10.2136/sssaj1988.03615995005200040048x

Potentially Available Nitrogen and Phosphorus Along a Chaparral Fire Cycle Chronosequence

  1. G. M. Marion  and
  2. C. H. Black
  1. San Diego State Univ., San Diego, Ca 92182

Abstract

Abstract

The objectives were to examine the effect of time, aspect, and soil horizon on N and P availabilities across a 4- to 85-yr-old post-fire chaparral chronosequence. Nitrogen and P availabilites were measured with plant bioassays, soil incubations, soil chemical extractions, and field leaf analyses. The A horizons contained significantly higher levels of available N and P than B horizons. In general, N availability was higher in north aspect stands than in south aspects stands, while P availability was higher in south aspect stands than in north aspect stands. Nitrogen availability increased with increasing stand age up to 50 to 60 yr (aggradation phase); beyond 60 yr, N availability declined (degradation phase). Phosphorus availability decreased logarithmically with increasing age. Declining N availability in the older stands was due to declining total soil N and a decline in the fraction available; the declining P availability in the older stands was due to a decline in the fraction available. The lowering of both soil and plant N and P concentrations in older stands may contribute to stand senescence.

Contribution from the Systems Ecology Res. Group. This work was funded by NSF Grant DEB-8025977 to San Diego State Univ.

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