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This article in SSSAJ

  1. Vol. 70 No. 1, p. 153-162
     
    Received: May 19, 2004


    * Corresponding author(s): drvann@sas.upenn.edu
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doi:10.2136/sssaj2004.0173

Litter Quality and Climate Decouple Nitrogen Mineralization and Productivity in Chilean Temperate Rainforests

  1. Amishi B. Joshi,
  2. David R. Vann and
  3. Arthur H. Johnson *
  1. Dep. of Earth and Environmental Science, The Univ. of Pennsylvania. 240 S. 33rd St., Philadelphia, PA 19104

Abstract

We measured litter quality, N mineralization, air and soil temperatures, soil moisture, and aboveground net primary production (ANPP) at 18 plots in three forest types typical of full-stature forests found on western slopes of the Cordillera de Piuchué (CP) on Isla de Chiloé in southern Chile. The primary objectives were to examine the range of net N mineralization across forest types that have different vegetation and litter composition, assess probable controls on mineral N production and leaching, and to determine if the relationship between N mineralization and ANPP was similar to that observed in cool temperate northern hemisphere forests. Average annual litter lignin/N ratios were high in the evergreen montane broadleaf forest plots (50:1) and very high in the montane conifer plots (80:1). Net N mineralization during the summer months was correspondingly low (1.2 and 2.2 kg ha−1, respectively). The high litter lignin content and associated low rate of N mineralization can explain the extremely low concentrations of mineral N in soils and upland streams of this region. In the broadleaf evergreen coastal forest plots, lignin/N ratio was lower (23:1) and N mineralized was considerably greater over the same measurement period than in the montane forest plots (14 kg ha−1). In contrast to findings in many cool temperate northern hemisphere forests, ANNP in the broadleaf forest type was high (average 11.1 Mg ha−1 yr−1) in spite of the low net N mineralization rates, and ANPP and net N mineralized were not correlated. Net N mineralization was best correlated with litter quality, soil temperature, and soil moisture content, and ANPP was best correlated with growing degree days.

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