Get access

Primary production and carbon allocation in relation to nutrient supply in a tropical experimental forest

Authors

  • Christian P. Giardina,

    Corresponding author
    1. Department of Natural Resources and Environmental Management, University of Hawai'i at Manoa, Honolulu, HI 96822, USA,
      Christian P. Giardina, US Department of Agriculture-Forest Service, North Central Research Station, 410 MacInnes Drive, Houghton, MI 49931, USA, tel. +906-482-6303, fax +906-482-6355, e-mail: cgiardina@fs.fed.us
    Search for more papers by this author
  • Michael G. Ryan,

    1. Department of Natural Resources and Environmental Management, University of Hawai'i at Manoa, Honolulu, HI 96822, USA,
    2. Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA,
    3. Department of Forest Sciences, Colorado State University, Fort Collins, CO 80523, USA
    Search for more papers by this author
  • Dan Binkley,

    1. Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA,
    2. Department of Forest Sciences, Colorado State University, Fort Collins, CO 80523, USA
    Search for more papers by this author
  • James H. Fownes

    1. Department of Natural Resources and Environmental Management, University of Hawai'i at Manoa, Honolulu, HI 96822, USA,
    Search for more papers by this author

Christian P. Giardina, US Department of Agriculture-Forest Service, North Central Research Station, 410 MacInnes Drive, Houghton, MI 49931, USA, tel. +906-482-6303, fax +906-482-6355, e-mail: cgiardina@fs.fed.us

Abstract

Nutrient supply commonly limits aboveground plant productivity in forests, but the effects of an altered nutrient supply on gross primary production (GPP) and patterns of carbon (C) allocation remain poorly characterized. Increased nutrient supply may lead to a higher aboveground net primary production (ANPP), but a lower total belowground carbon allocation (TBCA), with little change in either aboveground plant respiration (APR) or GPP. Alternatively, increases in nutrient supply may increase GPP, with the quantity of GPP allocated aboveground increasing more steeply than the quantity of GPP allocated belowground. To examine the effects of an elevated nutrient supply on the C allocation patterns in forests, we determined whole-ecosystem C budgets in unfertilized plots of Eucalyptus saligna and in adjacent plots receiving regular additions of 65 kg N ha−1, 31 kg P ha−1, 46 kg K ha−1, and macro- and micronutrients. We measured the absolute flux of C allocated to the components of GPP (ANPP, TBCA and APR), as well as the fraction of GPP allocated to these components.

Fertilization dramatically increased GPP. Averaged over 3 years, GPP in the fertilized plots was 34% higher than that in the unfertilized controls (3.95 vs. 2.95 kg C m−2 yr−1). Fertilization-related increases in GPP were allocated entirely aboveground – ANPP was 85% higher and APR was 57% higher in the fertilized than in the control plots, while TBCA did not differ significantly between treatments. Carbon use efficiency (NPP/GPP) was slightly higher in the fertilized (0.53) compared with the control plots (0.51). Overall, fertilization increased ANPP and APR, and these increases were related to a greater GPP and an increase in the fraction of GPP allocated aboveground.

Get access to the full text of this article

Ancillary