Above-ground forest biomass is not consistently related to wood density in tropical forests

Authors

  • James C. Stegen,

    Corresponding author
    1. Department of Ecology and Evolutionary Biology, University of Arizona, Biosciences West 310, Tucson, AZ 85721, USA
    Search for more papers by this author
  • Nathan G. Swenson,

    1. Center for Tropical Forest Science – Asia Program Arnold Arboretum, Harvard University, Cambridge, MA 02138, USA
    Search for more papers by this author
  • Renato Valencia,

    1. Laboratorio de Ecología de Plantas, Escuela de Ciencias Biológicas, Pontificia Universidad Católica del Ecuador, Apartado 17-01-2184, Quito, Ecuador
    Search for more papers by this author
  • Brian J. Enquist,

    1. Department of Ecology and Evolutionary Biology, University of Arizona, Biosciences West 310, Tucson, AZ 85721, USA
    2. The Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501, USA
    3. Center for Applied Biodiversity, Science Conservation International, 2011 Crystal Drive, Suite 500, Arlington, VA 22202, USA
    Search for more papers by this author
  • Jill Thompson

    1. Institute for Tropical Ecosystem Studies, University of Puerto Rico, Rio Piedras, Puerto Rico 00931
    Search for more papers by this author

*Correspondence: James C. Stegen, 1041 E. Lowell Street, Biosciences West Room 310, Tucson, AZ 85721, USA.
E-mail: stegen@u.arizona.edu

ABSTRACT

Aim  It is increasingly accepted that the mean wood density of trees within a forest is tightly coupled to above-ground forest biomass. It is unknown, however, if a positive relationship between forest biomass and mean community wood density is a general phenomenon across forests. Understanding spatial variation in biomass as a function of wood density both within and among forests is important for predicting changes in stored carbon in response to global change, and here we evaluated the generality of a positive biomass–wood density relationship within and among six tropical forests.

Location  Costa Rica, Panama, Puerto Rico and Ecuador.

Methods  Individual stem data, including diameter at breast height and spatial position, for six forest dynamics plots were merged with an extensive wood density database. Individual stem biomass values were calculated from these data using published statistical models. Total above ground biomass, total basal area and mean community wood density were also quantified across a range of subcommunity plot sizes within each forest.

Results  Among forests, biomass did not vary with mean community wood density. The relationship between subcommunity biomass and mean wood density within a forest varied from negative to null to positive depending on the size of subcommunities and forest identity. The direction of correlation was determined by the associated total basal area–mean wood density correlation, the slope of which increased strongly with whole forest mean wood density.

Main conclusions  There is no general relationship between forest biomass and wood density, and in some forests, stored carbon is highest where wood density is lowest. Our results suggest that declining wood density, due to global change, will result in decreased or increased stored carbon in forests with high or low mean wood density, respectively.

Ancillary