Annual wood production in a tropical rain forest in NE Costa Rica linked to climatic variation but not to increasing CO2

Authors

  • DAVID B. CLARK,

    1. Department of Biology, University of Missouri—St. Louis, St. Louis, MO 63121, USA
    2. La Selva Biological Station, Puerto Viejo de Sarapiquí, Costa Rica
    Search for more papers by this author
  • DEBORAH A. CLARK,

    1. Department of Biology, University of Missouri—St. Louis, St. Louis, MO 63121, USA
    2. La Selva Biological Station, Puerto Viejo de Sarapiquí, Costa Rica
    Search for more papers by this author
  • STEVEN F. OBERBAUER

    1. Department of Biological Sciences, Florida International University, Miami, FL 33199, USA
    2. Fairchild Tropical Botanic Garden, 11935 Old Cutler Road, Miami, FL 33156, USA
    Search for more papers by this author

David B. Clark, O.T.S., Interlink 341, PO Box 025635, Miami, FL 33102, USA, tel. +1 506 2766 6565, ext. 146, fax +1 506 2766 6535, e-mail: dbclark@sloth.ots.ac.cr

Abstract

Increased atmospheric [CO2] could theoretically lead to increased forest productivity (‘CO2 fertilization’). This mechanism was hypothesized as a possible explanation for biomass increases reported from tropical forests in the last 30+ years. We used unique long-term records of annually measured stands (eighteen 0.5 ha plots, 10 years) and focal tree species (six species, 24 years) to assess the effects of rainfall, temperature, and atmospheric [CO2] on annual wood production in a neotropical rain forest. Our study area was a meso-scale section (600 ha) of old-growth Tropical Wet Forest in NE Costa Rica. Using the repeated remeasurements we directly assessed the relative effects of interannual climatic variation and increasing atmospheric [CO2] on wood production. A remarkably simple two-factor model explained 91% of the interannual variance in stand-level tree growth; the statistically independent factors were total dry season rainfall (positive effect, r2=0.85) and night-time temperature (negative effect, r2=0.42). Stand-level tree mortality increased significantly with night-time temperature. After accounting for dry season rainfall and night-time temperature, there was no effect of annual [CO2] on tree growth in either the stand or focal species data. Tree growth in this Tropical Wet Forest was surprisingly sensitive to the current range of dry season conditions and to variations in mean annual night-time temperature of 1–2°. Our results suggest that wood production in the lowland rainforests of NE Costa Rica (and by extension in other tropical regions) may be severely reduced in future climates that are only slightly drier and/or warmer.

Ancillary