Nutrient additions to a tropical rain forest drive substantial soil carbon dioxide losses to the atmosphere

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Terrestrial biosphere-atmosphere carbon dioxide (CO2) exchange is dominated by tropical forests, where photosynthetic carbon (C) uptake is thought to be phosphorus (P)-limited. In P-poor tropical forests, P may also limit organic matter decomposition and soil C losses. We conducted a field-fertilization experiment to show that P fertilization stimulates soil respiration in a lowland tropical rain forest in Costa Rica. In the early wet season, when soluble organic matter inputs to soil are high, P fertilization drove large increases in soil respiration. Although the P-stimulated increase in soil respiration was largely confined to the dry-to-wet season transition, the seasonal increase was sufficient to drive an 18% annual increase in CO 2 efflux from the P-fertilized plots. Nitrogen (N) fertilization caused similar responses, and the net increases in soil respiration in response to the additions of N and P approached annual soil C fluxes in mid-latitude forests. Human activities are altering natural patterns of tropical soil N and P availability by land conversion and enhanced atmospheric deposition. Although our data suggest that the mechanisms driving the observed respiratory responses to increased N and P may be different, the large CO2 losses stimulated by N and P fertilization suggest that knowledge of such patterns and their effects on soil CO2 efflux is critical for understanding the role of tropical forests in a rapidly changing global C cycle.

    Original languageEnglish
    Pages (from-to)10316-10321
    Number of pages6
    JournalProceedings of the National Academy of Sciences of the United States of America
    Volume103
    Issue number27
    DOIs
    StatePublished - Jul 4 2006

    Keywords

    • Carbon cycle
    • Nitrogen
    • Nutrient availability
    • Phosphorus
    • Soil respiration

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