Effects of nutrient additions on ecosystem carbon cycle in a Puerto Rican tropical wet forest

Authors

  • YIQING LI,

    1. Department of Ecology, Evolution and Natural Resources, Rutgers University, 14 College Farm Road, New Brunswick, NJ 08901-8551, USA,
    2. Xishuangbanna Tropical Botanical Garden, The Chinese Academy of Sciences, 88 Xuefu Road, Kunming, Yunnan 650223, China,
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  • MING XU,

    1. Department of Ecology, Evolution and Natural Resources, Rutgers University, 14 College Farm Road, New Brunswick, NJ 08901-8551, USA,
    2. College of Forestry, The Northwest Sci-Tech University of Agriculture and Forestry, Yangling, Shaanxi 712100, China,
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  • XIAOMING ZOU

    1. Xishuangbanna Tropical Botanical Garden, The Chinese Academy of Sciences, 88 Xuefu Road, Kunming, Yunnan 650223, China,
    2. Institute for Tropical Ecosystem Studies, University of Puerto Rico, San Juan, PR 00931, USA
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Yiqing Li, Department of Ecology, Evolution and Natural Resources, Rutgers University, 14 College Farm Road, New Brunswick, NJ 08901-8551, USA, tel. +1 732 932 9211; fax +1 732 932 3222, e-mail: yiqingli@crssa.rutgers.edu

Abstract

Wet tropical forests play a critical role in global ecosystem carbon (C) cycle, but C allocation and the response of different C pools to nutrient addition in these forests remain poorly understood. We measured soil organic carbon (SOC), litterfall, root biomass, microbial biomass and soil physical and chemical properties in a wet tropical forest from May 1996 to July 1997 following a 7-year continuous fertilization. We found that although there was no significant difference in total SOC in the top 0–10 cm of the soils between the fertilization plots (5.42±0.18 kg m−2) and the control plots (5.27±0.22 kg m−2), the proportion of the heavy-fraction organic C in the total SOC was significantly higher in the fertilized plots (59%) than in the control plots (46%) (P<0.05). The annual decomposition rate of fertilized leaf litter was 13% higher than that of the control leaf litter. We also found that fertilization significantly increased microbial biomass (fungi+bacteria) with 952±48 mg kg−1soil in the fertilized plots and 755±37 mg kg−1soil in the control plots. Our results suggest that fertilization in tropical forests may enhance long-term C sequestration in the soils of tropical wet forests.

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