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Effects of an induced drought on soil carbon dioxide (CO2) efflux and soil CO2 production in an Eastern Amazonian rainforest, Brazil

Authors

  • ELENEIDE DOFF SOTTA,

    1. Institute of Soil Science and Forest Nutrition, University of Göttingen, Büsgenweg 2, D-37077, Göttingen, Germany,
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  • EDZO VELDKAMP,

    1. Institute of Soil Science and Forest Nutrition, University of Göttingen, Büsgenweg 2, D-37077, Göttingen, Germany,
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  • LUITGARD SCHWENDENMANN,

    1. Institute of Silviculture, University of Göttingen, Büsgenweg 1, D-37077, Göttingen, Germany,
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  • BRENDA ROCHA GUIMARÃES,

    1. Museu Paraense Emilio Goeldi – Campus de Pesquisa, Coordenacao de Ciencias da Terra e Ecologia. TerraFirme, Av. Perimetral 1901, CEP 66077530, Belém, PA, Brazil,
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  • ROSIENE KEILA PAIXÃO,

    1. Museu Paraense Emilio Goeldi – Campus de Pesquisa, Coordenacao de Ciencias da Terra e Ecologia. TerraFirme, Av. Perimetral 1901, CEP 66077530, Belém, PA, Brazil,
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  • MARIA de LOURDES P. RUIVO,

    1. Museu Paraense Emilio Goeldi – Campus de Pesquisa, Coordenacao de Ciencias da Terra e Ecologia. TerraFirme, Av. Perimetral 1901, CEP 66077530, Belém, PA, Brazil,
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  • ANTONIO CARLOS LOLA da COSTA,

    1. Departamento de Meteorologia, Centro de Geociências, Universidade Federal do Pará, Avenida Augusto Correa s/n, Guamá, CEP 66075900, Belem, PA, Brasil
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  • PATRICK MEIR

    1. School of GeoSciences, University of Edinburgh, Drummond Street, Edinburgh, UK,
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Edzo Veldkamp, tel. +49 551 397339, fax +49 551 393310, e-mail: eveldka@gwdg.de

Abstract

In the next few decades, climate of the Amazon basin is expected to change, as a result of deforestation and rising temperatures, which may lead to feedback mechanisms in carbon (C) cycling that are presently unknown. Here, we report how a throughfall exclusion (TFE) experiment affected soil carbon dioxide (CO2) production in a deeply weathered sandy Oxisol of Caxiuanã (Eastern Amazon). Over the course of 2 years, we measured soil CO2 efflux and soil CO2 concentrations, soil temperature and moisture in pits down to 3 m depth. Over a period of 2 years, TFE reduced on average soil CO2 efflux from 4.3±0.1 μmol CO2 m−2 s−1 (control) to 3.2±0.1 μmol CO2 m−2 s−1 (TFE). The contribution of the subsoil (below 0.5 m depth) to the total soil CO2 production was higher in the TFE plot (28%) compared with the control plot (17%), and it did not differ between years. We distinguished three phases of drying after the TFE was started. The first phase was characterized by a translocation of water uptake (and accompanying root activity) to deeper layers and not enough water stress to affect microbial activity and/or total root respiration. During the second phase a reduction in total soil CO2 efflux in the TFE plot was related to a reduction of soil and litter decomposers activity. The third phase of drying, characterized by a continuing decrease in soil CO2 production was dominated by a water stress-induced decrease in total root respiration. Our results contrast to results of a drought experiment on clay Oxisols, which may be related to differences in soil water retention characteristics and depth of rooting zone. These results show that large differences exist in drought sensitivity among Amazonian forest ecosystems, which primarily seem to be affected by the combined effects of texture (affecting water holding capacity) and depth of rooting zone.

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