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This article in SSSAJ

  1. Vol. 62 No. 4, p. 951-958
     
    Received: Apr 30, 1997
    Published: July, 1998


    * Corresponding author(s): j.h.vanginkel@ab.dlo.nl
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doi:10.2136/sssaj1998.03615995006200040015x

In Situ Decomposition of Grass Roots as Affected by Elevated Atmospheric Carbon Dioxide

  1. J. H. van Ginkel  and
  2. A. Gorissen
  1. DLO Research Inst. for Agrobiology and Soil Fertility (AB-DLO), Dep. of Soil Ecology, P.O. Box 14, 6700 AA Wageningen, the Netherlands

Abstract

Abstract

The effects of elevated CO2 on belowground C input, on decomposition of roots in situ vs. decomposition of disturbed roots, and on soil microbial biomass were investigated in a perennial grass species. Forty ryegrass (Lolium perenne L.) plants were homogeneously 14C-labeled in two controlled environments for 115 d in a continuous 14CO2 atmosphere at 350 and 700 µL CO2 L-1 and two soil N levels (low, LN, and high, HN). Thereafter, some of the plants were destructively harvested. Undisturbed root systems of the remaining plants were incubated in situ (IRS) for comparison with a disturbed incubation of the dried and ground roots (DRS) in their original soils. At the start of the incubation, elevated CO2 had increased total 14C-labeled soil C input by 44 and 27% at LN and HN, respectively, compared with input at ambient CO2. After incubation for 230 d, 40% of 14C soil content was mineralized to 14CO2 in the disturbed system and 52% in the intact system. Native soil organic matter (SOM) decomposition of the DRS was lower than the SOM decomposition of the IRS. The formation of 14C-labeled soil microbial biomass (14C-SMB) in the soil with DRS was 130% higher than in the soil with the IRS. Elevated CO2 decreased the decomposition of roots and root-derived products by 10% and increased the size of the 14C-SMB by 28% for both IRS and DRS, whereas the decomposition of SOM was not affected by CO2 at either LN or HN. After plant growth and in situ incubation, the 14C-labeled C in the soil solution showed a highly positive correlation with the amount of 14C-SMB. The ratio between 14C-labeled microorganisms and total 14CO2 evolved was not affected by elevated CO2. It seems that microorganisms adapt to changing soil C input under elevated CO2 and there is no effect on their turnover and behavior.

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