In Situ Decomposition of Grass Roots as Affected by Elevated Atmospheric Carbon Dioxide
- J. H. van Ginkel and
- A. Gorissen
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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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