IMPACT4SOIL OpenAire Research@WUR Crossref Microsoft Academic Graph Soil Biology and Biochemistry Restricted 2004-09-30 Abstract The net flux of soil C is determined by the balance between soil C input and microbial decomposition, both of which might be altered under prolonged elevated atmospheric CO 2 . In this study, we determined the effect of elevated CO 2 on decomposition of grass root material ( Lolium perenne L.). 14 C-labeled root material, produced under ambient (35 Pa pCO 2 ) or elevated CO 2 (70 Pa pCO 2 ) was incubated in soil for 64 days. The soils were taken from a pasture ecosystem which had been exposed to ambient (35 Pa pCO 2 ) or elevated CO 2 (60 Pa pCO 2 ) under FACE-conditions for 10 years and two fertilizer N rates: 140 and 560 kg N ha −1  year −1 . In soil exposed to elevated CO 2 , decomposition rates of root material grown at either ambient or elevated CO 2 were always lower than in the control soil exposed to ambient CO 2 , demonstrating a change in microbial activity. In the soil that received the high rate of N fertilizer, decomposition of root material grown at elevated CO 2 decreased by approximately 17% after incubation for 64 days compared to root material grown at ambient CO 2 . The amount of 14 CO 2 respired per amount of 14 C incorporated in the microbial biomass ( q 14 CO 2 ) was significantly lower when roots were grown under high CO 2 compared to roots grown under low CO 2 . We hypothesize that this decrease is the result of a shift in the microbial community, causing an increase in metabolic efficiency. Soils exposed to elevated CO 2 tended to respire more native SOC, both with and without the addition of the root material, probably resulting from a higher C supply to the soil during the 10 years of treatment with elevated CO 2 . The results show the importance of using soils adapted to elevated CO 2 in studies of decomposition of roots grown under elevated CO 2 . Our results further suggest that negative priming effects may obscure CO 2 data in incubation experiments with unlabeled substrates. From the results obtained, we conclude that a slower turnover of root material grown in an ‘elevated-CO 2 world’ may result in a limited net increase in C storage in ryegrass swards. organic-matter dynamics 2. Zero hunger microbial biomass atmospheric carbon-dioxide turnover fine roots 04 agricultural and veterinary sciences 15. Life on land 01 natural sciences forest soils tallgrass prairie trifolium-repens l lolium-perenne litter quality 0401 agriculture, forestry, and fisheries 0105 earth and related environmental sciences Dave Harris, A. Gorissen, Kees Jan van Groenigen, Kees Jan van Groenigen, Peter Kuikman, Chris van Kessel, Johan Six, Jan Willem van Groenigen, 2005-03-01 journalpaper Abstract The net flux of soil C is determined by the balance between soil C input and microbial decomposition, both of which might be altered under prolonged elevated atmospheric CO 2 . In this study, we determined the effect of elevated CO 2 on decomposition of grass root material ( Lolium perenne L.). 14 C-labeled root material, produced under ambient (35 Pa pCO 2 ) or elevated CO 2 (70 Pa pCO 2 ) was incubated in soil for 64 days. The soils were taken from a pasture ecosystem which had been exposed to ambient (35 Pa pCO 2 ) or elevated CO 2 (60 Pa pCO 2 ) under FACE-conditions for 10 years and two fertilizer N rates: 140 and 560 kg N ha −1  year −1 . In soil exposed to elevated CO 2 , decomposition rates of root material grown at either ambient or elevated CO 2 were always lower than in the control soil exposed to ambient CO 2 , demonstrating a change in microbial activity. In the soil that received the high rate of N fertilizer, decomposition of root material grown at elevated CO 2 decreased by approximately 17% after incubation for 64 days compared to root material grown at ambient CO 2 . The amount of 14 CO 2 respired per amount of 14 C incorporated in the microbial biomass ( q 14 CO 2 ) was significantly lower when roots were grown under high CO 2 compared to roots grown under low CO 2 . We hypothesize that this decrease is the result of a shift in the microbial community, causing an increase in metabolic efficiency. Soils exposed to elevated CO 2 tended to respire more native SOC, both with and without the addition of the root material, probably resulting from a higher C supply to the soil during the 10 years of treatment with elevated CO 2 . The results show the importance of using soils adapted to elevated CO 2 in studies of decomposition of roots grown under elevated CO 2 . Our results further suggest that negative priming effects may obscure CO 2 data in incubation experiments with unlabeled substrates. From the results obtained, we conclude that a slower turnover of root material grown in an ‘elevated-CO 2 world’ may result in a limited net increase in C storage in ryegrass swards. Decomposition Of C-14-Labeled Roots In A Pasture Soil Exposed To 10 Years Of Elevated Co2 10.1016/j.soilbio.2004.08.013 https://doi.org/10.1016/j.soilbio.2004.08.013