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Research Project: Improving Computational Modeling in Support of Better Erosion and Sediment Movement Control in Agricultural Watersheds

Location: Watershed Physical Processes Research

Title: Lasting effect of soil warming on organic matter decomposition depends on tillage practices

Author
item Hou, Ruixing - Chinese Academy Of Sciences
item Ouyang, Zhu - Chinese Academy Of Sciences
item Maxim, Dorodnikov - University Of Gottingen
item Wilson, Glenn
item Kuzyakov, Yakov - University Of Gottingen

Submitted to: Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2015
Publication Date: 1/19/2016
Publication URL: http://handle.nal.usda.gov/10113/62685
Citation: Hou, R., Ouyang, Z., Maxim, D., Wilson, G.V., Kuzyakov, Y. 2016. Lasting effect of soil warming on organic matter decomposition depends on tillage practices. Soil Biology and Biochemistry. 95:243-249.

Interpretive Summary: Global warming can accelerate soil organic matter (SOM) decomposition and therefore affect the atmospheric CO2 concentration. However, few studies focused on the effect of sustained soil warming on microbial activity associated with SOM decomposition. This study addressed whether microbial communities adjusted to stable conditions because of substrate exhaustion or maintained an in microbial activity with accelerated decomposition of recalcitrant SOM pools when exposed to long-term warmer conditions than present. This is especially important with no-till crop systems due to the concentration of plant residue at the soil surface and therefore more susceptible to warming effects. Soil samples were collected from field plots of a four-year warming experiment with till and no-till practices and incubated in the laboratory under three temperatures: 15, 21, and 27 °C. The CO2 efflux was analyzed along with changes in organic C pools. Warmed soils released significantly more CO2 than the control treatment (no warming) at each incubation temperature, and the largest differences were observed under 15 °C (26% increase). The difference in CO2 efflux between NT and CT increased with incubation temperature due to the vulnerability of the high surface C pool in NT to warming. The respiration rate, which reflects the sensitivity of SOM decomposition to warming, was lower for warmed than non-warmed soil indicating better acclimation of microbes or lower C availability during long term warming. The activity of three extracellular enzymes: b-glucosidase, chitinase, sulphatase, reflecting the response of C, N and S cycles to warming, were significantly higher under warming and especially under NT compared to the other treatments. The CO2 released during 2 months of incubation consisted of 85% decomposition-resistant SOM and the remaining 15% released was from microbial biomass and extractable organic C. The dominance of CO2 from resistant SOM was especially pronounced in NT. We concluded that the accelerated decomposition of resistant SOM was sustainable due to stimulation of microorganisms by warming. Consequently, predictions of redistribution or even accumulation of C in the topsoil of no-till should be taken with high caution, as global warming could potentially sustain high rates of decomposition under warming.

Technical Abstract: Global warming affects various parts of carbon (C) cycle including acceleration of soil organic matter (SOM) decomposition with strong feedback to atmospheric CO2 concentration. Despite many soil warming studies showed changes of microbial community structure, very few were focused on the effect of sustained soil warming on microbial activity associated with SOM decomposition. Two hypotheses have been proposed but never proven under long term field conditions: 1) acclimation to stable conditions because of substrate exhaustion and 2) sustained increase of microbial activity with accelerated decomposition of recalcitrant SOM pools. This is especially important with no-till crop systems due to the redistribution of organic C at the soil surface, which is much susceptible to warming effects than the rest of the profile. We incubated soil samples collected from a four-year warming experiment with till and no-till practice under three temperatures: 15, 21, and 27 °C and analyzed the CO2 efflux as changes of organic C pools. Warmed soils released significantly more CO2 than the control treatment (no warming) at each incubation temperature, and the largest differences were observed under 15 °C (26% increase). The difference in CO2 efflux between NT to CT increased with incubation temperature due to the vulnerability of the high surface C pool in NT to warming. The Q10 value reflecting the sensitivity of SOM decomposition to warming was lower for warmed than non-warmed soil indicating better acclimation of microbes or lower C availability during long term warming. The activity of three extracellular enzymes: b-glucosidase, chitinase, sulphatase, reflecting the response of C, N and S cycles to warming, were significantly higher under warming and especially under NT compared to two other respective treatments. The CO2 released during 2 months of incubation consisted of 85% recalcitrant SOM and the remaining 15% released was from microbial biomass and extractable organic C. The dominance of CO2 from recalcitrant SOM was especially pronounced in NT. We conclude that the accelerated decomposition of recalcitrant SOM due to stimulation of microorganisms by warming is sustainable. Consequently, predictions of redistribution or even accumulation of C in the topsoil of no-till should be taken with high caution, as global warming could potentially sustain high rates of decomposition under warming.