Warming effects on carbon dynamics and microbial communities in soils of diverse texture


Yanni, S.F., Helgason, B.L., Janzen, H.H., Ellert, B.H., Gregorich, E.G. (2020). Warming effects on carbon dynamics and microbial communities in soils of diverse texture. Soil Biology & Biochemistry, [online] 140 http://dx.doi.org/10.1016/j.soilbio.2019.107631

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This study examines the influence of soil warming and soil texture on the decomposition of crop residues and native soil organic matter. Soil organic matter and the conversion of crop residues to soil organic matter is critical for plant productivity and soil health. How these factors might change in response to climate warming is important to understand future challenges and to devise appropriate responses. This study used cutting-edge techniques, including crop residues that had been labelled with stable isotopes, and metagenomics analyses of the soil microbial community to investigate soil organic matter dynamics. Soil organic matter decomposition increased with temperature, regardless of contrasting microbial communities and textures (relative amounts of sand, silt and clay). Contrary to expectations, greater clay contents did not appear to stabilize soil organic matter against decomposition.


Climate change may profoundly influence soil organic carbon (SOC) dynamics through effects on soil temperature and water, but the mechanisms and magnitude of those effects remain uncertain. We measured the response of residue-C and native SOC in six soils with diverse texture subjected to artificial heating after transplanting to a common field site. The soils, three from each of two climatic zones in Canada, were amended with 13C labelled oat (Avena sativa) residue to distinguish turnover of recently-applied C and native SOC. The soils were either kept at ambient temperature or heated to 5 °C above ambient and CO2 emission was monitored over two growing seasons. Temperature was the primary factor regulating soil respiration across all six soils; water content did not have any additional explanatory effect, probably because the study site conditions were generally wet and thus decomposition was not limited by water. Soil aggregation and loss of residue-C (68% after 295 days) were not affected by warming. Compared to residue-C, native-SOC was more sensitive to loss by warming. The effect of physical aggregate protection against loss of SOC under warming was not evident. Bacterial community structure (16S rRNA gene sequencing) showed that there was a strong and persistent legacy effect on microbial communities. These differences among soils were far greater than those between heating and ambient treatments despite transplanting to a common location. Our results show that decomposition of residue-C and SOC were strongly governed by soil temperature rather than water content, even among transplanted soils with different textures and bacterial communities.

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