Litter composition has stronger influence on the structure of soil fungal than bacterial communities

Citation

Habtewold, J.Z., Helgason, B.L., Yanni, S.F., Janzen, H.H., Ellert, B.H., Gregorich, E.G. (2020). Litter composition has stronger influence on the structure of soil fungal than bacterial communities. European Journal of Soil Biology, [online] 98 http://dx.doi.org/10.1016/j.ejsobi.2020.103190

Plain language summary

Little is known about how the composition of the soil microbial community responds to litter quality. To evaluate this, we applied 13C-labelled oat leaf or stem litter to soil and incubated it for 170 days. We measured total C
mineralized and litter-derived C remaining in soil over the incubation. Quantitative real-time PCR and Illumina
MiSeq sequencing of marker genes showed unique shifts in the abundance and composition of both bacteria
and fungi. There was no difference in either type of litter remaining in the soils at any time during the incubation; but more C was mineralized and lost as CO2 from soil amended with leaf litter than those amended with stems, suggesting that leaf litter enhanced decomposition of the native soil organic matter. Both types of litter supported the growth of bacteria and fungi, but fungal growth and the fungal to bacterial ratio were
more pronounced with the addition of stem litter. These changes highlight the importance of
fungi in degrading relatively resistant fractions of the lignin-enriched stem litter. Our findings show that litter
composition has a stronger influence on the composition of fungal than bacterial communities. Also, some key fungal taxa have greater advantage in degrading relatively resistant plant material and thereby support the growth of other bacterial and fungal taxa through release of simple, more degradable, compounds.

Abstract

The soil microbial community regulates decomposition of plant litter, but little is known about how the composition of the community responds to litter quality. To evaluate this, we applied 13C-labelled oat [Avena sativa] leaf or stem litter to soil at a rate of 5 mg C g−1 soil and incubated it at 20 °C for 170 days. We measured total C mineralized and litter-derived C remaining in soil over the incubation. Quantitative real-time PCR and Illumina MiSeq sequencing of marker genes were used to characterize shifts in abundance and composition of bacteria and fungi. We found no difference in litter-derived C remaining in the amended soils during the incubation; but more C (~23%) was mineralized from soil amended with leaf litter than those amended with stems, suggesting that leaf litter enhanced decomposition of the native soil organic matter. Leaf and stem litter supported the growth of bacteria and fungi throughout the incubation, but fungal growth and the fungal to bacterial ratio were more pronounced with the addition of stem litter. These changes in relative abundance as well as more pronounced shifts in fungal community structure in stem vs. leaf litter amended soils highlights the importance of fungi in degrading relatively resistant fractions of the lignin-enriched stem litter. Unlike the control soil (no litter added), the modularity (i.e., communities with some degree of independence) of co-occurrence in microbial networks increased, and this coincided litter-induced enrichment of specific taxa and with reduced alpha diversity. Leaf addition enriched a few bacterial (e.g., Bacilli) and many fungal (e.g., Nectriaceae, Didymellaceae, and Stachybotryaceae) taxa, whereas stem addition caused enrichment of fungi (e.g., Trichocomaceae and Chaetomiaceae) that are known to degrade resistant plant material. The findings of this study show that litter composition has a stronger influence on the composition of fungal than bacterial communities. Our results also suggest that some key fungal taxa have greater advantage in degrading relatively resistant plant material thereby supporting the growth of other bacterial and fungal taxa through release of simple, more degradable, compounds.

Publication date

2020-05-01

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