BayCEER Workshop 2020

Priming effects in a meadow to forest transitional zone

O 1.4 in Session 1: Soil Secrets Revealed

29.10.2020, 10:00-10:15, online via Zoom

The dynamics of priming effect depend on a complex interplay of abiotic and biotic controls such as substrate availability, and soil microbial structure and activity. Arbuscular mycorrhizal fungi (AMF, dominant mycorrhizal fungal species in the meadow) and ectomycorrhizal fungi (ECM, dominant mycorrhizal fungal species in the temperate forest) have different saprotrophic capability, leading to distinct outcome of interaction with soil microorganisms. However, it still remains largely unclear how relative abundance of AMF and ECM affects the outcome of interaction with soil microorganisms on priming effect. A field experiment was conducted in a meadow to forest transitional zone, and ingrowth core (IGC) made out of 25 μm nylon mesh is applied to exclude mycoorhizal effect on soil microbial community. Undisturbed soil and soil from the IGC was incubated with or without ¹⁴C glucose addition to investigate priming effect.

Glucose-derived C and SOM-derived C in undisturbed soil was significantly lower than that in soil from IGC, and the differences of SOM-derived C between treatments largely increased as meadow transitioned to forest. To explore soil microbial functional diversity, the Tax4Fun database was applied to predict microbial function based on sequenced rRNA gene information. The abundance of microbial function related to C cycling, C degradation, and N cycling was higher in soil from IGC than that in undisturbed soil. Moreover, principal component 1 of microbial function involved in N cycling positively linear correlated with glucose-derived C and SOM derived C with or without glucose addition. We conclude that competition between mycorrhizal fungi and other microorganisms for soil nutrients aggravate nutrient limitation for microbial growth leading to increased relative abundance of oligotrophs and decreased abundance of microbial function involved in C and N cycling, which further decelerates SOM decomposition.

Keywords: priming effect, soil organic matter decomposition, arbuscular mycorrhizal fungi, ectomycorrhizal fungi, soil mcirobial functional diversity

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