Modelling the Rhizosphere Priming Effect in Combination with Soil Food Webs to Quantify Interaction between Living Plant, Soil Biota and Soil Organic Matter

Abstract

A model of rhizosphere priming effect under impact of root exudate input into rhizosphere soil was developed as an important process of the plant-soil interaction. The model was based on the concept of nitrogen (N) mining, compensating for the N scarcity in exudates for microbial growth by accelerating SOM mineralisation. In the model, N deficiency for microbial growth is covered (“mined”) by the increased SOM mineralisation depending on the C:N ratio of the soil and exudates. The new aspect in the model is a food web procedure, which calculates soil fauna feeding on microorganisms, the return of faunal by-products to SOM and mineral N production for root uptake. The model verification demonstrated similar magnitude of the priming effect in simulations as in the published experimental data. Model testing revealed high sensitivity of the simulation results to N content in exudates. Simulated CO2 emission from the priming can reach 10–40% of CO2 emission from the whole Ah horizon of boreal forest soil depending on root exudation rates. This modeling approach with including food web activity allows quantifying wider aspects of the priming effect functioning including ecologically important available N production.

Advances in Plant–Soil Feedback Driven by Root Exudates in Forest Ecosystems

“…The model based on the experiment can guide the understanding of soil aggregate stability mechanisms [207]. A quantitative model was developed to simulate and predict the impact of root exudates with varying C:N ratios on plant rhizosphere microorganisms and soil organic matter [208]. This model can also estimate CO 2 emissions and available N resulting from root exudate input in terrestrial ecosystems [208].…”

“…A quantitative model was developed to simulate and predict the impact of root exudates with varying C:N ratios on plant rhizosphere microorganisms and soil organic matter [208]. This model can also estimate CO 2 emissions and available N resulting from root exudate input in terrestrial ecosystems [208]. Models involving the interaction between root exudates and microbes are more widely used in agriculture compared to forestry [209].…”

Microbial utilisation of maize rhizodeposits applied to an agricultural soil at a range of concentrations

“…Current models either lack an explicit representation of microbial degradation activities or follow simplified linear degradation kinetics (Kirk et al, 1999; Landl et al, 2021). More advanced models (Chertov et al, 2022; Finzi et al, 2015) need to be rigorously validated against experimental data obtained in the plant-soil environment, as the microbial parameters in rhizosphere models are traditionally derived from pure culture studies (Zelenev et al, 2000). Integrating biological activity into rhizosphere models remains a challenge due to the lack of quantitative data, leaving a gap in the modelling of rhizosphere processes (Schnepf et al, 2022).…”