Linking plant and microbial traits to soil organic carbon dynamics: A functional approach

Soil organic carbon (SOC) is not only a key indicator of soil health but also essential for biodiversity, water retention, and nutrient cycling. SOC underpins climate resilience, sustainable agriculture, and ecosystem functionality. This study explored the role of functional biodiversity in soil C dynamics, emphasizing plant and microbial diversity in agricultural soils. The research addressed four key questions: (i) How does functional diversity explain variations in SOC and water-extractable organic carbon (WEOC)? (ii) How do interactions between microbial groups and plant traits influence SOC and WEOC dynamics? (iii) Do farming practices affect plant and microbial functional groups involved in SOC turnover? (iv) What is the impact of farming practices on SOC-related functional diversity? Data collected from seven experimental sites across Europe and Turkey revealed that approximately 60 % of SOC and WEOC variability was determined by functional biodiversity. Structural equation modelling indicated that while plant functional groups did not directly affect SOC, traits such as specific leaf area, the presence of perennials, and grass-like species significantly influenced bacterial and fungal functional groups. These microbial groups negatively impacted SOC and were highly responsive to farming practices. This study, the first of its kind to integrate plant, bacterial, and fungal community functionality, highlights the critical role of functional biodiversity in SOC turnover. The findings underscore the importance of incorporating functional approaches into sustainable soil management practices to enhance soil monitoring and agrosystem design at multiple scales. • Functional diversity explained about 60 % of the variance of SOC in agricultural soils. • Plant traits and functional bacterial and fungal groups, which are critical to SOC turnover, were identified. • Farming practices act as filters, steering plant and microbial functionality and ultimately soil organic carbon dynamics.