Seasonal plasticity is more important than population variability in effects on white clover architecture and productivity

The drivers of white clover (Trifolium repens) architecture and productivity are still imperfectly understood. Our aim here was to investigate the impact of genetic background, neighbourhood and season on different architectural traits, clover and total biomass yield, as well as the relationship between those traits and yield. We grew eight white clover populations in pure stands and in mixed stands with contrasting mixture partners. Over four consecutive regrowth periods within 1 year, we measured trait sizes and determined clover and total yield amounts. The size of the architectural traits differed between populations and changed in response to neighbourhood and season. Population did not affect the sign or degree of those changes. Among the tested factors, season was by far the most important driver of white clover architecture, with the seasonal pattern notably differing between architectural traits. Clover and total yield were positively related to the architectural traits leaf area, petiole length, internode length and specific leaf area. Whereas the direction of the relationship was widely unaffected, its magnitude was clearly altered by neighbourhood and season. Our results show that seasonal effects are the key for a deeper understanding of the architecture of white clover individuals and to improve the productivity of white clover communities.