To converge or diverge? Phenological shifts driven by plant genome size and functional traits under nitrogen deposition and mowing

Abstract Linkages between genome size (GS) and phenology underscore the diversification of functional traits, which are indicative of life‐history and resource acquisition strategies. Functional traits may contribute to the asynchronous phenological changes as commonly observed among plants with different GS, which are still underexplored. In a Eurasian meadow steppe, where nitrogen (N) deposition and mowing are prevalent, we investigated the phenological dynamics of six plant species with varying GS. Enlightened by the large genome constraint hypothesis and asymmetric light competition, we delved into analyses of plant functional traits, alongside water use efficiency (WUE) across N addition and mowing. With increasing GS, N enrichment tended to reduce reproductive phenology duration (RPD), due to enhanced resource competitiveness, reminiscent of K ‐strategists. In contrast, N addition advanced the flowering to extend the RPD with a decrease in GS due to decreased plant height and thus limited light capture, requiring more time for flower and fruit production. This pattern of advancing phenophases was also observed under mowing with decreasing GS, suggesting plants display traits typical of r ‐strategists. These phenological responses led to a convergence among species of different GS, driven by enhanced light competition with increasing GS under N addition and with decreasing GS under mowing. In conclusion, the balance of reproductive phenology among plants with diverse GS is attained through a trade‐off between soil resource acquisition and light competition, as evidenced by their functional traits. These findings enhance our understanding of the relationship between GS and r / K selection, shedding light on species co‐evolutionary in response to human disturbances and environmental changes in grasslands. Read the free Plain Language Summary for this article on the Journal blog.