Plant community restoration time is a key factor affecting plant nutrient and species richness

Nitrogen (N) and phosphorus (P) are vital nutrients in terrestrial ecosystems, essential for vegetation growth, plant survival, development, and the maintenance of plant diversity. While the effects of N and P additions on plant nutrient concentrations and diversity have been extensively studied, the impact of various stages of natural forest ecosystem restoration after disturbance, particularly on plant N, P nutrients, and diversity, is less understood. This study investigates the influence of anthropogenic disturbance on soil N: P ratios, plant community-level N: P, and species diversity in Liaodong oak forests in northern China during early (about 10 years), mid-to-late (about 30 years), and late (about 40 years) restoration stages (it is a space for time substitution method). We observed that soil total nitrogen to total phosphorus ratio (TN: TP) and soil available nitrogen to phosphorus ratio (AN: AP) were significantly lower in the mid-to-late and late stages of restoration compared to the early restoration stages. Concurrently, plant community level leaf nitrogen-phosphorus ratio (CWM_{N: P}) were notably lower in these later stages. Additionally, species richness showed a decline as restoration time increased. These findings highlight that decreasing soil N: P ratio over time exacerbates plant N limitation and reduces plant richness, emphasizing the critical role of soil nutrient dynamics in forest restoration post-disturbance. Our results provide important insights for forest management and restoration practices, contributing to a better understanding of ecosystem restoration processes.