Population dynamics and its relationship with functional traits in different succession stages of temperate mixed coniferous broad-leaved forest in Northeast China.

Functional traits regulate plant response to environmental changes, with consequences on population dynamics. However, how plant functional traits impact population dynamics, including growth, mortality, and recruitment, remains elusive in temperate forests across different successional stages. In this study, we compiled data on population dynamics and eight functional traits, encompassing hydraulic, wood, and leaf traits, from 35 species commonly found in a secondary poplar-birch forest and a broad-leaved Korean pine forest in Northeast China. We quantified the intrinsic relationships between plant population dynamics and assessed how plant functional traits influenced these dynamics. The results demonstrated a gradual increase in the correlation among population dynamics as forest succession progressed. In the secondary forest, tree growth rate and mortality rate were negatively correlated, while growth-death rate and growth-recruitment rate were not related. Conversely, in the broad-leaved Korean pine forest, there was a significant negative correlation between tree growth rate and mortality rate, as well as between growth rate and recruitment rate, while tree mortality rate positively correlated with recruitment rate. Additionally, functional traits effectively predicted population dynamics, but the predictive ability varied across successional stages. Functional traits, particularly xylem hydraulic traits (<i>e.g</i>., Huber value) and anatomical traits (<i>e.g</i>., mean xylem conduit diameter), were stronger predictors of tree growth, mortality, and recruitment rates at the late successional stage compared with the early stage. These findings indicated that population dynamics and functional traits exhibited strong regularity in the late successional stage of broad-leaved Korean pine forests.