Using the Forest Maturity Index to model understory regeneration of post-agricultural forest in the NE Carpathians

Abstract

The regeneration dynamics of understory vegetation in recent forests, arising from extensive agricultural land abandonment, is closely related to soil properties and proximity to ancient forests. However, the role of topography in shaping this regeneration process, especially in mountainous regions, remains unclear.This study addresses this gap by investigating the regeneration rate of understory vegetation in mountainous recent forests within the NE Carpathians, a region profoundly shaped by large-scale population displacements in the 1940s, leading to widespread agricultural land abandonment and the subsequent development of new forests.We quantified the understory regeneration rate of recent forests through extensive phytosociological relevé surveys conducted in one vegetation season. Data were collected from 194 randomly selected plots of recent forests and 100 plots of ancient forests, each exhibiting diverse topographic characteristics. By calculating the Forest Maturity Index based on ancient forest species and employing a parametrized multiple regression model, we identified key factors influencing the understory regeneration process. We further used the obtained regression formula to model the forest regeneration rate across the entire study area (40,975 ha).Proximity to ancient forests positively influenced understory regeneration. Elevation and slope also emerged as significant determinants, with the understory regeneration rate decreasing with elevation and increasing with slope steepness. Furthermore, a higher cover of pine in the tree stand had a suppressive effect. The above-mentioned dependencies resulted in substantial variations in the modeled understory regeneration of post-agricultural forests.The utilization of the Forest Maturity Index offers invaluable insights into identifying and subsequently safeguarding well-regenerated forests. Given the prevalence of forest secondary succession in various regions, this index emerges as a key indicator for future assessments and management strategies.