What question did this study set out to answer?

This study aims to quantify the drivers of understory biodiversity in chestnut forests, focusing on microclimatic and structural influences.

June 19, 2026Open Access

Modeling the Environmental Drivers of Understory Diversity and Rarity in Chestnut (Castanea sativa L.) Forests: The Role of Microclimatic Buffering and Stand Structure

Key Points

This study aims to quantify the drivers of understory biodiversity in chestnut forests, focusing on microclimatic and structural influences.
Used a nested plot design (n = 30) for data collection on understory communities.
Integrated in situ microclimatic monitoring with hemispherical photography for canopy architecture assessment.
Applied Generalized Additive Models (GAMs) to analyze Shannon Diversity (H’) and a weighted rarity index (RSR).
Tree slenderness served as a robust proxy for stand competition, affecting light availability and microclimatic stability.
Shannon diversity peaked in closed forests with lower temperatures and lower slenderness values (explaining 66.1% of the variance).
Species rarity was primarily influenced by stand slenderness and low disturbance levels, with rare species prevalent in undisturbed stands (explaining 54.6% of the variance).

Abstract

Understory vegetation communities in chestnut (Castanea sativa L.) forests feature unique biodiversity patterns and high conservation value, yet the complex drivers of these communities remain poorly quantified. This study investigates the combined effects of structural, microclimatic, and topographic parameters on understory biodiversity in the mountainous region of Chalkidiki, Northern Greece. Using a nested plot design (n = 30), we integrated analytical in situ microclimatic monitoring with hemispherical photography (HemiView canopy image analysis system) to accurately quantify canopy architecture (canopy cover and solar radiation parameters), while a detailed vegetation inventory of vascular plants was performed to determine plant community structure and composition. Generalized Additive Models (GAMs) were employed to model Shannon Diversity (H’) and a weighted rarity index (RSR) representing complementary aspects of understory biodiversity. Our results reveal that the tree slenderness of the dominant stand serves as a robust proxy for stand competition and compactness. Lower slenderness values, reflecting reduced overstory competition, were significantly associated with enhanced light availability and potentially with microclimatic stability, which in turn supported higher levels of species diversity and rarity. Distinct ecological trends were observed between diversity and rarity. Shannon diversity was highest in closed forest environments characterized by lower temperatures, low stand slenderness values, southern aspects, and lower elevations, with the final model explaining 66.1% of the variance (n = 27). In contrast, species rarity was primarily driven by stand slenderness and low disturbance levels (explaining 54.6% of the variance), with the majority of rare species occurring in undisturbed stands (n = 30). These findings suggest that targeted, low-intensity management for competition promotes structurally stable stands and microclimatic buffering, facilitating the preservation of understory biodiversity.

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