# Associations of Biotic and Abiotic Factors with Phylogenetic Community Structure Across Temperate Forests in South Korea

## TL;DR

This study explores how environmental and biological factors influence the diversity of tree species in Korean forests, aiming to improve forest resilience to climate change.

## Contribution

The study reveals stand-type-specific relationships between environmental factors, tree traits, and phylogenetic structure in temperate forests.

## Key findings

- Functional trait-related variables were most important in broadleaved and conifer stands.
- Species richness played the dominant role in mixed stands.
- Environmental factors like elevation and precipitation influenced SES.MPD through indirect pathways.

## Abstract

Forests contain many different tree species that are linked to each other through a long evolutionary history. Which species grow together in a given stand depends not only on the climate and soil, but also on chance events such as where seeds arrive and how past disturbances have reshaped the forest. In this study, a nationwide forest inventory and phylogenetic trees of all recorded woody species were used to examine how Korean temperate forests are assembled and which factors matter most in different forest stand types. More than two thousand forest plots across broadleaved, conifer, and mixed stands were analyzed, incorporating both environmental conditions and key tree traits, such as specific leaf area and maximum tree height, and species richness. Overall, SES.MPD in most plots showed weak net deviation from the null-model baseline, while the main correlates of phylogenetic community structure differed among stand types: functional trait-related variables were most important in broadleaved and conifer stands, whereas species richness played the dominant role in mixed stands. These results provide a basis for designing forest management and restoration strategies that combine species with diverse traits and evolutionary histories, helping to build forests that are more resilient to future climate change, pests, and other disturbances.

Understanding how environmental conditions, functional composition, and species richness jointly relate to phylogenetic community structure is important for sustainable forest management under environmental change. Using 2858 plots from the 7th National Forest Inventory of South Korea, phylogenetic community structure as the standardized effect size of mean pairwise phylogenetic distance (SES.MPD) was quantified for broadleaved, conifer, and mixed stands. Associations between SES.MPD and abiotic factors such as elevation, mean annual precipitation, stand age, as well as biotic factors such as species richness and community-weighted means of specific leaf area and maximum height were assessed using multi-model inference and piecewise structural equation models (pSEM). Across stand types, SES.MPD values in most plots were not significantly different from the null-model baseline under the chosen randomization procedure, indicating weak net departures from null-model-relative phylogenetic dispersion at the national scale; meanwhile, mean SES.MPD tended to be slightly negative in broadleaved stands and positive in conifer and mixed stands. In multi-model inference analysis, the strongest associations with SES.MPD differed among stand types: trait composition—especially community-weighted specific leaf area—showed the strongest association in total stands and broadleaved stands, whereas species richness was the dominant correlate in mixed stands and precipitation showed the strongest association in conifer stands. The pSEM revealed that elevation, precipitation, and stand age were linked to SES.MPD largely through indirect pathways via trait composition and species richness, consistent with trait- and richness-mediated environmental filtering. These results highlight stand-type-specific linkages among environment, traits, richness, and phylogenetic structure and support trait- and phylogeny-informed forest management and restoration to enhance resilience under ongoing environmental change.