Moisture-driven transitions in the controls of ecosystem multifunctionality and its spatial stability across temperate forests of South Korea

Effective ecosystem management requires insight not only into ecosystem structure but also into the methods used to evaluate and interpret ecosystem functions. This study investigates ecosystem multifunctionality (EMF) and its spatial stability along a moisture gradient. We examined how EMF responds to the combined effects of biotic attributes (taxonomic, functional, and stand structure diversity, as well as community-weighted mean traits), abiotic conditions (topography and climate), and successional stage characteristics (stand age). In addition, we assessed the roles of interspecies co-occurrence patterns and interactions among ecosystem functions in shaping the spatial stability of EMF. Our analysis was based on 2859 natural forest plots drawn from the 7th National Forest Inventory of South Korea. Using piecewise structural equation modeling complemented by simple regression analyses, we identified the relative importance and functional pathways of the major controlling factors influencing EMF and its spatial stability. The effects of aridity index and species richness varied distinctly along the moisture gradient, showing clear differences among moist, intermediate, and dry conditions. Spatial stability also displayed contrasting patterns across the moisture gradient: under high moisture level, the influence of several controlling factors diminished, whereas under low moisture level, biotic factors became more dominant. Synergistic interspecies co-occurrence enhanced EMF stability, while inter-ecosystem function interactions increased functional synchrony, ultimately decreasing stability. Overall, our findings reveal that the mechanisms regulating EMF and its spatial stability do not operate uniformly but shift systematically with changes in moisture availability. These results offer critical ecological insight for designing gradient-responsive forest management strategies under ongoing climate change.