Variation in Culturable Rhizosphere Fungal Communities of Abies koreana in Mt. Jiri, Korea, in Relation to Topographic and Physicochemical Soil Properties.

Abstract

This study was aimed at characterizing the culturable rhizosphere fungal community of Abies koreana on Mt. Jiri, Korea and to investigate the influence of topographic and physicochemical soil properties on them. Samples were collected from two contrasting sites: the Seseok Plateau (gentle-slope basin with poor drainage) and Oesamsinbong (steep slope with excellent drainage). A total of 620 isolates spanning four phyla, 11 classes, 21 orders, 34 families, and 51 genera were identified. Penicillium was the dominant genus, comprising 367 isolates. Shannon's diversity index increased as Penicillium dominance decreased, indicating that reduced exclusive dominance enhanced community evenness. Although both sites had loamy soils, their chemical properties varied significantly with topography. The Seseok Plateau showed extreme acidification (pH 3.80-4.20) and severe cation leaching with a very low average base saturation (BS) of 4.9%. In contrast, Oesamsinbong maintained higher BS (avg. 12.3%) because the steep terrain inhibited acid accumulation. Penicillium dominance was significantly higher in Oesamsinbong (72.7-76.0%) than in the Seseok Plateau (31.9-48.9%). Pearson's correlation revealed a strong positive relationship between the BS and Penicillium dominance (r = 0.957, p = 0.0028). Although available phosphate was higher in the Seseok Plateau, the high Penicillium dominance in Oesamsinbong supports a potential hypothesis regarding microbial contribution to phosphorus availability for the host. Overall, the reduced vigor of A. koreana in the Seseok Plateau was likely associated with impaired microbe-mediated nutrient uptake under extreme acidic stress. Enhancing the rhizosphere fungal ecosystem is crucial for ensuring the sustainability of endangered subalpine conifer forests.