Massive oak forest survey reveals 594 plant species across South Korea’s Gangwon mountains

Deep in the mountainous province of Gangwon-do, South Korea, an oak forest quietly shelters one of the region’s richest storehouses of plant life. A new five-year survey has documented 594 vascular plant taxa across 1,098 plots of pure Mongolian oak stands, creating one of the most detailed plot-based floristic inventories ever compiled for this iconic temperate forest type. The findings, published in the Biodiversity Data Journal, reveal that these oak-dominated woodlands are far more than a single-species canopy: they harbour dozens of endemic, endangered and rare plants, alongside a handful of alien invaders that could reshape the ecosystem if left unchecked.

The research team drew on field surveys conducted between 2019 and 2023 as part of South Korea’s 5th National Ecosystem Survey, a nationwide effort to catalogue the country’s biological heritage. Rather than sampling a handful of sites, the researchers compiled occurrence records from 1,098 plots in which Quercus mongolica — the Mongolian oak — dominated the canopy layer. The resulting dataset contains 20,906 individual plot-level occurrence records, each linking a plant species to a specific location, elevation, slope and soil condition. This structure transforms what could have been a simple species list into a reusable scientific resource capable of supporting decades of future monitoring.

Quercus mongolica is one of the most widespread and ecologically important oak species in Northeast Asia, forming broad-leaved forests across the Korean Peninsula, north-eastern China and the Japanese archipelago. In South Korea, these forests occupy mountain ridges and slopes throughout the Baekdudaegan mountain range, the country’s ecological backbone. Previous Korean studies have examined the community structure, succession patterns and restoration potential of these forests, but large-scale floristic inventories focused specifically on stands where the oak dominates the canopy have remained surprisingly scarce. The new dataset fills that gap with unprecedented resolution.

The taxonomic breakdown reveals a flora of remarkable breadth. The 594 recorded taxa span 103 families and 288 genera, comprising 539 species, 45 varieties, seven subspecies and three forms. The aster family (Asteraceae) led with 52 taxa, followed by the rose family (Rosaceae) with 44, the lily family (Liliaceae) with 37, the buttercup family (Ranunculaceae) with 29, the grass family (Poaceae) with 21 and the legume family (Fabaceae) with 20. Plot-level richness varied dramatically, from as few as 5 taxa in some plots to as many as 55 in others, with a mean of 19.04 taxa per plot. This variation likely reflects differences in microtopography, stand structure, disturbance history and understorey development across the surveyed landscape.

Beyond the canopy-dominant oak itself, certain companion species appeared again and again. Lindera obtusiloba, Acer pseudosieboldianum, Fraxinus rhynchophylla, Carex siderosticta, Rhododendron schlippenbachii, Lespedeza maximowiczii, Symplocos sawafutagi, Ainsliaea acerifolia and Rhododendron mucronulatum were among the most frequently recorded taxa. These understorey trees, shrubs and forest-floor herbs form the ecological fabric of the oak woodland, and their consistent presence across hundreds of plots suggests they are reliable indicators of the pure Q. mongolica forest type in Gangwon-do.

The conservation findings are perhaps the most striking element of the study. Among the 594 recorded taxa, 32 are endemic to the Korean Peninsula — species found nowhere else on Earth. One taxon is listed as a Class II endangered wild plant under South Korea’s Wildlife Protection and Management Act. Twenty-one taxa appear on the Korean Red List, including four classified as Endangered and three as Near Threatened. On the global stage, 85 taxa match entries on the IUCN Red List, though most of these are currently assessed as Least Concern. Perhaps most significantly for regional conservation planning, 172 taxa qualified as floristic target plants — a national classification system that flags species of phytogeographical importance — with 42 in the highest-priority Grade I and five in Grade V, the category reserved for taxa with the most restricted distributions.

The study also documented seven alien plant taxa and two ecosystem-disturbing plant taxa within the surveyed stands. While the researchers caution that their data cannot quantify invasion intensity, the mere presence of these management-relevant species in relatively undisturbed oak forest underscores the need for ongoing vigilance. Invasive plants can spread rapidly when environmental conditions or human disturbance change, and the plot-level occurrence records now publicly available through the Global Biodiversity Information Facility (GBIF) provide a baseline against which future spread can be measured.

Environmental metadata accompanying the occurrence records paint a vivid picture of where these oak forests thrive. The plots spanned elevations from 24 metres to 1,450 metres above sea level, with a mean of 732.6 metres. Slopes ranged from nearly flat to a steep 45.5 degrees, averaging 19.3 degrees. Most plots sat on upper or middle slopes — 513 and 303 plots respectively — under mesic moisture conditions, with brown forest soil dominating (1,024 plots) and igneous or metamorphic bedrock underlying the majority of sites. Drainage was generally good, with 859 plots classified as very well drained and 228 as well drained. Nearly all plots fell within the northern temperate deciduous broad-leaved forest zone, the climatic band where Q. mongolica reaches its greatest prominence in South Korea.

The researchers were careful to define their target habitat precisely. The term pure Q. mongolica stand was used as an operational definition, referring to plots in which the oak was recorded as the dominant canopy species in the original survey records — not to monospecific stands devoid of other woody species. This distinction matters scientifically: by filtering out mixed forests where Q. mongolica appears alongside other canopy trees, the dataset offers a cleaner floristic reference for a specific forest type, reducing the interpretive ambiguity that has complicated comparisons in earlier studies.

The dataset’s value extends well beyond Gangwon-do. Plot-based vegetation data of this kind have become foundational resources for international biodiversity science, underpinning large vegetation databases and broad-scale analyses of community patterns. By linking occurrence records with environmental metadata, the new inventory can support future studies of species distributions, habitat preferences, taxon richness and floristic change — and, as climate change alters green-up dates and potentially suitable habitats across Northeast Asia, repeated surveys using this baseline could reveal how one of Korea’s most characteristic forest types responds. For now, the 594 taxa documented across these oak stands stand as both a celebration of temperate forest diversity and a warning that even seemingly stable ecosystems require careful, sustained attention.

Subject of Research: Floristic inventory and conservation assessment of vascular plants in pure Quercus mongolica stands in Gangwon-do, South Korea

Article Title: Inventory of vascular plants and conservation-related taxa in pure Quercus mongolica stands in Gangwon-do, South Korea

Article References: Lee, S. J., Kim, Y.-K., Hong, Y.-S., & Cho, K. J. (2026). Inventory of vascular plants and conservation-related taxa in pure Quercus mongolica stands in Gangwon-do, South Korea. Biodiversity Data Journal, 14, Article e206902. https://doi.org/10.3897/bdj.14.e206902

Image Credits: AI Generated

DOI: 10.3897/BDJ.14.e206902

Keywords: Quercus mongolica, Mongolian oak, Gangwon-do, vascular plants, floristic inventory, Korean endemics, Red List species, floristic target taxa, biodiversity monitoring, temperate deciduous forest, GBIF, conservation