1 Hierarchical Environmental Factors affecting the 2 Distribution of Abies koreana on the Korean 3 Peninsula 4

Regional declines of the Korean fir (Abies koreana) have been observed since the 1980s on 14 the subalpine region. To explain this decline, it is fundamental to investigate the degree to which 15 environmental factors have contributed to plant distributions on diverse spatial scales. We applied 16 a hierarchical regression model to determine quantitatively the relationship between the abundance 17 of Korean fir (seedlings) and diverse environmental factors across two different ecological scales. 18 We measured Korean fir density and the occurrence of its seedlings in 102 (84) plots nested at five 19 sites and collected a range of environmental factors at the same plots. Our model included 20 hierarchical explanatory variables at both site-level (weather conditions) and plot-level (micro21 topographic factors, soil properties, and competing species). The occurrence of Korean fir seedlings 22 was positively associated with moss cover and rock cover but negatively related to dwarf bamboo 23 cover. On site-level, winter precipitation was significantly positively related to the occurrence of 24 seedlings. A hierarchical Poisson regression model revealed that Korean fir density were negatively 25 associated with slope aspect, topographic position index, Quercus mongolica cover, and mean 26 summer temperature. Our results suggest that drought and competition with other species are 27 factors which halt the survival of Korean fir. We can predict that the population of Korean fir will 28 continue to decline on the Korean Peninsula due to rising temperatures and seasonal drought, and 29 only a few Korean fir will survive on northern slopes or valleys where competition with dwarf 30 bamboo and Q. mongolica can be avoided. 31