Large-scale patterns of Fagus regeneration in China

Natural regeneration is important for the study of vegetation dynamics under the background of global climate change, as well as for forest production management. Fagus species are an important component of temperate forests in the Northern Hemisphere and also have significant socio-economic value. However, large-scale studies on the regeneration of Fagus populations are currently insufficient. This study, based on community survey data from 150 natural Fagus forest plots, explores the large-scale pattern of Fagus population regeneration in China and analyzes the impacts of various factors, including natural disturbances, stand age, community structure, climate, soil physicochemical properties, and topography. The results showed that the density of Fagus seedlings generally exhibited a geographical pattern of being higher in the north and lower in the south, higher in the west and lower in the east, and increasing with elevation. Multiple regression analysis indicated that the density of standing dead trees (indicating disturbances), average tree height, and the density of Fagus trees in the canopy layer have relatively greater positive effects on the density of Fagus seedlings, while stand age and annual average temperature have relatively greater negative effects. Structural equation modeling further showed that the impact of mean annual temperature on the density of Fagus seedlings was mainly a direct negative effect. Stand age, on the one hand, had a directly negative impact on the density of Fagus seedlings, and on the other hand, had a indirectly opposite effect by reducing the density of Fagus trees in the canopy layer and increasing the average tree height. The density of standing dead trees had a direct promoting effect on the density of Fagus seedlings. The study results emphasize the importance of spatial scale in regeneration research, as well as the potential application of using the quantity of dead wood to represent small-scale disturbances in large-scale regeneration studies. They also provide a theoretical reference for the protection and utilization of Fagus resources in China.