Population structure and regeneration dynamics of Quercus variabilis along latitudinal and longitudinal gradients.Ecosphere 8(4):e01737. 10.1002/ecs2.1737Abstract. The upcoming climatic variability is expected to influence the population dynamics of tree species, but few empirical studies have been performed over broad geographical scales, which may be more convincing to address tree range shift under climate change. In the present study, the population structure and regeneration dynamics of Quercus variabilis were investigated along latitudinal and longitudinal gradients over its full range in China. The size structure, density, mortality rate (b), conversion rate (CR), initial recruitment (y 0 ), and survival from birth to the highest class of regeneration (survival rate [SR]) were analyzed. The results showed the following: (1) The population structure of Q. variabilis exhibited an inverse-J shape throughout the latitudinal gradient, and the relative seedling density was significantly higher in the middle populations than in the north and the south. In addition, the y 0 and SR exhibited the highest values in the middle, but no significant differences in the density and total basal area of adults were found across latitudes. (2) Along the longitudinal gradient, an inverse-J-type population structure was present in the west populations, but was not observed in the east due to the scarcity of individuals in regenerated populations. The total basal area and density of adults were similar across longitudes, but both the seedling density and the relative seedling density, along with the y 0 and SR, were higher in the middle than in the east and the west. The b of adults was lower in the middle-longitude populations than in the west and the east. (3) Climate (annual average temperature) was identified as the primary factor affecting regeneration. In addition, local factors, including the soil and stand conditions, were also found to play a significant role in determining the regeneration dynamics. Based on these results, we speculate that populations of Q. variabilis at the range edges would decline in the context of climate change, particularly in the south and the east.

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