Distribution characteristics and geographical interpretation of the upper limit of montane deciduous broad-leaved forests in the eastern monsoon region of China

The deciduous broad-leaved forests are a typical vegetation in the eastern monsoon region of China. This work utilizes the fine classification data of surface cover of composite elevation information to extract the upper limit of montane deciduous broad-leaved forests. We examine the distribution characteristics of the upper limit and its factors influencing the montane deciduous broad- leaved forests by constructing cloud models of the upper limit height. Moreover, this work constructs multiple linear regression models (with the upper limit of deciduous broad- leaved forests at multiple scales (regional, mountain, and local) as the dependent variable and the influencing factors as the independent variables), and a weight coefficient cloud model of influencing factors. Furthermore, this work compares and analyzes the scale changes and spatial differences of the effect of influencing factors on the upper limit of deciduous broad-leaved forests. The sensitivity differences of different montane deciduous broad-leaved forest upper limits to climate factors are also explored. Results show that: (1) The upper limit height of the deciduous broad-leaved forest in the eastern monsoon region of China first increases and then decreases from north to south. The expectation (Ex), entropy (En), and hyper entropy (He) of the distribution height cloud model are 965.77- 1993.52 m, 132.80-514.09 m, and 27.58-205.34 m, respectively. (2) Significant scale changes can be observed in the impact mechanism of the upper limit of deciduous broad-leaved forests in the mountainous areas: at the regional scale, the dominant factor for non- climatic and climatic forest lines is mountain base elevation, with contribution rates of 71.36% and 44.06%, respectively. The climatic forest line is more affected by temperature than by precipitation. Meanwhile, non-climatic forest line is more affected by precipitation than by temperature. At the mountain scale, the upper limit of deciduous broad- leaved forests in the mountainous areas is mainly influenced by January average temperature and annual precipitation, and the role of January average temperature in most mountainous areas is larger than that of annual precipitation. On a local scale, except for the Dabie Mountains, the mountaintop effect has the highest weight on the upper limit of deciduous broad- leaved forests in each mountainous area (Ex: 44.84%-68.15%). In addition, the expectation weight of annual precipitation (Ex: 15.45%-41.86%) is higher than that of the January average temperature (Ex: 4.3%- 9.97%). (3) The deciduous broad- leaved forests in the Dabie Mountains and Taihang Mountains are most sensitive to annual precipitation (Ex: 40.24% and 18.95%; He: 0.96% and 1.89%). Lvliang Mountains are the most sensitive to January average temperature (Ex: 8.31%; He: 1.09%). Exploring the spatial distribution characteristics and influencing factors of the upper limit of deciduous broadleaved forests in the mountainous areas can promote the study of differences in altitudinal belt response to climate change and provide theoretical support for the construction and management of regional ecological security monitoring systems. © 2024 Science Press. All rights reserved.