Abstract: Objective: To understand the dynamic changes of forest resources in the Cangshan Erhai National Nature Reserve in Yunnan Province （hereinafter referred to as the "Reserve"） over the past 20 years, and provide guidance for the preparation of
management plans for the Reserve. Methods: Based on the forest resource survey data of the research area in 2005 and 2015,
monitoring data of forest, grassland and wetland in 2021, and data of the third national land survey in the study area, use GIS
technology was used to carry out dynamic analysis of forest resources in Reserve. Results: Among various categories in Reserve, the area of forest is the largest and increasing year by year. In the three survey years, the forest and shrub were the main areas of forestry land, accounting for over 60.82% of the total area of the Reserve. The forest coverage rate of the Reserve has increased year by year between 2005 and 2015, and the forest cover increase between 2015 and 2021. The storage volume is mainly composed of forest land and increases year by year. The area and growing stock of arbor forests is mainly composed of Quercus spp. Pinus yunnanensis, Pinus armandi, and Abies delavayi. The area and growing stock of each tree species is increasing year by year; The proportion of young, middle-aged, near mature, and mature forests in the arbor forest is relatively balanced, while the area of over mature forests is relatively small; The degree of crown density in each year is mainly medium, and the area and growing stock of arbor forests with a crown density level of medium and dense have been increasing year by year. Conclusion: The forest quality and ecological protection function of the Reserve have been improving year by year, and the management of forest resources in the later stage is mainly to increase broad-leaved forests such as Fagaceae.

Key words: forest resources, dynamic analysis, forest quality, Cangshan Erhai National Nature Reserve