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Identifying and protecting refugia is a priority for conservation management under projected anthropogenic climate change. We have two main objectives: the first is to explore the spatial (East Asia) and temporal (Last Glacial Maximum to year 2070) distribution patterns of dominant Castanopsis species of evergreen broad-leaved forests, also the relation with their niche breadths; the second is to identify long-term stable refugia for preserving these species and provide a framework of conservation strategies. We find that there is an extraordinary richness with 32 dominant Castanopsis species, and they form both a geographically and climatically almost unbroken connection from ca. 5°N to 38°N, having thus ecological significance. During the Mid-Holocene and, particularly, the Last Glacial Maximum, the predicted suitable areas of the species as a whole were larger than those in the present. By 2070, potentially suitable areas with high richness of dominant Castanopsis species will be reduced by 94.5 % on average. No correlation between species niche breadths and distribution ranges is found, which could be due to regional climate stability. Mountains of southwestern and southern Yunnan in China are identified as climatically long-term stable refugia for 7¿9 Castanopsis species. We recommend that these refugia have the highest priority of conservation to prevent their extinction. Our suggested urgent measures include improving the effectiveness of currently protected Castanopsis species and expanding the network of protected areas to cover a larger fraction of the refugia, as well as ensuring Castanopsis species natural regeneration potential in fragmented and natural secondary forest areas., This study received financial support from the Major Program for Basic Research Project of Yunnan Province, China (202101BC070002), the Science and Technology Department of Yunnan University, China (2019YNU002), the Ministry of Science and Technology of China (2015FY210200-15), the Spanish Ministry of Science and Innovation (grant PID2020-119163GB-I00 funded by MCIN/AEI/10.13039/501100011033), the Environment Research and Technology Development Fund of the Environmental Restoration and Conservation Agency of Japan (JPMEERF20202002), and the Northeastern Research Institute of Petrified Wood and Mineral Resources, Nakhon Ratchasima Rajabhat University, Thailand., Keywords 1. Introduction 2. Materials and methods 2.1. Data collection and notations 2.2. Ecological niche modeling 2.3. Data analyses 3. Results 3.1. Dominant Castanopsis species in East Asia today: richness and distribution patterns 3.2. Richness of dominant Castanopsis species shaped by climate change 3.3. Niche groups and niche breadths of dominant Castanopsis species 3.4. Climatically long-term stable refugia 4. Discussion 4.1. Richness of dominant Castanopsis species shaped by climate change 4.2. Niche groups and niche breadths of dominant Castanopsis species 4.3. Long-term stable refugia and conservation strategies 5. Conclusions CRediT authorship contribution statement Declaration of competing interest Acknowledgements Appendix A. Supplementary material References

Seedling,made up of small individuals of woody plant species in the understorey,is an important component of many forests and considered as an important source for natural restoration in forest ecosystems.Simultaneously seedling plays an important role in the regeneration of numerous tree species.Based on space-for-time substitution method,we treated coniferous and broad-leaved mixed forest,secondary monsoon evergreen broad-leaved forest(MEBF),primary MEBF in the same area as three different stages of secondary succession of MEBF.Eight sampling plots representing the three different stages distribute in Caiyanghe nature reserve,surrounding the areas of Meizihu and Xinfang reservoir of Puer,in Yunnan Province,the southwest of China.We investigated seedling regeneration characteristics of woody plants of MEBF during secondary succession by looking at species composition,density,height level and the relationship with environmental factors.Overall,we found 2014 individuals of woody seedlings belonging to 101 species(dominated by understory tree species) in the eight plots covering 144-m2 area.The species richness of tree seedling,shrub seedling and liana seedling were 50,29 and 22 respectively,and their corresponding individuals were 1499,299 and 216.Tree seedling was the main component of woody plant seedling,such as Castanopsis echidnocarpa.Pinus kesiya var.langbianensis are dominant species in coniferous and broad-leaved mixed forest,however,their seedlings rarely appeared in the understory.The pine seedling stages need more light than shade-tolerant species which can conserve seedling bank in understory and waited for appropriate chance to regeneration.The woody plant seedling density of coniferous and broad-leaved mixed forest,secondary and mature MEBF was 183±5.69,240±20.31 and 372.5±4.5 individuals per 18m2.As succession progresses,the density of total woody seedlings,tree seedlings and liana seedlings all increased,while the density of shrub seedlings did not change significantly.Celastrus virens as a liana was particularly conspicuous in mature MEBF.Species richness of liana seedlings tended to increase,while species richness of tree seedlings and shrub seedlings remained relatively stable along the succession gradient.The Shannon-Wiener index of woody seedlings was significantly lower in primary MEBF than those in mixed forest and secondary MEBF.The abundance of woody seedlings in secondary and primary MEBF decreased with the increase of height level,while in mixed forest,the abundance of woody seedlings form a unimodal pattern with peak at 20 cm.Species richness,however,showed consistent(increasing or decreasing) pattern with the increase of height level in all these forest types.Distribution of woody seedlings abundance concentrated in 0—20 cm in the three community types.Woody seedlings species richness of mature MEBF was significantly lower than coniferous and broad-leaved mixed forest when height level was at Ⅰand Ⅱ.Srensen index indicated a close link between tree and liana seedlings and the species composition of the community.Moreover,tree seedling density distribution was significantly negatively correlated with the slope of the plot,while shrub seedling density was significantly positively related to soil pH.