Format: ORAL

Bikram Pandey1,2, Fengying Zhang3, Basu Dev Poudel4, Rong Li2, Mohammed A. Dakhil5,6, Tashi Norbu7, Yawen Gan7, Ziyan Liao1, Lin Zhang1

1 CAS Key Laboratory of Mountain Ecological Restoration and Bio-resource Utilization and Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, Sichuan, China. 2 CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, Yunnan, China. 3 Sichuan Provincial Institute of Forestry and Grassland Inventory and Planning, Chengdu 610081, Sichuan, China 4 Environmental Services Nepal, Kathmandu, Nepal 5 School of Ecology and Environment, Northwestern Polytechnical University, Xi'an, China 6 Botany and Microbiology Department, Faculty of Science, Helwan University, Cairo, Egypt 7 Institute of Agriculture Research, Tibet Academy of Agriculture and Animal Husbandry Sciences, Lhasa 850032, Tibet, China

Macroecological research aims to understand factors influencing species composition and diversity. Understanding the distribution patterns of species is essential for prioritizing areas for conservation. This study investigates the alpha () and beta () diversity facets of Fagaceae across past (historical), present, and future timelines in Southwestern China. We used over 11,000 geographical observations to predict the spatial patterns of the - and -diversity of 120 species. We modeled the -diversity via stacking prediction using an individual species distribution model at 50 km 50 km grid cells. We used pairwise Srensen dissimilarity to quantify total -diversity and its components - turnover (SIM) and nestedness (NES). We integrated climate variables along with topographic and edaphic predictors to understand the species diversity. Finally, simultaneous autoregression (SAR) model was used to evaluate the effects of predictor variables on the - and - diversity patterns. Our results indicate a temporal decline in the -diversity from 120 during the past to 49 in the future. However, species occurrence area has expanded, fostering an increase in the -diversity, and it may potentially continue to increase in the future. At present, the southern region exhibits the highest -diversity, while high -diversity occurs in the central region. The findings underscore that the species SIM is a driving factor of differing species composition during the past and present periods, while NES will be a dominant factor in the future. During the past, climatic and topographic factors significantly influenced the -diversity, and similar factors continue to impact the -diversity and its components. In the future, climatic variables will play a significant role in determining the diversity patterns.