Karst　landforms　in　Yunnan　is　one　of　the　priorities　of　karst　desertification　management　in　Yunnan⁃Guangxi⁃　Guizhou　provinces.　Exploring　the　community　assembly　characteristics　of　succession　stages　under　climate　warming　and　humidification　is　essential　for　ecological　restoration　and　sustainable　forest　management.　In　the　context　of　climate　warming　and　humidification,　karst　tiankeng　was　taken　as　the　natural　“open　top　chamber”　and　the　underground　forest　on　tiankeng′s　south　slope　as　the　community　succession　apex.　The　community　assembly　mechanism　in　successional　sequences　(mixed　coniferous　forest　outside　the　tiankeng,　evergreen　broadleaf　forest　outside　the　tiankeng,　and　evergreen　broadleaf　forest　inside　the　tiankeng)　is　explored,　which　is　based　on　phylogenetic　and　functional　traits.　The　results　showed　that:　(1)　the　phylogenetic　signals　of　plant　traits　were　lower　in　the　early　succession　stage,　with　significant　phylogenetic　signals　for　leaf　aspect　ratio,　leaf　area,　leaf　thickness,　and　specific　leaf　area,　while　functional　traits　were　less　conserved.　In　the　late　succession　stages,　the　plant　traits　evolved　convergently　and　none　of　the　phylogenetic　signals　were　significant.　(2)　The　phylogenetic　diversity　of　plant　communities　gradually　decreased　during　the　succession　stage,　and　was　significantly　and　positively　correlated　with　species　richness.　(3)　The　phylogenetic　indices　for　NRI　(Net　Relatedness　Index)　and　NTI　(Nearest　Taxon　Index)　shifted　from　less　than　0　to　greater　than　0,　and　the　functional　trait　structure　indices　for　TraitSESMPD　(Standard　Effect　Size　of　Mean　Pairwise　Trait　Distance)　and　TraitSESMNTD　(Standard　Effect　Size　of　Mean　Nearest　Trait　Distance)　were　both　greater　than　0.　Community　assembly　processes　in　successional　stages　were　driven　by　environmental　filtering　and　interspecific　interaction.　(4)　Phylogenetic　and　functional　trait　structure　indices　were　negatively　correlated　with　soil　water　content,　total　phosphorus,　and　available　potassium.　Under　the　successional　stage,　the　community　tended　to　assemble　when　soil　water　and　nutrients　were　limited,　and　the　community　assembly　process　supported　the　ecological　niche　hypothesis.　Our　findings　will　contribute　new　perspectives　to　the　community　assembly　mechanism　of　karst　plant　and　provide　scientific　reference　for　community　structure　optimization.　©　2024　Science　Press.　All　rights　reserved.