Karst　tiankeng　is　a　typical　terrestrial　habitat　island-like　system,　known　as　an　oasis　in　a　degraded　karst　landscape.　However,　we　know　little　about　the　composition,　structure,　and　life　strategies　of　soil　microbial　communities　in　the　karst　tiankeng　ecosystem.　In　this　study,　we　use　amplicon　sequencing　to　investigate　the　soil　bacteria　and　fungi　of　26　karst　tiankeng　in　two　typical　karst　tiankeng　groups.　The　results　showed　that　the　composition　and　structure　of　bacterial　and　fungal　communities　were　significantly　different　at　two　dimensions　(among　and　within　the　karst　tiankeng　group).　Bacteria　showed　more　sensitivity　to　variation　in　the　karst　tiankeng　area　and　isolation　than　fungi.　With　the　increase　of　karst　tiankeng　area　and　isolation,　the　bacterial　life　strategies　shift　from　K-strategist　to　r-strategist,　likely　due　to　the　changes　in　soil　properties　(total　phosphorus,　Ca,　and　soil　water　content).　Abundant　and　rare　taxa　play　different　roles　in　karst　tiankeng　ecosystems;　abundant　taxa　serve　a　key　role　in　nutrient　cycles　and　life　strategy　shifts　by　occupying　the　key　status　in　networks.　Considering　the　key　role　of　soil　microbes　in　ecosystems,　more　attention　must　be　paid　to　the　impact　of　habitat　loss　on　soil　microbial　life　strategies,　particularly　in　the　ecological　impact　of　life　strategies　change　of　abundant　and　rare　taxa