Abstract: We explored the effects of land use types and ecological restoration modes on soil phosphorus (P) characteristics in karst ecosystems, with three land-use types (orchard (loquat), pastureland, and disturbed land) and four restoration modes (evergreen forest, deciduous forest, evergreen-deciduous mixed forest, and naturally restored forest) being selected. We measured soil phosphorus \[(total phosphorus (TP), available phosphorus (AP) content, microbial biomass phosphorus (MBP)\] and analyzed the relationships between the three P variables and soil pH, organic carbon (SOC), total nitrogen (TN), ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^--N), exchangeable calcium (Ca), magnesium (Mg), microbial biomass carbon (MBC), and nitrogen (MBN). Results showed that soil TP across different land-use types was higher than that across different restoration modes, while MBP showed an opposite pattern. Among the land-use types, pasture had the highest TP and AP and lowest MBP, orchard had the highest MBP, and disturbed land had the lowest TP and AP. Across the restoration modes, soil AP and MBP in the naturally restored forest and deciduous forest were significantly higher than those in evergreen-deciduous mixed forest and evergreen forest. Soil TP was not different among the four restoration modes and was positively correlated with SOC, TN, and exchangeable Ca. Soil AP was positively correlated with pH, MBC, MBN, MBP, and exchangeable Mg, while soil MBP was positively correlated with exchangeable Ca and Mg, MBC, and AP. Results of redundancy analysis showed that soil MBC and MBN significantly influenced the variations in soil P content across different land-use types and restoration modes, indicating that soil P availability in these karst ecosystems was extremely affected by soil microbial activities. The orchard had higher soil TP, AP, and MBP across three land-use types, with values approximating that in the naturally restored forest, suggesting that it would be an appropriate land-use type. The deciduous forest had higher soil TP, AP, and MBP than those in evergreen-deciduous mixed forest and evergreen forest, similarly to the naturally restored forest, which suggested that deciduous tree species can be planted in the recovered areas to enhance vegetation restoration in karst ecosystems.

Key words: karst ecosystem, human disturbance, land use, ecological restoration, soil phosphorus.