Vegetation restoration improves phosphorus content and availability in tailings slag

Phosphorus (P) is the primary limiting nutrient for plant growth, and enhancing soil P content and availability is a core goal of vegetation restoration in degraded ecosystems. However, the effect of vegetation restoration on soil P fractions and availability, and the driving factors, remain poorly understood in mining areas. Hence, this study collected soilsfrom unrestored mine tailings (S) and three restoration treatments planted with Lespedeza cuneata (LC), Juniperus chinensis (JC) or Koelreuteria paniculata (KP) in the Xiangtan manganese mining area, Hunan Province, China. Soil P fractions, soil physiochemical properties, alkaline phosphatase (ALP) and acid phosphatase (ACP) activities were analyzed. Results showed that the content of all soil P fractions differed significantly in S, LC, JC and KP (P < 0.05). The KP treatment remarkably enhanced total inorganic P (Pi) and inorganic phosphorus fractions except for HCl-Pi, compared to the S treatment. Yet, all vegetation restoration treatments significantly increased total organic P (Po) and NaOH-Po. The labile P and moderately labile P increased by 50 % and 62 % in the LC treatment, 103 % and 25 % in the JC treatment, and 205 % and 68 % in the KP treatment relative to those in the S treatment. This indicated that the KP treatment particularly enhanced the P availability in the mining area. Correlation analysis showed that soil phosphorus fractions were mainly driven by soil pH, soil water content (SWC), ACP, ALP, and silt and clay content. Partial least squares path model (PLS-PM) further revealed that vegetation restoration improved SWC and silt content, increased ALP activity, and ultimately enhanced P availability. The restoration vegetation species strongly influenced soil P content and availability, highlighting its importance for the ecological rehabilitation of manganese mining area.