Effects of different restoration methods and lithology on ecological stoichiometry of karst soil

This study investigated the elemental composition and stoichiometric patterns of soil carbon (C), nitrogen (N), phosphorus (P), and potassium (K) under different lithological backgrounds and vegetation restoration strategies in a karst landscape. Using correlation and redundancy analyses, soils from artificial and secondary forests established on dolomite and limestone were compared to identify key drivers shaping nutrient dynamics, with the goal of informing lithology-specific restoration practices. Results showed that: (1) Secondary forests on both dolomite and limestone exhibited significantly higher concentrations of soil C and P than corresponding plantations, while N and K contents did not differ significantly between dolomite forest types. (2) Stoichiometric ratios of C∶P and N∶P were significantly lower in limestone soils than in dolomite, whereas C∶N ratios showed no significant differences. Across all samples, mean C∶N, C∶P, and N∶P values ranged from 9.05–11.50, 8.68–27.75, and 0.86–3.11, respectively, substantially below national benchmarks (12.01, 61, and 5.2), indicating widespread nutrient limitations. Notably, limestone plantations exhibited the lowest C∶N, C∶P, and N∶P, reflecting pronounced N deficiency. In contrast, dolomite soils exhibited significantly lower C∶K, N∶K, and K∶P ratios compared to limestone, with N∶K>2.1 and K∶P<3.4 in dolomite secondary forests, indicating that plant growth was more susceptible to K limitation. (3) Multivariate analyses identified Ca content, soil water-holding capacity (WHC), and mean annual precipitation (MAP) as primary drivers of nutrient dynamics in dolomite systems, whereas WHC, MAP, and soil pH were most influential in limestone soils. Overall, plantation soils exhibited greater depletion of C, N, and P relative to secondary forests, highlighting the need to prioritize vegetation restoration on dolomite substrates. Furthermore, K supplementation should be implemented in secondary forests to alleviate nutrient limitations, while N deficiency must be addressed in artificial restoration efforts on limestone soils.