Revegetation intervention of drought-prone coal-mined spoils using Caragana korshinskii under variable water and nitrogen-phosphorus resources

Coal-mine spoils are typically drought-prone and deficient in essential nutrients thus creating conditions, which significantly limit plant growth and development. Here, we searched for suitable combinations of key resources [water (W) and fertilizers (nitrogen, N and phosphorus, P)] to improve physiological and biochemical adaptations of Caragana korshinskii to coal-mined spoils. We observed that under low W and N-P resource availability, C. korshinskii displayed poor growth performance in coal-degraded spoils. Negative growth of C. korshinskii was associated with reduced photosynthetic rate, decreased water status and increased contents of reactive oxygen species (ROS) and malondialdehyde. Low resource availability to C. korshinskii resulted in enhanced levels of compatible solutes, including proline and soluble sugars that contributed to osmotic adjustment, and also increased activities of superoxide dismutase, peroxidase, catalase and ascorbate peroxidase, which ultimately conferred enhanced oxidative stress protection. Moderate-to-high W and N-P doses greatly enhanced C. korshinskii performance in coal-spoils by improving photosynthesis traits, water status and growth-related attributes. Increasing supply of W and N-P also helped C. korshinskii to reduce oxidative stress, as evidenced by low accumulation of ROS and malondialdehyde, and lower induction of antioxidant enzyme activities. The addition of N and P also improved drought resistance of C. korshinskii. Overall, we found that optimum growth of C. korshinskii in coal-mined spoils was achieved under W additions corresponding to 68% of field capacity (1.85 mm d¹), N and P at 52.0 and 37.0 mg kg¹ soil, respectively. These findings suggest that under appropriate W, N and P doses, C. korshinskii has greater potential to grow and persist in coal-mined spoils and could thus be used for revegetation interventions in drought-prone areas in north-western China, and perhaps across other coal-degraded areas worldwide.