Background Vegetation restoration is an important measure for ecological governance in southwestern China. Ecological degradation may occur in both karst or non-karst areas, where significant differences exist in habitat conditions, soil and plant nutrient characteristics, and plant responses to soil properties. However, there is currently a lack of research comparing soil and plant characteristics across between different vegetation restoration models in karst and non-karst areas. Ecological stoichiometry is a discipline that examines the balance of energy and element within ecosystems. Carbon, nitrogen, and phosphorus are key components of nutrient cycling between plants and soil and are central topics in ecological stoichiometry.

Methods Different artificial forests (Eucalyptus maideni and Pinus yunnanensis) in spatially adjacent karst and non-karst areas of southern Yunnan province were selected as the research objects. The research analyzed the nutrient contents and ecological stoichiometric characteristics of plant leaves and soil in four sample plots (KE, KP, NE and NP), to determine the habitat differences between karst and non-karst areas, and the interrelationship of aboveground and underground nutrients in the artificial forests under two geological backgrounds.

Results 1) The contents of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) in karst forests were significantly higher than in non-karst forests. The SOC, TN, and TP contents were higher in KE than in KP. The soil C∶N and C∶P ratios of KE were significantly lower than in NE, while these indicators showed the opposite trend between KP and NP. The above results indicated that forest soils in karst areas had a stronger capacity to retain nutrients, there were species-specific differences in nutrient use efficiency. 2) The leaf nitrogen (N) and phosphorus (P) contents in non-karst forests were significantly higher than those karst forests. Additionally, the leaf N∶P ratio in karst forests exceeded 16, indicating forests were limited by phosphorus in karst areas. 3) Forests adopt different nutrient acquisition and utilization strategies depending in karst and non-karst areas, and soil nutrient status was the key factor determining of leaf nutrient use efficiency.

Conclusions The study reveals differences in soil–plant nutrient coupling in E. maideni and P. yunnanensis forests under different geological backgrounds. Therefore, afforestation efforts should consider species-specifice nutrient utilization and allocation structure in different geological background areas to optimize vegetation restoration and management strategies.