Multi-functional characteristics of artificial forests of Caragana korshinskii Kom with different plantation ages in the hilly and sandy area of Northwest Shanxi, China

To explore the multi-functional characteristics of an artificial Caragana korshinskii ecosystem with different plantation ages, we assessed the differences in ecosystem multi-functionality, the main influencing factors, and recovery dynamics over 6, 12, 18, 40, and 50 years. The results showed a binomial correlation between planting age and regulatory function (p < 0.05, R-2 = 0.459), and a significant linear positive correlation between the multi-functionality index and supporting and provisioning services. Meanwhile, a significant trinomial correlation was observed among planting age, nutrient transformation, and nutrient cycle (p < 0.01, R-2 = 0.754), whereas a linear positive correlation (p < 0.05) was detected between plantation age and plant nutrient uptake, soil fertility, maintenance of plant diversity, aboveground primary productivity, and ecosystem multi-functionality. The multi-functionality index was significantly positively correlated with plant nutrient uptake, soil fertility, maintenance of plant diversity, and aboveground primary productivity. Plant diversity maintenance, aboveground primary productivity, and water conservation all had significant effects on the multi-functionality index. The ecosystem multi-functionality of C. korshinskii forests significantly increased with the increase of plantation age, and C. korshinskii establishment considerably improved plant nutrient uptake, soil fertility, maintenance of plant diversity, aboveground primary productivity, and ecosystem multi-functionality. The water conservation function of the ecosystem peaked 12 years after planting C. korshinskii, and considerably decreased 40 years after planting, indicating that the limiting factors must be accounted for when evaluating ecosystem multi-functionality in arid and semi-arid areas.