Forest management interventions affect the trade-offs of multiple vegetation and soil ecosystem services in walnut forests in the Taihang Mountains, China

Artificial forests provide various ecosystem services (ESs) and contribute to mitigating global climate change. However, the differences and trade-offs among ESs under different interventions remain unclear. This study investigated the variations in ESs and their trade-offs in artificial walnut forests in the Taihang Mountains under four human interventions: original shrubgrassland, long-term unmanaged walnut forests, walnut forests with clearing of shrubs and grasses, and walnut forests with clearing of shrubs and grasses and application of fertilizers. These interventions were established after a walnut plantation on shrub-grass-dominated slopes in 2003. Four ESs were evaluated using the entropy weight method: maintenance of plant diversity, carbon sequestration, soil and water conservation, and soil nutrient maintenance. Trade-offs among ESs were analyzed using the root mean square deviation (RMSD). Results showed that: (1) both the ESs composite value and the average trade-off value between ESs initially increased, then decreased, with increasing human intervention. The highest ESs composite value (ESs = 0.5655) and the lowest average trade-off value (RMSD = 0.149) were observed in walnut forests with clearing of shrubs and grasses. (2) Most paired ESs exhibited moderate or high trade-offs with each other, but differences existed between the walnut forests and the original shrubgrassland. The original shrub-grassland showed lower trade-offs between maintenance of plant diversity and carbon sequestration, and between maintenance of plant diversity and soil nutrient maintenance, while these trade-offs increased after the conversion to walnut forests. (3) Redundancy analysis and Pearson correlation analysis revealed that aboveground biomass explained 63.9 % of the variation in ESs indicators in the walnut forests, and soil phosphorus storage was significantly correlated with the trade-offs between most paired ESs, indicating significant influences of vegetation and soil factors on ESs indicators and trade-offs. Our findings suggest that shrub and grass removal is a key intervention affecting ecosystem trade-offs in artificial forests. Therefore, effective management of plantation vegetation is necessary to support the multifunctional balance of ESs and promote plantation ecosystem stability.