Changes in litter traits induced by vegetation restoration accelerate litter decomposition in Robinia pseudoacacia plantations

Abstract The chemical traits of litter are among the most critical factors that affect its decomposition. During vegetation restoration of planted forests, increasing age of the planted species and succession of the understory species may lead to significant changes in litter traits. However, it is unclear how these changes occur and how they affect litter decomposition. Therefore, we studied the decomposition of litter from four Robinia pseudoacacia plantations in the Loess Plateau in China with stand ages of 10–43 years using an indoor simulation test. We measured changes in litter substrate quality and chemical diversity, structural properties of the litter microbial community, activity of litter enzymes, and mixed decomposition effects during vegetation restoration. Their relationships to changes in litter decomposition rate were analyzed using structural equation modeling. Improvements in substrate quality of forest litter induced by vegetation restoration drove changes in fungal community composition during late decomposition (day 358), which in turn increased the activity of lignin‐decomposing enzymes and ultimately accelerated litter decomposition. At the same time, decreases in the chemical diversity of forest litter induced by vegetation restoration reduced the diversity of litter fungi during middle and late decomposition (days 182 and 358). This caused significant negative mixed decomposition effects, thereby inhibiting litter decomposition. However, improvements in litter substrate quality dominated the changes in litter decomposition rate, and the decomposition rate of R. pseudoacacia plantation litter thus increased over the course of vegetation restoration.