Soil and litter microbiomes as joint drivers of ecosystem multifunctionality in a 60-year-old forest plantation

Afforestation is considered an effective strategy to mitigate a changing climate. However, it remains unclear how ecosystem multifunctionality (EMF) changes under long-term afforestation and the role of soil and litter microbiomes in this process. To address this, we studied a well-characterised 60-year-old plantation and analysed soil and litter microbial communities influencing EMF variations. We found that long-term plantations significantly enhance forest EMF, largely due to the joint contributions of soil and litter microbial communities. In older stands (60 years), the stability of microbial interaction networks increased, while the α (Shannon) diversity of soil bacteria and litter fungi significantly decreased during succession. This transition suggests that microbial communities shifted towards more stable interactions rather than increased diversity, a strategic adaptation that potentially allows microbes to effectively utilize the continuously increasing resource supply, ultimately enhancing forest EMF. Structural equation modelling revealed that biotic factors, including composition of soil and litter microbial communities and their network stability, coupled with abiotic factors such as soil and litter physicochemical properties, jointly explained 98 % of EMF variation. This study highlighted the role of both soil and litter microbes in enhancing EMF in long-term plantation forests, offering new insights into the ecosystem service functions of plantations.