Growth processes in subtropical Eucalyptus plantations alter the soil bacterial community composition and soil multifunctionality

Short-rotation forestry is a common practice worldwide for efficient timber harvesting. However, determining the appropriate rotation period to minimize disturbance to plantation-soil ecosystems remains a controversial topic. The microbial community structure is a sensitive indicator of soil quality in plantation forests. Therefore, we analyzed the soil bacterial community composition, co-occurrence network, functional characteristics and influencing factors in subtropical Eucalyptus plantation forests of different ages and revealed the mechanisms through which soil ecosystem function is affected. Soil carbon (C), nitrogen ( N) and phosphorus (P) decreased and then increased with forest age, and there was temporal variability in the composition and function of the soil bacterial communities; the bacterial community composition and diversity and function of young and overmature forest stands contributed most. Changes in total nitrogen (TN), dissolved organic nitrogen (DON), total phosphorus (TP), and available phosphorus (AP) supported the bacterial community pattern, which was dominated by Acidobacteria and Proteobacteria. The distributions of Acidobacteria and Proteobacteria were stable during the growth phase of the Eucalyptus plantation. The low-abundance bacterial communities WPS-2, Actinobacteria, Firmicutes, and Bacteroidetes contributed to the main functions of the bacterial communities, among which WPS-2 and Actinobacteria dominated the soil C fixation and N cycle functions. This study evaluated the response of bacterial communities to soil environmental factors during plantation forest development and elucidated the microbial controls on soil multifunctionality, which is important for improving ecosystem simulation models in subtropical Eucalyptus plantation forests and planning sustainable management during rotational logging periods.