Influence of reforestation tree species on decomposition of larch stumps and coarse roots: role of wood microbial communities and soil properties

Abstract Stumps and coarse roots are the most important coarse woody debris component in managed forests. However, their decomposition is still poorly understood, especially the influence of the characteristics of the microbial communities on wood decomposition. In this study, we investigated decaying larch (Larix olgensis Henry) stumps and coarse roots in reforestations of birch (Betula pendula Roth.), ash (Fraxinus mandshurica Rupr.), pine (Pinus sylvestris var. Mongolica), and larch in the northeast of China. We measured wood density loss, cellulose, and lignin concentrations, analyzed microbial community composition, and assessed the physical and chemical properties of woodland soils. Our findings reveal that larch stumps and coarse roots experienced the most rapid decomposition within birch reforestation areas, exhibiting significant density loss in stumps (33.84%) and coarse roots (43.68%). Bacterial diversity on larch stumps and coarse roots was highest in birch reforestation, with dominant phyla including Proteobacteria, Actinobacteriota, and Bacteroidota. Fungal diversity was also highest in birch reforestation, with Ascomycota as the dominant phylum in larch stumps and coarse roots. Furthermore, a mantel test analysis indicated that soil pH and temperature were significant factors in wood decomposition which affected microbial communities. This suggests that the choice of the reforestation tree species affects the decomposition of stumps and coarse roots by affecting soil properties and wood microbial communities. Understanding this process is vital for refining carbon balance evaluations, and enhancing ecosystem-level carbon modeling.