Unraveling the Role of Bacteria in Nitrogen Cycling: Insights from Leaf Litter Decomposition in the Knyszyn Forest

Microorganisms are vital in leaf litter decomposition and contribute significantly to global nutrient cycling. However, there is a need for improved understanding of the taxonomic and functional diversity of litter-associated bacteria. The Knyszyn Forest comprises a unique ecosystem providing diverse microhabitats for microorganisms in central Europe, similar to the southwestern taiga in many respects. This study presents the results of high-throughput sequencing performed for Betula pendula, B. pubescens, and Carpinus betulus litter-associated microbial communities from northern Poland. Microbial assemblage composition and structure at different stages of litter decomposition revealed the domination of phyllosphere-associated taxa of Sphingomonas and Pseudomonas in bacterial communities in the early stages. Meanwhile, at the later stages of decomposition, the representation of soil-associated bacterial communities, such as Pedobacter, was higher. This study identifies key bacteria (Pedobacter, Mucilaginibacter, and Luteibacter) as pivotal in nutrient cycling through cellulose and hemicellulose decomposition, dominating later decomposition phases. Taxonomic analysis based on functional markers associated with nitrogen metabolism highlights the pivotal role of specific Pseudomonadota (Proteobacteria) taxa in driving nitrogen cycling dynamics during litter decomposition. Most of these taxa were unclassified at the genus level, particularly in the later stages of litter decomposition, and are crucial in mediating nitrogen transformation processes, underscoring their significance in ecosystem nutrient cycling.