Geographic Origin and Functional Group Type Affect the Decomposability of Peatland Plant Litter Through Biochemical Properties

Peatlands are the most important global soil carbon reservoirs due to low decomposition rates. However, the influence of peatland plant litter quality and geographic environment on decomposition remains poorly understood. This article aims to explore the interactive effects of geographical origin and plant functional groups on the initial chemical characteristics and decomposition processes of peatland litter, elucidating how climate-driven biochemical legacies regulate decomposition dynamics. Plant materials were collected from three peatlands in East China spanning distinct bioclimatic regimes along a latitudinal gradient: Dajiuhu (31°29'N), Hani (42°13'N), and Mangui (52°19'N) peatlands. A 3-year decomposition experiment was conducted in Hani peatland starting in October 2014, using standardized litter bags containing nine species from three functional groups: mosses (<i>Sphagnum</i>), graminoids (<i>Carex</i>), and shrubs (<i>Betula</i>). Fresh plant materials from all sites was translocated to Hani peatland for decomposition experiment. Decomposition rates and key biochemical traits were quantified through sequential destructive sampling at 0-, 1-, 2-, and 3-year post-deployment. Results showed decomposition rates of plant litter descending as <i>Carex</i> > <i>Betula</i> > <i>Sphagnum</i>. Latitudinal origin significantly affected decomposition; the northernmost Mangui litter exhibited the lowest mean decomposition (41.1%) compared to Hani (45.4%) and Dajiuhu (44.4%). Total phenolics (β = -0.62) and lignin (including <i>Sphagnum</i>-specific lignin-like substances, β = -0.93) significantly inhibited decomposition. Interactive effects between geographical origin and functional group were significant, with <i>Carex</i> decomposition most sensitive to latitude. These findings demonstrate that geographic environment and plant functional group type jointly regulate peatland litter decomposability through biochemical traits. Climate warming may accelerate decomposability, potentially diminishing the carbon accumulation function of peatlands, underscoring the necessity to integrate latitudinal gradients and functional diversity into peatland carbon models.