Regional variation and component-specific carbon and nutrient characteristics of aboveground dead organic matter in Picea schrenkiana forests

Objective Litter and coarse woody debris (CWD) are the two major components of forest aboveground dead organic matter pools. However, their responses in nutrient dynamics and carbon storage, as well as their relative contributions to dead organic matter pools, remain poorly understood across regional scales. Understanding the spatial variation in carbon and nutrient characteristics of different dead organic matter components is essential for elucidating the composition of forest carbon pools and nutrient cycling processes.

Method Natural Schrenk spruce (Picea schrenkiana) forests located in five representative regions of the Tianshan Mountains, including Zhaosu, Xinyuan, Hutubi, Tianchi, and Qitai, were selected for this study. Concentrations of carbon (C), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) in litter and CWD were determined to evaluate their stoichiometric characteristics and carbon storage patterns.

Result (1) Significant regional differences were observed in nutrient concentrations and stoichiometric characteristics of litter, whereas nutrient composition in CWD was comparatively stable, with only P, K, and Mg varying significantly among regions. (2) Compared with litter, CWD exhibited higher C∶N and C∶P ratios and greater stoichiometric variability, indicating enhanced elemental losses and retention during long-term decomposition. (3) Regional variation in aboveground dead organic matter carbon storage was primarily driven by litter and generally increased from west to east across the Tianshan Mountains. Although the relative contributions of litter and CWD differed substantially among regions, total aboveground dead organic matter carbon storage showed no significant regional differences. Litter and CWD accounted for 57.2% ~ 86.6% and 13.4% ~ 42.8% of total aboveground dead organic matter carbon storage, respectively.

Conclusion The spatial pattern of the aboveground dead organic matter C pool in Tianshan spruce forests is jointly shaped by regional variation in the C and nutrient characteristics of litter and CWD and in their relative contributions to C storage. These findings improve our understanding of the formation and nutrient cycling processes of aboveground dead organic matter pools in mountain forests of arid regions.