Plant species determine elementome differentiation and element coupling during deadwood decay

The elemental dynamics and interactions within deadwood profoundly influence carbon sequestration and nutrient cycling in forest ecosystems. Recent studies have investigated macronutrient cycling during deadwood decay of specific plants, yet the dynamics and interactions of micronutrients, trace elements, and the elementome across species and decay stages remain unexplored. Here, we investigated the elementome and their coupling relationships across five decay stages of downed deadwood (DDW) from four dominant species (Hippophae rhamnoides, Populus purdomii, Abies fabri, and Picea brachytyla) along the Hailuogou Glacier primary successional chronosequence. Element coupling was evaluated following the framework of mean correlation of all elements in absolute value and null modeling. We observed species-specific elementome differentiation during DDW decay, with interspecific distances greater in the initial and later decay stages and lower in the intermediate stage. Notably, shrub H. rhamnoides exhibited distinct initial elementomes and remained robust multi-element coupling throughout decay. Conversely, element couplings for tree species declined with decay, particularly for P. purdomii and A. fabri, reaching decoupling from Stage III. Non-essential elements of Al, V, and Ti remained robust coupling, while key nutrients of N, P, and Ca decoupled as decay progressed. The individual element coupling was negatively correlated with their enrichment levels, with lower coupling observed for anthropogenically enriched metals. Our results reveal the importance of plant species in elementome differentiation and element coupling during deadwood decay, while atmospheric heavy metal deposition mediates individual element coupling, underscoring species-specific deadwood management strategies and monitoring of heavy metal deposition to optimize forest ecosystem functions and stability.