Print PageLong-term patterns of litter decay often correlate with initial lignin and/or lignin:nitrogen content. In contrast, early stages of litter decay show sensitivity to characteristics of both the decomposer community and more labile litter pools. However, this early phase is often ignored in long-term studies despite evidence of significant consequences to carbon sequestration and element cycling. We used a mechanistic, microbial-based model of litter decomposition to evaluate the impacts of fine-scale differences in chemistry on litter decay in a laboratory study of fine roots for 4 maize genotypes that differed primarily in lignin content. Comparisons between simulations and observations directed data analyses elucidating patterns of controls over time, and relationships between microbial activity and litter chemistry.
Results/Conclusions
Initial patterns (0-36 days) of respiration and changes in litter chemistry demonstrated interactions between litter polysaccharide content and microbial colonization controlling decomposition rate. Subsequent patterns (36-112 days) showed a convergence in rates most closely related to ligno-cellulose index (LCI). Nonetheless, differences appearing in the first 36 days persisted throughout the study (800 days). A stepwise analysis of differences between model behavior and observations revealed that microbial responses are much more rapid than typically included in decomposition models (0.25-0.48 d-1), and that both the sensitivity of early microbial response to litter quality and transition to later LCI control are related to hemi-cellulose x lignin linkages at values of LCI normally considered too low to influence decay rates (LCI = 0.2).
