Plant litter decomposition is regulated by its phosphorus content in the short term and soil enzymes in the long term

Plant litter decomposition plays a vital role in soil carbon (C) cycling and nutrient release, significantly influencing agricultural resource utilization and soil fertility management. Litter quality—defined by its C, nitrogen (N), and phosphorus (P) contents, as well as C:N:P stoichiometry—is a key factor regulating its decomposition. However, the influence of litter C:P ratios on plant litter decomposition, particularly in relation to changes in soil C:N:P stoichiometry, microbial biomass, and extracellular enzyme activities, remains unclear, especially in agroecosystems. In this study, the effects of litter C:P ratios on its decomposition were investigated using 13C-labeled plant litter with naturally occurring gradients of C:P ratios (ranging from 377 to 1,288) in an 84-day incubation experiment. After 84 days, cumulative 13CO2 emissions derived from litter accounted for approximately 50 % of total CO2 emissions. Litter with higher P content increased 13CO2 emissions, whereas higher litter C:P ratios suppressed emissions, indicating that litter with lower C:P ratios decomposed more rapidly in the short-term (14 days). In contrast, elevated soil exoenzymatic C:P and N:P ratios stimulated 13CO2 emissions during long-term decomposition (84 days). These findings suggest that litter P content primarily regulates short-term decomposition, while soil enzyme activity plays a key role in long-term decomposition. Overall, this study highlights the pivotal role of P limitation in litter decomposition, particularly in the early stages, and underscores the potential benefits of P fertilization in enhancing decomposition rates, thereby improving resource efficiency and soil fertility in agroecosystems.