Elevated CO2 and nitrogen addition diminish the inhibitory effects of cadmium on leaf litter decomposition and nutrient release

Aims Rising atmospheric CO 2 concentrations and nitrogen (N) deposition alter litter decomposition processes that control soil carbon (C) and nutrient cycles. However, few studies have explored such impacts on litter decomposition and micronutrient and macronutrient (C, N, phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)) release in a heavy-metal-contaminated environment. Methods We performed an open-top chamber experiment to explore the effects of 15-month elevated CO 2 and N addition on leaf litter decomposition rate and nutrient release of Cinnamomum camphora (non-N-fixing species) and Acacia auriculiformis (N-fixing species) during litter decomposition in cadmium (Cd)-contaminated environment. Results We found that Cd addition consistently reduced leaf litter nutrient (C, N, P, K, Ca, and Mg) loss, while these negative effects were offset by elevated CO 2 (average 10.6%) and N addition (average 23.9%). The mitigative effects of elevated CO 2 and N addition together ( β = −0.78) far exceeded the effects of each ( β = −0.15 for elevated CO 2 and β = −0.42 for N addition) separately. Such mitigative effects were related to higher litter quality (the increased N, P and Ca in the initial litter), and higher soil microbial activities (higher ligninase and cellulase activities). Additionally, these mitigative effects on leaf litter nutrient release were greater in C. camphora litter than in A. auriculiformis litter, due to its higher C:N and cellulose: N ratios. Conclusions Our results suggest that N addition and elevated CO 2 concentration may diminish the negative effects of Cd addition on leaf litter decomposition and increase nutrient cycle, especially in non-N fixing trees under the global change.