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Litter decomposition impacts carbon (C) and nutrient cycling. Nitrogen (N) and phosphorus (P) addition as well as litter age impact litter decomposition. Effects of nutrient addition and litter age on litter decomposition may impact emissions of soil nitrous oxide (N2O), which is an important greenhouse gas. However, no study has examined the effects of interactions between litter age and nutrient addition on soil N2O emissions, and explored the underlining mechanisms simultaneously, thus limiting our evaluation of litter decomposition effects on N2O emissions. Litter with different age was collected from Cunninghamia lanceolata plantations experienced N and P addition treatments to examine the effects of nutrient addition and litter age on N2O emissions by incubation study. Litter age generally increased N2O emissions via a decrease in litter C:N ratio. While P addition decreased N2O emissions, N addition increased them mainly by positive effects on soil enzymes as indicated by microbial functional genes associated with N2O production and negative effects on litter C:N ratio. Litter age and nutrient addition interacted to impact soil N2O emissions. In future forest management, both nutrient addition and litter age should be considered in evaluation of management effects on N2O emissions, especially thinning or selectively cutting involving litter input with different age. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) and carbon dioxide (CO2) emitted from forest soil are main greenhouse gases (GHGs). The nutrients released during litter decomposition and phosphorus (P) addition in forest soil may directly affect soil GHGs emissions. Cinnamomum camphora plantations are generally cultivated for leaf-harvesting for industrial purpose. Since C. camphora plantations are generally distributed in P-limited area, interactions between leaf-harvesting and P application may impact soil GHG emissions, which however, has rarely been studied. We conducted an in situ study to examine the effects of leaf-harvesting and P addition on soil N2O and CO2 emissions over 14 months using full-factorial complete-randomized design. Litter removal was performed by removing all litter above the soil surface and P was added as nutrient solution. The results showed that N2O emission rates mainly depended on litter removal and its interaction with P treatment. Specifically, litter removal enhanced N2O emissions by 108%, while P addition reduced this enhancement by 39.7%. However, while P addition increased soil CO2 emission rates by 6.7%, neither litter removal nor its interaction with P addition influenced soil CO2 emissions. The results suggested that leaf-harvesting practice potentially enhanced N2O emissions from C. camphora plantation soil, while P management mitigated the enhancement. This study has implications for the management of leaf-harvesting C. camphora plantations concerning soil nutrient conservation and mitigation of forest soil GHG emissions, especially in forestry or agricultural soils in subtropical regions experiencing intensive leaf-harvesting management and fertilization practice. [ABSTRACT FROM AUTHOR]

Global warming and nitrogen (N) deposition are important factors impacting soil carbon (C) and N cycling. Termites are important ecosystem engineers that can also strongly affect C and N cycling, potentially in interaction with warming and N deposition. In addition, non-additive effects that magnify or reduce their impacts on soil element cycles may occur when termite nests and adjacent soils are mixed due to their divergent properties but this has not been investigated. Here, we collected termite nests and trails built in wood (“termite nest soils”) and adjacent control soils in forests at Lu Mountain (Jiangxi, China) to investigate effects of termites, warming, and N deposition on C and N processes. We measured CO 2 emissions, N 2 O emissions, net N mineralization, and net nitrification when soils were incubated at different temperatures (15 °C, 25 °C, or 35 °C) and levels of N deposition (control vs. 4 g N m − 2 ). Termite nest soils were characterized by higher dissolved organic C and CO 2 emissions. CO 2 emissions decreased with N addition and increased with temperature. N 2 O emissions increased with N deposition and increased with temperature, especially in termite nest soils and mixed soils. Net N mineralization rates increased with temperature but increases were smaller and more gradual in control and mixed soils than in termite soils. Mixing termite nest soils and control soils imposed synergistic (N mineralization: up to 57% higher than expected; nitrification: up to 170% higher; N 2 O emissions without N addition: 18% higher) and antagonistic (CO 2 emissions: 7% lower; N 2 O emissions with N addition: 28% lower) mixing effects, indicating termite impacts on soil C and N cycling might be under- and over-estimated, respectively, based on each soil alone. In light of the remarkable abundance of termites, the effects of mixing termite nest soils and the control soils on soil C and N cycling should be considered in the context of global change. [ABSTRACT FROM AUTHOR]