Litter removal enhances soil N2O emissions: Implications for management of leaf-harvesting Cinnamomum camphora plantations

Abstract

Nitrous oxide (N2O) and carbon dioxide (CO2) contribute substantially to global climate. Understanding N2O and CO2 emission intensity from forest soil is important for greenhouse gas (GHG) budget and climate change mitigation. Litter decomposition and nitrogen (N) addition are two crucial factors impacting soil GHG production, but magnitude depends on litter characteristics. Cinnamomum camphora is used for leaf-harvesting for essential oil extractions, which may disturb litter input and hence soil GHG emissions. We conducted an in situ study over fourteen months in C. camphora plantations to compare litter removal to litter control, combined with N addition, quantify production of N2O and CO2 in full-factorial complete-randomized design. Soil N2O emission rates were significantly influenced by litter and N treatment, while CO2 emissions were only impacted by interactions between litter and N treatment. Specifically, soil N2O emission rates were increased by 681%, while copy number of five functional microbial genes associated with N2O productions were increased by 2.8 to 71.4 times following litter removal. C. camphora litter might have released chemicals associated with inhibition of related microbial activities. Soil CO2 emission rates were 25% higher with litter removed and 34% lower with litter when N was added, further indicating inhibition effects of C. camphora litter on microbial activities. In future management of C. camphora plantations with intensive defoliation management and fertilization practice, litter regimes with more litter input should be considered in mitigation of soil GHG emissions, and hence global climate change.