Journal Article Moso bamboo and Japanese cedar seedlings differently affected soil N_(2)O emissions

毛竹和日本柳杉幼苗对土壤氧化亚氮排放的影响及微生物机制

Moso bamboo expansions into Japanese cedar forests are common.The expansion effects on soil nitrous oxide(N_(2)O)emissions have not been thoroughly understood,and the underlying microbial mechanisms remain unclear.We studied bacterial and fungal contribution to soil N_(2)O emissions under moso bamboo or Japanese cedar by applying bacterial or fungal inhibitors using streptomycin and iprodione,respectively.Soil N_(2)O emissions were measured and the relative contribution of bacteria and fungi to soil N_(2)O emissions was calculated.N_(2)O emission from soil with moso bamboo was significantly higher than under Japanese cedar.Compared with control,bacterial or fungal inhibitor or their combination decreased N_(2)O emissions,indicating substantial contribution of microbial activities to N_(2)O emissions.However,the relative contribution of bacteria and fungi to N_(2)O emissions was not affected by plants.Soil organic carbon,total and ammonium nitrogen were lower in soil under moso bamboo than Japanese cedar,suggesting faster microbial decomposition under moso bamboo.Fungal inhibitor and plants interactively affected soil pH,total phosphorus and ammonium nitrogen,while bacterial inhibitor and plants interactively affected total nitrogen,indicating substantial dependence of effects by microbial communities on plant species.Moso bamboo and Japanese cedar differed in their effects on soil N_(2)O emissions with higher emissions under moso bamboo.Stimulation of N_(2)O emission under moso bamboo might occur due to higher nitrogen mineralization and subsequent denitrification induced by high root exudation.These results highlight the need to consider the effect of species shifts on N_(2)O emissions in forests.

毛竹(Phyllostachys edulis)向日本柳杉(Cryptomeria japonica)林的扩张现象越发普遍,其扩张对大气重要温室气体氧化亚氮(N_(2)O)排放的影响也引起了更多的关注,而其微生物机制尚不明确。本研究通过添加微生物抑制剂链霉素和扑海因分别抑制细菌和真菌活性,连续观测土壤N_(2)O排放速率以及相关土壤养分和植物生物量。研究结果表明:(i)毛竹土壤N_(2)O的排放速率显著高于日本柳杉;与对照相比,细菌抑制剂、真菌抑制剂及其交互作用均对N_(2)O排放速率具有显著抑制效应,但三者之间无显著差异;(ii)毛竹生物量显著高于日本柳杉;(iii)日本柳杉土壤有机质、全氮和铵态氮显著高于毛竹土壤,日本柳杉土壤pH和全磷显著低于毛竹土壤。真菌抑制剂降低了土壤有机质含量,细菌抑制剂降低了土壤硝态氮含量。真菌抑制剂与物种在影响土壤pH、全磷和铵态氮方面具有显著交互作用。细菌抑制剂与物种在影响土壤全氮方面有显著交互作用。综上所述,毛竹和日本柳杉在生长过程中土壤N_(2)O排放速率不同,毛竹幼苗土壤N_(2)O排放及生物量均高于日本柳杉。细菌抑制剂和真菌抑制剂对N_(2)O的排放速率均具有一定抑制作用。因而,在全球气候变化背景下,应进一步深入了解森林生态系统物种组成和变化对N_(2)O排放的影响,以有效评估毛竹扩张等导致的生物多样性变化对全球N_(2)O排放的贡献。