武功山日本柳杉林与草甸土壤碳氮特征和pH比较

【目的】通过研究日本柳杉Cryptomeria japonica(L.f.)D.Don造林34年后与其山地草甸土壤碳氮特征和pH的比较,为武功山山地草甸脆弱生态系统恢复建设提供理论依据。【方法】以江西武功山山地草甸为研究对象,选择具有代表性样地,采用五点取样法,采集小区内0~20cm土层的土样,收集草甸地上凋落物,对草甸与日本柳杉林土壤凋落物碳氮指标与pH进行测定。【结果】造林会显著增加土壤全氮、铵态氮、硝态氮、有效态氮、可溶性有机氮、可溶性有机碳、微生物量碳含量、凋落物有机态碳、凋落物全氮(P<0.05),但是却显著降低土壤pH(P<0.05);土壤pH与土壤有机质碳、全氮、铵态氮、硝态氮、有效态氮、可溶性有机氮、可溶性有机碳、微生物量碳含量、凋落物有机态碳、凋落物全氮呈显著负相关(P<0.05)。【结论】日本柳杉造林对土壤微生物活性、土壤质量以及N矿化能力具有积极效应;造林可降低土壤pH值,土壤pH与有机物质分解存在紧密联系。

氮添加背景下土壤真菌和细菌对不同种源入侵植物乌桕生长特征的影响

为了解氮添加背景下土壤真菌和细菌对不同种源入侵植物生长的影响,该实验以本地和入侵地种源不同种群乌桕(Triadica sebifera)为研究对象,通过氮添加处理,施用细菌抑制剂(链霉素)和真菌抑制剂(扑海因)调控土壤细菌、真菌活性,探究土壤细菌和真菌对不同种源乌桕生长的影响,以揭示乌桕成功入侵机制,为有效预测和管理入侵植物提供理论依据。结果表明:(1)入侵地种源乌桕在株高、叶片数和生物量方面均显著高于本地种源,入侵地种源乌桕相较于本地种源具有显著生长优势。(2)添加细菌和真菌抑制剂显著降低了乌桕地上生物量,且乌桕生长对土壤细菌的依赖性更强。(3)氮添加及其与土壤细菌和真菌的交互作用对于乌桕生长和资源分配有显著影响,增强了乌桕对资源的竞争优势,可能是影响乌桕入侵成功的重要因素。

Litter age interacted with N and P addition to impact soil N_(2)O emissions in Cunninghamia lanceolata plantations

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(N_(2)O),which is an important greenhouse gas.However,no study has examined the effects of interactions between litter age and nutrient addition on soil N_(2)O emissions,and explored the underlining mechanisms simultaneously,thus limiting our evaluation of litter decomposition effects on N_(2)O 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 N_(2)O emissions by incubation study.Litter age generally increased N_(2)O emissions via a decrease in litter C:N ratio.While P addition decreased N_(2)O emissions,N addition increased them mainly by positive effects on soil enzymes as indicated by microbial functional genes associated with N_(2)O production and negative effects on litter C:N ratio.Litter age and nutrient addition interacted to impact soil N_(2)O emissions.In future forest management,both nutrient addition and litter age should be considered in evaluation of management effects on N_(2)O emissions,especially thinning or selectively cutting involving litter input with different age.

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

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.