【摘要】 细根在植物的养分获取和生态系统物质循环中有重要的作用,日益增加的氮沉降改变了土壤pH值和养分可利用性,潜在地影响着细根特性。为揭示氮沉降增加对木本植物细根寿命和形态的影响,于2013年5月至2015年9月在亚热带次生常绿阔叶林中开展每月一次的氮添加试验,共设对照(CK,0 g·m^-2·a^-1)、低氮(LN,5 g·m^-2·a^-1)、高氮(HN,15 g·m^-2·a^-1)3个水平。以该林分建群种扁刺栲（Castanopsis platyacantha）为研究对象,于2014年4月至2015年9月,每月采用微根管技术获取根系影像,室内分析后得到各样地的扁刺栲细根生物量、寿命和形态指标。2014年11月取0-10 cm土壤分析土壤pH值、铵态氮和硝态氮含量。结果表明:扁刺栲0-45 cm土层细根生物量为128.30 g·m^-3,细根平均寿命范围为113-186天;氮添加处理未显著影响扁刺栲0-45 cm土层细根寿命和生物量;低氮处理显著降低了0-15 cm土层细根根段表面积;高氮处理显著降低了表层土壤pH值。研究表明短期氮添加通过影响该次生林土壤无机氮含量,导致表层土壤酸化,对表层土壤扁刺栲细根的形态特征造成一定的影响;短期氮添加对扁刺栲细根生物量、寿命和深层细根的形态未产生显著影响。更多还原

【Abstract】 Aims Fine roots are the principal parts for plant nutrients acquisition and play an important role in the underground ecosystem.Increased nitrogen（N） deposition has changed the soil environment and thus has a potential influence on fine roots.The purpose of this study is to reveal the effect of N deposition on biomass,lifespan and morphology of fine root.Methods A field N addition experiment was conducted in a secondary broad-leaved forest in subtropical China from May 2013 to September 2015.Three levels of N treatments:CK（no N added）,LN(5 g·m^-2·a^-1),and HN(15 g·m^-2·a^-1) were applied monthly.Responses of fine root biomass,lifespan,and morphology of Castanopsis platyacantha to N addition were analyzed by using a minirhizotron image system from April 2014 to September 2015.Surface soil sample（0-10 cm） was collected in November 2014 and soil pH value,and concentrations of NH₄⁺-N and NO₃^--N were measured.Important findings The biomass and average lifespan of the fine roots of C.platyacantha were 128.30 g·m^-3 and 113-186 days,respectively,in 0-45 cm soil layer.Nitrogen addition had no significant effect on either fine root biomass or lifespan in 0-45 cm soil layer.However,LN treatment significantly decreased C.platyacantha root superficial area in 0-15 cm soil layer.HN treatment significantly decreased soil pH value.Our study indicated that short-term N addition influences soil inorganic N concentration and thus decreased pH value in surface soil,and thereafter affect fine root morphology.Short-term N addition,however,did not affect the fine root biomass,lifespan and morphology in subsoil.更多还原