模拟氮沉降对天山云杉细根分解及其养分释放的影响

采用野外模拟试验,设计4种氮处理——对照(不施氮,CK)、低氮(施氮5kg·hm-2·a-1,LN)、中氮(施氮10kg·hm-2·a-1,MN)、高氮(施氮15kg·hm-2·a-1,HN),研究氮沉降对天山云杉细根分解及养分释放的影响。结果表明:(1)不同氮处理分解2年后天山云杉细根残留率依次为74.044%(HN)、71.967%(MN)、68.156%(CK)、61.933%(LN),且差异显著。(2)天山云杉的细根月分解速率在试验前期不同氮处理下规律不明显;而在试验后期呈现为对照中氮低氮高氮。(3)4种氮处理下天山云杉细根分解50%需要的时间依次为3.31年(LN)、3.67年(CK)、4.28年(MN)、4.64年(HN),分解95%需要的时间依次为14.39年(LN)、15.93年(CK)、18.58年(MN)和20.17年(HN)。(4)天山云杉细根C元素迁移模式总体表现为直接释放,N元氮为富集-释放模式,残留率呈现波动式下降趋势。(5)不同氮处理下天山云杉细根分解率与C元素浓度间均呈线性负相关关系;对照和低氮处理下,天山云杉细根分解率与N元素浓度间均为线性负相关关系,中氮和高氮处理下,细根分解率随N元素浓度的增加呈先增加后降低的趋势。

Effect of Simulated Nitrogen Deposition on the Fine Root Decomposition and Related Nutrient Release of Picea schrenkiana var.tianshanica

A field simulated experiment was conducted to study the effects of nitrogen deposition on the fine root decomposition and related nutrient release of Picea schrenkiana var.tianshanica.Four treatments were designed as CK(control,Non-addition nitrogen),LN(Low nitrogen,5 kg·hm^-2·a^-1),MN(Mid nitrogen,10 kg·hm^-2·a^-1) and HN(High nitrogen,15 kg·hm^-2·a^-1).The results showed that:(1)After two years decomposition,the fine root remaining percentage of P.schrenkiana var.tianshanica ranked as HN(74.044%),MN(71.967%),CK(68.156%),LN(61.933%),and the difference was significant in four treatments.(2)The rule of monthly decomposition rate in former stage was not obvious under four treatments,while it was CK>MN>LN>HN in final stage.(3)The required time to fine root decomposition 50% ranked as LN(3.31a),CK(3.67a),MN(4.28a),HN(4.64a),while it was 14.39a(LN),15.93a(CK),18.58a(MN) and 20.17a(HN) for decomposition 95%.(4)The transfer model for C in fine root was direct releasing,while it was riching-releasing model for N.(5)The relationships between fine root decomposition rate and C concentration in fine root were negative linear correlation in four treatments;the relationships between fine root decomposition rate and N concentration were negative linear correlation in CK and LN.The decomposition rate was increased first and decreased then as the N concentration increasing in MN and HN.