模拟氮沉降对天山云杉细根分解及其养分释放的影响

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

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。

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 decomposi- tion, 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（3.31 a）,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.