油松不同径级细根分解对林地氮添加的响应

发布时间：2018-01-11 07:10

本文关键词：油松不同径级细根分解对林地氮添加的响应　出处：《中国科学院大学(中国科学院教育部水土保持与生态环境研究中心)》2017年硕士论文　论文类型：学位论文

【摘要】：氮(N)沉降正在对全球森林生态系统产生显著影响,了解森林生态系统物质循环和能量流动对N沉降的响应情况,对于维护森林生态系统健康具有重要意义。N沉降同时也深刻地影响着细根的分解过程,细根分解是森林生态系统养分循环的关键环节。研究细根分解过程对N沉降的响应,有利于揭示生态系统物质循环对环境变化的响应机制,对森林生态系统管理提供参考依据。但是在全球大气N沉降持续增加的背景下,土壤有效N增加如何影响不同径级细根分解的过程以及养分释放过程是如何变化的目前尚不清楚,制约着人们对森林生态系统养分循环过程和机制的认识以及相关生态模型的发展。本文以4个梯度的林地氮添加(N0、N3、N6和N9依次为0、3、6和9 g N·m-2 yr-1)为基础,通过分解袋实验,研究了N添加对油松不同径级细根分解过程的影响。结果表明:(1)不同径级细根的分解过程可分为快速(0-120d)和慢速分解(120-300d)两个阶段。0-0.4mm(主要由1和2级根系组成)细根分解系数k值在0.148-0.205kg·kg-1·a-1之间变化,0.4-1mm(2和3级根系)细根k值在0.236-0.260 kg·kg-1·a-1之间变化,1-2mm(4级以上根系)细根k值在0.301-0.350 kg·kg-1·a-1之间变化,其中较细的根系分解较慢。N添加显著降低了0-0.4mm细根的分解速率,对0.4-1mm和1-2mm细根的分解速率无显著影响。(2)N添加改变了细根元素和化学组分含量,并且不同元素和组分含量对N添加的响应有所差异。细根分解过程中C、N、P元素以及可溶性糖、淀粉含量是波动式下降,而木质素含量均呈波动式上升,并且变化的趋势不受外源N的输入而显著改变。但是N添加对其变化的幅度因细根径级不同和施N水平不同影响程度不同。(3)N添加提高了0-0.4、0.4-1mm细根中C、N元素残留率和木质素残留率,对1-2mm细根内C、N元素残留率和木质素残留率无显著影响;N添加对不同径级细根P元素残留率和可溶性糖、淀粉残留率均无显著影响。0-0.4、0.4-1mm细根C、N、P元素迁移模式总体均表现为直接释放,1-2mm细根C、P元素为直接释放,而N元素为富集-释放模式。(4)C、N、P、木质素、C/N、木质素/N等都是常见的预测细根分解速率的化学指标。不同施N处理下,分解300d左右的细根残留率与C、C/N、木质素/N具有显著负相关关系,而与N、P、木质素呈显著正相关。整个研究期内,细根分解过程中C、N、P的残留率与干物质残留率之间呈极显著的正相关关系,木质素/N、木质素/P与细根残留率之间呈现负的相关关系。但总体来看,施N处理并没有改变细根养分残留率与干物质残留率之间的相关关系方向,但是相关性强度有所改变。(5)在300d的研究期内,不同径级细根酶活性大体表现出先增加后降低的趋势。施N显著影响不同径级细根纤维二糖酶活性,并且低氮处理增加了酸性磷酸酶活性,而高氮抑制了该酶活性。0-0.4mm细根C、N含量与酶活性显著正相关,不同径级细根酶活性与P含量均呈正相关关系,不同N添加水平下酶活性与细根分解率均呈现正相关关系。总之,N添加可能通过影响较细两级根系化学组分从而影响森林生态系统细根分解和养分释放过程,以及整个森林生态系统的物质循环过程。
[Abstract]:Nitrogen (N) deposition is significant impact on global forest ecosystem, understand the material circulation and energy flow in forest ecosystem in response to N settlement, for the maintenance of forest ecosystem health has important significance of.N deposition also profoundly affect the decomposition process of fine root decomposition is a key link in the nutrient cycle of forest ecosystem study. During decomposition of fine roots in response to N settlement, to reveal the response mechanism of material circulation in the ecosystem to environmental changes, to provide reference for forest ecosystem management. But in the global atmospheric N precipitation increasing background, increase soil N how to influence the fine roots decomposition and nutrient release process how to change is unclear, restricts the understanding of forest ecosystem nutrient cycling process and mechanism and related ecological model The development of the forest. 4 nitrogen gradient (N0, N3, addition of N6 and N9 were 0,3,6 and 9 g N, m-2 yr-1) as the foundation, through the experimental study of N bags, add different effects on Pinus tabulaeformis decomposition of fine roots. The results show that: (1) fine roots the decomposition process can be divided into fast and slow decomposition (0-120d) (120-300d) two stages.0-0.4mm (mainly by the 1 and 2 grade root composition) fine root decomposition coefficient K value changes between 0.148-0.205kg - kg-1 - A-1, 0.4-1mm (2 and 3 roots) fine root K varied between 0.236-0.260 kg kg-1. A-1, 1-2mm (more than 4 root root) k value changes between 0.301-0.350 kg kg-1 A-1, the fine root decomposition is slow.N addition significantly reduced the fine root decomposition rate of 0-0.4mm, had no significant effect on the decomposition rate of 0.4-1mm and 1-2mm fine. (2) N addition changed the root elements and chemical group the contents, and The different elements and different components in response to N added. Fine root decomposition in the process of C, N, P elements and soluble sugar, starch content is fluctuant decreased, but the lignin content was increasing, and the change trend is not affected by exogenous N input change significantly. But N added to the magnitude of change because of fine roots of different N application levels and different effects. (3) N addition increased 0-0.4,0.4-1mm root C, N element residual rate and residual rate of lignin, 1-2mm root C, N elements and the residual rate of lignin residue rate had no significant effect of N addition on different size; fine root P element residual rate and soluble sugar, starch residue rate have no significant effect on.0-0.4,0.4-1mm C N, P root, element migration mode overall showed direct release, 1-2mm root C, P elements and N elements for direct release accumulation release mode. (4) C, N, P, lignin C/N, wood. The quality of /N are chemical indicators to predict the rate of fine root decomposition common. Different fertilizer N, decomposition of about 300D root residue rate and C, C/N, /N lignin has a significant negative correlation, and N, P was positively related to lignin. During the whole study period, fine root decomposition process in C, N, P and the residual rate of stem showed a significant positive correlation between the rate of lignin residues, /N, /P and root lignin residue showed negative correlation between rate. However, N treatment did not change the residual rate of dry matter and root nutrient residual correlation between the rate of direction however, the correlation intensity changes. (5) in the study period in the 300D of fine roots in enzyme activity showed first increasing and then decreasing. N significantly affected the enzyme activity of two different diameters of fine fiber, and low nitrogen treatment increased acid phosphatase activity, and high nitrogen The inhibition of the enzyme activity of.0-0.4mm root C, a significant positive correlation between N content and enzyme activity of different diameter root enzyme activity and P content were positively correlated with fine root enzyme activity of different N levels of decomposition rate were positively correlated. In short, N addition may affect the fine root level two chemical components thus affecting the forest ecosystem of fine root decomposition and nutrient release process, material recycling process and the whole forest ecosystem.

【学位授予单位】：中国科学院大学(中国科学院教育部水土保持与生态环境研究中心)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S791.254

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