油松不同徑級細根分解對林地氮添加的響應

發(fā)布時間：2018-01-11 07:10

本文關鍵詞：油松不同徑級細根分解對林地氮添加的響應　出處：《中國科學院大學(中國科學院教育部水土保持與生態(tài)環(huán)境研究中心)》2017年碩士論文　論文類型：學位論文

【摘要】：氮(N)沉降正在對全球森林生態(tài)系統(tǒng)產(chǎn)生顯著影響,了解森林生態(tài)系統(tǒng)物質(zhì)循環(huán)和能量流動對N沉降的響應情況,對于維護森林生態(tài)系統(tǒng)健康具有重要意義。N沉降同時也深刻地影響著細根的分解過程,細根分解是森林生態(tài)系統(tǒng)養(yǎng)分循環(huán)的關鍵環(huán)節(jié)。研究細根分解過程對N沉降的響應,有利于揭示生態(tài)系統(tǒng)物質(zhì)循環(huán)對環(huán)境變化的響應機制,對森林生態(tài)系統(tǒng)管理提供參考依據(jù)。但是在全球大氣N沉降持續(xù)增加的背景下,土壤有效N增加如何影響不同徑級細根分解的過程以及養(yǎng)分釋放過程是如何變化的目前尚不清楚,制約著人們對森林生態(tài)系統(tǒng)養(yǎng)分循環(huán)過程和機制的認識以及相關生態(tài)模型的發(fā)展。本文以4個梯度的林地氮添加(N0、N3、N6和N9依次為0、3、6和9 g N·m-2 yr-1)為基礎,通過分解袋實驗,研究了N添加對油松不同徑級細根分解過程的影響。結(jié)果表明:(1)不同徑級細根的分解過程可分為快速(0-120d)和慢速分解(120-300d)兩個階段。0-0.4mm(主要由1和2級根系組成)細根分解系數(shù)k值在0.148-0.205kg·kg-1·a-1之間變化,0.4-1mm(2和3級根系)細根k值在0.236-0.260 kg·kg-1·a-1之間變化,1-2mm(4級以上根系)細根k值在0.301-0.350 kg·kg-1·a-1之間變化,其中較細的根系分解較慢。N添加顯著降低了0-0.4mm細根的分解速率,對0.4-1mm和1-2mm細根的分解速率無顯著影響。(2)N添加改變了細根元素和化學組分含量,并且不同元素和組分含量對N添加的響應有所差異。細根分解過程中C、N、P元素以及可溶性糖、淀粉含量是波動式下降,而木質(zhì)素含量均呈波動式上升,并且變化的趨勢不受外源N的輸入而顯著改變。但是N添加對其變化的幅度因細根徑級不同和施N水平不同影響程度不同。(3)N添加提高了0-0.4、0.4-1mm細根中C、N元素殘留率和木質(zhì)素殘留率,對1-2mm細根內(nèi)C、N元素殘留率和木質(zhì)素殘留率無顯著影響;N添加對不同徑級細根P元素殘留率和可溶性糖、淀粉殘留率均無顯著影響。0-0.4、0.4-1mm細根C、N、P元素遷移模式總體均表現(xiàn)為直接釋放,1-2mm細根C、P元素為直接釋放,而N元素為富集-釋放模式。(4)C、N、P、木質(zhì)素、C/N、木質(zhì)素/N等都是常見的預測細根分解速率的化學指標。不同施N處理下,分解300d左右的細根殘留率與C、C/N、木質(zhì)素/N具有顯著負相關關系,而與N、P、木質(zhì)素呈顯著正相關。整個研究期內(nèi),細根分解過程中C、N、P的殘留率與干物質(zhì)殘留率之間呈極顯著的正相關關系,木質(zhì)素/N、木質(zhì)素/P與細根殘留率之間呈現(xiàn)負的相關關系。但總體來看,施N處理并沒有改變細根養(yǎng)分殘留率與干物質(zhì)殘留率之間的相關關系方向,但是相關性強度有所改變。(5)在300d的研究期內(nèi),不同徑級細根酶活性大體表現(xiàn)出先增加后降低的趨勢。施N顯著影響不同徑級細根纖維二糖酶活性,并且低氮處理增加了酸性磷酸酶活性,而高氮抑制了該酶活性。0-0.4mm細根C、N含量與酶活性顯著正相關,不同徑級細根酶活性與P含量均呈正相關關系,不同N添加水平下酶活性與細根分解率均呈現(xiàn)正相關關系�？傊�,N添加可能通過影響較細兩級根系化學組分從而影響森林生態(tài)系統(tǒng)細根分解和養(yǎng)分釋放過程,以及整個森林生態(tài)系統(tǒng)的物質(zhì)循環(huán)過程。
[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.

【學位授予單位】：中國科學院大學(中國科學院教育部水土保持與生態(tài)環(huán)境研究中心)
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：S791.254

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