模拟氮沉降对森林残落物分解及养分动态的影响

发布时间：2018-05-29 22:09

本文选题：氮沉降 + 残落物　；参考：《江西农业大学》2017年硕士论文

【摘要】：氮(N)沉降是全球性的重大环境问题之一,中国已成为继欧美之后的第三大N沉降区,N沉降对森林生态系统的影响是当前的研究热点和科学前沿。森林残落物是森林生态系统重要的碳库和养分库,对维持森林生态系统结构和功能至关重要。开展N沉降对森林残落物分解速率和养分动态的影响研究,可为深入探讨N沉降对森林生态系统物质循环和能量流动提供科学参考。本研究选取了亚热带6种不同质量(C:N:P化学计量比)残落物为对象,采用实验室微宇宙法,开展为期720天的分解试验,比较N沉降对不同类型残落物分解速率与养分动态的影响。与此同时,采用了99.99%~(15)N同位素示踪技术监测残落物对N沉降的固持量,利用Saiya-Cork的微孔板荧光法测定5种酶活性,以期揭示N沉降对残落物分解过程的影响及其N沉降本身的去向和酶活性的响应机制。主要研究结果如下:(1)6种残落物初始化学组成及其化学计量比差异显著(P0.05),初始C/N比从高到低的顺序为:合欢(Albizia julibrissin)凋落叶(AJL)、枫香(Liquidambar formosana)凋落叶(LQL)、杉木(Cunninghamia lanceolata)+枫香混合凋落叶(CLL+LQL)、苔藓(Bryophyte)残体(BRL)、杉木凋落叶(CLL)、马尾松(Pinus massoniana)木屑(PWL),初始N、P浓度为CLL+LQL、LQL和AJL高于PWL、BRL和CLL,各残落物分解速率与其初始C、N、P浓度及其化学计量比等指标中2个或2个以上显著相关。(2)N添加处理总体显著降低各残落物的分解速率。经过720d的分解试验,对照处理残落物的重量残留率为:BRL(82.07%)、PWL(81.95%)CLL(54.97%)CLL+LQL(41.87%)、LQL(41.48%)AJL(27.77%),N添加处理的各残落物重量残留率为:PWL(86.03%)BRL(84.23%)CLL(78.62%)CLL+LQL(70.38%)LQL(62.00%)AJL(33.51%)。(3)与对照处理相比,N添加处理减缓了PWL、BRL、CLL和CLL+LQL的C释放,促进了LQL和AJL的C释放;N添加处理除对AJL分解过程N净释放影响不显著外,对其它5种残落物N净固持与释放影响显著;N添加处理降低各残落物的P浓度,不同程度地加快PWL、BRL、CLL+LQL、LQL和AJL的P净释放。(4)N添加处理各残落物~(15)N丰度变化趋势基本一致,前期或中期呈上升趋势,中期或后期呈下降趋势;PWL、CLL、BRL、CLL+LQL、LQL和AJL固持~(15)N的丰度分别为6.73‰、13.15‰、11.37‰、13.65‰、14.30‰和5.81‰,而释放则分别为8.35‰、19.24‰、17.55‰、14.52‰、15.95‰和5.81‰,可见,不同残落物对外源N的固持与释放的强度及其转换规律各异,与其质量(C/N、C/P和N/P)有关。(5)N添加处理对残落物分解的5种酶活性的影响因残落物类型而各异,整体提高了各残落物酸性磷酸酶和L-亮氨酸基态酶的活性,降低了β-1,4-葡萄糖苷酶、半纤维素酶和乙酰葡萄胺糖苷酶的活性。综上所述,N添加处理对残落物分解速率与养分动态的影响以及外源N的去向与残落物质量、分解阶段、酶活性等因素有关。残落物初始C/N和C/P比及其随分解过程的动态变化是解释N沉降影响效应的关键特征。N沉降对亚热带森林生态系统残落物分解及养分的归还仍需加强原位的模拟研究。
[Abstract]:Nitrogen (N) settlement is one of the most important environmental problems in the world. China has become the third largest N settlement area after Europe and America. The impact of N settlement on forest ecosystem is the current research hotspot and scientific frontier. Forest residues are important carbon and nutrient storage in forest ecosystem, and it is critical to maintain the structure and function of forest ecosystem. The study on the effect of N settlement on the decomposition rate and nutrient dynamics of forest residues can provide a scientific reference for the material circulation and energy flow of the forest ecosystem by N settlement. This study selected 6 subtropical mass (C:N:P stoichiometric) residues as the object, and carried out a 720 laboratory microcosm method. The effect of N deposition on the decomposition rate and nutrient dynamics of different types of residues was compared. At the same time, the 99.99%~ (15) N isotope tracer technique was used to monitor the retention of the residues on the N settlement, and the activity of the 5 enzymes was measured by the Saiya-Cork microplate fluorescence method, in order to reveal the effect of N settlement on the decomposition process of the residue and the effect of the precipitation on the decomposition process of the residues. The main results are as follows: (1) the initial chemical composition and stoichiometry of 6 species of residues are significant (P0.05), and the order of initial C/N ratio from high to low is: Albizia julibrissin (AJL), maple (Liquidambar formosana) litter (LQL), and Sugiki (Cunninghamia LAN) Ceolata) + CLL+LQL, moss (Bryophyte) residue (BRL), Chinese fir litter (CLL), Pinus massoniana (Pinus massoniana) wood chip (PWL), initial N, P concentration is CLL+LQL, LQL and other residues are higher than those of 2 or more than 2. (2) The decomposition rate of the residue was significantly reduced by the addition treatment. After the 720d decomposition test, the residual weight residue rate of the controlled residue was BRL (82.07%), PWL (81.95%) CLL (54.97%) CLL+LQL (41.87%), LQL (41.48%) AJL (27.77%), and the residue of N addition treated residues was PWL (86.03%) BRL (84.23%) CLL (78.62%) CLL+LQL (70.38%)). 62%) AJL (33.51%). (3) compared with the control treatment, N addition treatment slowed down the C release of PWL, BRL, CLL and CLL+LQL, and promoted the release of LQL and AJL C; N addition treatment had no significant influence on the net release of the AJL decomposition process, and had a significant effect on the other 5 residues. To accelerate the net release of P in PWL, BRL, CLL+LQL, LQL and AJL. (4) the variation trend of ~ (15) N abundances in N addition treatment was basically consistent, in the early or middle period, the trend was rising, and in the middle or later period, the trend was decreasing; PWL, CLL, BRL, CLL+LQL, 13.15, 11.37, 13.65, 14.30 and 5.81 per thousand, respectively, for the abundance of PWL, CLL, BRL, CLL+LQL, 11.37, 13.65, and 13.65. It is 8.35 per thousand, 19.24 per thousand, 17.55 per thousand, 14.52 per thousand, 15.95 per thousand and 5.81 per thousand. It can be seen that the strength and conversion of different residues on the fixation and release of exogenous N are different, and their mass (C/N, C/P and N/P). (5) the effects of N addition treatment on the viability of the 5 enzymes in the residues are different from the residue types, and the whole residues are improved as a whole. The activity of acid phosphatase and L- leucine Base State Enzyme reduced the activity of glucosidase, hemicellulase and acetylglucosidase in beta -1,4-. In summary, the effects of N addition on the decomposition rate and nutrient dynamics of the residues and the quality of residue, decomposition stage, enzyme activity and other factors were related to the origin of exogenous N. The C/N and C/P ratio and the dynamic changes with the decomposition process are the key characteristics to explain the effect of N deposition..N deposition in the subtropical forest ecosystem residue decomposition and the return of nutrients still need to be strengthened in situ.
【学位授予单位】：江西农业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S714

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