不同经营模式对毛竹林土壤固氮菌群落结构和丰度的影响

发布时间：2019-01-07 11:08

【摘要】：毛竹(Phyllostachys pubescens)又称楠竹,是中国分布最广、面积最大的主要经济竹种,截至2013年,我国毛竹林的面积为443万公顷,目前生产上主要采用粗放和集约经营2种模式。毛竹是喜氮植物,生物固氮是土壤氮素的重要来源,但对人为干扰较为敏感。本研究分别采集5个不同经营时间的粗放经营和集约经营毛竹林表层(0~20 cm)和表下层(20~40 cm)土壤,应用PCR-DGGE和荧光定量PCR方法研究了不同经营模式毛竹林土壤固氮菌群落结构和丰度的变化,并利用冗余分析(RDA)研究影响土壤固氮菌群落的主要环境因素,旨在揭示毛竹纯林土壤固氮菌群落结构特征的影响及其演变规律。结果如下:粗放经营毛竹林。种植时间分别为5年(5a)、9年(9a)、15年(15a)和18年(18a)粗放经营毛竹林,以立地条件相似的天然马尾松林为对照(CK)。(1)表层(0~20 cm)土壤固氮菌群落Shannon多样性指数在马尾松林改造成毛竹林5年后均明显提高,而随着栽培年限的延长逐渐降低,但仍高于对照。主成分分析(PCA)表明,不同栽培年限毛竹林地土壤固氮微生物群落组成发生了较大变化,5a和9a样品分别与对照在第一主成分和第二主成分上差异明显,而15a和18a样品与对照差异逐渐降低,统计分析表明不同处理之间差异显著(r=0.901,p=0.001)。马尾松林改造成毛竹林后,土壤固氮菌nif H基因丰度明显提高,表现为5a最高,至9a时又急剧降低,随后逐渐稳定。冗余分析(RDA)结果表明,不同栽培年限毛竹林地土壤p H,有效磷、有机质和有效钾含量的变化是影响土壤固氮菌群落结构变异的主要因素;(2)表下层20~40 cm土壤固氮菌群落的变化规律与表层(0~20 cm)相似,只是多样性和丰度的最大值出现在15a处理。表层土壤固氮菌nif H基因丰度多于表下层;RDA分析结果同时表明速效钾、有效磷、碱解氮、硝态氮和有机质显著影响固氮菌。长期集约经营毛竹林。选择了不施肥(CK)和集约经营10年(10a)、15年(15a)、20年(20a)、25(25a)年毛竹林土壤。(1)集约经营10年时表层(0~20 cm)土壤固氮菌群落结构与对照(CK)差异不大,持续到15a和20a时则发生了明显变化,而到25a时有所缓和。固氮菌多样性指数和nif H基因丰度均呈现先减少后增加的趋势,经营15a时达到最小值。冗余分析表明表层(0~20 cm)土壤有效磷、土壤速效钾、硝态氮和水解氮的含量与固氮菌群落结构的变化具有较强的相关性,但未达显著水平,它们合计解释了31%的样品总变异;而表下层(20~40 cm)土壤p H、有机质、硝态氮和碱解氮含量的变化是影响土壤固氮菌群落结构变异的主要因素,且达显著水平。短期集约经营毛竹林。采集集约经营时间分别为0年(CK)、1年(1a)和7年(7a)的毛竹林土壤。集约经营1a毛竹林土壤固氮菌的多样性大于7a毛竹林,且集约经营对毛竹林表层土壤固氮菌的影响大于表下层;随着集约经营年限的增加,表层土壤固氮菌nif H基因丰度整体呈先下降后上升的趋势,而表下层土壤固氮菌nif H丰度的变化与之相反。
[Abstract]:Pyllostachys pubescens, also known as Nangzhu, is the main economic bamboo species with the largest distribution and the largest area in China. As of 2013, the area of the bamboo forest in China is 4.43 million hectares, and the current production mainly adopts two modes of extensive and intensive operation. Phyllostachys pubescens is a nitrogen plant, and the biological nitrogen fixation is an important source of soil nitrogen, but it is more sensitive to human disturbance. The structure and abundance of nitrogen-fixing bacteria in different operating modes were studied by PCR-DGGE and fluorescence quantitative PCR. The main environmental factors of the nitrogen-fixing bacteria community in the soil were studied by the RDA method, and the effects of the structure of the nitrogen-fixing bacteria in the soil of the pure forest of Phyllostachys pubescens were studied. The results are as follows: the crude bamboo forest is put into operation. The planting time was 5 years (5a), 9 years (9a), 15 years (15a) and 18 years (18a). (1) The Shannon diversity index of the nitrogen-fixing bacteria community in the surface layer (0-20 cm) was obviously improved after 5 years of transformation of the Pinus massoniana forest into the bamboo forest, but with the increase of the year of cultivation, it was still higher than that of the control. The principal component analysis (PCA) indicated that the composition of the soil-fixing microbial community in the soil with different cultivation years has changed greatly, and the samples of 5a and 9a are obviously different from the control in the first main component and the second main component, and the difference of the 15a and 18a sample and the control difference is gradually reduced, The statistical analysis indicated that the difference between different treatments was significant (r = 0.901, p = 0.001). After the transformation of Pinus massoniana forest into the bamboo forest, the abundance of the nif H gene of the soil of the soil is obviously improved, the expression is the highest, and the expression of the nitrogen-fixing bacteria nif H is up to 9a, and then is gradually stabilized. The results of RDA show that the change of soil p H, effective phosphorus, organic matter and effective potassium in different cultivation years is the main factor affecting the structure variation of the nitrogen-fixing bacteria in the soil. (2) The variation law of the nitrogen-fixing bacteria community in the lower layer of the table was similar to that of the surface layer (0-20 cm), but the maximum value of the diversity and abundance appeared in the 15a treatment. The Nif H gene abundance in the surface soil is more abundant than that of the lower layer; the results of the RDA analysis show that the available potassium, effective phosphorus, alkali and nitrogen, nitrate nitrogen and organic matter have a significant effect on the nitrogen-fixing bacteria. Long-term intensive management of the bamboo forest. Non-fertilization (CK) and intensive management for 10 years (10a), 15 years (15a), 20 years (20a) and 25 (25a) were selected. (1) The structure of the nitrogen-fixing bacteria in the surface layer (0-20 cm) and the control (CK) of the surface layer (0-20 cm) were not large when the intensive operation was used for 10 years, and the difference between the nitrogen-fixing bacteria community structure and the control (CK) of the soil continued to 15a and 20a. The diversity index of the nitrogen-fixing bacteria and the abundance of the nif H gene both show a tendency to increase after the first reduction, and the minimum value is reached at the time of the operation of the operation 15a. The redundant analysis indicated that the content of available P, available K, N and N in the surface of the surface layer (0-20 cm) had a strong correlation with the change of the nitrogen-fixing bacteria community structure, but did not reach a significant level, and they accounted for 31% of the total variation of the sample. The changes of the content of p H, organic matter, nitrate nitrogen and alkali in the lower layer (20 ~ 40 cm) in the lower layer (20 ~ 40 cm) are the main factors that affect the structure variation of the nitrogen-fixing bacteria in the soil and reach a significant level. Short-term intensive management of the bamboo forest. The intensive operation time was 0 years (CK), 1 year (1a) and 7 years (7a). In the intensive management, the diversity of the nitrogen-fixing bacteria in the soil of the Phyllostachys pubescens forest is greater than that of the bamboo forest, and the effect of intensive management on the nitrogen-fixing bacteria of the surface soil of the bamboo forest is larger than that of the lower layer of the table; with the increase of the intensive operation period, the abundance of the nif H gene of the surface soil nitrogen-fixing bacteria is decreased firstly and then rises, The change of the nif H abundance of the nitrogen-fixing bacteria in the lower-layer soil is the opposite.
【学位授予单位】：浙江农林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S795.7;S714.3

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