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Scientia Silvae Sinicae ›› 2015, Vol. 51 ›› Issue (4): 96-102.doi: 10.11707/j.1001-7488.20150412

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Response of the N-Cycling Associated Soil Microorganism to Simulated N Deposition in a Plantation of Cunninghamia lanceolata

Liu Caixia1, Jiao Ruzhen1, Dong Yuhong1, Sun Qiwu1, Zhou Xinhua2, Li Fengqing2   

  1. 1. Key Laboratory of Tree Breeding and Cultivation of State Forestry Administration State Key Laboratory of Tree Genetics and Breeding Research Institute of Forestry, CAF Beijing 100091;
    2. Centre of Subtropical Forestry, CAF Fenyi 336600
  • Received:2014-03-27 Revised:2015-02-25 Online:2015-04-25 Published:2015-05-20

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Abstract:

【Objective】 The number of microorganism in soil is an important index in determining the change of the biochemical function of soil nitrogen cycle. While the current studies mostly focus on the microbial flora, the research on nitrogen cycling associated microorganisms is little. In this paper, the influence of deposition amount of short-term nitrogen deposition in different nitrogen forms on soil culturable azotobacter, nitric acid bacteria, nitrous acid bacteria and denitrifying bacteria is studied by a field simulation experiment. The change trend at early stage in response to the N-deposition is an important knowledge for forest nitrogen regulation and environmental management, and this study would provide reference for the further research on effects of nitrogen deposition on Chinese fir plantation ecosystem.【Method】 In May 2013, 30 plots of 1 m×1 m were established in a Cunninghamia lanceolata plantation to simulate nitrogen loadings at 5 levels: N0, N1, N2, N3, and N4 with 0, 20, 40, 60 and 80 kg·hm-2a-1, respectively. Soil samples were collected in 0-10 cm and 10-20 cm soil layers in June, August and October 2013, respectively. The dilution plate counting method was used to determine the amount of nitrogen fixing bacteria, and the MPN-Griess colorimetry for measuring nitrate and nitrite bacteria, and the phenol two sulfonyl colorimetric method for denitrifying bacteria (anaerobic).【Result】 The results showed: the amount of azotobacter in the 0-10 cm soil layer was more than in 10-20 cm. Along with the increase of N deposition, the amount of azotobacter showed a trend that it firstly increased and then decreased. Moreover, ammonium nitrogen deposition(0-60 kg·hm-2a-1) was in favor of the amount of azotobacter. The amount of nitrite bacteria first increased and then decreased with the increasing ammonium nitrogen, and obtained maximum value in N1 or N2 treatment. The amount of nitrite bacteria showed an almost opposite change patterns in response to nitrate nitrogen addition. In June, nitrite bacteria appeared extremely significant difference with the same ammonium and nitrate nitrogen in 0-10 cm soil layer, and there also was significant difference in 10-20 cm soil layer. The amount of nitrobacteria showed the same trend in August and October, that was first increase and then decrease and the change showed no significant difference between the two nitrogen forms treatments. The changing trend of denitrobacteria with ammonium nitrogen deposition was opposite between the two soil layers (0-10 cm, 10-20 cm). Nitrate deposition had no significant effect on denitrobacteria, and the high concentration of nitrogen lightly restrained growth of denitrobacteria.【Conclusion】 The amount of azotobacter in 0-10 cm soil layer was greater than that in the 10-20 cm layer. Ammonium nitrogen (0-60 kg·hm-2 a-1) promoted the growth of azotobacter, so did the nitrate nitrogen (0-80 kg·hm-2 a-1). For the two nitrogen forms, the trend was inconsistent, low ammonium nitrogen promoted the nitrite bacteria growth, and the low nitrate nitrogen inhibited it. Nitrogen deposition forms had no significant effects on nitrate bacteria, low nitrogen deposition promoted the growth, and the high concentration restrained the growth. The quantity of nitrogen deposition had no significant effect on denitrifying bacteria.

Key words: nitrogen deposition, azotobacter, nitrobacteria, nitrite bacteria, denitrobacteria

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