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Effects of Freezing and Thawing Alternation on Soil Nitrogen Pool in the Alpine Meadow

Author: XuJunJun
Tutor: ZhangXinQuan；WuNing；WuYan
School: Sichuan Agricultural University
Course: Grassland
Keywords: Freeze- Microbial biomass carbon and nitrogen Organic nitrogen Soluble organic matter Nitrogen mineralization Free amino acids
CLC: S812.2
Type: Master's thesis
Year: 2010
Downloads: 207
Quote: 1
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Abstract


Qinghai-Tibet Plateau is considered to be one of the global changes in the promoter region of the alpine meadow area at the eastern edge of the Tibetan Plateau is ecologist research hotspots. The country has some exploratory research on the Tibetan Plateau forest line change, soil erosion and global climate change. But so far, the the Tibetan Plateau long-term frequent occurrence of freezing and thawing alternately events on soil nitrogen has not been reported. Sunny and shady slopes, alpine meadow area vegetation pattern characteristics differences, as well as frequent freeze-thaw cycles experienced in the sunny winter without snow covered zone alternately phenomenon, this article taken from Alpine Meadow of Songpan County Kaka ditch soil The indoor samples freeze-thaw alternans test, analyzed and measured in different freezing and thawing time (one day, three days, five days, 25 days, 60 days) and freeze-thaw temperature (4 ℃ controls, -4 ℃ control , -4-4 ℃ and -20-4 ℃) soil microbial biomass, MBC / of MBN, each component of the organic nitrogen, free amino acids, soluble organic matter, DOC / DON, nitrate, ammonium nitrogen and soil solution of soluble organic matter content of the changes to the analysis of freeze-thaw alternately on the Tibetan Plateau soil nitrogen. The results are as follows: 1. Changes in time with the freeze-thaw, the soil microbial biomass carbon and nitrogen changes characterized by decreased and then increased trend. After freeze-thaw 1d, microbial biomass carbon and nitrogen content reaches a minimum. Each temperature treatment, the decline of the microbial biomass carbon were 61.74%, 30.47%, 37.20% and 46.17%, respectively; microbial biomass nitrogen decline of 50.37%, 57.47%, 37.79% and 37.51%, respectively. The short-term cycle of freezing and thawing of the soil microbial biomass carbon and nitrogen significantly (P lt; 0.05), the freezing and thawing of the change of time is the main cause changes in carbon and nitrogen content of the soil microbial biomass. MBC / MBN ratio of size to characterize the microbial population in the soil freezing and thawing alternately under the soil MBC / MBN ratio first increases and then decreases, indicating that the fungi / bacteria ratio in the process of freezing and thawing alternately. With freezing and thawing time of change in soil organic nitrogen content of each component change significantly. Among them, the same trend of amino acid nitrogen and amino sugar nitrogen, characterized first and then decreased, and reaches a maximum in the freeze-thaw 1d reduce the change in the overall trend of ammonia nitrogen increased, but slightly different. Temperature treatment under acidolysis unknown inconsistent variation nitrogen, reduce its similar characteristics as the first increase. Freeze-thaw alternation soluble carbon and nitrogen content in the soil significantly soluble organic carbon (DOC) and dissolved organic nitrogen (DON) content variation, showing a decreasing trend after the first increase. After freezing and thawing 1d, DOC and DON content peaked. DOC / DON ratio of the size of soil characterization of dissolved organic matter content (DOM) in the present study, the DOC / DON ratio first increases and then decreases, indoor freezing and thawing alternately conditions, the increase or decrease of the microbial biomass in the soil DOM main source of change. Freeze-significant effect on soil nitrogen mineralization, which, the first increase after reducing nitrate content is presented with the freezing and thawing time change trend, reaching a maximum after freeze-thaw 1d each temperature processing content 2.20,1.99,2.34 and 2.42 times the pre-treatment; variation of ammonium nitrogen content and nitrate. After freezing and thawing 1d, and its content, respectively, prior to treatment 1.78,2.42,3.45 and 4.24 times. Soil solution DOC content of DON with the freezing and thawing time change first increases and then decreasing trend. In the early days of freezing and thawing, the soil solution DOC, DON content a substantial increase in the same time under freeze-thaw, -4 ℃ (CK2) temperature treatment in the soil solution DON content was significantly higher than the remaining three temperature treatments. These studies have shown that the alternate freezing and thawing to have a significant impact on the alpine meadow soil nitrogen. Freezing and thawing alternately alpine meadow soil nitrogen, helps to explain the lower soil N mineralization rate in alpine regions, Nitrogen Cycle and its ecological effect for the mountain regions to provide a theoretical basis.

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CLC: > Agricultural Sciences > Livestock, animal medicine,hunting,silkworm,bee > General Animal Science > Grassland Science,prairie school > Grassland soil science
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