Soil Microbial Activity under Different Management Treatments in a Temperate Grassland

View/ Open
Author(s)
Primary Supervisor
Xu, Zhihong
Other Supervisors
He, Jizheng
Year published
2017
Metadata
Show full item recordAbstract
Nitrogen (N) deposition is increasing at unprecedentedly rate due to anthropogenic activities. The N deposition is altering the microbial activity and coupled C and N cycling through changing soil pH, N and carbon (C) availability.
(1) N-related functional genes (NFGs) (N fixation, nifH; N mineralization, chiA; nitrification, AOA- and AOB-amoA;denitrification,narG,nirK,nirS and nosZ) regulate the main N transformation processes. However, empirically simulated N deposition experiments have been exclusively conducted through large and infrequent N fertilization, which may have caused contrasting effects on N cycling, compared ...
View more >Nitrogen (N) deposition is increasing at unprecedentedly rate due to anthropogenic activities. The N deposition is altering the microbial activity and coupled C and N cycling through changing soil pH, N and carbon (C) availability. (1) N-related functional genes (NFGs) (N fixation, nifH; N mineralization, chiA; nitrification, AOA- and AOB-amoA;denitrification,narG,nirK,nirS and nosZ) regulate the main N transformation processes. However, empirically simulated N deposition experiments have been exclusively conducted through large and infrequent N fertilization, which may have caused contrasting effects on N cycling, compared with small and frequent N additions which were close to natural N deposition. Independently manipulated different rates (0-50 g N m–2yr–1) and frequencies (2 and 12 times per year) were selected to quantify the NFG abundances in Xilingol grassland, Inner Mongolia. The nifH, AOA-amoA, nirS, and nosZ gene abundances increased due to improved available N at low N rates, but were suppressed by salt toxicity and acidification at high N rates. The significant lower abundances of nifH, nirS, and nosZ were detected under the infrequent N addition plots due to stronger suppression by soil acidification and salt toxicity. The AOB-amoA gene abundance increased with increasing N rates and had higher abundance in the infrequent plots due to the higher NH4+-N concentration. The results demonstrated that small and frequent N addition should be employed to project the effects of N deposition on microbial functional groups as well as on N transformations.
View less >
View more >Nitrogen (N) deposition is increasing at unprecedentedly rate due to anthropogenic activities. The N deposition is altering the microbial activity and coupled C and N cycling through changing soil pH, N and carbon (C) availability. (1) N-related functional genes (NFGs) (N fixation, nifH; N mineralization, chiA; nitrification, AOA- and AOB-amoA;denitrification,narG,nirK,nirS and nosZ) regulate the main N transformation processes. However, empirically simulated N deposition experiments have been exclusively conducted through large and infrequent N fertilization, which may have caused contrasting effects on N cycling, compared with small and frequent N additions which were close to natural N deposition. Independently manipulated different rates (0-50 g N m–2yr–1) and frequencies (2 and 12 times per year) were selected to quantify the NFG abundances in Xilingol grassland, Inner Mongolia. The nifH, AOA-amoA, nirS, and nosZ gene abundances increased due to improved available N at low N rates, but were suppressed by salt toxicity and acidification at high N rates. The significant lower abundances of nifH, nirS, and nosZ were detected under the infrequent N addition plots due to stronger suppression by soil acidification and salt toxicity. The AOB-amoA gene abundance increased with increasing N rates and had higher abundance in the infrequent plots due to the higher NH4+-N concentration. The results demonstrated that small and frequent N addition should be employed to project the effects of N deposition on microbial functional groups as well as on N transformations.
View less >
Thesis Type
Thesis (PhD Doctorate)
Degree Program
Doctor of Philosophy (PhD)
School
School of Natural Sciences
Copyright Statement
The author owns the copyright in this thesis, unless stated otherwise.
Subject
Nitrogen deposition
Nitrogen in soils
Microbial activity in soils
Soil chemistry
Temperate grassland soils