4 results on '"Huajun Fang"'
Search Results
2. Contrasting effects of NH4+ and NO3− amendments on amount and chemical characteristics of different density organic matter fractions in a boreal forest soil
- Author
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Shulan Cheng, Jing Geng, Huajun Fang, Guirui Yu, Shun He, Jiangzhou Xia, Jing Tian, and Guangxia Yu
- Subjects
chemistry.chemical_classification ,Biogeochemical cycle ,010504 meteorology & atmospheric sciences ,Soil organic matter ,Soil Science ,chemistry.chemical_element ,Soil chemistry ,04 agricultural and veterinary sciences ,Soil carbon ,01 natural sciences ,Nitrogen ,chemistry ,Environmental chemistry ,Soil water ,040103 agronomy & agriculture ,Humin ,0401 agriculture, forestry, and fisheries ,Organic matter ,0105 earth and related environmental sciences - Abstract
Elevated nitrogen (N) deposition variously affects the soil carbon (C) cycle. It is not clear how deposited NH 4 + and NO 3 − divergently affect the amount and stability of soil organic C (SOC) in the N-limiting forests. A multi-form N addition experiment was conducted in a boreal forest in the Great Khingan mountain in 2010. Three fertilizers, NH 4 Cl, KNO 3 and NH 4 NO 3 , were applied at four rates of 0, 10, 20, and 40 kg N ha − 1 yr − 1 . Solid-state 13 C nuclear magnetic resonance spectroscopy and elemental analysis were used to determine the chemical structure and C contents in bulk soils and/or two density fractions ( − 3 light fraction and > 1.70 g cm − 3 heavy fraction). NH 4 Cl addition significantly decreased the SOC contents in the organic layer by 28.35% to 54.23%, but KNO 3 addition significantly increased the SOC contents in the organic layer and mineral layer by 26.53% and 87.44%, respectively. Nitrogen addition rates significantly influenced the degradability (alkyl-C/O-alkyl-C) and hydrophobicity ((alkyl C + aromatic C)/(O-alkyl C + carboxyl C)) of light and heavy fractions, whereas N addition forms only impacted their aromaticity (aromatic C/(aromatic C + alkyl C + O-alkyl C)). The movement between residue-C and stable humin fraction, as well as the chemical stability of SOM could profoundly affect the storage of SOC under N enrichment. Overall, added NH 4 + and NO 3 − differently affect C sequestration in the N-limiting forest soils. This should be differentiated in the biogeochemical models of C N cycle coupling.
- Published
- 2017
3. Organic nitrogen addition causes decoupling of microbial nitrogen cycles by stimulating gross nitrogen transformation in a temperate forest soil
- Author
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Mingzhu Lu, Y. Li, Jinbo Zhang, Huajun Fang, Yan Yang, Christoph Müller, Shulan Cheng, and Meng Xu
- Subjects
Chemistry ,Heterotroph ,Soil Science ,Temperate forest ,chemistry.chemical_element ,04 agricultural and veterinary sciences ,Mineralization (soil science) ,010501 environmental sciences ,01 natural sciences ,Nitrogen ,Environmental chemistry ,Soil water ,040103 agronomy & agriculture ,0401 agriculture, forestry, and fisheries ,Nitrification ,Autotroph ,Nitrogen cycle ,0105 earth and related environmental sciences - Abstract
External inorganic and organic nitrogen (N) inputs can contrastingly affect the transformation and availability of N in forest soils. Studies have mainly focused on the effects of inorganic N enrichment, whereas little is known about the effects of organic N input on soil gross N transformation and the underlying microbial mechanisms. Here we conducted a laboratory 15N tracing study in a temperate needle-broadleaved mixed forest with a fertilization rate of 0, 20, 60, and 120 kg urea-N ha−1 yr−1 over three years. We investigated the key drivers of soil N transformation processes using a 15N tracing model in the context of selected soil chemical properties and microbial characteristics. Urea addition did not change soil gross N mineralization rates, while stimulating mineralization of labile organic N (MNlab). Urea addition at a rate of 120 kg N ha−1 yr−1 significantly increased autotrophic nitrification and gross nitrification rates by 88% and 96%, respectively. In contrast, all the three levels of urea addition significantly reduced gross microbial N immobilization by 28% to 52%, leading to an increase in the accumulation of soil NO3−-N in the top 10 cm soil layer by 38% to 88%. The changes in autotrophic nitrification were primarily driven by acid-tolerant ammonia-oxidizing archaea (AOA). Fungi were responsible for the change in heterotrophic nitrification under organic N enrichment. Gross N transformation rates were predominately regulated by AOA and fungal abundances as well as soil NO3−-N content under high level of organic N addition. The response of soil N transformation to exogenous organic N input depended on N addition level with the threshold rate being estimated to be 60–120 kg N ha−1 yr−1. All lines of evidence showed that the temperate needle-broadleaved mixed forest is moving towards an opener microbial N cycle under elevated organic N deposition. Our finding suggests that the effect of organic N input on soil gross N transformation is different from that of inorganic N input, which should be considered in ecosystem process models.
- Published
- 2021
4. Low-level nitrogen deposition significantly inhibits methane uptake from an alpine meadow soil on the Qinghai–Tibetan Plateau
- Author
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Xusheng Dang, Yingnian Li, Yongsheng Wang, Shulan Cheng, Linsen Li, Guirui Yu, Minjie Xu, Huajun Fang, and Jules Cooch
- Subjects
Water balance ,chemistry ,Agronomy ,Atmospheric methane ,Soil pH ,Soil Science ,chemistry.chemical_element ,Terrestrial ecosystem ,Soil fertility ,complex mixtures ,Nitrogen ,Water content ,Deposition (chemistry) - Abstract
It is crucial to understand the effects of enhanced nitrogen (N) deposition on soil methane (CH4) uptake to develop a better comprehension of carbon (C) dynamics in terrestrial ecosystems. A two-year field study was conducted to assess the effects of various forms of N (NH4+ and N-3(-)) and associated N deposition rates (0, 10,20 and 40 kg N ha(-1) yr(-1)) on alpine meadow soil CH4 fluxes on the Qinghai-Tibetan Plateau, China. Soil CH4 fluxes, soil temperature, and soil moisture were monitored weekly using the static chamber technique and gas chromatography. Soil inorganic N pools, soil pH and aboveground biomass were measured monthly to examine the key controlling factors of soil CH4 flux. Our results showed that N addition significantly promoted plant growth and changed soil water-filled pore space (WFPS), but did not alter soil inorganic N storages over the short term. Low rates of N addition significantly decreased the seasonal amount of CH4 uptake by 8.6% compared with the control. Soil CH4 fluxes were mainly determined by soil WFPS, followed by inorganic N availability. N addition increased the contribution of soil WFPS, pH and soil NO3- storage. The observed reduction in CH4 uptake caused by N addition may be largely due to a decrease in physical diffusion, as the biochemical inhibition effects on methanotrophic bacteria are minor. These results suggest that soil inorganic N is a regulatory factor of soil CH4 uptake, and its promotion or inhibition to soil CH4 uptake depends on the N status in terrestrial ecosystems. (C) 2013 Elsevier B.V. All rights reserved.
- Published
- 2014
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