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Su J, Ma Y, Xu Z, Liu Y, Zhao Y, Li X, Hu Y. Cumulative effects of experimental nitrogen deposition on soil chemistry in a desert steppe: A 12-year field study. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 950:175388. [PMID: 39122050 DOI: 10.1016/j.scitotenv.2024.175388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2024] [Revised: 07/10/2024] [Accepted: 08/06/2024] [Indexed: 08/12/2024]
Abstract
Although the effects of human-enhanced atmospheric nitrogen (N) deposition are well documented, the response of dryland soils to N deposition remains unclear owing to the divergence in hydrological outputs and soil heterogeneity. We selected a typical desert steppe in western China to simulate the effects of long-term N deposition by applying 0 (CK), 3.5, 7, and 14 g N m-2 yr-1 for 12 consecutive years. We found that, compared with the CK plots, the total N content of the upper (0-10 cm) and lower (10-20 cm) soil layers in fertilized plots increased by 8.3-14.6 % and 2.4-8.2 %, respectively. Correspondingly, the available, NH4+-, and NO3--N contents in the upper soil significantly increased by 25.5-68.3 %. However, in the lower soil, available and NO3--N contents were significantly lower than those in the CK plots, and their variation trend was opposite to that of NH4+-N, implying N turnover and leaching. As a result, the upper and lower soil pH in fertilized plots significantly decreased by 0.36-0.53 and 0.31-0.37 units; however, their CaCO3 content significantly increased by 9.8-22.8 % and 7.2-30.3 %, respectively. The total phosphorus (P) content in the upper and lower soil layers in fertilized plots significantly increased and decreased by 3.6-51.3 % and 16.7-62.5 %, respectively, however, both significantly decreased along the N fertilization gradient. Furthermore, the upper and lower soil organic carbon (SOC) content in the fertilized plots significantly increased by 57.7-78.1 % and 19.2-27.4 %, respectively. Pearson's correlation analysis revealed that available soil P was significantly negatively correlated with plant shoot Mn content (a proxy for rhizosphere carboxylates), whereas dissolved OC, SOC, and CaCO3 were significantly positively correlated, suggesting that Ca cycling is involved in P cycling and SOC sequestration. Our study suggests that long-term N input exacerbates P limitation in desert steppes, however, enhances SOC sequestration.
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Affiliation(s)
- Jieqiong Su
- Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands and Shapotou Desert Research and Experiment Station, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
| | - Ying Ma
- Institute of Agricultural Resources and Environment, Ningxia Academy of Agriculture and Forestry Sciences, Yinchuan 750002, China
| | - Zhihao Xu
- MOE Key Laboratory of Western China's Environmental Systems and Gansu Key Laboratory for Environmental Pollution Prediction and Control, College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China
| | - Yinzhu Liu
- MOE Key Laboratory of Western China's Environmental Systems and Gansu Key Laboratory for Environmental Pollution Prediction and Control, College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China
| | - Yang Zhao
- Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands and Shapotou Desert Research and Experiment Station, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Xinrong Li
- Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands and Shapotou Desert Research and Experiment Station, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Yahu Hu
- MOE Key Laboratory of Western China's Environmental Systems and Gansu Key Laboratory for Environmental Pollution Prediction and Control, College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China.
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Osborne BB, Bestelmeyer BT, Currier CM, Homyak PM, Throop HL, Young K, Reed SC. The consequences of climate change for dryland biogeochemistry. THE NEW PHYTOLOGIST 2022; 236:15-20. [PMID: 35706381 DOI: 10.1111/nph.18312] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 06/05/2022] [Indexed: 06/15/2023]
Abstract
Drylands, which cover > 40% of Earth's terrestrial surface, are dominant drivers of global biogeochemical cycling and home to more than one third of the global human population. Climate projections predict warming, drought frequency and severity, and evaporative demand will increase in drylands at faster rates than global means. As a consequence of extreme temperatures and high biological dependency on limited water availability, drylands are predicted to be exceptionally sensitive to climate change and, indeed, significant climate impacts are already being observed. However, our understanding and ability to forecast climate change effects on dryland biogeochemistry and ecosystem functions lag behind many mesic systems. To improve our capacity to forecast ecosystem change, we propose focusing on the controls and consequences of two key characteristics affecting dryland biogeochemistry: (1) high spatial and temporal heterogeneity in environmental conditions and (2) generalized resource scarcity. In addition to climate change, drylands are experiencing accelerating land-use change. Building our understanding of dryland biogeochemistry in both intact and disturbed systems will better equip us to address the interacting effects of climate change and landscape degradation. Responding to these challenges will require a diverse, globally distributed and interdisciplinary community of dryland experts united towards better understanding these vast and important ecosystems.
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Affiliation(s)
- Brooke B Osborne
- Southwest Biological Science Center, US Geological Survey, Moab, UT, 84532, USA
| | - Brandon T Bestelmeyer
- Jornada Experimental Range, US Department of Agriculture, Las Cruces, NM, 88003, USA
| | - Courtney M Currier
- School of Life Sciences, Arizona State University, Tempe, AZ, 85287, USA
| | - Peter M Homyak
- Department of Environmental Sciences, University of California, Riverside, CA, 92521, USA
| | - Heather L Throop
- School of Life Sciences, Arizona State University, Tempe, AZ, 85287, USA
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, 85287, USA
| | - Kristina Young
- Department of Extension Agriculture and Natural Resources, Utah State University, Moab, UT, 84532, USA
| | - Sasha C Reed
- Southwest Biological Science Center, US Geological Survey, Moab, UT, 84532, USA
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Rong X, Zhou X, Li X, Yao M, Lu Y, Xu P, Yin B, Li Y, Aanderud ZT, Zhang Y. Biocrust diazotrophs and bacteria rather than fungi are sensitive to chronic low N deposition. Environ Microbiol 2022; 24:5450-5466. [PMID: 35844197 DOI: 10.1111/1462-2920.16095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 06/03/2022] [Indexed: 11/03/2022]
Abstract
Anthropogenic long-term nitrogen (N) deposition may dramatically impact biocrusts due to the overarching N limitation of soil biota in deserts. Even low levels of N may reach a critical loading threshold altering biocrust constituents and function. To identify the impact of chronic and continuous low levels of N deposition on biocrusts, we created a realistic gradient mirroring anthropogenic N addition rate (2:1 NH4 + : NO3 - rates: 0.3, 0.5, 1.0, 1.5, 3 g N m-2 yr-1 ) and measured the response of bacteria and fungi within cyanobacterial-dominated biocrusts over 8 years in a temperate desert, the Gurbantunggut Desert, China. We found that once N deposition reached 1.5 g N m-2 yr-1 biocrust bacterial communities, including diazotrophs, were altered while no such tipping point existed for fungi. Above the threshold, bacterial richness was enhanced, the relative abundance of Chloroflexi, FBP and Gemmatimonadetes was elevated, and diazotrophs shifted from being dominated by Nostocaceae and Scytonemataceae (Cyanobacteria) to free-living Bradyrhizobiaceae (Alphaproteobacteria). Alternatively, the relative recovery of a few fungal species within the Lecanorales, Pleosporales and Verrucariales became either enriched or diminished due to N deposition. The chronic addition of N resulted in a dense and interconnected bacterial co-occurrence network that accentuated a functional shift from networks dominated by phototrophic species within the Nostocaceae, Xenococcaceae, Phormidiaceae and Scytonemataceae (Cyanobacteria) to ammonia-oxidizing species within the Nitrosomonadaceae (Betaproteobacteria) and nitrifying bacteria [i.e. Nitrospiraceae (Nitrospirae)]. Based on structural equation models, the effects of N additions on biocrust constituents were imposed through indirect effects on pH, soil electrical conductivity and ammonium concentrations. In summary, biocrust constituents are generally insensitive to chronic low levels of N depositions until rates reach above 1.5 g N m-2 yr-1 with diazotrophs being the most sensitive biocrust constituents followed by bacteria and finally fungi. Ultimately once the threshold is reached N deposition favours biocrust constituents utilizing inorganic N and other C sources over relying on phototrophic and/or N-fixing cyanobacteria for C and N.
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Affiliation(s)
- Xiaoying Rong
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, China
| | - Xiaobing Zhou
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, China
| | - Xiangzhen Li
- Key Laboratory of Environmental and Applied Microbiology, Chinese Academy of Sciences, and Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China
| | - Minjie Yao
- College of Resources and Environment, Fujian Agriculture and Forest University, Fuzhou, China
| | - Yongxing Lu
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, China.,University of the Chinese Academy of Sciences, Beijing, China
| | - Peng Xu
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, China.,University of the Chinese Academy of Sciences, Beijing, China
| | - Benfeng Yin
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, China
| | - Yonggang Li
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, China
| | - Zachary T Aanderud
- Department of Plant and Wildlife Sciences, Brigham Young University, Provo, Utah, USA
| | - Yuanming Zhang
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, China
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Choi RT, Reed SC, Tucker CL. Multiple resource limitation of dryland soil microbial carbon cycling on the Colorado Plateau. Ecology 2022; 103:e3671. [PMID: 35233760 DOI: 10.1002/ecy.3671] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 10/20/2021] [Accepted: 11/11/2021] [Indexed: 11/06/2022]
Abstract
Understanding interactions among biogeochemical cycles is increasingly important as anthropogenic alterations of global climate and of carbon (C), nitrogen (N), and phosphorus (P) cycles interactively affect the Earth system. Ecosystem processes in the dryland biome, which makes up over 40% of Earth's terrestrial surface, are often distinctively sensitive to small changes in resource availability, likely because levels of many resources are low. However, data also suggest that simultaneous changes in the availability of multiple resources may be necessary to affect a response in these low-resource systems, offering an opportunity to test patterns and controls of co-limitation, serial limitation, and individual limitation in soil environments. While drylands may play a governing role in key aspects of Earth's C cycle, and while an improved understanding of resource limitation could substantially improve our forecasts of dryland responses to change, our understanding of interacting controls on soil C cycle processes remains notably poor in these dry systems. Here, we address multiple fundamental hypotheses of resource controls over ecosystem function to test how water, C, N, and P regulate soil C cycling individually and interactively in a dryland ecosystem on the Colorado Plateau. Using a series of laboratory incubations, we found that while water, C, and N limited C cycling through serial limitation, water alone resulted in an extremely small respiratory response from target organisms, whereas water + C resulted in a dramatic increase in soil C cycling, suggesting a degree of functional co-limitation. Nitrogen additions alone resulted in no changes to soil C cycling, but when N was added in concert with water and C, N greatly increased soil C cycling rates relative to additions of water and C without N. Phosphorus additions had no effect on the C cycle either alone or synergistically. These patterns were consistent with the stoichiometry of the system, and interactions among resources were surprising in ways that inform our understanding of critical theories in ecology, such as the Transient Maxima Hypothesis, supporting the suggestion that multiple resource limitation explains pulse-dynamic C cycling in drylands better than water limitation alone.
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Affiliation(s)
- Ryan T Choi
- Department of Wildland Resources, Utah State University and the Ecology Center, Logan, UT, USA
| | - Sasha C Reed
- U.S. Geological Survey, Southwest Biological Science Center, Moab, UT, USA
| | - Colin L Tucker
- U.S. Geological Survey, Southwest Biological Science Center, Moab, UT, USA.,U.S.D.A Forest Service, Northern Research Station, Houghton, MI, USA
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Bebber DP. The gap between atmospheric nitrogen deposition experiments and reality. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 801:149774. [PMID: 34470727 DOI: 10.1016/j.scitotenv.2021.149774] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 08/14/2021] [Accepted: 08/16/2021] [Indexed: 06/13/2023]
Abstract
Anthropogenic activities have dramatically altered the global nitrogen (N) cycle. Atmospheric N deposition, primarily from combustion of biomass and fossil fuels, has caused acidification of precipitation and freshwater, and triggered intense research into ecosystem responses to this pollutant. Experimental simulations of N deposition have been the main scientific tool to understand ecosystem responses, revealing dramatic impacts on soil microbes, plants, and higher trophic levels. However, comparison of the experimental treatments applied in the vast majority of studies with observational and modelled N deposition reveals a wide gulf between research and reality. While the majority of experimental treatments exceed 100 kg N ha-1 y-1, global median land surface deposition rates are around 1 kg N ha-1 y-1 and only exceed 10 kg N ha-1 y-1 in certain regions, primarily in industrialized areas of Europe and Asia and particularly in forests. Experimental N deposition treatments are in fact similar to mineral fertilizer application rates in agriculture. Some ecological guilds, such as saprotrophic fungi, are highly sensitive to N and respond differently to low and high N availability. In addition, very high levels of N application cause changes in soil chemistry, such as acidification, meaning that unrealistic experimental treatments are unlikely to reveal true ecosystem responses to N. Hence, despite decades of research, past experiments can tell us little about how the biosphere has responded to anthropogenic N deposition. A new approach is required to improve our understanding of this important phenomenon. First, characterization of N response functions using observed N deposition gradients. Second, application of experimental N addition gradients at realistic levels over long periods to detect cumulative effects. Third, application of non-linear meta-regressions to detect non-linear responses in meta-analyses of experimental studies.
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Affiliation(s)
- Daniel P Bebber
- Department of Biosciences, University of Exeter, Exeter, UK.
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