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Namuhan, Wang J, Yang G, Song Y, Yu Y, Wang J, Wang X, Shi Y, Shen Y, Han X, Wuyunna, Zhang H. Mechanisms of biodiversity loss under nitrogen enrichment: unveiling a shift from light competition to cation toxicity. THE NEW PHYTOLOGIST 2024; 243:1966-1979. [PMID: 38970455 DOI: 10.1111/nph.19941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Accepted: 06/16/2024] [Indexed: 07/08/2024]
Abstract
The primary mechanisms contributing to nitrogen (N) addition induced grassland biodiversity loss, namely light competition and soil cation toxicity, are often examined separately in various studies. However, their relative significance in governing biodiversity loss along N addition gradient remains unclear. We conducted a 4-yr field experiment with five N addition rates (0, 2, 10, 20, and 50 g N m-2 yr-1) and performed a meta-analysis using global data from 239 observations in N-fertilized grassland ecosystems. Results from our field experiment and meta-analysis indicate that both light competition and soil cation (e.g. Mn2+ and Al3+) toxicity contribute to plant diversity loss under N enrichment. The relative importance of these mechanisms varied with N enrichment intensity. Light competition played a more significant role in influencing species richness under low N addition (≤ 10 g m-2 yr-1), while cation toxicity became increasingly dominant in reducing biodiversity under high N addition (>10 g m-2 yr-1). Therefore, a transition from light competition to cation toxicity occurs with increasing N availability. These findings imply that the biodiversity loss along the N gradient is regulated by distinct mechanisms, necessitating the adoption of differential management strategies to mitigate diversity loss under varying intensities of N enrichment.
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Affiliation(s)
- Namuhan
- College of Environmental and Resource Sciences, Dalian Minzu University, Dalian, 116600, China
- College of Bioscience and Biotechnology, Shenyang Agricultural University, Shenyang, 110866, China
| | - Jing Wang
- School of Life Sciences, Institute of Life Science and Green Development, Hebei University, Baoding, 071002, China
| | - Guojiao Yang
- College of Ecology and Environment, Hainan University, Hainan, 570228, China
| | - Yantao Song
- College of Environmental and Resource Sciences, Dalian Minzu University, Dalian, 116600, China
| | - Yunguang Yu
- College of Environmental and Resource Sciences, Dalian Minzu University, Dalian, 116600, China
| | - Jidong Wang
- College of Environmental and Resource Sciences, Dalian Minzu University, Dalian, 116600, China
| | - Xiaoguang Wang
- College of Environmental and Resource Sciences, Dalian Minzu University, Dalian, 116600, China
| | - Yiping Shi
- College of Environmental and Resource Sciences, Dalian Minzu University, Dalian, 116600, China
| | - Yue Shen
- College of Environmental and Resource Sciences, Dalian Minzu University, Dalian, 116600, China
| | - Xingguo Han
- School of Life Sciences, Institute of Life Science and Green Development, Hebei University, Baoding, 071002, China
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Wuyunna
- College of Environmental and Resource Sciences, Dalian Minzu University, Dalian, 116600, China
- College of Bioscience and Biotechnology, Shenyang Agricultural University, Shenyang, 110866, China
| | - Haiyang Zhang
- School of Life Sciences, Institute of Life Science and Green Development, Hebei University, Baoding, 071002, China
- School of Life Sciences, Hebei Basic Science Center for Biotic Interaction, Hebei University, Baoding, 071002, China
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Assessing the roles of nitrogen, biomass, and niche dimensionality as drivers of species loss in grassland communities. Proc Natl Acad Sci U S A 2022; 119:e2112010119. [PMID: 35235460 PMCID: PMC8915794 DOI: 10.1073/pnas.2112010119] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Nutrient enrichment of natural ecosystems is a primary characteristic of the Anthropocene and a known cause of biodiversity loss, particularly in grasslands. In a global meta-analysis of 630 resource addition experiments, we conduct a simultaneous test of the three most prominent explanations of this phenomenon. Our results conclusively indicate that nitrogen is the leading cause of species loss. This result is important because of the increase in nitrogen deposition and the frequent use of nitrogen-based fertilizers worldwide. Our findings provide global-scale, experimental evidence that minimizing nitrogen inputs to ecological systems may help to conserve the diversity of grassland ecosystems. Eutrophication is a major driver of species loss in plant communities worldwide. However, the underlying mechanisms of this phenomenon are controversial. Previous studies have raised three main explanations: 1) High levels of soil resources increase standing biomass, thereby intensifying competitive interactions (the “biomass-driven competition hypothesis”). 2) High levels of soil resources reduce the potential for resource-based niche partitioning (the “niche dimension hypothesis”). 3) Increasing soil nitrogen causes stress by changing the abiotic or biotic conditions (the “nitrogen detriment hypothesis”). Despite several syntheses of resource addition experiments, so far, no study has tested all of the hypotheses together. This is a major shortcoming, since the mechanisms underlying the three hypotheses are not independent. Here, we conduct a simultaneous test of the three hypotheses by integrating data from 630 resource addition experiments located in 99 sites worldwide. Our results provide strong support for the nitrogen detriment hypothesis, weaker support for the biomass-driven competition hypothesis, and negligible support for the niche dimension hypothesis. The results further show that the indirect effect of nitrogen through its effect on biomass is minor compared to its direct effect and is much larger than that of all other resources (phosphorus, potassium, and water). Thus, we conclude that nitrogen-specific mechanisms are more important than biomass or niche dimensionality as drivers of species loss under high levels of soil resources. This conclusion is highly relevant for future attempts to reduce biodiversity loss caused by global eutrophication.
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Tan Q, Hao T, Gao S, Liu X, Wang G, Yu Q. Soil organic carbon turnover recovers faster than plant diversity in the grassland when high nitrogen addition is ceased: Derived from soil 14C evidences. Glob Ecol Conserv 2020. [DOI: 10.1016/j.gecco.2020.e01229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Chen S, Hao T, Goulding K, Misselbrook T, Liu X. Impact of 13-years of nitrogen addition on nitrous oxide and methane fluxes and ecosystem respiration in a temperate grassland. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2019; 252:675-681. [PMID: 31185356 DOI: 10.1016/j.envpol.2019.03.069] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Revised: 02/23/2019] [Accepted: 03/17/2019] [Indexed: 06/09/2023]
Abstract
Nitrogen (N) fertilizer application and atmospheric N deposition will profoundly affect greenhouse gas (GHGs) emissions, especially nitrous oxide (N2O) and methane (CH4) fluxes and ecosystem respiration (Re, i.e. CO2 emissions). However, the impacts of long-term N inputs and the often associated N-induced soil acidification on GHG fluxes in arid and semi-arid ecosystems, especially temperate grasslands, are still uncertain. An in situ experiment was conducted to investigate the effect of long-term (13-years) N addition on N2O and CH4 fluxes and Re from a temperate grassland in Inner Mongolia, northeast China, from April 2017 to October 2018. Soil pH values in the 0-5 cm layer receiving 120 (N120) and 240 (N240) kg N ha-1 decreased from 7.12 to 4.37 and 4.18, respectively, after 13 years of N inputs. Soil CH4 uptake was significantly reduced, but N2O emission was enhanced significantly by N addition. However, N addition had no impact on Re. Structural Equation Modeling indicated that soil NH4+-N content was the dominant control of N2O emissions, but with less effect of the decreasing pH. In contrast, CH4 uptake was generally controlled by soil pH and NO3--N content, and Re by forb biomass. The measured changes in N2O and CH4 fluxes and Re from temperate grassland will have a profoundly impact on climate change.
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Affiliation(s)
- Si Chen
- College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China
| | - Tianxiang Hao
- College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China
| | - Keith Goulding
- Sustainable Agricultural Sciences Department, Rothamsted Research, Harpenden, AL5 2JQ, UK
| | | | - Xuejun Liu
- College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China.
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Tan Q, Wang G, Liu X, Hao T, Tan W. Responses of soil organic carbon turnover to nitrogen deposition are associated with nitrogen input rates: Derived from soil 14C evidences. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2018; 238:500-507. [PMID: 29604563 DOI: 10.1016/j.envpol.2018.03.071] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Revised: 03/20/2018] [Accepted: 03/20/2018] [Indexed: 06/08/2023]
Abstract
Elevated atmospheric nitrogen (N) deposition has exerted profound influences on ecosystems. Understanding the effects of N deposition on the dynamics of soil organic carbon (SOC) is important in the studies of global carbon cycle. Although many studies have examined the effects of N deposition on SOC turnover using N addition experiments, the effects were reported to be different across studies. Thus, we lack a predictive understanding of how SOC turnover respond to atmospheric N deposition. The inconsistent results could be associated with ecosystem types and N addition rates. This study mainly wants to confirm the argument that the response of SOC turnover to N deposition is related with N input rates. We conducted a field experiment with multiple N addition levels (0, 3, 6, 12, and 24 g N m-2·yr-1) in Inner Mongolia Grassland, China. To better reveal the responses of SOC turnover to N enrichment, this study measured the soil 14C contents, because it can indicate SOC turnover directly. Compared with the control treatment (0 g N m-2·yr-1), N addition inhibits SOC turnover at the addition rate of 3 g N m-2·yr-1, whereas SOC turnover is not affected when N addition rate was 6, 12, and 24 g N m-2·yr-1. Our results suggest that N input rates affect the responses of SOC turnover to N enrichment. Thus, this study can confirm the argument mentioned above. Based on this study, it should be considered in the climate prediction model that varied atmospheric N deposition levels across regions may have different impacts on local SOC turnover. In addition, we also carried out a soil incubation to compare between the results obtained in incubation and that in 14C measurements. Two results are found to be inconsistent with each other. This indicates that soil respiration from incubation experiments could not comprehensively assess the effects of N deposition on SOC turnover.
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Affiliation(s)
- Qiqi Tan
- Beijing Key Laboratory of Farmland Soil Pollution Prevention-control and Remediation, Department of Environmental Sciences and Engineering, College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China
| | - Guoan Wang
- Beijing Key Laboratory of Farmland Soil Pollution Prevention-control and Remediation, Department of Environmental Sciences and Engineering, College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China.
| | - Xuejun Liu
- Beijing Key Laboratory of Farmland Soil Pollution Prevention-control and Remediation, Department of Environmental Sciences and Engineering, College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China
| | - Tianxiang Hao
- Beijing Key Laboratory of Farmland Soil Pollution Prevention-control and Remediation, Department of Environmental Sciences and Engineering, College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China
| | - Wenbing Tan
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China
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