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Jörgensen K, Clemmensen KE, Wallander H, Lindahl BD. Ectomycorrhizal fungi are more sensitive to high soil nitrogen levels in forests exposed to nitrogen deposition. THE NEW PHYTOLOGIST 2024; 242:1725-1738. [PMID: 38213001 DOI: 10.1111/nph.19509] [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: 09/18/2023] [Accepted: 12/11/2023] [Indexed: 01/13/2024]
Abstract
Ectomycorrhizal fungi are essential for nitrogen (N) cycling in many temperate forests and responsive to anthropogenic N addition, which generally decreases host carbon (C) allocation to the fungi. In the boreal region, however, ectomycorrhizal fungal biomass has been found to correlate positively with soil N availability. Still, responses to anthropogenic N input, for instance through atmospheric deposition, are commonly negative. To elucidate whether variation in N supply affects ectomycorrhizal fungi differently depending on geographical context, we investigated ectomycorrhizal fungal communities along fertility gradients located in two nemo-boreal forest regions with similar ranges in soil N : C ratios and inorganic N availability but contrasting rates of N deposition. Ectomycorrhizal biomass and community composition remained relatively stable across the N gradient with low atmospheric N deposition, but biomass decreased and the community changed more drastically with increasing N availability in the gradient subjected to higher rates of N deposition. Moreover, potential activities of enzymes involved in ectomycorrhizal mobilisation of organic N decreased as N availability increased. In forests with low external input, we propose that stabilising feedbacks in tree-fungal interactions maintain ectomycorrhizal fungal biomass and communities even in N-rich soils. By contrast, anthropogenic N input seems to impair ectomycorrhizal functions.
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Affiliation(s)
- Karolina Jörgensen
- Department of Soil and Environment, Swedish University of Agricultural Sciences, Box 7014, SE-750 07, Uppsala, Sweden
| | - Karina E Clemmensen
- Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Box 7026, SE-750 07, Uppsala, Sweden
| | - Håkan Wallander
- Department of Biology, Lund University, Sölvegatan 37, 223 26, Lund, Sweden
| | - Björn D Lindahl
- Department of Soil and Environment, Swedish University of Agricultural Sciences, Box 7014, SE-750 07, Uppsala, Sweden
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Argiroff WA, Zak DR, Pellitier PT, Upchurch RA, Belke JP. Decay by ectomycorrhizal fungi couples soil organic matter to nitrogen availability. Ecol Lett 2021; 25:391-404. [PMID: 34787356 DOI: 10.1111/ele.13923] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 10/21/2021] [Accepted: 10/30/2021] [Indexed: 01/04/2023]
Abstract
Interactions between soil nitrogen (N) availability, fungal community composition, and soil organic matter (SOM) regulate soil carbon (C) dynamics in many forest ecosystems, but context dependency in these relationships has precluded general predictive theory. We found that ectomycorrhizal (ECM) fungi with peroxidases decreased with increasing inorganic N availability across a natural inorganic N gradient in northern temperate forests, whereas ligninolytic fungal saprotrophs exhibited no response. Lignin-derived SOM and soil C were negatively correlated with ECM fungi with peroxidases and were positively correlated with inorganic N availability, suggesting decay of lignin-derived SOM by these ECM fungi reduced soil C storage. The correlations we observed link SOM decay in temperate forests to tradeoffs in tree N nutrition and ECM composition, and we propose SOM varies along a single continuum across temperate and boreal ecosystems depending upon how tree allocation to functionally distinct ECM taxa and environmental stress covary with soil N availability.
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Affiliation(s)
- William A Argiroff
- School for Environment and Sustainability, University of Michigan, Ann Arbor, Michigan, USA
| | - Donald R Zak
- School for Environment and Sustainability, University of Michigan, Ann Arbor, Michigan, USA.,Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Peter T Pellitier
- School for Environment and Sustainability, University of Michigan, Ann Arbor, Michigan, USA
| | - Rima A Upchurch
- School for Environment and Sustainability, University of Michigan, Ann Arbor, Michigan, USA
| | - Julia P Belke
- Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan, USA
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Argiroff WA, Zak DR, Upchurch RA, Salley SO, Grandy AS. Anthropogenic N deposition alters soil organic matter biochemistry and microbial communities on decaying fine roots. GLOBAL CHANGE BIOLOGY 2019; 25:4369-4382. [PMID: 31314956 DOI: 10.1111/gcb.14770] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 07/06/2019] [Indexed: 06/10/2023]
Abstract
Fine root litter is a primary source of soil organic matter (SOM), which is a globally important pool of C that is responsive to climate change. We previously established that ~20 years of experimental nitrogen (N) deposition has slowed fine root decay and increased the storage of soil carbon (C; +18%) across a widespread northern hardwood forest ecosystem. However, the microbial mechanisms that have directly slowed fine root decay are unknown. Here, we show that experimental N deposition has decreased the relative abundance of Agaricales fungi (-31%) and increased that of partially ligninolytic Actinobacteria (+24%) on decaying fine roots. Moreover, experimental N deposition has increased the relative abundance of lignin-derived compounds residing in SOM (+53%), and this biochemical response is significantly related to shifts in both fungal and bacterial community composition. Specifically, the accumulation of lignin-derived compounds in SOM is negatively related to the relative abundance of ligninolytic Mycena and Kuehneromyces fungi, and positively related to Microbacteriaceae. Our findings suggest that by altering the composition of microbial communities on decaying fine roots such that their capacity for lignin degradation is reduced, experimental N deposition has slowed fine root litter decay, and increased the contribution of lignin-derived compounds from fine roots to SOM. The microbial responses we observed may explain widespread findings that anthropogenic N deposition increases soil C storage in terrestrial ecosystems. More broadly, our findings directly link composition to function in soil microbial communities, and implicate compositional shifts in mediating biogeochemical processes of global significance.
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Affiliation(s)
- William A Argiroff
- School for Environment and Sustainability, University of Michigan, Ann Arbor, MI, USA
| | - Donald R Zak
- School for Environment and Sustainability, University of Michigan, Ann Arbor, MI, USA
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA
| | - Rima A Upchurch
- School for Environment and Sustainability, University of Michigan, Ann Arbor, MI, USA
| | - Sydney O Salley
- School for Environment and Sustainability, University of Michigan, Ann Arbor, MI, USA
| | - A Stuart Grandy
- Department of Natural Resources and the Environment, University of New Hampshire, Durham, NH, USA
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Zak DR, Argiroff WA, Freedman ZB, Upchurch RA, Entwistle EM, Romanowicz KJ. Anthropogenic N deposition, fungal gene expression, and an increasing soil carbon sink in the Northern Hemisphere. Ecology 2019; 100:e02804. [PMID: 31257580 DOI: 10.1002/ecy.2804] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 05/23/2019] [Accepted: 06/13/2019] [Indexed: 11/07/2022]
Abstract
Terrestrial ecosystems in the Northern Hemisphere are a globally important sink for anthropogenic CO2 in the Earth's atmosphere, slowing its accumulation as well as the pace of climate warming. With the use of a long-term field experiment (ca. 20 yr), we show that the expression of fungal class II peroxidase genes, which encode enzymes mediating the rate-limiting step of organic matter decay, are significantly downregulated (-60 to -80%) because of increases in anthropogenic N deposition; this response was consistent with a decline in extracellular peroxidase enzyme activity in soil, the slowing of organic-matter decay, and greater soil C storage. The reduction in peroxidase expression we document here occurred in the absence of a compositional shift in metabolically active fungi, indicating that an overall reduction in peroxidase expression underlies the slowing of decay and increases in soil C storage. This molecular mechanism has global implications for soil C storage and should be represented in coupled climate-biogeochemical models simulating the influence of enhanced terrestrial C storage on atmospheric CO2 and the future climate of an N-enriched Earth.
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Affiliation(s)
- Donald R Zak
- School for Environment and Sustainability, University of Michigan, Ann Arbor, Michigan, 48109, USA.,Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan, 48109, USA
| | - William A Argiroff
- School for Environment and Sustainability, University of Michigan, Ann Arbor, Michigan, 48109, USA
| | - Zachary B Freedman
- School for Environment and Sustainability, University of Michigan, Ann Arbor, Michigan, 48109, USA.,Division of Plant and Soil Sciences, West Virginia University, Morgantown, West Virginia, 26506, USA
| | - Rima A Upchurch
- School for Environment and Sustainability, University of Michigan, Ann Arbor, Michigan, 48109, USA
| | - Elizabeth M Entwistle
- School for Environment and Sustainability, University of Michigan, Ann Arbor, Michigan, 48109, USA.,Department of Biology, University of Alabama at Birmingham, Birmingham, Alabama, 35233, USA
| | - Karl J Romanowicz
- School for Environment and Sustainability, University of Michigan, Ann Arbor, Michigan, 48109, USA
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