Ungulate populations are increasing across Europe with important implications for forest plant communities. Concurrently, atmospheric nitrogen (N) deposition continues to eutrophicate forests, threatening many rare, often more nutrient-efficient, plant species. These pressures may critically interact to shape biodiversity as in grassland and tundra systems, yet any potential interactions in forests remain poorly understood. Here, we combined vegetation resurveys from 52 sites across 13 European countries to test how changes in ungulate herbivory and eutrophication drive long-term changes in forest understorey communities. Increases in herbivory were associated with elevated temporal species turnover, however, identities of winner and loser species depended on N levels. Under low levels of N-deposition, herbivory favored threatened and small-ranged species while reducing the proportion of non-native and nutrient-demanding species. Yet all these trends were reversed under high levels of N-deposition. Herbivores also reduced shrub cover, likely exacerbating N effects by increasing light levels in the understorey. Eutrophication levels may therefore determine whether herbivory acts as a catalyst for the "N time bomb" or as a conservation tool in temperate forests.

Bialowieza Geobotanical Station Faculty of Biology University of Warsaw Sportowa 19 17 230 Bialowieza Poland

CIBIO Universidade do Porto Porto Portugal

Department of Biology University of West Florida Pensacola FL USA

Department of Botany Faculty of Biological Sciences University of Wroclaw Kanonia 6 8 PL 50 328 Wroclaw Poland

Department of Botany Faculty of Science Palacký University in Olomouc Olomouc Czech Republic

Department of Botany University of Wisconsin Madison Madison WI USA

Department of Forest Botany Dendrology and Geobiocoenology Faculty of Forestry and Wood Technology Mendel University in Brno Brno Czech Republic

Department of Plant Systematics Ecology and Theoretical Biology Institute of Biology Loránd Eötvös University Pázmány s 1 C H 1117 Budapest Hungary

Department of Silviculture and Forest Ecology of the Temperate Zones University of Göttingen Göttingen Germany

Environment Agency Austria Spittelauer Lände 5 1090 Vienna Austria

Faculty of Forestry and Wood Sciences Czech University of Life Sciences Prague Kamýcká 129 CZ 165 21 Praha 6 Suchdol Czech Republic

Faculty of Forestry Technical University in Zvolen Zvolen Slovakia

Forest and Nature Lab Ghent University Gontrode Belgium

German Centre for Integrative Biodiversity Research Halle Jena Leipzig Leipzig Germany

Institute of Biology Biotechnology and Environmental Protection Faculty of Natural Sciences University of Silesia Katowice Poland

Institute of Biology Leipzig University Leipzig Germany

Institute of Biology Martin Luther University Halle Wittenberg Halle Germany

Institute of Biology University of Pécs Pécs Hungary

Institute of Botany Czech Academy of Sciences Brno Czech Republic

Institute of Botany Faculty of Biology Jagiellonian University Kraków Poland

Institute of Botany of the Czech Academy of Sciences Zámek 1 CZ 252 43 Pruhonice Czech Republic

Institute of Ecology and Evolution Friedrich Schiller University Jena Jena Germany

Leibniz Centre for Agricultural Landscape Research Muencheberg Germany

Leibniz Centre for Agricultural Landscape Research Research Area 2 Müncheberg Germany

MTA DE Biodiversity and Ecosystem Services Research Group Egyetem tér 1 H 4032 Debrecen Hungary

Museum of Natural History University of Wroclaw Sienkiewicza 21 PL 50 335 Wroclaw Poland

National Forest Centre Zvolen Slovakia

Southern Swedish Forest Research Centre Swedish University of Agricultural Sciences Alnarp Sweden

University of Potsdam Institute of Biochemistry and Biology Maulbeerallee 3 14469 Potsdam Germany

UUMR CNRS 7058 Ecologie et Dynamique des Systèmes Anthropisés Université de Picardie Jules Verne 1 rue des Louvels F 80000 Amiens France

Zobrazit více v PubMed

FAO. Global forest resources assessment. www.fao.org/publications (2015).

Finlayson, M. et al. A Report of the Millennium Ecosystem Assessment. (The Cropper Foundation, 2005).

Lal, R., & Lorenz, K. In Recarbonizationof theBiosphere: Ecosystems and the Global Carbon Cycle (eds Lal, R., Lorenz, K., Hüttl, R. F., Schneider, B. U. & von Braun, J.) Ch. 9 (Springer, 2012).

Gilliam FS. Forest ecosystems of temperate climatic regions: from ancient use to climate change. N. Phytologist. 2016;212:871–887. doi: 10.1111/nph.14255. PubMed DOI

de Gouvenain, R. C. & Silander, J. A. Temperate forests in Reference Module in Life Sciences (Elsevier, 2017).

Keith SA, Newton AC, Morecroft MD, Bealey CE, Bullock JM. Taxonomic homogenization of woodland plant communities over 70 years. Proc. R. Soc. B: Biol. Sci. 2009;276:3539–3544. doi: 10.1098/rspb.2009.0938. PubMed DOI PMC

Rackham O. Ancient woodlands: modern threats. N. Phytologist. 2008;180:571–586. doi: 10.1111/j.1469-8137.2008.02579.x. PubMed DOI

Bernhardt-Römermann M, et al. Drivers of temporal changes in temperate forest plant diversity vary across spatial scales. Glob. Chang. Biol. 2015;21:3726–3737. doi: 10.1111/gcb.12993. PubMed DOI PMC

Waller DM, Alverson WS. The white-tailed deer: a keystone herbivore. Wildl. Soc. Bull. 1997;25:217–226.

Ramirez JI. Uncovering the different scales in deer–forest interactions. Ecol. Evol. 2021;11:5017–5024. doi: 10.1002/ece3.7439. PubMed DOI PMC

Rooney, T. P., Wiegmann, S. M., Rogers, D. A. & Waller, D. M. Biotic impoverishment and homogenization in unfragmented forest understory communities. Conserv. Biol.18, 787–798 (2004).

Stockton SA, Allombert S, Gaston AJ, Martin JL. A natural experiment on the effects of high deer densities on the native flora of coastal temperate rain forests. Biol. Conserv. 2005;126:118–128. doi: 10.1016/j.biocon.2005.06.006. DOI

Hegland SJ, Lilleeng MS, Moe SR. Old-growth forest floor richness increases with red deer herbivory intensity. Ecol. Manag. 2013;310:267–274. doi: 10.1016/j.foreco.2013.08.031. DOI

Simončič T, Bončina A, Jarni K, Klopčič M. Assessment of the long-term impact of deer on understory vegetation in mixed temperate forests. J. Veg. Sci. 2019;30:108–120. doi: 10.1111/jvs.12702. DOI

Vild O, et al. The paradox of long-term ungulate impact: increase of plant species richness in a temperate forest. Appl. Veg. Sci. 2017;20:282–292. doi: 10.1111/avsc.12289. PubMed DOI PMC

Russell FL, Zippin DB, Fowler NL. Effects of white-tailed deer (Odocoileus virginianus) on plants, plant populations and communities: a review. Am. Midl. Nat. 2001;146:1–26. doi: 10.1674/0003-0031(2001)146[0001:EOWTDO]2.0.CO;2. DOI

Öllerer K, et al. Beyond the obvious impact of domestic livestock grazing on temperate forest vegetation–A global review. Biol. Conserv. 2019;237:209–219. doi: 10.1016/j.biocon.2019.07.007. DOI

Borer ET, et al. Nutrients cause grassland biomass to outpace herbivory. Nat. Commun. 2020;11:1–8. doi: 10.1038/s41467-020-19870-y. PubMed DOI PMC

Kaarlejärvi E, Eskelinen A, Olofsson J. Herbivores rescue diversity in warming tundra by modulating trait-dependent species losses and gains. Nat. Commun. 2017;8:1–8. PubMed PMC

Simkin SM, et al. Conditional vulnerability of plant diversity to atmospheric nitrogen deposition across the United States. Proc. Natl Acad. Sci. USA. 2016;113:4086–4091. doi: 10.1073/pnas.1515241113. PubMed DOI PMC

Bobbink R, et al. Global assessment of nitrogen deposition effects on terrestrial plant diversity: A synthesis. Ecol. Appl. 2010;20:30–59. doi: 10.1890/08-1140.1. PubMed DOI

Reinecke J, Klemm G, Heinken T. Vegetation change and homogenization of species composition in temperate nutrient deficient Scots pine forests after 45 yr. J. Veg. Sci. 2014;25:113–121. doi: 10.1111/jvs.12069. DOI

Speed JDM, Austrheim G, Kolstad AL, Solberg EJ. Long-term changes in northern large-herbivore communities reveal differential rewilding rates in space and time. PLoS ONE. 2019;14:e0217166. doi: 10.1371/journal.pone.0217166. PubMed DOI PMC

Valente AM, Acevedo P, Figueiredo AM, Fonseca C, Torres RT. Overabundant wild ungulate populations in Europe: management with consideration of socio-ecological consequences. Mamm. Rev. 2020;50:353–366. doi: 10.1111/mam.12202. DOI

Linnell, J. D. C. et al. The challenges and opportunities of coexisting with wild ungulates in the human-dominated landscapes of Europe’s Anthropocene. Biol. Conserv.244, 108500 (2020).

Waller, D. M. The Herbaceous Layer in Forests of Eastern North America (ed. Gilliam, F.) Ch. 16 (Oxford Univ. Press, 2014).

Kerley, G. I. H., Kowalczyk, R. & Cromsigt, J. P. G. M. Conservation implications of the refugee species concept and the European bison: king of the forest or refugee in a marginal habitat? Ecography35, 519–529 (2011).

Svenning JC. A review of natural vegetation openness in north-western Europe. Biol. Conserv. 2002;104:133–148. doi: 10.1016/S0006-3207(01)00162-8. DOI

Sandom CJ, Ejrnaes R, Hansen MDD, Svenning JC. High herbivore density associated with vegetation diversity in interglacial ecosystems. Proc. Natl Acad. Sci. USA. 2014;111:4162–4167. doi: 10.1073/pnas.1311014111. PubMed DOI PMC

Ramirez JI, Jansen PA, den Ouden J, Goudzwaard L, Poorter L. Long-term effects of wild ungulates on the structure, composition and succession of temperate forests. Ecol. Manag. 2019;432:478–488. doi: 10.1016/j.foreco.2018.09.049. DOI

Ramirez JI, Jansen PA, Poorter L. Effects of wild ungulates on the regeneration, structure and functioning of temperate forests: A semi-quantitative review. Ecol. Manag. 2018;424:406–419. doi: 10.1016/j.foreco.2018.05.016. DOI

Albert A, et al. Seed dispersal by ungulates as an ecological filter: a trait-based meta-analysis. Oikos. 2015;124:1109–1120. doi: 10.1111/oik.02512. DOI

McNaughton SJ. Grazing lawns: on domesticated and wild grazers. Am. Nat. 1986;128:937–939. doi: 10.1086/284615. DOI

Cromsigt JPGM, Kuijper DPJ. Revisiting the browsing lawn concept: evolutionary Interactions or pruning herbivores? Perspect. Plant Ecol. 2011;13:207–215. doi: 10.1016/j.ppees.2011.04.004. DOI

Ramirez JI, et al. Temperate forests respond in a non-linear way to a population gradient of wild deer. Forestry. 2021;94:502–511. doi: 10.1093/forestry/cpaa049. DOI

Boulanger V, et al. Ungulates increase forest plant species richness to the benefit of non‐forest specialists. Glob. Chang. Biol. 2018;24:e485–e495. doi: 10.1111/gcb.13899. PubMed DOI

Kirby KJ. The impact of deer on the ground flora of British broadleaved woodland. Forestry. 2001;74:219–229. doi: 10.1093/forestry/74.3.219. DOI

Royo, A. A., Collins, R., Adams, M. B., Kirschbaum, C. & Carson, W. P. Pervasive interactions between ungulate browsers and disturbance regimes promote temperate forest herbaceous diversity. Ecology91, 93–105 (2010). PubMed

Happonen K, et al. Trait-based responses to land use and canopy dynamics modify long-term diversity changes in forest understories. Glob. Ecol. Biogeogr. 2021;30:1863–1875. doi: 10.1111/geb.13351. DOI

Peñuelas J, Sardans J. The global nitrogen-phosphorus imbalance. Science. 2022;375:266–267. doi: 10.1126/science.abl4827. PubMed DOI

Staude IR, et al. Replacements of small- by large-ranged species scale up to diversity loss in Europe’s temperate forest biome. Nat. Ecol. Evol. 2020;4:802–808. doi: 10.1038/s41559-020-1176-8. PubMed DOI

Newbold T, et al. Widespread winners and narrow-ranged losers: Land use homogenizes biodiversity in local assemblages worldwide. PLoS Biol. 2018;16:e2006841. doi: 10.1371/journal.pbio.2006841. PubMed DOI PMC

Verheyen K, et al. Driving factors behind the eutrophication signal in understorey plant communities of deciduous temperate forests. Br. Ecol. Soc. J. Ecol. 2012;100:352–365.

Gilliam FS. Response of the herbaceous layer of forest ecosystems to excess nitrogen deposition. J. Ecol. 2006;94:1176–1191. doi: 10.1111/j.1365-2745.2006.01155.x. DOI

de Schrijver A, et al. Cumulative nitrogen input drives species loss in terrestrial ecosystems. Glob. Ecol. Biogeogr. 2011;652:803–816. doi: 10.1111/j.1466-8238.2011.00652.x. DOI

de Frenne P, et al. Light accelerates plant responses to warming. Nat. Plants. 2015;1:15110. doi: 10.1038/nplants.2015.110. PubMed DOI

Baeten L, et al. Herb layer changes (1954-2000) related to the conversion of coppice-with-standards forest and soil acidification. Appl. Veg. Sci. 2009;12:187–197. doi: 10.1111/j.1654-109X.2009.01013.x. DOI

Becker T, Spanka J, Schröder L, Leuschner C. Forty years of vegetation change in former coppice-with-standards woodlands as a result of management change and N deposition. Appl. Veg. Sci. 2017;20:304–313. doi: 10.1111/avsc.12282. DOI

van Calster H, et al. Diverging effects of overstorey conversion scenarios on the understorey vegetation in a former coppice-with-standards forest. Ecol. Manag. 2008;256:519–528. doi: 10.1016/j.foreco.2008.04.042. DOI

Luyssaert S, et al. The European carbon balance. Part 3: forests. Glob. Chang. Biol. 2010;16:1429–1450. doi: 10.1111/j.1365-2486.2009.02056.x. DOI

Kirby KJ, et al. Five decades of ground flora changes in a temperate forest: the good, the bad and the ambiguous in biodiversity terms. Ecol. Manag. 2022;505:119896. doi: 10.1016/j.foreco.2021.119896. DOI

Hautier Y, Niklaus PA, Hector A. Competition for light causes plant biodiversity loss after eutrophication. Science. 2009;324:636–638. doi: 10.1126/science.1169640. PubMed DOI

Kowalczyk, R., Kamiński, T. & Borowik, T. Do large herbivores maintain open habitats in temperate forests? For. Ecol. Manag.494, 119310 (2021).

Dormann CF, et al. Plant species richness increases with light availability, but not variability, in temperate forests understorey. BMC Ecol. 2020;20:1–9. doi: 10.1186/s12898-020-00311-9. PubMed DOI PMC

Dirnböck T, et al. Forest floor vegetation response to nitrogen deposition in Europe. Glob. Chang. Biol. 2014;20:429–440. doi: 10.1111/gcb.12440. PubMed DOI

Perring MP, et al. Understanding context dependency in the response of forest understorey plant communities to nitrogen deposition. Environ. Pollut. 2018;242:1787–1799. doi: 10.1016/j.envpol.2018.07.089. PubMed DOI

Anderson TM, et al. Herbivory and eutrophication mediate grassland plant nutrient responses across a global climatic gradient. Ecology. 2018;99:822–831. doi: 10.1002/ecy.2175. PubMed DOI

Gough L, Grace JB. Herbivore effects on plant species density at varying productivity levels. Ecology. 1998;79:1586–1594. doi: 10.1890/0012-9658(1998)079[1586:HEOPSD]2.0.CO;2. DOI

Eskelinen, A., Harpole, W. S., Jessen, M.-T., Virtanen, R. & Hautier, Y. Light competition drives herbivore and nutrient effects on plant diversity. Nature611, 301–305 (2022). PubMed PMC

Knight TM, Dunn JL, Smith LA, Davis JA, Kalisz S. Deer facilitate invasive plant success in a Pennsylvania forest understory. Nat. Areas. 2009;29:110–116. doi: 10.3375/043.029.0202. DOI

Beguin, J., Pothier, D. & Côté, S. D. Deer browsing and soil disturbance induce cascading effects on plant communities: a multilevel path analysis. Ecol. Appl.21, 439–451 (2011). PubMed

Gilliam FS, et al. Twenty-five-year response of the herbaceous layer of a temperate hardwood forest to elevated nitrogen deposition. Ecosphere. 2016;7:e01250. doi: 10.1002/ecs2.1250. DOI

de Frenne P, et al. Microclimate moderates plant responses to macroclimate warming. Proc. Natl Acad. Sci. USA. 2013;110:18561–18565. doi: 10.1073/pnas.1311190110. PubMed DOI PMC

Hedwall, P. O. et al. Half a century of multiple anthropogenic stressors has altered northern forest understory plant communities. Ecol. Appl.29, e01874 (2019). PubMed

Perring MP, et al. Global environmental change effects on plant community composition trajectories depend upon management legacies. Glob. Chang. Biol. 2018;24:1722–1740. doi: 10.1111/gcb.14030. PubMed DOI

Boulanger V, et al. Decreasing deer browsing pressure influenced understory vegetation dynamics over 30 years. Ann. Sci. 2015;72:367–378. doi: 10.1007/s13595-014-0431-z. DOI

Bernes C, et al. Manipulating ungulate herbivory in temperate and boreal forests: effects on vegetation and invertebrates. A systematic review. Environ. Evid. 2018;7:1–32. doi: 10.1186/s13750-018-0125-3. DOI

Reimoser F. Steering the impacts of ungulates on temperate forests. J. Nat. Conserv. 2003;10:243–252. doi: 10.1078/1617-1381-00024. DOI

Vavra M, Parks CG, Wisdom MJ. Biodiversity, exotic plant species, and herbivory: the good, the bad, and the ungulate. Ecol. Manag. 2007;246:66–72. doi: 10.1016/j.foreco.2007.03.051. DOI

Depauw L, et al. Light availability and land-use history drive biodiversity and functional changes in forest herb layer communities. J. Ecol. 2020;108:1411–1425. doi: 10.1111/1365-2745.13339. DOI

Chevaux, L. et al. Effects of stand structure and ungulates on understory vegetation in managed and unmanaged forests. Ecol. Appl.32, e01874 (2022). PubMed

Gordon IJ. Browsing and grazing ruminants: are they different beasts? Ecol. Manag. 2003;181:13–21. doi: 10.1016/S0378-1127(03)00124-5. DOI

Brasseur B, et al. What deep‐soil profiles can teach us on deep‐time pH dynamics after land use change? Land Degrad. Dev. 2018;29:2951–2961. doi: 10.1002/ldr.3065. DOI

Schmitz A, et al. Responses of forest ecosystems in Europe to decreasing nitrogen deposition. Environ. Pollut. 2019;244:980–994. doi: 10.1016/j.envpol.2018.09.101. PubMed DOI

Dirnböck T, et al. Currently legislated decreases in nitrogen deposition will yield only limited plant species recovery in European forests. Environ. Res. Lett. 2018;13:125010. doi: 10.1088/1748-9326/aaf26b. DOI

Peterken, G. F. Natural Woodland: Ecology and Conservation in Northern Temperate Regions (Cambridge Univ. Press, 1996).

Chamberlain, S. A. & Boettiger, C. R Python, and Ruby clients for GBIF species occurrence data. preprint. PeerJ Preprints5, e3304v1 (2017).

Chamberlain SA, Szöcs E. taxize: taxonomic search and retrieval in R. F1000Res. 2013;2:191. doi: 10.12688/f1000research.2-191.v1. PubMed DOI PMC

Hédl R, Kopecký M, Komárek J. Half a century of succession in a temperate oakwood: from species-rich community to mesic forest. Divers Distrib. 2010;16:267–276. doi: 10.1111/j.1472-4642.2010.00637.x. DOI

Giménez-Anaya A, Herrero J, Rosell C, Couto S, García-Serrano A. Food habits of wild boars (Sus scrofa) in a Mediterranean coastal wetland. Wetlands. 2008;28:197–203. doi: 10.1672/07-18.1. DOI

Barrios-Garcia MN, Ballari SA. Impact of wild boar (Sus scrofa) in its introduced and native range: a review. Biol. Invasions. 2012;14:2283–2300. doi: 10.1007/s10530-012-0229-6. DOI

Andersen R, et al. An overview of the progress and challenges of peatland restoration in Western Europe. Restor. Ecol. 2017;25:271–282. doi: 10.1111/rec.12415. DOI

Faurby S, et al. PHYLACINE 1.2: the phylogenetic atlas of mammal macroecology. Ecology. 2018;99:2626. doi: 10.1002/ecy.2443. PubMed DOI

van den Berg LJL, et al. Evidence for differential effects of reduced and oxidised nitrogen deposition on vegetation independent of nitrogen load. Environ. Pollut. 2016;208:890–897. doi: 10.1016/j.envpol.2015.09.017. PubMed DOI

McNaughton SJ, Oesterheld M, Frank DA, Williams KJ. Ecosystem-level patterns of primary productivity and herbivory in terrestrial habitats. Nature. 1989;341:142–144. doi: 10.1038/341142a0. PubMed DOI

Koerner SE, et al. Change in dominance determines herbivore effects on plant biodiversity. Nat. Ecol. Evol. 2018;2:1925–1932. doi: 10.1038/s41559-018-0696-y. PubMed DOI

Fréjaville T, Garzón MB. The EuMedClim database: yearly climate data (1901-2014) of 1 km resolution grids for Europe and the Mediterranean Basin. Front. Ecol. Evol. 2018;6:1–5. doi: 10.3389/fevo.2018.00031. DOI

Al‐Yaari A, et al. Asymmetric responses of ecosystem productivity to rainfall anomalies vary inversely with mean annual rainfall over the conterminous United States. Glob. Chang. Biol. 2020;26:6959–6973. doi: 10.1111/gcb.15345. PubMed DOI

Szabó P, Hédl R. Advancing the integration of history and ecology for conservation. Conserv. Biol. 2011;25:680–687. doi: 10.1111/j.1523-1739.2011.01710.x. PubMed DOI

Hedges LV, Gurevitch J, Curtis PS. The meta-analysis of response ratios in experimental ecology. Spec. Feature Ecol. 1999;80:1150–1156.

Hillebrand H, et al. Biodiversity change is uncoupled from species richness trends: consequences for conservation and monitoring. J. Appl. Ecol. 2018;55:169–184. doi: 10.1111/1365-2664.12959. DOI

Holz H, Segar J, Valdez J, Staude IR. Assessing extinction risk across the geographic ranges of plant species in Europe. Plants People Planet. 2022;4:303–311. doi: 10.1002/ppp3.10251. DOI

Staude IR, et al. Directional turnover towards larger‐ranged plants over time and across habitats. Ecol. Lett. 2021;25:466–482. doi: 10.1111/ele.13937. PubMed DOI

Ellenberg, H., Weber, H. E., Düll, R., Wirth, V. & Werner, W. Zeigerwerte von Pflanzen in Mitteleuropa (Verlag Wrich Goltze, 2001).

Chytrý, M., Tichý, L., Dřevojan, P., Sádlo, J. & Zelený, D. Ellenbergtype indicator values for the Czech flora. Preslia90, 83–103 (2018).

Bürkner P-C. brms: an R package for Bayesian multilevel models using Stan. J. Stat. Softw. 2017;80:1–28. doi: 10.18637/jss.v080.i01. DOI

Brooks SP, Gelman A. General methods for monitoring convergence of iterative simulations. J. Comput. Graph. Stat. 1998;7:434–455.

Dushoff J, Kain MP, Bolker BM. I can see clearly now: reinterpreting statistical significance. Methods Ecol. Evol. 2019;10:756–759. doi: 10.1111/2041-210X.13159. DOI

Bradshaw L, Waller DM. Impacts of white-tailed deer on regional patterns of forest tree recruitment. Ecol. Manag. 2016;375:1–11. doi: 10.1016/j.foreco.2016.05.019. DOI

McGarvey, J. C., Bourg, N. A., Thompson, J. R., McShea, W. J. & Shen, X. Effects of twenty years of deer exclusion on woody vegetation at three life-history stages in a mid-atlantic temperate deciduous forest. Northeast. Nat. 20, 451–468 (2013).

Nuttle, T., Ristau, T. E. & Royo, A. A. Long-term biological legacies of herbivore density in a landscape-scale experiment: forest understoreys reflect past deer density treatments for at least 20 years. J. Ecol. 102, 221–228 (2013).

Long-term nitrogen deposition reduces the diversity of nitrogen-fixing plants