title: Nutrient enrichment modifies temperature-biodiversity relationships in large-scale field experiments.
abstract: Climate effects and human impacts, that is, nutrient enrichment, simultaneously drive spatial biodiversity patterns. However, there is little consensus about their independent effects on biodiversity. Here we manipulate nutrient enrichment in aquatic microcosms in subtropical and subarctic regions (China and Norway, respectively) to show clear segregation of bacterial species along temperature gradients, and decreasing alpha and gamma diversity toward higher nutrients. The temperature dependence of species richness is greatest at extreme nutrient levels, whereas the nutrient dependence of species richness is strongest at intermediate temperatures. For species turnover rates, temperature effects are strongest at intermediate and two extreme ends of nutrient gradients in subtropical and subarctic regions, respectively. Species turnover rates caused by nutrients do not increase toward higher temperatures. These findings illustrate direct effects of temperature and nutrients on biodiversity, and indirect effects via primary productivity, thus providing insights into how nutrient enrichment could alter biodiversity under future climate scenarios.
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academic of Sciences, Nanjing 210008, China.|Department of Geosciences and Geography, University of Helsinki, Helsinki FIN-00014, Finland.
authors.forename: Jianjun
authors.identifier: 0000-0001-7039-7136
authors.initials: J
authors.lastname: Wang
authors.affiliation: Jiangsu Key Laboratory for Molecular and Medical Biotechnology, Nanjing Normal University, Nanjing 210023, China.
authors.forename: Feiyan
authors.initials: F
authors.lastname: Pan
authors.affiliation: Department of Geosciences and Geography, University of Helsinki, Helsinki FIN-00014, Finland.
authors.forename: Janne
authors.initials: J
authors.lastname: Soininen
authors.affiliation: Finnish Environment Institute, Natural Environment Centre, Biodiversity, Oulu FI-90014, Finland.
authors.forename: Jani
authors.initials: J
authors.lastname: Heino
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academic of Sciences, Nanjing 210008, China.
authors.forename: Ji
authors.initials: J
authors.lastname: Shen