Isotopic evidence for oligotrophication of terrestrial ecosystems.
Craine JMJonah Ventures, Boulder, CO, USA. josephmcraine@gmail.com.
Elmore AJAppalachian Laboratory, University of Maryland Center for Environmental Science, Frostburg, MD, USA.
Wang LDepartment of Earth Sciences, Indiana University-Purdue University Indianapolis, Indianapolis, IN, USA.
Aranibar JFacultad de Ciencias Exactas y Naturales (FCEN-UNCuyo), Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA-CONICET), Mendoza, Argentina.
Marañón-Jiménez SDepartment of Ecology, Faculty of Sciences, University of Granada, Granada, Spain.
McGlynn TPDepartment of Biology, California State University Dominguez Hills, Carson, CA, USA.
McNeil BEDepartment of Geology and Geography, West Virginia University, Morgantown, WV, USA.
Mosher SGDepartment of Geology , University of Cincinnati, Cincinnati, OH, USA.
Nelson DMAppalachian Laboratory, University of Maryland Center for Environmental Science, Frostburg, MD, USA.
Peri PLInstituto Nacional de Tecnología Agropecuaria, CONICET Universidad Nacional de la Patagonia Austral, Río Gallegos, Argentina.
Roggy JCINRA, UMR Ecologie des Forêts de Guyane, Campus Agronomique, Kourou, Guyane Française, France.
Sanders-DeMott RDepartment of Biology, Boston University, Boston, MA, USA.
Song MKey Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.
Szpak PDepartment of Anthropology, Trent University, Peterborough, Ontario, Canada.
Templer PHDepartment of Biology, Boston University, Boston, MA, USA.
Van der Colff DSouth African National Biodiversity Institute, Cape Town, South Africa.
Werner CEcosystem Physiology, University of Freiburg, Freiburg, Germany.
Xu XDepartment of Natural Resources and the Environment, University of New Hampshire, Durham, NH, USA.
Yang YKey Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China.
Yu GKey Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.
Zmudczyńska-Skarbek KFaculty of Biology, Department of Vertebrate Ecology and Zoology, University of Gdańsk, Gdańsk, Poland.
English
Human societies depend on an Earth system that operates within a constrained range of nutrient availability, yet the recent trajectory of terrestrial nitrogen (N) availability is uncertain. Examining patterns of foliar N concentrations and isotope ratios (δ15N) from more than 43,000 samples acquired over 37 years, here we show that foliar N concentration declined by 9% and foliar δ15N declined by 0.6-1.6‰. Examining patterns across different climate spaces, foliar δ15N declined across the entire range of mean annual temperature and mean annual precipitation tested. These results suggest declines in N supply relative to plant demand at the global scale. In all, there are now multiple lines of evidence of declining N availability in many unfertilized terrestrial ecosystems, including declines in δ15N of tree rings and leaves from herbarium samples over the past 75-150 years. These patterns are consistent with the proposed consequences of elevated atmospheric carbon dioxide and longer growing seasons. These declines will limit future terrestrial carbon uptake and increase nutritional stress for herbivores.