Increased nutrient inputs due to anthropogenic activity are expected to increase primary productivity across terrestrial ecosystems, but changes in allocation aboveground versus belowground with nutrient addition have different implications for soil carbon (C) storage. Thus, given that roots are major contributors to soil C storage, understanding belowground net primary productivity (BNPP) and biomass responses to changes in nutrient availability is essential to predicting carbon–climate feedbacks in the context of interacting global environmental changes. To address this knowledge gap, we tested whether a decade of nitrogen (N) and phosphorus (P) fertilization consistently influenced aboveground and belowground biomass and productivity at nine grassland sites spanning a wide range of climatic and edaphic conditions in the continental United States. Fertilization effects were strong aboveground, with both N and P addition stimulating aboveground biomass at nearly all sites (by 30% and 36%, respectively, on average). P addition consistently increased root production (by 15% on average), whereas other belowground responses to fertilization were more variable, ranging from positive to negative across sites. Site-specific responses to P were not predicted by the measured covariates. Atmospheric N deposition mediated the effect of N fertilization on root biomass and turnover. Specifically, atmospheric N deposition was positively correlated with root turnover rates, and this relationship was amplified with N addition. Nitrogen addition increased root biomass at sites with low N deposition but decreased it at sites with high N deposition. Overall, these results suggest that the effects of nutrient supply on belowground plant properties are context dependent, particularly with regard to background N supply rates, demonstrating that site conditions must be considered when predicting how grassland ecosystems will respond to increased nutrient loading from anthropogenic activity.
Bibliographical noteFunding Information:
information Agricultural Research Service, Grant/Award Number: 58-3098-7-007; National Science Foundation, Grant/Award Numbers: 1556418, 1556529, 1655499, 183194; Pacific Northwest National Laboratory; U.S. Department of Energy; Oak Ridge National Laboratory This work was supported by grants from the National Science Foundation (NSF) Cedar Creek Long Term Ecological Research (183194) and Ecosystem Studies (1556529, 1556418) programs, and from the NSF Sevilleta Long Term Ecological Research program (1655499). Soil analyses were supported, in part, by USDA-ARS Grant 58-3098-7-007 to ETB. Pacific Northwest National Laboratory is a multiprogram national laboratory operated by Battelle for the U.S. Department of Energy under Contract DE-AC05-76RL01830. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, under Contract DE-AC05-00OR22725 with the U.S. Department of Energy. We thank Colby Carlisle, Hanan Farah, Ingrid Holstrom, Ben Huber, Kristine Jecha, Brennan Lauer, Joe Rippke, David Sanneruud, Kaitlin Truong, Colleen Unsworth, Rylee Werden, and Esther Young for assistance in the field and laboratory. This manuscript was authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-publicaccess-plan).
© 2022 The Authors. Ecology published by Wiley Periodicals LLC on behalf of The Ecological Society of America.
- Nutrient Network
- belowground net primary productivity
- nutrient pollution
- root response
PubMed: MeSH publication types
- Journal Article
- Research Support, U.S. Gov't, Non-P.H.S.