Extreme drought impacts have been underestimated in grasslands and shrublands globally
Melinda D. Smith, Kate Wilkins, Martin C. Holdrege, Peter A. Wilfahrt, Scott L. Collins, Alan K. Knapp, Osvaldo E. Sala, Jeffrey S. Dukes, Richard P. Phillips, Laura Yahdjian, Laureano Gherardi, Timothy Ohlert, Claus Beier, Lauchlan H. Fraser, Anke Jentsch, Michael E. Loik, Fernando T. Maestre, Sally A. Power, Qiang Yu, Andrew J. Felton, Seth M. Munson, Yiqi Luo, H Abdoli, Mehdi Abedi, Concepción L. Alados, Juan Alberti, Moshe Alon, Hui An, Brian L. Anacker, Maggie Anderson, Harald Auge, Seton Bachle, Khadijeh Bahalkeh, Michael Bahn, Amgaa Batbaatar, Taryn L. Bauerle, Karen H. Beard, Kai Behn, Ilka Beil, Lucio Biancari, Irmgard Blindow, Viviana F. Bondaruk, Elizabeth T. Borer, Edward W. Bork, Carlos Martín Bruschetti, Kerry Byrne, James F. Cahill, Dianela A. Calvo, Michele Carbognani, Augusto Cardoni, Cameron N. Carlyle, Miguel Castillo-García, Scott X. Chang, Jeff Chieppa, Marcus Vinícius Cianciaruso, Ofer Cohen, Amanda L. Cordeiro, Daniela Cusack, Sven Dahlke, Pedro Daleo, Carla M. D’Antonio, Lee H. Dietterich, Tim S. Doherty, Maren Dubbert, Anne Ebeling, Nico Eisenhauer, Felícia M. Fischer, T’ai G. W. Forte, Tobias Gebauer, Beatriz Gozalo, Aaron C. Greenville, Karlo G. Guidoni‐Martins, Heather Hannusch, Siri Vatsø Haugum, Yann Hautier, Mariet M. Hefting, Hugh A. L. Henry, Daniela Hoss, Johannes Ingrisch, Oscar Iribarne, Forest Isbell, Yari Johnson, Samuel Jordan, Eugene F. Kelly, Kaitlin Kimmel, Jüergen Kreyling, György Kröel‐Dulay, Alicia Kröpfl, Angelika Kübert, Andrew Kulmatiski, Eric G. Lamb, Klaus Steenberg Larsen, Julie E. Larson, J.B. Lawson, Cintia V. Leder, Anja Linstädter, Jielin Liu, Shirong Liu, Alexandra G. Lodge, Grisel Longo
Abstract
Climate change is increasing the frequency and severity of short-term (~1 y) drought events-the most common duration of drought-globally. Yet the impact of this intensification of drought on ecosystem functioning remains poorly resolved. This is due in part to the widely disparate approaches ecologists have employed to study drought, variation in the severity and duration of drought studied, and differences among ecosystems in vegetation, edaphic and climatic attributes that can mediate drought impacts. To overcome these problems and better identify the factors that modulate drought responses, we used a coordinated distributed experiment to quantify the impact of short-term drought on grassland and shrubland ecosystems. With a standardized approach, we imposed ~a single year of drought at 100 sites on six continents. Here we show that loss of a foundational ecosystem function-aboveground net primary production (ANPP)-was 60% greater at sites that experienced statistically extreme drought (1-in-100-y event) vs. those sites where drought was nominal (historically more common) in magnitude (35% vs. 21%, respectively). This reduction in a key carbon cycle process with a single year of extreme drought greatly exceeds previously reported losses for grasslands and shrublands. Our global experiment also revealed high variability in drought response but that relative reductions in ANPP were greater in drier ecosystems and those with fewer plant species. Overall, our results demonstrate with unprecedented rigor that the global impacts of projected increases in drought severity have been significantly underestimated and that drier and less diverse sites are likely to be most vulnerable to extreme drought.