Dry grass: Research project explores the effect of multi-year drought on grasslands

As a dry spell stretches from months to years, grasslands can adapt — to a point.
Photo Credit: Scientific Frontline / Heidi-Ann Fourkiller

A recent paper in the journal Science, “Drought intensity and duration interact to magnify losses in primary productivity,” explores how moderate and extreme droughts affect grasslands around the world. The paper has more than 180 international co-authors, with Binghamton University Assistant Professor of Ecosystem Science Amber Churchill among them.

Known as a distributed network, research projects of this type call upon collaborators to perform the same experiments locally, Churchill explained.

“The idea is that everyone uses the same methodology, but each local site is independently responsible for the maintenance of their site, data collection and ongoing measurements,” she said. “Often, individual sites will collect data in addition to the core project’s data.”

The experiment measured productivity, or how much plant biomass grows in a year. Less rain typically means less productivity, but the long-term picture is complicated by a number of factors. For one, not all grasslands are created equal; they come in a variety of types, with varying precipitation levels. Removing 10% of rainfall in an arid grassland is the equivalent of removing 40% of the precipitation in a wetter ecosystem, according to the research.

Binghamton University Assistant Professor of Ecosystem Science Amber Churchill, center, instructs her ENVI 382B: Measuring the Natural World class at Nuthatch Hollow.
Photo Credit: Jonathan Cohen.

For her part of the project, Churchill focused on one of the wetter grasslands. She contributed to the coordination and data processing for the Cedar Creek Ecosystem Science Reserve in Minnesota, where she had been a postdoctoral research associate in the University of Minnesota’s Isbell Biodiversity Lab.

Cedar Creek is an oak savannah, which combines elements of a grassland and a forest. Unlike northeastern forests, the oak trees are spaced widely, with grasses growing in between. This unusual landscape has been historically maintained by a combination of fire and grazing bison. Once widespread, oak savannahs have dwindled to around 3% of their former reach due to the impact of agriculture and urban development.

“Drought plays a large role in how grasslands contribute to global carbon and climate modeling,” Churchill said. “For example, we know that grasslands drive much of the inter-annual differences in carbon sequestration on a global scale.”

How ecosystems adapt

Researchers found that moderate droughts didn’t lead to compounding losses in biomass over time. Here’s why: When drought conditions linger over a period of years, drought-sensitive plants will be replaced by more hardy species, keeping the biomass relatively constant. In short, the grasslands acclimatize to the new conditions.

“It’s more than just the number of species, but the identity of what’s there,” Churchill explained. “Ecosystems that are more acclimatized to drought are comprised of species that can better withstand drought at different durations.”

Extreme droughts, on the other hand, can lead to less abundant plant life and overall species loss. While these extreme droughts have typically occurred once every hundred years, global climate change is making them more common.

“This can give us a predictor about what we might expect for grassland productivity on a global scale in the future,” Churchill said.

The plant ecologist is still affiliated with Cedar Creek, although now she mostly works with Northeastern grasslands — essentially, lawns. The Northeast is less concerned with drought than other regions of the country; dry spells are typically measured in months rather than successive years. Too much rather than too little rain tends to be more of a problem.

“I’ve pivoted a bit. I’m still thinking about water availability, but now I’m focusing on how we can use biodiversity to mitigate impacts of flooding for our local grassland ecosystems,” she said.

The massive distributed network behind the Science article also created a new ecosystem — this one of scientists around the globe. While most will never meet in person, they wove connections with one another in multiple ways: by sharing data, offering comments during the revision process and commenting on the suggestions of others.

“Ultimately, it creates this entire community of grassland drought experts that you can go to with new questions as you run into new circumstances,” Churchill reflected. “It’s a benefit on the human side of things.”

In other words, grasslands are more responsive to changes in weather conditions and can fluctuate significantly from one year to the next. Forests, on the other hand, take up carbon at a steadier rate.

Cedar Creek experienced an extreme drought during the first year of the study and moderate drought in subsequent years, which enabled the ecosystem to recover, Churchill said.

Published in journal: Science

Title: Drought intensity and duration interact to magnify losses in primary productivity

Authors: Timothy Ohlert, Melinda D. Smith, Scott L. Collins, Alan K. Knapp, Jeffrey S. Dukes, Osvaldo Sala, Kate D. Wilkins, Seth M. Munson, Maggie I. Anderson, Meghan L. Avolio, Anping Chen, Meghan T. Hayden, Martin C. Holdrege, Ingrid J. Slette, Peter Wilfahrt, Claus Beier, Lauchlan H. Fraser, Anke Jentsch, Michael E. Loik, Yiqi Luo, Fernando T. Maestre, Richard P. Phillips, Sally A. Power, Laura Yahdjian, Qiang Yu, Angel Chen, Andrew J. Felton, Laureano A. Gherardi, Nicholas J. Lyon, Hamed Abdoli, Mehdi Abedi, Juan Alberti, Antonio I. Arroyo, Heidi Asbjornsen, Harald Auge, Seton Bachle, Amgaa Batbaatar, Taryn L. Bauerle, Karen H. Beard, Kai Behn, Ilka Beil, Lucio Biancari, Irmgard Blindow, Viviana Florencia Bondaruk, Elizabeth T. Borer, Edward W. Bork, Carlos Martin Bruschetti, Kerry M. Byrne, James F. Cahill Jr., Dianela A. Calvo, Michele Carbognani, Cameron N. Carlyle, Karen Castillioni, Miguel Castillo-Garcia, Manjunatha H. Chandregowda, Scott X. Chang, Jeff Chieppa, Amber C. Churchill, Marcus Vinicius Cianciaruso, Amanda L Cordeiro, Sara A. O. Cousins, Daniela F. Cusack, Sven Dahlke, Pedro Daleo, Lee H. Dietterich, Maren Dubbert, Nico Eisenhauer, T’Ai G. W. Forte, Flavia A. Funk, Darcy Galiano, Aaron C. Greenville, Liebao Han, Siri Vatsø Haugum, Yann Hautier, Andy Hector, Hugh A. L. Henry, Daniela Hoss, Forest Isbell, Samuel E. Jordan, Yuguang Ke, Eugene F. Kelly, Sally E. Koerner, Juergen Kreyling, György Kröel-Dulay, Alicia I. Kröpfl, Angelika Kübert, Andrew Kulmatiski, Eric G. Lamb, Klaus Steenberg Larsen, Steven Lee, Smriti Pehim Limbu, Anja Linstädter, Shirong Liu, Grisel Longo, Alejandro Loydi, Junwei Luan, F. Curtis Lubbe, Andrey V. Malyshev, Cameron D. Mcintire, Daniel B. Metcalfe, Malesela Vincent Mokoka, Akira S. Mori, Edwin Mudongo, Gregory S. Newman, Uffe N. Nielsen, Raúl Ochoa-Hueso, Rory C. O’Connor, Romà Ogaya, Gastón R. Oñatibia, Ildikó Orbán, Brooke B. Osborne, Rafael Otfinowski, Meelis Pärtel, Jesús Pascual, Josep Peñuelas, Pablo L. Peri, David S. Pescador, Guadalupe Peter, Alessandro Petraglia, Catherine Picon-Cochard, Valério D. Pillar, Juan M. Piñeiro-Guerra, Laura Weber Ploughe, Robert M. Plowes, Cristy Portales-Reyes, Suzanne M. Prober, Yolanda Pueyo, Golsa Rahmati, Sasha C. Reed, Dana Aylén Rodríguez, William E. Rogers, Christiane Roscher, David W. Rowley, Ana M. Sánchez, Bráulio A. Santos, Michael P. Schellenberg, Michael Scherer-Lorenzen, Eric W. Seabloom, Ruonan Shen, Baoku Shi, Lara Souza, Andreas Stampfli, Rachel J. Standish, Marcelo Sternberg, Wei Sun, Marie Sünnemann, Michelle Tedder, Tyson J. Terry, Pål Thorvaldsen, Katja Tielbörger, Maud Tissink, Matthew A. Vadeboncoeur, Alejandro Valdecantos, Liesbeth Van Den Brink, Vigdis Vandvik, Liv Guri Velle, Svenja Wanke, Glenda M. Wardle, Cunzheng Wei, Christiane Werner, Georg Wiehl, Jennifer L. Williams, Amelia A. Wolf, Honghui Wu, Chong Xu, Xuechen Yang, Yadong Yang, Jenifer L. Yost, Alyssa L. Young, Ping Yue, Juan M. Zeberio, Michaela Zeiter, Haiyang Zhang, Juntao Zhu, and Xiaoan Zuo

Source/Credit: Binghamton University | Jennifer Micale

Reference Number: env110625_03

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