Grassland Research

Belowground Controls of Primary Productivity

Water Availability Controls on Above-Belowground Productivity Partitioning: Herbivory versus Plant Response

Funding
National Science Foundation, Division of Environmental Biology: DEB 1456631

Principal Investigators
Diana Wall and Osvaldo Sala

Timeline
June 2015 — May 2018

Net primary productivity is the sum of aboveground net primary production (ANPP: leaves etc.) and the less frequently studied belowground net primary productivity (BNPP: roots etc.). Understanding of BNPP is a key process in terrestrial ecosystem functioning because in most water-limited ecosystems, BNPP accounts for a larger flow of carbon than ANPP.

The objective of this study is to elucidate the differential effects of temporal and spatial changes in water availability on BNPP and the ecological mechanisms behind those patterns. There is general agreement that precipitation is a major control of ANPP in different ecosystems, however this relationship is less clear for BNPP. Ecological interactions are also likely to play a role in BNPP since plant roots are consumed by animals such as herbivorous nematodes, which are in turn preyed upon by predatory nematodes.

This work aims to test three novel hypotheses based on: (1) a plant-response mechanism, suggesting decreased belowground allocation with increasing water availability, and (2) a trophic-cascade mechanism, suggesting the opposite pattern derived from the differential sensitivity of root feeders and their predators to water availability. A final hypothesis (3) suggests that the magnitude of plant responses decreases from arid to mesic grasslands while the magnitude of the trophic-cascade phenomenon increases. The trophic-cascade mechanism may be constrained by the abundance of belowground predators in arid grasslands, which is greater in mesic ecosystems. The experimental design includes complementary field and microcosm experiments located in three different ecosystem types: Chihuahuan Desert Grassland, NM, Shortgrass Steppe, CO, and Tallgrass Prairie, KS. The field experiment includes additions and reductions of precipitation at each site. The microcosm experiment is based on monoliths subjected to 4 soil fauna treatments x 5 water manipulation levels. Soil fauna treatments consist of (1) soil devoid of fauna (just native bacteria and fungi), (2) defaunated soil inoculated with nematode root feeders, (3) defaunated soil inoculated with nematode root feeders and nematode predators, and (4) control. Microcosm tubes will be located in each of the water manipulation plots using individuals of the dominant grass species of each ecosystem type. Key for the implementation of our microcosm is finding a method for defaunating large volume of soil in a way that is effective and efficient. One of our first publications assessed alternative defaunation methods and identified a simple method that meets our criteria (Franco et al. 2017).

References

Franco ALC, Knox MA, Andriuzzi WS, de Tomasel CM, Sala OE, and Wall DH (2017) Nematode exclusion and recolonization in experimental soil microcosms. Soil Biology and Biochemistry 108: 78-83.

Presentations

Gherardi, LA; Sala, OE; Currier, CM, Franco ALC; Wall, DH (2017) Partitioning of above-belowground productivity: Spatial and temporal controls of water availability. 2017 Ecological Society of America Annual Meeting, Portland, USA.

Franco ALC; Gherardi, LA; de Tomasel CM; Andriuzzi, WS; Shaw, EA; Ankrom, KE; Sala, OE; Wall, DH (2017) Cross-site responses of soil nematodes to abnormal growing-season precipitation. 2017 Ecological Society of America Annual Meeting, Portland, USA.

Eden Senay, André Franco, Cecilia Tomasel, Diana Wall. An Endoparasitic Nematode Hunts a Suitable Host: Exploring the Dominant Grasses From the Shortgrass and Tallgrass Prairies, Front Range Student Ecology Symposium, Fort Collins, CO. February 2017.

Franco ALC; Knox, MA; Andriuzzi, WS; Tomasel, CM; Wall, DH (2016) Nematode exclusion and recolonization for experimental soil microcosms. 2016 Ecological Society of America Annual Meeting. Fort Lauderdale, USA.

Diana H. Wall. Soil biodiversity: necessary for life. UNCBD GSBI Side Event to Launch the Global Soil Biodiversity Atlas, Cancun, Mexico, December 2016.

Diana H. Wall. Common Ground: soil biodiversity for humanity and ecosystems. NRC Board on International Scientific Organizations Symposium. Soils: The Foundation of Life. National Academy of Sciences, Washington, DC, December 2016.

Diana H. Wall. Common Ground: Soil biodiversity and sustainability. California Academy of Sciences, keynote lecture at the Annual Fellows Gathering, San Francisco, November 2016.

Diana H. Wall. Meeting global challenges through soil ecology. EU COST Action First Training School, ‘Soil Fauna – key to soil organic matter dynamics and modeling”, Coimbra, Portugal, October 2016.

Diana H. Wall. Soil Nematology: bringing a wealth of knowledge to sustainability. Society of Nematologists – Organization of Tropical American Nematologists, Quebec City, July 2016.

Diana H. Wall. Our Common Ground: soil biodiversity and sustainability. UN Environmental Assembly, Green Room Event, Symposium to Launch the Global Soil Biodiversity Atlas, Nairobi, Kenya, May 2016.

Osvaldo Sala, The effect of climate change on arid and semi-arid ecosystems, Distinguish Ecologist Program, Colorado State University, Fort Collins, CO, March 2016.

Osvaldo Sala, Climate change in arid lands: prediction, mitigation and communication. Grantham Institute, Imperial College, London, April 2016.

Osvaldo Sala, The effect of climate change on ecosystem functioning, University of Puerto Rico, April 2016

Osvaldo Sala, Above-belowground partitioning of primary production as modulated by precipitation amount. Jornada Experimental Range Annual Meeting, New Mexico State University, NM, July 2016

Laureano A. Gherardi, and Osvaldo E. Sala,. Effects of contrasting rooting distribution patterns on plant transpiration along a precipitation gradient. 2016 Ecological Society of America Annual Meeting, Fort Lauderdale, FL. August 2016

Osvaldo Sala. The Effects of climate change on ecosystem functioning. Purdue University, August 2016

Osvaldo Sala, Effects of Climate Change on Drylands, Institute of Ecology, Xalapa, Mexico. October 2016

 

Stained root-lesion nematode (P. penetrans) and its egg inside roots of Big bluestem, a dominant grass species at the Shortgrass Steppe. Photo: André Franco (2016)

 

A view of the greenhouse microcosm experiment ran on Summer 2017 testing the sensitivity to water availability of soil-plant interactions. Photo: André Franco (2017)

 

IMG_5072

A view of the field experiment at the Shortgrass Steppe, Colorado. Photo: André Franco (2016)

Belowground productivity measurements at the Shortgrass Steppe, CO. Photo: André Franco (2016)

 

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