Source: COLORADO STATE UNIVERSITY submitted to
INVESTIGATING RANGELAND RESPONSES TO ALTERED PRECIPITATION VARIABILITY: CAN EXTREME LARGE EVENTS SUSTAIN FORAGE PRODUCTION DURING DROUGHT?
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
AFRI COMPETITIVE GRANT
Reporting Frequency
Annual
Accession No.
1019261
Grant No.
2019-67011-29615
Cumulative Award Amt.
$118,426.00
Proposal No.
2018-07844
Multistate No.
(N/A)
Project Start Date
May 1, 2019
Project End Date
Apr 30, 2022
Grant Year
2019
Program Code
[A7101]- AFRI Predoctoral Fellowships
Project Director
Slette, I.
Recipient Organization
COLORADO STATE UNIVERSITY
(N/A)
FORT COLLINS,CO 80523
Performing Department
Ecology
Non Technical Summary
Rangelands are economically and ecologically important systems occupying almost 50% of the global land surface (>30% in the U.S.). The functions (e.g. production of forage for livestock) of these agroecosystems are primarily controlled by water availability.Rainfall variability is predicted to increase as a result of more frequent extreme large rain events (EPEs, extreme precipitation events) and more frequent and intense droughts. Altered rainfall variability may impact critical rangeland functions and make sustainable management of rangeland services more challenging. We don't currently know how altered rainfall variability may affect the relationship between rainfall and productivity. Specifically, we don't know whether EPEs will ameliorate or exacerbate the impacts of drought. My goal is to assess the effects of combined EPEs and droughts on rangeland productivity and more specifically to test the hypothesis that, under some conditions, EPEs can sustain productivity during drought. I will experimentally impose concurrent EPEs and mild to extreme droughts at a semi-arid rangeland research site in Colorado and quantify how these changes affect productivity. To extend the inference of this experiment, I will also assess how EPE-drought interactions vary among rangelands by analyzing long-term observational datasets of rainfall and productivity from numerous grassland ecosystems across the United States. I expect that EPEs will only sustain productivity during mild to moderate droughts at the experiment site. Comparing across grasslands, I expect that large rainfall events will sustain production at higher levels during droughts in drier systems than in wetter systems. The new knowledge that is generated by this project will be shared with scientists, rangeland managers and producers, and the general public through publication and presentation of results online, in scientific journals, and at meetings and conferences.Sustaining rangeland natural resources into the future will require management that is grounded in a thorough knowledge of the relationship between productivity and rainfall.Understanding how rangelands will respond to altered environmental variability (due to more frequent droughts and EPEs) will be essential for assessing risk and sustainably managing productivity and natural resources into the future. This project will improve our ability to manage rangeland functions (e.g. sustain high forage and livestock production levels) under changing environmental conditions by improving our understanding of how rainfall variability affects productivity.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
12107991070100%
Knowledge Area
121 - Management of Range Resources;

Subject Of Investigation
0799 - Rangelands and grasslands, general;

Field Of Science
1070 - Ecology;
Goals / Objectives
The goal of this project is to assess the impacts of combined EPEs and droughts on rangeland primary production and more specifically to test the hypothesis that, under some conditions, EPEs can sustain productivity during drought. Theobjectives of this projectare: (1) Quantify the response of forage production (ANPP), BNPP, and associated C fluxes (e.g. soil CO2flux) to concurrently- imposed experimental EPEs and droughts of various intensities. (2) Extend the inference of thisfield experiment by evaluating how EPE-drought interactions vary among grassland types, using long-term observational datasets from numerous sites to compare production in drought years that differed in the proportion of PPT delivered in large events. (3) Disseminate new knowledge of how altered climatic variability will impact rangeland function and sustainability.
Project Methods
Field Experiment: Research will be conducted at the USDA-ARS Central Plains Experimental Range (CPER) in northeastern Colorado. This semi-arid grassland (330 mm mean annual precipitation, ~6,300 ha) is representative of the remaining ~20 million ha of this ecosystem type, and is known to respond strongly to changes in precipitation (PPT). The CPER has a rich history of ecological researchand is both a Long-Term Agroecosystem Research (LTAR) and National Ecological Observatory Network (NEON) site. My proposed experiment will be established in coordination with the CPER's extensive sensor networks (including rain gauges, soil moisture probes, and meteorological stations), which I will utilize to monitor PPT and to contextualize my results. Additionally, I will take advantage of the CPER's established network of producer- researcher partnerships (e.g. the Collaborative Adaptive Rangeland Management [CARM] Experiment) to share my results with land managers and ARS outreach staff.Drought will be imposed by reducing growing season PPT (GSP) by 20%, 40%, 60%, or 80% using rainout shelters (clear acrylic strips over a 2x2 m area with a 1 m2sampling plot). EPEs will be simulated by adding 40 mm of water to half of the plots at each PPT level, including ambient control plots ([5 PPT levels x2 PPT patterns] x3 replicates = 30 plots). A 40 mm event exceeds the 99thpercentile of historic individual event sizes (excluding ineffective events <2 mm) and is ~20% of average GSP. This design thus includes paired treatments with roughly equivalent total PPT amount but different variability (e.g.: -40% GSP + EPE =- 20% GSP). Water additions (via portable water tank, pump, flow meter, hose) will occur in mid-July (when soil water becomes strongly limiting). Flashing will be installed around each plot to prevent PPT run-on and -off. To extend the range of PPT treatments, I will repeat this experiment in two consecutive years, taking advantage of the naturally high inter-annual variability in GSP at the CPER (only twice in the past 45 years has GSP differedby >1 standard error of average between consecutive years). New plots will be established for the second year to avoid confounding legacy effects of the first year. This will ultimately result in 20 treatment combinations ([5 PPT levels x2 PPT patterns] x2 years). Plots will be located in an experimental pasture grazed by cattle. Plots will be protected from grazing during the study, but vegetation and soil will reflect the cumulative impacts of long-term grazing.Forage production (ANPP) will be assessed via end-of-season vegetation harvests (0.1 m2clip plots, n=2/plot/year, sorted by functional group). BNPP will be assessed via root ingrowth cores (30 cm deep, analyzed in 10 cm depth increments to assess BNPP depth distribution, n=2/plot/growing season, sorted by functional group). Rain Use Efficiency (RUE) ofANPP and BNPP (g/m2/mm) will be calculated for all treatments. Soil moisture, temperature, and CO2flux; and plant water potential, photosynthetic rate, growth rate, and phenology will be measured throughout the experiment, using well-established methods and in coordination with CPER staff.Data will be analyzed using R statistical software. Analyses will include: fitting linear and non-linear models to PPT-ANPP, PPT-BNPP, and PPT-RUE regressions and using Akaike Information criteria (AIC function in base R) to select the best fit; and comparing production between EPE vs. non-EPE treatments with equivalent total PPT amounts (paired t-tests).A potential pitfall of this approach is that ambient PPT during the experiment could be extremely high or low in both years. Although unlikely, if ambient PPT patterns are highly unusual, I can add water to plots as needed. If total ambient PPT is abnormally high, the proposed reductions are large enough that extreme drought will still be imposed (80% GSP reduction from wettest year on record is an extreme [<1stpercentile] dry year). Another concern is PPT runoff from plots. Flashing and a slow rate of water addition will minimize this. Note that my goal is not to simulate high rainfall intensity, but the deep soil water infiltration typical of an EPE. Trial runs have shown that even very large amounts of water are quickly absorbed and runoff is negligible. The time and effort required for this project will be significant, but I have extensive experience performing field manipulations and collecting and processing both ANPP and BNPP from multiple ecosystems, including the proposed study site. With support from my dissertation advisor, Dr. Alan Knapp, and assistance from undergraduate researchers, the goals of my project are feasible within the specified timeframe.Cross-Site Comparison: To evaluate how the impacts of combined droughts and EPEs may differ among rangelands, I will analyze long-term observational datasets of PPT and production from numerous sites. I will gather data (via online public databases and communication with site staff) from grasslands across many ecological and agricultural networks (e.g. LTAR, LTER, ILTER, NEON, CZO) to assess how variability in PPT event size (even a single EPE strongly alters mean event size) affects the relationship between production and PPT during very dry years, and how this differs among sites (e.g. along a gradient of mean annual PPT, from arid to mesic grasslands). Specifically, for each site, I will compare ANPP in drought years when PPT events are relatively few and large vs. numerous and small.

Progress 05/01/19 to 04/30/22

Outputs
Target Audience: The target audiences that I reached during this projectincluded undergraduate and graduate studentvolunteers who assisted with research, numerous graduate studentsand faculty members who attended a variety of meetings where I presented project updates, a broad network of scientists and journalists and other members of the public who interacted with project posts online and onsocial media (e.g., Twitter, CSU Knapp Lab website, etc.), a range of scientists and attendees at both the Ecological Societyof America and the American Geophysical Union annual conferences in every year of the projectwho viewed and interacted with presentations that I gave related to the project, research staff and project managers at the USDA-ARS research site where I conducted research, journal editors and scientific peers who reviewed manuscripts detailing project results, and the readers of the multiple manuscripts related to the project. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? The project provided many opportunities for training and professional development for me, including opportunities to present research results at multiple scientific conferences, where I also attended various professional development workshops and seminars, and networked with numerous other scientists and researchers in my field (ranging from undergraduate students to senior scientists). I also attended numerous research training and professional development seminars and workshops at my university. In addition, the project also provided opportunities for training and professional development of undergraduate research volunteers who gained experience in conducting hands- on ecological research in the field and laboratory. How have the results been disseminated to communities of interest? Results have been disseminated via presentations at multiple scientific conference and other meetings, numerous social media and blog posts and updates, the creation of two differentwebsites that includeinformation about the project, and several manuscripts which have been published or are currently in progress. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? The response of forage production (aka aboveground net primary production or ANPP), belowground net primary production (BNPP), and associated key C fluxes (e.g. soil CO2 flux) to concurrently-imposed Extreme large Precipitation Events (EPEs) and drought was successfully quantified at the site level via a field experiment conducted in a shortgrass prairie ecosystem, in accordance with project goals (objective 1). An assessment of how EPE-drought interactions vary among grassland types, using long-term observational datasets from numerous sites to compare production in drought years that differed in the proportion of total precipitation received as large events was successfully carried out,and a manuscript detailing thatassessment is currently being completed, in accordance with project goals (objective 2). Knowledge that was gained during the project was disseminated to a broad audience (via scientific conferences and meeting presentations, publications, social media updates, blog posts, the creation and updating of a website, etc.), in accordance with project goals (objective 3).

Publications

  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Slette, I.J., Liebert, A. & Knapp, A.K. (2021). Fire history as a key determinant of grassland soil CO2 flux. Plant and Soil 460, 579592. https://doi.org/10.1007/s11104-020-04781-0
  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Griffin-Nolan, R. J., Slette, I. J., & Knapp, A. K. (2021). Deconstructing precipitation variability: Rainfall event size and timing uniquely alter ecosystem dynamics. Journal of Ecology, 109, 3356 3369.
  • Type: Journal Articles Status: Published Year Published: 2022 Citation: Slette, I.J., Blair, J.M., Fay, P.A., Smith, M.D. & Knapp, A.K. (2022). Effects of Compounded Precipitation Pattern Intensification and Drought Occur Belowground in a Mesic Grassland. Ecosystems 25, 12651278.
  • Type: Theses/Dissertations Status: Published Year Published: 2022 Citation: Slette, I.J. (2022). Impacts of Compound Precipitation Extremes on Belowground Dynamics in a Mesic Grassland. Colorado State University.
  • Type: Journal Articles Status: Published Year Published: 2022 Citation: Hoover, D. L., Hajek, O. L., Smith, M. D., Wilkins, K., Slette, I. J., & Knapp, A. K. (2022). Compound hydroclimatic extremes in a semi-arid grassland: Drought, deluge, and the carbon cycle. Global Change Biology, 28, 2611 2621.
  • Type: Journal Articles Status: Published Year Published: 2022 Citation: Slette, I.J., Hoover, D.L., Smith, M.D. and Knapp, A.K. (2022), Repeated extreme droughts decrease root production, but not the potential for post-drought recovery of root production, in a mesic grassland. Oikos. e08899.
  • Type: Journal Articles Status: Published Year Published: 2023 Citation: Griffin-Nolan, R.J., Felton, A.J., Slette, I.J., Smith, M.D. and Knapp, A.K. (2023). Traits that distinguish dominant species across aridity gradients differ from those that respond to soil moisture. Oecologia 201: 311322.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Slette, I., A. Knapp, M. Smith. Precipitation legacies alter ecosystem sensitivity to extreme drought. 2020 Ecological Society of America Annual Meeting.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Slette, I., A. Knapp. History of chronically increased precipitation variability alters grass production allocation during extreme drought. 2020 American Geophysical Union Fall Meeting.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2021 Citation: Slette, I.J., Blair, J.M., Fay, P.A., Smith, M.D. & Knapp, A.K. Compound effects of intensified precipitation patterns and drought occur belowground in a Central US grassland. 2021 American Geophysical Union Fall Meeting.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2021 Citation: Slette, I.J., Knapp, A.K. Effects of compounded precipitation pattern intensification and drought occur belowground in a mesic grassland. 2021 Graduate Climate Conference.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2021 Citation: Slette, I.J., Blair, J.M., Fay, P.A., Smith, M.D. & Knapp, A.K. Legacy of increased precipitation variability increases drought sensitivity of tallgrass prairie plant production belowground, but not aboveground. 2021 Ecological Society of America Annual Meeting.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2022 Citation: Slette, I.J., Hoover, D.L., Knapp, A.K. Exploring change over time in aboveground net primary production, its drivers, and their relationship, on the US Great Plains. 2022 Ecological Society of America Annual Meeting.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2022 Citation: Slette, I.J., Hoover, D.L., Knapp, A.K. Changes in climate, aboveground net primary productivity, and their relationship on the US Great Plains over the last 40 years. 2022 American Geophysical Union Fall Meeting.
  • Type: Websites Status: Published Year Published: 2020 Citation: csuknapplab.weebly.com
  • Type: Websites Status: Awaiting Publication Year Published: 2023 Citation: ingridsletteecology.weebly.com
  • Type: Conference Papers and Presentations Status: Submitted Year Published: 2023 Citation: Slette, I.J., Hoover, D.L., Knapp, A.K. Changes in precipitation and aboveground net primary production, but not the relationship between precipitation and aboveground net primary production, on the US Plains over the last 40 years. 2023 Ecological Society of America Annual Meeting.
  • Type: Journal Articles Status: Other Year Published: 2023 Citation: Slette, I.J., Hoover, D.L., Knapp, A.K. Changes in precipitation and aboveground net primary production, but not the relationship between precipitation and aboveground net primary production, on the US Plains over the last 40 years. In progress.


Progress 05/01/20 to 04/30/21

Outputs
Target Audience: The target audiences that I reached during this reporting period included undergraduate volunteerswho assisted with research, numerous graduate students, and faculty memberswho attended a variety of meetings where I presentedproject updates, a broad network of scientists and journalists and other members of the publicwho interacted with project posts on social media(e.g., Twitter, CSU Knapp Lab website, etc.), a range of scientists and attendees at both the Ecological Society of America and the American Geophysical Union annual conferences in 2020who viewed and interacted with presentations that I gave related to the project, research staff and project managers at the USDA-ARS research site where I conducted research, as well as journal editors and scientific peers who reviewedmanuscripts detailing project results. Changes/Problems:Restrictions that werein placeat my university and field research siteduring the COVID-19 pandemic limited my ability to carry out some field and laboratory operations as planned. Thus, for part of this reporting period, I focused onvirtual computer-based work (e.g., a combination ofdata syntheses, meta-analyses, literature reviews, etc.). During this time, I was able to greatly expand upon the originally planned cross-site data synthesis, adding more locations and more biotic and abiotic variables to the analysis.I was ultimately able to address and fulfillthe project aims and requirements for this reporting period, though via slightly different methods than originally planned. What opportunities for training and professional development has the project provided? The project has provided many opportunities for training and professional development for me, including opportunities to presentresearch resultsat multiple scientific conferences, where I alsoattended various professional development workshops and seminars, and networked with numerous other scientists and researchers in my field (ranging from undergraduate studentsto senior scientists). I have also attended numerous research training and professional development seminars and workshops at my university. In addition, the project has also provided opportunities for training and professional development of undergraduate research volunteers who gained experience in conducting hands- on ecological research in the field and laboratory. How have the results been disseminated to communities of interest? Results have been disseminated via multiple conference and meeting presentations, numerous social media and blog posts and updates, the creation of a website that includes information about the project, and severalmanuscripts which have been published or are currently under review at peer-reviewed journals. What do you plan to do during the next reporting period to accomplish the goals? During the next reporting period, I plan to finalizemy assessment of how the impacts ofconcurrent extreme precipitation eventsvary among grassland types, using long-term observational datasets from numerous locations to compare production in drought years that differed in the proportion of precipitationdelivered in large events. I also plan to expand upon this analysis by similarlyassessing the impacts of various other aspects of precipitation pattern and timing as well as temperature and ambient CO2 concentration on plant production.I also plan to attend several more conferences and meetings, where I will present results from the project, network with other scientists, and continue developing the skills necessary for professional success. I plan to write several more manuscripts for publication in peer-reviewed scientific journals to disseminate project results to the scientific community, in addition to posting on social media and blogs in order to reach a broader audience. I will also continue generating various research products, including datasets, databases, code for statistical analysis of data, etc.

Impacts
What was accomplished under these goals? The response of forage production (aka aboveground net primary production orANPP), belowground net primary production (BNPP), and associated key C fluxes (e.g. soil CO2flux) to concurrently-imposed Extreme large Precipitation Events (EPEs) and drought was successfully quantified at the site level via a field experiment conducted in a shortgrass prairie ecosystem, in accordance with project goals (objective 1). An assessment of how EPE-drought interactions vary among grassland types, using long-term observational datasets from numerous sites to compare production in drought years that differed in the proportion of totalprecipitation receivedaslarge events, is currently underway. Appropriate grassland sites with the necessary data available have been identified, data from these sites has beencollected and cleaned, necessary metrics have been calculated, data has been statistically analyzed, and a manuscript detailing the results of that analysis is currently underway, inaccordance with project goals (objective 2). Knowledge that has been gained during the projectthus far has been disseminated to a broad audience (via scientific conference and meeting presentations, publications, social media updates,blog posts, thecreation and updating of a website,etc.), in accordance with project goals (objective 3).

Publications

  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Slette, I.J., Liebert, A. & Knapp, A.K. (2021). Fire history as a key determinant of grassland soil CO2 flux. Plant Soil 460, 579592. https://doi.org/10.1007/s11104-020-04781-0
  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Griffin-Nolan, R. J., Slette, I. J., & Knapp, A. K. (2021). Deconstructing precipitation variability: Rainfall event size and timing uniquely alter ecosystem dynamics. Journal of Ecology, 00, 114. https://doi. org/10.1111/1365-2745.13724
  • Type: Journal Articles Status: Under Review Year Published: 2021 Citation: Slette, I.J., Blair, J., Fay, P., Smith, M.D. & Knapp, A.K. Compound effects of intensified precipitation patterns and drought occur belowground in a mesic grassland. Under review at Ecosystems.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Slette, I., A. Knapp, M. Smith. Precipitation legacies alter ecosystem sensitivity to extreme drought. 2020 Ecological Society of America Annual Meeting.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Slette, I., A. Knapp. History of chronically increased precipitation variability alters grass production allocation during extreme drought. 2020 American Geophysical Union Fall Meeting.
  • Type: Websites Status: Published Year Published: 2020 Citation: csuknapplab.weebly.com


Progress 05/01/19 to 04/30/20

Outputs
Target Audience:The target audiences reachedby my efforts during this reporting period included undergraduate volunteers interested in science careers who assisted with field and laboratory research, graduate students and faculty members who attended a variety of meetings where project updates were given,a broad network of scientists and journals who interacted with project posts on social media and blogs(e.g. Twitter, PLoS Ecology blog, CSU Knapp Lab website), a range of scientists and attendeesatboth the Ecological Society of America and the American Geophysical Union annualconferences in 2019 who viewed oral presentations that I gaverelated to theproject, research staff and project managers at the USDA-ARS research site where I conducted a field experiment,as well as journal editors and scientificpeers who are reviewing a manuscript detailing project results. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The project has provided many opportunities for training and professional development for me(Project Director andPhD candidate Ingrid Slette), including opportunities to travel to multiple scientific conferences where I presented research results, attended various professional development workshops and seminars, and networked with numerous other scientists and researchers in my field(ranging from early career to senior scientists). I have also attended numerous research training and professional development seminars and workshops at my university.In addition, the project has also provided opportunities for training and professional developmentof undergraduate research volunteers who gained experience in conducting hands-on ecological research in the field and laboratory. How have the results been disseminated to communities of interest?Results have been disseminated via multiple conference and meeting presentations,several social media and blog posts, the creation of a website that includes information about the project, and a manuscript which is currently under review. What do you plan to do during the next reporting period to accomplish the goals?During the next reporting period, I plan to complete myassessment ofhow EPE-drought interactions vary among grassland types, using long-term observational datasets from numerous sites to compare production in drought years that differed in the proportion of PPT delivered in large events. I also plan to attend several more conferences and meetings, where I will present results from the project, network with other scientists, and continue developing skills necessary for professional success. I planto write several manuscripts for publication in peer-reviewed scientific journals to disseminate project results to the scientific community, in addition to posting on social media and blogs in order to reach a broader audience.

Impacts
What was accomplished under these goals? The response of forage production (aboveground net primary production, ANPP), belowground net primary production (BNPP),and associated C fluxes (e.g. soil CO2flux) to concurrently-imposed experimental Extreme large Precipitation Events (EPEs)and drought was successfully quantified at the site level via a field experiment conducted in a shortgrass prairie ecosystem, in accordance with project goals (objective 1). An assessment ofhow EPE-drought interactions vary among grassland types, using long-term observational datasets from numerous sites to compare production in drought years that differed in the proportion of PPT delivered in large events, is currently underway. Appropriate grassland sites with the necessary data available have been identified and data is being collected, in accordance with project goals (objective 2). Knowledge gained thus far regarding howaltered climatic variability will impact rangeland function and sustainability has been disseminated to a broad scientific audience (via conference and meeting presentations, publication, social media, and blog posts, etc.), in accordance with project goals (objective 3).

Publications

  • Type: Journal Articles Status: Under Review Year Published: 2020 Citation: Slette, I.J., Liebert, A., & Knapp, A.K. Fire versus fire history as key determinants of grassland soil CO2 flux. Under Review at Plant and Soil.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Legacies of altered precipitation variability affect ecosystem sensitivity to extreme drought I Slette, MD Smith, A Knapp - AGUFM, 2019
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Legacies of precipitation change alter belowground production during and after extreme drought. IJ Slette, AK Knapp, MD Smith - 2019 ESA Annual Meeting (August 11--16), 2019
  • Type: Websites Status: Published Year Published: 2020 Citation: csuknapplab.weebly.com