Source: UTAH STATE UNIVERSITY submitted to
PRECIPITATION INTENSITY EFFECTS ON DRYLAND WHEAT AND SAFFLOWER VARIETIES
Sponsoring Institution
State Agricultural Experiment Station
Project Status
NEW
Funding Source
Reporting Frequency
Annual
Accession No.
1016480
Grant No.
(N/A)
Project No.
UTA-01404
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Jul 1, 2018
Project End Date
Jun 30, 2023
Grant Year
(N/A)
Project Director
Kulmatiski, AN, .
Recipient Organization
UTAH STATE UNIVERSITY
(N/A)
LOGAN,UT 84322
Performing Department
Wildland Resources
Non Technical Summary
With each degree Celsius increase in temperature, air holds roughly seven percent more water vapor. A consequence of this physical process is that as the air warms, precipitation events become fewer, but larger. This effect has been observed over the past 100 years in many parts of the world including northern Utah. Changes in precipitation intensity are particularly important in semi-arid systems where plant productivity can double in wet years. Many experiments have tested the effects of increasing or decreasing total precipitation, but relatively little is known about the effects of increasing precipitation intensity. The few studies that have examined the effects of precipitation intensity have produced variable results. In some cases, intense events can increase plant productivity by increasing water infiltration into the soil. In other cases, intense events can decrease plant productivity by increasing runoff. Experiments are needed to better parameterize models of water flow and plant productivity under various climate conditions to determine when increased precipitation intensity will increase plant productivity and when it will decrease plant productivity. Results from two current studies in northern Utah highlight this need. One experiment in a rangeland site increased soil water infiltration and shrub growth, while another experiment in a dryland agricultural site increased soil water infiltration but decreased winter wheat growth. The fact that some species in the area increased growth under increased precipitation intensity, while other species decreased growth, suggests that it may be possible to identify dryland crop varieties that respond positively rather than negatively to observed and anticipated precipitation patterns. Here we propose to test the effects of increased precipitation intensity on three varieties of winter wheat and two varieties of safflower to identify plant varieties that can best convert large precipitation events into crop production. Experimental results will be used to parameterize and test predictions of an ecohydrological model that can be used to predict how different crop varieties are likely to respond to anticipated climate conditions.
Animal Health Component
0%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
10201991070100%
Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships;

Subject Of Investigation
0199 - Soil and land, general;

Field Of Science
1070 - Ecology;
Goals / Objectives
The overarching goal of the proposed research is to determine how increases in precipitation intensity are likely to affect dryland crop production in northern Utah. In pursuing this objective, we expect to identify crop traits that are likely to improve dryland crop production in the future. The more specific objective is to measure the response of three winter wheat and two safflower varieties to precipitation intensity levels anticipated to occur with -1, 0, 1, 2, 3, 5 and 10° C warming. Results from these experiments will be used to parameterize and test predictions of ecohydrological models of water and energy flow and plant production (i.e., Hydrus 1D; Fig. 6). Rather than attempt to replicate climate conditions that are currently predicted for the study site (e.g., wetter winters, drier summers and higher temperatures throughout the year; Gillies et al. 2012), our goal is to test a wide range of precipitation event sizes on water and energy flows and plant productivity. This data will allow us to parameterize a model that can then be used to explore the effects of different seasonal effects or temperature changes on plant growth and water cycling.Climate and plant growth data in experimental plots will be used to parameterize and test ecohydrological models that can then be used to predict the consequences of a wide range of climate conditions on plant growth. The goal of this research is not necessarily to replicate anticipated climate conditions for this area, but to parameterize and test an ecohydrological model that can be used to predict plant growth responses to a wide range of potential climate conditions. More specifically, we are interested in isolating and testing the effects of precipitation intensity. To accomplish this goal we propose to manipulate only precipitation intensity. So that model simulations can provide inference across a wide range of conditions precipitation intensity will be manipulated across a wide range of values (i.e., associated with increasing atmospheric temperatures of -1 to +10° C). By performing these experiments over several years, and across a range of treatment levels, our experiments will allow us to parameterize and test an ecohydrological model across a wide range of conditions (i.e., wet Fall, dry Fall, intense summer precipitation, less intense summer precipitation). So while constraining treatments to conditions predicted for the local site may provide better inference to our study site, this same approach is likely to limit our inference to conditions at our site. By using a wide range of treatments, applied over several years and using this data to parameterize and test an ecoydrological model, we expect to provide broad inference to the effects of a wider range of potential climate scenarios that may be applicable not only to Cache Valley, but also to ecosystems around the Intermountain West.Objectives will be addressed by answering the following questions:1) How does precipitation intensity affect water cycling and dryland forage production in Cache Valley, Utah?2) How do common dryland crop roots respond to increased precipitation intensity?3) How do common dryland crops adjust gas exchange in response to precipitation intensity?
Project Methods
Broadly, this research will use experimental roofs to collect rain and snow and re-deposit collected precipitation as relatively large, intense events. Treatments collect and redeposit rain at a rate of roughly 1 cm in 10 minutes. Precipitation data collected every 15 minutes on the USU campus over the past 45 years suggests that this rate occurred in 14 of 7375 observed time periods with precipitation (i.e., treatments create 'intense' precipitation events). It is likely that natural events may be more intense over very short time periods than our drip irrigation lines. These very short, intense events are more likely to disturb the soil surface, but are unlikely to produce different infiltration rates except on very steep slopes. In short, treatments redistribute ambient precipitation as fewer, larger events that are very intense relative to historical precipitation recorded in 15-minute intervals.The experimental design will generally follow that of Kulmatiski and Beard (2013) with several important improvements. Control shelters will be used that immediately redeposit collected precipitation. This will allow a test of shelter artifacts. Second, both rain and snow events will be manipulated. Third, rather than comparing plant and soil water responses in one set of treated plots and one set of control plots, a combined ANOVA / regression experimental design will be used. This combined approach will provide inference to a broader range of precipitation intensity conditions. This approach has been recommended because it produces data that is needed by large-scale biosphere-atmosphere models (Smith et al. 2014). Finally, 100% roofing will be used allowing better control of precipitation patterns.Study Site: Our dryland agriculture site is at the Emily Godfrey Fonnesbeck Research Farm in Clarkston, UT (41° 53' 44" N; 112° 2' 39" W; elevation 1485 m). The area has mean annual precipitation of 44 cm (including 45 cm of snow) and mean monthly temperatures from -3.7 °C in January to 23.6 °C in July. The plots and surrounding area are in a crop rotation consisting of alternating years of winter wheat and fallow. The area was historically a shrub steppe ecosystem.Experimental Design: Precipitation manipulations will be achieved using 11, 2.1 m x 2.5 m x 2 m (w x l x h) shelters and three shelter-free control plots. Treatments began spring 2016. Rainwater from roofs is collected in holding tanks adjacent to the plots. For the three sheltered-control plots, water from the tanks is routed onto the plot passively through gravity-fed drip irrigation lines immediately as it is collected. For treatments associated with roughly -1, 1, 2, 3, 5 and 10 °C increases in atmospheric temperature, water is held in the tanks until there was enough water to create 2, 3, 5, 9, and 21 mm rain events at which point floating outlets or 'flouts' in the tanks sink and allow the water to run onto the plots via drip irrigation lines. There are three replicates of the 0 and 3 °C treatments. Remaining treatments have one replicate each. Treatment levels represent a 7% increase in average precipitation event sizes for each 1 °C of warming. For example, if average precipitation event sizes were 10 mm a 1°C treatment would receive precipitation events with an average size of 10.7mm. The -1°C treatments are achieved by routing water from the tanks back onto the plot between rain events, thereby creating additional small (~1 mm) "rain events." To be clear, all plots receive the same total amount of precipitation. As with the rainfall manipulations, snowfall manipulations are used to create fewer, larger precipitation events. Snow treatments are applied by shoveling collected snow 9, 8, 7, 6, 5, 4, and 2 times during the growing season. These snow addition frequencies are roughly based on historical data (1928-2014) of snow events >4 cm. When historical snow event sizes are increased by 7% for each 1 °C of anticipated warming (removing the smallest events so that the yearly totals remains unchanged) then there is a median of 13, 11, 10, 8, 7 and 4 events per year for increases of 0 °C (unchanged), 1 °C, 2 °C, 3 °C, 5 °C and 10 °C, respectively. We used fewer snow additions than this because snow treatments were not applied for the entire winter. As with rain the -1 °C treatment increased the frequency of snow events.Crop plantings will follow the schedule designed by the farm manager. Plots will be seeded at a rate of roughly 125 kg/ha with a row spacing of 15 cm, using a plot seed planting drill. Wheat will be harvested late July each growing season. Herbicide (Roundup PowerMax) will be used once each spring for weed suppression. Safflower will be planted in the Fall of 2019 and 2021.Soil moisture will be measured roughly biweekly during the growing season at six depths in each plot (time domain reflectrometry; Sentek Sensors, Stepney Australia). Hourly measurements of soil water potential (Campbell Scientific 229 heat dissipation sensors; Logan, UT, USA) will be taken at one sheltered-control plot and one 3 °C treatment plot.At the end of each growing season, the target crop will be harvested from a 1 m x 1 m subplot at plot. Wet biomass will be recorded and seed will be collected using a stationary thresher, and wet and dried seed mass measured (oven dried to constant weight at 60 °C). Total crop mass from the remaining plot will be harvested and weighed wet and dry. Wet and dry weed biomass (primarily Lactuca serriola) will also be measured for each plot. Mean plant height will also be recorded prior to harvest. Additional within-season measures of growth will include leaf area index (LAI; AccuPAR LP-80, Meter Group, Inc. Pullman, WA), normalized difference vegetation index measurements (NDVI; Spectral reflectance sensor for NDVI, Meter Group, Inc. Pullman, WA), photochemical reflectance index (PRI; spectral reflectance sensor for PRI, Meter Group, Inc. Pullman, WA), and canopy temperature (infrared radiometer SI-421, Apogee Instruments, Logan, UT).Root growth will be measured using one root observation chamber in each plot (Bartz Technology Co, Carpenteria, CA) and two soil cores (0-15cm) will be taken from each plot during peak growing season.Regressions of above and belowground and seed biomass as a function of treatment (i.e., Fig. 4) will be conducted. The repeated measures data (LAI, NDVI etc.) will be analyzed use a mixed effects model with fixed effects of treatment and time and random effect of plot ("lmer" function in the lme4 package; Bates et al. 2015). Due to the hybrid experimental design, regression analyses, as described above, will be conducted using all treatment levels and mixed models will be run using just the treatments with replicated plots (shelter-less control, sheltered control, and 3°C treatment). Statistical analysis will be done using R (R Core Team 2017).Additional analyses will be performed using the Hydrus 1D model (Šim?nek et al. 1999). This model describes water movement through the soil profile and through plant tissues. Environmental parameters needed by this model (i.e. temperature, relative humidity, precipitation, wind speed and light intensity) will be obtained from a nearby meteorological station and we have soil texture data. Root profiles will be determined from rhizotron samples. LAI will be measured directly as described above. Soil moisture data collected during the experiment will be used to validate Hydrus predictions of soil moisture content (and thus ecohydrological consequences of fewer, larger precipitation events).

Progress 10/01/19 to 09/30/20

Outputs
Target Audience:Dryland agricultural producers of the Intermountain West. Plant physiologists and ecologists. Changes/Problems:We identified a new site in which to establish plots that test the combined effects of increasing temperature and precipitation intensity. However, the student who began working on this project has decided to pursue different research directions. We are now looking for a new student to establish new plots. What opportunities for training and professional development has the project provided?We have a PhD student (Holdrege) and many undergraduates (see below) working on the project. We have published two papers describing the work in top-tiered journals (New Phytologist and Ecology). Holdrege and Kulmatiski are currently learning the STEPWAT2 program which will allow us to upscale our results. In addition to experimental design, Holdrege has learned data management, root image collection and analysis, plant physiology measurements and interpretation (NDVI, PRI, IR, stomatal conductance, root growth, biomass, seed production, germination), Hydrus soil water flow modeling, stable isotope experimental design and analysis, STEPWAT2 ecohydrologial modeling, and received a master's in statistics. Our PhD student has also begun collaborating with an international research group (IDE: International Drought Experiment) based out of Colorado studying the effects of precipitation on dryland ecosystems. As a part of this group, he is learning to manage and analyze data from a large international group. In the past year, we have had nine undergraduates work extensively on our project. These students have learned about experimental design and fieldwork as well as plant physiology, community ecology, ecohydrology, image analysis, and data collection and preparation. These include Dakota Green, Tori Brummer, Finn Christenson, Stephanie Hall, Maria Catalana, Laura Beck, Ryan Choi, Emily Wilde, Cristana Chirvasa. We have also had additional PhD students, Leslie Forero and Ryan Choi help on the project. How have the results been disseminated to communities of interest?We have a poster describing our research at the Hardware Wildlife Management area. We presented a talk at the Utah Society for Range Management meeting in November, 2020 title: Rangeland responses to increased precipitation intensity. The PhD student and I published a paper including data from this experiment in the top-tiered research journal New Phytologist. This paper describes new approaches to understanding large-scale vegetation changes in semi-arid ecosystems. The PhD student and I have published the first paper from his thesis describing this research at Ecology. Our PhD student has described our research in several meetings to the International Drought Experiment. What do you plan to do during the next reporting period to accomplish the goals?We continue to process isotope samples from our tracer experiment, summer 2020. In the next nine months, we anticipate preparing an additional manuscript describing the six years of the study including the tracer experiment. We continue to learn the STEPWAT2 program, which will allow us to scale-up our results to a landscape / regional level. We anticipate completing these analyses and preparing a manuscript describing these results in the next 12 months. This will allow us to both apply what we have learned to larger scales and conceptually test the effects of temperature and precipitation change. We are beginning to establish a new experiment that will test the effects of increased precipitation intensity and increased temperature on rangeland plants.

Impacts
What was accomplished under these goals? At our agricultural site, we have completed two crop years and two fallow years of treatments and collected all data. We have analyzed data and drafted a manuscript describing the work. We expect to submit this manuscript for review December 2020. Somewhat surprisingly, this research revealed no winter wheat response to a wide range of increasing precipitation intensity. This result was in contrast to results from a paired study in a rangeland site, where shrub growth increased in response to increasing precipitation intensity. There are two important implications from this work. First, winter wheat is highly resistant to changes in precipitation intensity. Inasmuch, producers do not need to worry about negative impacts of expected increases in precipitation intensity. It is important to note that our experiment isolated the effects of increased precipitation intensity. The role of increasing temperatures must be considered separately either through simulation modeling, literature review or additional experiments. The second implication is that there is potential to select winter wheat varieties that can make better use of an increase in soil moisture that is expected with fewer, larger precipitation events. Consistent with theoretical models, treatments increased deep soil moisture but winter wheat at our site was not able to convert this to increased growth or seed production. Varieties with deeper rooting profiles may be better able to respond positively to increased precipitation intensity. At our rangeland site, our first paper describing three years of treatments was recently published in Ecology. In this paper (which will be featured on the cover of Ecology), we report that increased rain and snow intensity 'pushed' water deeper into the soil and that shrub growth increased while grass and forb growth remained unchanged. These results suggest that the increase in precipitation intensity that has been predicted and observed to occur with atmospheric warming is likely to contribute to the shrub encroachment seen around the world. In Utah, this shrub encroachment is reflected in juniper expansion into rangelands and increased sagebrush growth. Our results suggest that increasing precipitation intensity is contributing to and will continue to contribute to juniper and sage growth in Utah. This is an important finding for rangeland managers because juniper and sage are poor forage relative to the grasses and forbs they replace. We have also completed two additional years of treatments at our rangeland site and we have removed our treatment shelters from the site. We are currently monitoring post-treatment responses at the site. This past year we performed an isotope tracer experiment at the site to describe plant rooting distributions in treated and control plots.

Publications


    Progress 10/01/18 to 09/30/19

    Outputs
    Target Audience:Dryland agricultural producers of the Intermountain West. Changes/Problems:We have not encountered problems this year. Things are running smoothly. What opportunities for training and professional development has the project provided?We have a PhD student and several undergraduates working on the project. The PhD has formed their committee, has one paper accepted and a second in review. In the past year he has learned how to use the Hydrus soil water movement model, Random Forest model and is now learning the STEPWAT2 program. Other analyses associated with this research include data management, root image collection and analysis, plant physiology measurements and interpretation (NDVI, PRI, IR, stomatal conductance, root growth, biomass, seed production, germination). Our PhD student has also begun collaborating with an international research group (IDE: International Drought Experiment) based out of Colorado studying the effects of precipitation on dryland ecosystems. As a part of this group, he is learning to manage and analyze data from a large international group. In the past year, we have had three undergraduates work extensively on our project. These students have learned about experimental design and fieldwork as well as plant physiology, community ecology, ecohydrology, image analysis, and data collection and preparation. How have the results been disseminated to communities of interest?We have a poster describing our research at the Hardware Wildlife Management area. The PhD and I have just had a paper accepted in the top-tiered research journal New Phytologist. This paper describes new approaches to understanding large-scale vegetation changes in semi-arid ecosystems. The PhD student has submitted the first paper from his thesis describing this research at Global Change Biology. Our PhD student has described our research in several meetings to the International Drought Experiment. What do you plan to do during the next reporting period to accomplish the goals?This spring is another planned fallow year at the study site. We will use time this winter and spring to prepare manuscripts, maintain our paired experiment in a sagebrush system. We plan to add an isotope tracer study to better describe the rooting distribution of plants in response to precipitation manipulation treatments to be executed spring 2020. Next steps for this research will be to test responses of different varieties and the response of crops to simultaneous increases in precipitation intensity and temperatures.

    Impacts
    What was accomplished under these goals? We have completed treatments on two winter wheat crops. Data is entered and preliminary analyses performed. We have submitted two manuscripts describing this research (one accepted, one in review). Our PhD student has selected their committee members and we are now working with a colleague to begin to scale our plot-level measurements to landscape scales. Initial results suggest that winter wheat is highly resistant to increases in precipitation intensity. However, results from a paired experiment in a rangeland system suggests that increased precipitation intensity can increase plant productivity by decreasing interception and evaporation and increasing deep soil water infiltration. Together, these results suggest that increasing precipitation intensity is unlikely to decrease dryland production and with appropriate management and variety selection, it may be possible to increase plant productivity under increasing precipitation intensity conditions.

    Publications


      Progress 07/01/18 to 09/30/18

      Outputs
      Target Audience:Dryland agricultural producers of the Intermountain West. Changes/Problems:Because snow pack is determined more by wind and topography than by the amount of precipitation, it is difficult to manipulate the snow pack. We have found that our rhizotron tubes produce poor data in the top 10-15 cm due to poor soil contact with the observation tubes . We are now using soil cores to obtain shallow root data. What opportunities for training and professional development has the project provided?The master's student on this project has become a PhD student who will also receive a master's in statistics. This student presented initial results at an international conference and has begun preparing a manuscript describing results from the first winter wheat crop in this experiment. How have the results been disseminated to communities of interest?Results were presented at the Ecological Society of America Conference. We are preparing a manuscript describing results from the first winter wheat crop responses to treatments. What do you plan to do during the next reporting period to accomplish the goals?Treatments will continue this winter and winter wheat responses will be monitored in the spring. Next year will be a fallow season. We expect to prepare and submit a manuscript this spring. We will also begin to contact extension agents with our results.

      Impacts
      What was accomplished under these goals? Treatment systems are in place and a new winter wheat crop was planted this fall. Treatments continue to be applied.

      Publications