Progress 06/15/23 to 06/14/24
Outputs
Target Audience:As noted in our prior report, this project is producing outcomes relevant to the conservation and agricultural sectors. Specifically, we are quantifying potential economic benefits of waterbirds foraging on flooded rice fields, while simultaneously investigating whether introducing fish to fields provides additional benefits to farmers. Ideally, the benefits provided by birds and fish to rice production might reduce barriers to winter field flooding and help further incentivize the practice, thereby bolstering farmland conservation. Uncovering diverse benefits from field flooding and fish introductions has important implications for growers and the rice industry more broadly. In year 2, most of our activities focused on experimental design and planned data collection. We made excellent progress connecting with target audiences in several dimensions. First, we established a strong working relationship with Montna Farms, one of the leading producers of premium, short-grain rice in California. Montna Farms graciously agreed to host our large-scale field experiments and are now integral partners in the work. We meet regularly with the vice president of operations for Montna Farms- Jon Munger- to integrate our experiment into their regular operations. In year one, Bruce Linquist joined our core scientific leadership team. As a Professor of Cooperative Extension specializing in rice production, Dr. Linquist brought practical knowledge that greatly improved our experimental designs, and were tractable for implementation in commercial-scale rice fields. Dr. Linquist is also a trusted partner and voice among the California rice community, which was important when we were searching for a host farm. Nonetheless, the experiment remains complex, with many moving parts, necessitating constant communication between Jon Munger and our team throughout the year. Second, we continued to maintain our relationship with key project partners (e.g., the California Rice Commission), updating them on our progress. Finally, we partnered with the UC Davis press office to develop a feature news story and video showcasing our project. The resulting products were featured in the College of Agricultural and Environmental Science's newsletter as well as other press outlets (https://caes.ucdavis.edu/news/birds-and-fish-flooded-rice-fields-promoting-biodiversity-and-climate-protection). Changes/Problems:As noted in our prior report, we had planned on implementing our first field season and major experimentation in Fall 2022/Winter 2023. However, after significant deliberation (detailed in our prior report), we delayed our first field season one year (until Fall 2023/Winter 2024). This proved a wise decision, as we were able to use the intervening time to train personnel and form a strong partnership with Montna Farms, which, in turn, allowed us to successfully complete our first field season. Surprisingly (and unfortunately), waterfowl were very rarely detected in plots during point counts. We attempted to remedy the situation by using decoys; however, this was unsuccessful. We also explored attracting birds with cracked corn, but federal regulations precluded baiting near hunted areas. Thus, we have limited ability to assess the effects of waterfowl in rice fields using data from our first year (as originally outlined in the proposal). Fortunately, however, piscivorous birds, including herons, egrets, and kingfishers, were frequently encountered in our study plots. Thus, the first-year experiment has necessarily shifted towards assessing predator-prey relationships between birds and fish as well as the effects of piscivorous birds on agronomic ecosystem services and greenhouse gas emissions. We are hopeful that waterfowl will visit our plot in the second field season, and we are considering other ways to attract birds (e.g. using legal spinning wing decoys shown to attract waterfowl). Indeed, waterfowl numbers and distributions were aberrant in 2023/24 compared to other years; birds arrived late and did not use some areas that traditionally have high numbers (affected by weather and habitat condition in the north and late rains in the valley). Our partners at Montna Farms said waterfowl are usually abundant in the plots we selected. What opportunities for training and professional development has the project provided?The project is creating diverse training and professional development opportunities for many early career scientists and students. Our scientific leadership team's complementary expertise in ornithology (Karp, Eadie), fish ecology (Rypel), aquatic invertebrate ecology (Lusardi), biogeochemistry (Horward), and agronomy (Linquist) allows us to collaboratively train students in diverse field and lab techniques from distinct disciplines. During this reporting period, one PhD student, three undergraduates, one junior specialist, and one short-term field technician were employed on this project. Students and technicians are provided with one-on-one training in field techniques and/or lab methods from at least two (and often more) of the PIs. In addition, we also organized voluntary training opportunities for many more undergraduate students; for example, teaching students how to PIT-tag fish at UC Davis. We have also prioritized the individual career development for our trainees. For example, graduate student Mensch completed an individual development plan with co-supervisors Karp and Rypel to help define priority growth areas and professional development opportunities for the next year. She then met with Karp and/or Rypel on a biweekly basis throughout the year to discuss research objective and help her realize her goals. Mensch was also provided opportunities to practice oral and written science communication skills. She wrote several graduate student grant applications, hosted lab meetings multiple times, and presented her at conferences. Mensch also took on leadership positions; for example, joining our departmental seminar committee and serving as co-chair of her graduate student association. How have the results been disseminated to communities of interest?Most of our focus in this review period has been on experimental design and data collection. As noted above, however, we partnered with the UC Davis press office to develop a feature news story and video showcasing our project. The resulting products were featured in the College of Agricultural and Environmental Science's newsletter as well as other press outlets (https://caes.ucdavis.edu/news/birds-and-fish-flooded-rice-fields-promoting-biodiversity-and-climate-protection). What do you plan to do during the next reporting period to accomplish the goals?Much of the next reporting period will focus on completing our second (and final field season). From June to September 2024, we will continue collecting soil and greenhouse gas samples throughout the summer rice growing period. Then, in September, we will collect data on crop yields, nutrient update, and weed biomass from each plot, immediately prior to harvest. Specifically, three quadrats will be selected from inside of each of the two plots per rice check (i.e., inside and outside each bird exclosure) and hand-harvested 5 cm above the soil surface using a sickle. Harvested plants will be separated into weeds, rice, and straw. Weeds will be weighed to quantify biomass. Rice and straw will be dried at 45 degrees C for 72 h and the rice will be threshed. Grain yield weight and above-ground dry biomass will be determined. Subsamples will be ground and analyzed for C, N, P, and K using standard methods. After harvest, our field will be re-engineered into 8 rice checks and the experiment described above will be repeated. Specifically, we will once again construct experimental bird exclosures, flood fields and introduce fish into fields. We will then begin monitoring plots for abiotic conditions, bird visitation, fish growth/survival, invertebrate abundance/composition, nutrient cycling, and greenhouse gas emissions, using the methods and approaches detailed above. We also expect our project to begin transitioning towards data analysis and communication phases over the coming year. We plan to conduct more preliminary analyses of data from year one, which can be finalized after our second year of data is collected. We are also excited to plan a media/field day next year, in which we bring key stakeholders and the popular press to our field site to showcase our work.
Impacts
What was accomplished under these goals?
This review period focused on experimental design, data collection, and laboratory analyses. From June-September 2023, we solidified methodologies, procured relevant supplies, and finished building our field team. Fieldwork began in early October 2023 when we partnered with staff at Montna Farms to engineer 8, 0.5-acre rice checks. In each check, we constructed one 24m2 PVC/mesh net exclosure to prevent birds from accessing the plot. In each check, we also delineated a 24m2 area to serve as a control (i.e., birds not excluded). In early November, checks were flooded and, once abiotic conditions were adequate (i.e., early December), fish were introduced to half of the rice checks. In this way, fish and bird presence were manipulated in a full-factorial design. Data collection began shortly after field flooding and is detailed below. Abiotic conditions: We placed one temperature/dissolved oxygen logger in each plot. Loggers recorded data on water conditions every hour throughout the period of field flooding (114 days). Just prior to field draining (late February), loggers were removed. Throughout the winter flooding period, water temperatures and dissolved oxygen values averaged ~11.7ºC and 7-7.5 mg/L, respectively. Neither temperature nor depth varied across treatments (all P> 0.05). We also monitored water depth throughout the experiment (N= 240 measurements total, across 10 sampling days). Water depths averaged ~11 inches throughout the experiment, and also did not significantly vary between treatments (p= 0.27). Once fields were re-flooded for rice planting, loggers were re-deployed in 4 plots to monitor temperature and dissolved oxygen throughout the summer growing season. Data are currently being collected for this time period. Bird visitation: To monitor bird activity within rice checks, we conducted bird surveys and deployed trail cameras to detect waterbird activity. Two trail cameras were placed in each rice check immediately after field flooding and were set to take photos every 10 minutes throughout the winter flooding season (N= >10k photos collected). Three bird surveys of each rice check were conducted on a weekly basis: one in the early morning, one in the evening, and one at night (using a night vision monocular). During each 10-minute count, observers identified all birds seen using each rice check to species and noted their behaviors every 30 seconds (e.g., feeding, loafing, etc.). Observers also recorded birds adjacent to plots as well as survey conditions (temperature, wind speed, weather conditions, etc.). In total, plots were surveyed 40 times throughout the winter flooding season. Data entry and analysis is ongoing. Fish growth and survival: We procured 8,805 fish (i.e., golden shiner) in early November, and, over the course of 2 weeks, surgically implanting one third of them (N= 2,902) of them with PIT tags so fish could be individually tracked for growth and survival. All fish with PIT tags were weighed, measured (i.e., length in mm), and then held at UC Davis until dissolve oxygen levels stabilized above 5 mg/L (i.e., December 4, 2023). Fish were then introduced into rice checks at a density of 2,200 fish/check. On a weekly to biweekly basis throughout the winter flooding period (9 sampling days), we placed minnow traps in each rice check to capture fish (N= 1108 fish). In late February, we began draining fields and, using a combination of Fyke nets, dip nets, and beach seine nets, we captured 2,379 fish from the four fish checks. Every captured fish in the experiment was weighed, measured, and unique IDs were obtained for PIT-tagged individuals. Fish grew over the experiment, increasing in weight from an average of 2.9 g to 4.4 g (50% increase), in length from 72mm to 78 mm (9% increase), and in condition factor (K) from 0.76 to 0.98 (28% increase). Growth was higher in absence of birds (0.41 g/day versus 0.45 g/day), but this effect was not significant. Preliminary results suggest birds likely reduced fish survival: 26% of the fish were recovered from the control plots versus 76% percent inside bird exclosures. Invertebrate sampling: We surveyed pelagic and benthic invertebrates throughout the winter to quantify resource competition between birds and fish as well as potential trophic cascades associated with fish introduction. Invertebrates were sampled at an approximately biweekly basis (i.e., 5 sampling events per plot). We used Wisconsin-style plankton nets for pelagic invertebrates and Hess samplers for benthic invertebrates (N= 80 samples for each sampling method). Invertebrates are currently being enumerated and identified to family in the laboratory. Nutrient cycling: We collected soil samples to assess whether birds and/or fish affect soil quality. After flooding and continuing throughout the year, soil samples were collected from each plot to a 15-cm soil depth using a Dutch auger. Sampling occurred on a weekly basis during the winter flooding period and then biweekly during the growing season. As of mid-June, we had collected 286 soil samples across 17 sampling events. In the lab, composite soil samples were processed for water content as well as phosphorus, NH4+, and NO3- availability, using standard methods. We are now processing soil samples for total C and total N. Beginning during winter flooding, we also collected porewater with a custom sampler for the determination of NH4+, NO3, and dissolved organic C (DOC). Because of issues with the sampler, only three sampling occasions occurred during winter. Sampler issues have been remedied, and porewater is now being collected on a biweekly basis. All samples from the winter flooding period and one from summer harvest have already been analyzed for NH4+ and NO3. Other nutrient analyses are ongoing. Greenhouse gas emissions: We are quantifying methane and nitrous oxide emissions from rice fields to determine whether fish and/or birds induce a trophic cascade that ultimately results in lower greenhouse gas emissions. Shortly after field flooding, we used a Li-COR methane and nitrous oxide gas analyzer to collect data on emissions. Samples were taken on a bi-weekly basis, with more frequent sampling occurring when emissions often peak (e.g., field draining). In total, we sampled greenhouse gases on 22 occasions through mid-June (N>700 measurements). We also measured redox potential using an ORP probe (N= 17 sampling events and 196 measurements, with no samples taken during dry periods). Preliminary analyses support our hypothesis that fish reduce methane in rice fields. Restricting analyses to the winter flooding period when fish were present in fields, models suggest fish reduced methane fluxes in flooded rice fields (p= 0.028). Specifically, models predicted emissions were three-times higher when fish were absent compared to when present (20 vs. 65 nmol+1m-2s-1). We also observed slightly higher emissions when birds were absent compared to when present, perhaps reflecting the predatory nature of bird/fish interactions; however, this was not significant. A key focus looking forward is development of a mechanistic understanding for how fish are reducing methane emissions. We are using porewater samples to help answer this question. First, methane is being directly measured in porewater to understand how concentrations change from the soil through the water column. Even more importantly, we are conducting stable isotope analyses of the porewater (i.e., measuring carbon-13 concentrations). These analyses will tell us whether, less methane is being produced in fish plots or if more methane is being consumed by methanotrophic bacteria. Our working hypothesis is that fish consume zooplankton which, in turn, consume methanotrophs. By adding fish to fields, a trophic cascade may be triggered whereby methanotrophic bacteria increase in abundance and consume more methane. Stable isotope analyses have been completed for half of the existing porewater samples.
Publications
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Progress 06/15/22 to 06/14/23
Outputs
Target Audience:Our project will produce outcomes of relevance to those working in conservation and agricultural sectors. Specifically, we seek to both quantify the potential economic benefits of waterbirds foraging on flooded rice fields, while simultaneously investigating whether introducing fish to fields could provide additional benefits to farmers. Ideally, the benefits provided by birds and fish to rice production might help reduce barriers to winter field flooding and help further incentivize the practice, thereby bolstering farmland conservation. Uncovering the economic benefits of field flooding and fish introductions would have important implications for growers and the rice industry more broadly. Our initial activities related to stakeholder outreach in year 1 have largely focused on solidifying strong relationships with the agricultural sector. Our strategy has been two-fold. First, we invited Bruce Linquist to join our core scientific leadership team. Linquist is a Professor of Cooperative Extension, the Vice Chair of Outreach and Extension within the UC Davis Plant Sciences Executive Committee, and one of the world's foremost experts in California rice production. Since joining our team, we have relied heavily on Linquist to develop experimental approaches that are both tractable to implement in commercial rice fields as well as likely to effectively evaluate our core questions. Linquist has been involved in multiple project-wide planning meetings and will continue to work with us throughout the duration of the project. Second, we developed attractive outreach documents that clearly articulate our project's goals and likely outcomes. We then shared these documents with individuals at the California Rice Commission as well as Central Valley rice farmers. Finally, to help promote grower/industry buy-in, we held group meetings with both stakeholder groups to exchange ideas about specific questions that we could investigate and potential methodologies. PIs Rypel and Karp have engaged the California Rice Commission on finding the right farm for conducting the work. PIs Rypel, Karp, and Eadie have all had conversations with potential growers who might be interested in hosting this project. PIs Karp and Rypel have also interacted with colleagues from Resource Renewal Institute who indicated a high interest in the project. Though most of our outreach efforts have focused on the agricultural sector to date, it will be essential to engage with a variety of conservation groups throughout project given the potential conservation implications. In the past year, we met with representatives from representatives from multiple organizations focused on conservation in working landscapes to discuss our project (e.g., Wild Farm Alliance, California Trout, and the Nature Conservancy). Changes/Problems:Under our original timeline, we had planned on implementing our first field season and major experimentation in Fall 2022/Winter 2023. After significant deliberation, we decided to delay our first field season one year (until Fall 2023/Winter 2024) for two core reasons. First, we did not receive funds until June 2023, which meant the earliest time that the graduate student that we recruited to join our project (Emily Mensch) could begin working with us was October 2023. Sticking to our original schedule would have required Mensch to immediately begin fieldwork upon arriving in California. We felt it would be best for the project to allow Mensch to relocate to California, complete her graduate coursework requirements, and gain familiarity with the rice agroecosystem before organizing the first major field season. This decision proved quite fruitful and allowed us to provide Mensch with significant training in field methods and fish husbandry in Winter 2024 (as well as complete all outstanding graduate coursework requirements). As a result, Mensch will be able to fully focus on fieldwork during our first field season. Second, the farm on which we had originally proposed conducting our experiment was sold, necessitating that we find a new location for our field experiments. Simultaneously, the historic multi-year California drought resulted in widespread fallowing of California rice as well as significant declines in winter field flooding. There were therefore few available study sites that would have been tractable in Fall 2022/Winter 2023. Fortuitously, the drought largely ended in winter 2023 and, as a result, there will likely be much more flooded rice fields next winter. Growers anticipate that, with the high volumes of precipitation and snowpack in 2022-23, there will be sufficient water supply for rice field flooding for the next two years. This positions our project exceptionally well for success, given the inevitable unpredictability of weather and precipitation. Thus, after significant outreach efforts, we are currently in the final stages of securing a rice grower partner for this project. What opportunities for training and professional development has the project provided?We recruited an excellent PhD student- Emily Mensch- to lead the experimentation for this project. Immediately after arriving at UC Davis, Mensch completed an individual development plan with co-supervisors Karp and Rypel to help define priority growth areas and professional development opportunities for the next year. Mensch then met with Karp and/or Rypel on a biweekly basis throughout the year to discuss research objective and help her realize her goals. In Winter 2023, Mensch shadowed graduate students and technicians working on a related project focused on assessing salmon growth and survival in rice fields. By accompanying the team to the field multiple times each week throughout the winter, Mensch gained exposure to best practices for working with fish in California rice fields, learning how to surgically implant PIT tags, capture fish in rice fields, collect morphometric measurements, and build experimental bird exclosures. As noted, she is receiving more training on aquatic invertebrate sampling this summer. Since arriving at UC Davis, Mensch was also provided opportunities to practice oral and written science communication skills. She wrote several graduate student grant applications (and was awarded two grants totaling >$6k funds to date), hosted lab meetings multiple times, and presented her masters research in the Department of Wildlife, Fish, and Conservation Biology's (WFCB) seminar series as well as in the Ecology Graduate Student Association's (EGSA) annual research symposium. Mensch also took on leadership positions, joining the WFCB seminar committee, editing for the EGSA's Brickyard magazine, and mentoring undergraduate students through the UC Davis oSTEM program. She also published two papers from her master's research in top tier journals (i.e., Scientific Reports and Journal of Chemical Ecology). Impressively, Mensch accomplished all of this while successfully completing her required graduate coursework and serving as a teaching assistant for the first time. How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?Our project will leverage a working rice farm in California's Central Valley to explore the individual and combined effects of waterbirds and fish on biodiversity and ecosystem services. Most of our activities for next year will focus on setting up and implementing our first field season. Specifically, in Fall 2023, we will work with a rice grower to engineer 8, 0.25-acre, independent rice checks, half of which will be stocked with fish and half will serve as controls. Fish treatments will be stocked at 6000 fish/acre (1500 fish/replicate). Within each rice check, we will construct a 6m by 4m by 1m cage to exclude waterbirds. Beneath the water, cages will be outfitted with mesh of size sufficient to exclude fish but permit movement of invertebrates. In each check, we will also delineate a 6m by 4m area to serve as a control (i.e., birds not excluded). After the rice checks are engineered and exclosures are erected, we will begin data collection (outlined below). Abiotic conditions and bird surveys: Immediately after fields are flooded in early November, we will place one HOBO temperature/dissolved oxygen logger in each plot. Loggers will continuously record data on water conditions throughout the entire period of field flooding. To monitor bird activity within rice checks, we will both conduct standardized point count surveys throughout the flooding period and deploy trail cameras to detect waterbird activity at night. Fish growth and survival: All fish will be weighed and measured (i.e., length in mm) before release in late November. Upon release, we will also tag 33% of fish with passive integrated transponders (PIT). In March, we capture all fish within each experimental bird exclosure. Fields will then be drained and the rest of the fish (i.e., those outside the bird exclosure) will be captured exiting the field. For each captured fish, we will record the weight, length, signs of disease, and whether it was previously marked using a PIT tag scanner. We will then quantify the growth, survival, and final abundance of fish in each field. Invertebrate sampling: To quantify potential resource competition between waterbirds and fish, we will survey pelagic and benthic invertebrates, visiting each plot and acquiring samples on a weekly basis. Sampling will begin once fields are flooded and continue until field draining. To quantify concentrations of pelagic and benthic invertebrates, we will use Wisconsin-style plankton nets and small Ponar dredges, respectively. Samples will be transferred to Mason jars, preserved with 95% ethanol, and identified to the lowest taxonomic level possible. Nutrient cycling: Immediately after flooding in early November and continuing throughout the year, soil samples will be collected from each plot to a 15-cm soil depth using a Dutch auger and composited. Composite field-moist soil samples will be mixed and subsampled for inorganic N determinations. Remaining soil samples will be dried at 60 degrees C for 72 h and processed for phosphorus availability, NH4+, NO3-, and C using standard methods. Porewater will also be collected right before soil sampling with a custom sampler for the determination of NH4+, NO3, dissolved organic C (DOC), dissolved inorganic C (DIC), and dissolved organic N (DON). The sample will then be collected and transported on ice to the laboratory and stored at 4oC. DOC, DIC, DON and total dissolved N will be measured using standard methods. Crop yields, weed control, and nutrient uptake: In Fall 2024, three quadrats will be selected from the inside of each of the two plots per rice check (i.e., inside and outside each bird exclosure) and hand-harvested 5 cm above the soil surface using a sickle. Harvested plants will be separated into weeds, rice, and straw. Weeds will be weighed to quantify biomass. Rice and straw will be dried at 45 degrees C for 72 h and the rice will be threshed. Grain yield weight and above-ground dry biomass will be determined. Subsamples will be ground and analyzed for C, N, P, and K using standard methods. Greenhouse gas emissions: We will quantify greenhouse gas emissions on a biweekly basis throughout the year, coincident with soil/porewater sampling. During each sampling event, gases will be measured within close-vented chambers from 10:00 am to 3:00. A PVC ring will be driven into soils 1 week before seasonal measurements, leaving 2-3 cm above the soil surface. Boardwalks (i.e., boards and cinderblocks) will be constructed to avoid soil disturbance during sampling. Before measurements are taken, chambers will be placed on rings and sealed with a wide rubber gasket. A fan will then mix the chamber headspace to avoid gas gradients. Next, 20 mL of air will be extracted from the chamber every 10 min during a 30 min period. Headspace samples will be transferred to 12 mL pre-vacuumed Exetainers and analyzed for CH4 and N2O on a GC-2014 gas chromatograph. Porewater for dissolved CH4 and pN2O analysis will be collected as described above. After the removal of 4 mL porewater for DOC analysis, the headspace of the exetainer with the remaining porewater will be replenished with helium and shaken vigorously with a vortex mixer for 1 min, followed by the extraction of the headspace gas for CH4 and N2O analysis.
Impacts
What was accomplished under these goals?
Because we decided to delay our field season for one year (see justification in 'major changes/problems' section below), most of our activities focused on recruiting, training, planning, and stakeholder outreach. First, we recruited a new PhD student (Emily Mensch) to lead the project and provided her with extensive training in field methods. After visiting rice fields throughout the winter, Mensch mastered fish husbandry and field skills needed for her to operate independently while leading fieldwork next winter. Specifically, she received training in fish capture, implantation with PIT tag devices, and collecting morphometric. Mensch also worked with the scientific leadership team (i.e., Karp, Rypel, Eadie, Horwath, and Linquist) to design and pilot experimental waterbird exclosures in working rice fields. The prototype was effective and will be implemented at scale during the first field season. Mensch also mentored an undergraduate student at UC Davis who assisted in the pilot experiments. Our team of Karp, Rypel, Eadie, Horwath, Linquist and Mensch meet regularly to coordinate work, work through issues, and plan for the upcoming field season. Finally, Mensch was connected with a graduate student studying aquatic invertebrate communities in California wetlands. Mensch is accompanying him during fieldwork this summer to master aquatic invertebrate sampling methods before her first field season. Second, we developed outreach materials and organized meetings with the California Rice Commission, rice growers, and representatives from conservation groups to exchange ideas about our project and seek feedback (see target audience section above). Third, we secured supplemental funding to support the experiments; specifically, graduate student grants that Mensch successfully applied for. Fourth, the scientific leadership team met 7 times throughout Fall and Winter (2022-2023) to refine our experimental and methodological approaches. In summary, delaying our first field season for one year gave us the time needed to fully prepare for our upcoming experiments.
Publications
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