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INVESTIGATOR: Eivazi, F.

PERFORMING INSTITUTION:
LINCOLN UNIVERSITY
JEFFERSON CITY, MISSOURI 65101

SPATIAL VARIABILITY OF SOIL GREENHOUSE GAS EMISSIONS AND SOIL MICROBIAL DIVERSITY AND FUNCTION IN CONVENTIONAL AND ALTERNATE LAND USE SYSTEMS IN FLOODPLAIN SOILS

NON-TECHNICAL SUMMARY: Agricultural sources continue to account for significant proportions of global anthropogenic production of major greenhouse gases (GHG), such as nitrous oxide and methane. Soil-based fluxes of GHG are produced primarily through plant and microbial processes and are affected by soil physical, chemical, and biological properties. The lower Missouri River Floodplain (MRF) region encompasses many different land use systems including agriculture and riparian forest. The effects of these different land use systems in the MRF on soil GHG (i.e., carbon dioxide, nitrous oxide and methane) emissions have been little studied. Likelihood of climate change induced frequent flooding may alter the GHG fluxes from these landscapes further. The specific objectives are to evaluate soil GHG emissions (CO2, CH4, N2O) in floodplain soils under agroforestry, row-crop agriculture, and forested systems in response to differences in soil water content, temperature, land use, and nitrogen inputs. Since, microbial processes are big drives of GHG emissions, efforts will be made to evaluate the microbial communities in these landscapes as well as in response to flooding. Characterization of the spatial variation of GHG emissions in these land-use systems in the Missouri River floodplain is also a needed area of study. Future GHG research projects within the region need a solid understanding of the systems for proper statistical design. Last but not least, this project aims to develop a curriculum for undergraduate research with an objective to build capacity for Lincoln University to train the next generation of environmental professionals from underrepresented communities.

OBJECTIVES: Soils contain the second largest global pool of C after ocean sediments, more than twice the amount contained in atmospheric and living biomass pools. Soil physical properties influence the exchange of gases between the soil surface and atmosphere. Similarly, soil microbial activity dominates soil CO2 production. Land management practices, such as tillage, compaction, removal of biomass, fertilizer applications, and vegetation changes alter GHG transportation and production factors, and consequently affect their emissions. Alteration of the hydrological cycle and frequent flooding (with associated deposition of sand and silt) can influence several of the above mentioned properties. It is essential to develop a better understanding of how such events influence emissions of greenhouse gases with higher frequency of predicted extreme weather events. Therefore the following objectives are proposed:Research ObjectivesTo determine the in-situ variations in GHG emissions among different land use systemsTo assess the impact of flooding to better understand how each system will be influenced by frequent extreme flooding using laboratory incubation.Compare the soil microbial communities in-situ and in response to the flood treatments.Educational ObjectiveTo increase students' knowledge and interest in agricultural sciences through experiential learning.

APPROACH: Objective 1Experiment 1: Characterize soil baseline properties to determine the effects of land use on soil C and N and other key indicators that are known to influence soil microbial communities and greenhouse gas emissions. Soil properties will be measured according to published analytical methods (Table 1). The relative proportions of labile and more stable soil C and N fractions due to changes in land use will be assessed through measurement of water-extractable organic C and N, particulate organic matter C and N and KMnO4-oxidizable C and N. These measurements of soil C and N have been sensitive indicators of the effects of management and have been tested widely (e.g., Culman et al., 2012) and been included in indices of soil quality (e.g., Gugino et al., 2009).Experiment 2: Measure in-situ greenhouse gas emissions in the various land use management practices using installed chambers.Relative soil GHG emissions will be quantified using the USDA-ARS GRACEnet chamber-based Trace Gas Flux Measurement Protocol (Parkin et al., 2003) and measurement will be done with a gas chromatograph. Soil water content and temperature will be determined at the time of each flux measurement to a depth of 10 cmObjective 2. To assess the impact of flooding to better understand how each system will be influenced by frequent extreme flooding using laboratory incubatio.Experiment: Incubation study to measure the impact of flooding on greenhouse gas emissions:Intact soil cores will be collected from the different land use systems and incubated for a period of 12 weeks for the measurement of GHG (CO2, N2O, & CH4) production. During testing the cores will remain intact inside to account for management induced soil structural changes. Three soil moisture regimes (60% WFPS (designated as OPT), flooded or 100% WFPS (designated as FLD), and fluctuation between 100% WFPS and 60% WFPS (designated as FLX)) will be used to simulate precipitation and the frequent flooding. To mimic real management conditions N fertilizer will be added to the agroforestry and agricultural soils in the form of a potassium nitrate (KNO3) solution and designated as AF-N and AG-N, respectively. Both management groups will receive either 0 or 0.20 g N kg-1 soil, approximately equivalent to a common field application rate of 180 kg N ha-1. Due to incubator and sampling space constrictions, replications will be divided into three groups within a randomized complete block design. Each sample block will be placed in the same location within the incubator and sampled at the same time. GHG emissions will be measured for a total of 20 times over the incubation period. Water regime will be managed on a weekly basis. Sampling will largely follow the vented field static chamber techniques set forth by the USDA GraceNET protocol (2003), with adaptations to accommodate laboratory measurements. At the initiation of each sampling period (Time 0), the chambers will be closed and flushed with He to alleviate the issue of diffusion resistance, the result of high concentration of atmospheric gases within the chamber headspace (Rochette and Eriksen-Hamel, 2008). Three 12 ml gas samples will be taken at 0, 20, and 40 minutes by syringe and immediately placed in an 8 ml pre-evacuated glass vial. The vials will be sealed with gray butyl rubber septas, considered to be minimally reactive to N2O and CH4 (Parkin et al., 2003). Samples will be stored at room temperature and processed as soon as possible to minimize the possibility of contamination. Gas concentration analysis will be carried out using a Shimadzu 2014 Gas Chromatograph (Columbia, MD) fitted with a methanizer, flame ionization detector, and electron capture detector. The three timed gas samples will be used to perform the efflux calculations. The gas efflux will be estimated at the ambient gas concentration tangent using linear regression.Objective 3: Compare the soil microbial communities in-situ and in response to the flood treatments.Experiment 1: Compare microbial community profiles in the different land use systems (both in-situ and incubation samples) using PCR-DGGE method: Soil samples will be collected from each management system and total soil DNA will be isolated. Purity of isolated DNA will be checked and amount of DNA quantified. A PCR reaction will then be carried out using primers specific to the V3 region of the bacterial 16S rRNA gene (Nakatsu et al., 2000) which will result in a fragment of approximately 180 bp in length. Purity of PCR fragments will be checked and will then be subjected to a denaturing gradient gel electrophoresis (DGGE) on a 8% polyacrylamide gel using a DCode universal mutation detection system (BioRad Laboratories, CA, USA) in order to generate bacterial community profiles for each sample. Unique and dominant bands in each profile will then be excised, purified, and cloned, and identified. Bacterial richness index and Shannon Weiner Diversity index will be calculated from the different DGGE profiles and linked with land use management.Experiment 2: Evaluating soil microbial enzyme activity.Dehydrogenase activity represents the intensity of intracellular microbial metabolism in soil. Dehydrogenase activity will be determined on for soils from under all management systems using a modified method based on von Mersi and Schinner (1991). β-Glucosidase enzyme activitywill bedetermined based on the procedure of Dick et al.(1996).Objective 4: To increase students' knowledge and interest in agricultural sciences through experiential learning.Undergraduate Research Program (URP), with experiential student research internshipsEach year 5 undergraduate students from LU will be selected to participate in URP. Student recruitment and informational campaigns will be conducted throughout the year by the Educational Coordinator and Educational Program Assistant based at LU and a special effort will be focused on recruiting underserved students. Recruitment activities will include: 1) developing an email flyer for distribution to STEM departments, 2) contacting faculty members in STEM departments directly to promote the program and seek nominations, 3) conducting program information sessions for science faculty and students, and 4) electronic advertisement (department, school and university websites and server lists). Selection criteria of the students will include academic performance, experience, maturity level and career plans and efforts will be made to insure diversity and a wide range of relevant disciplines (e.g., environmental sciences, biology, soil science, atmospheric sciences, and plant sciences) are represented in the group. These students will be intricately involved with all project activities with different investigators.

PROGRESS: 2020/03 TO 2021/02
Target Audience:Land owners, farmers, Missouir Dept of Soil and Water Conservation, DNR, EPA and other agencies; scientists, students. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?One graduate and one undergraduate student were trained. How have the results been disseminated to communities of interest?Conference presentations were made. What do you plan to do during the next reporting period to accomplish the goals?More data will be collected on GHG and soil analysis during spring and summer 2021.

IMPACT: 2020/03 TO 2021/02
What was accomplished under these goals? Concentrations of greenhouse gases (GHG) from anthropogenic and natural sources have increased in recent centuries with numerous potential changes on different natural and managed systems. Changes in land-use systems and management practices (e.g., tillage, fertilizer applications) affect soil microbial organisms and soil organic matter as well as soil GHG emissions. The hydrology of floodplains and their poorly drained soils often result in anaerobic conditions that impact the prevalence of differing soil microbial consortiums affecting soil GHG emissions. GHG (methane, nitrous oxide, and carbon dioxide) emissions were investigated over a growing season (May-October 2020) from three different land-use/land-cover systems agroforestry (AF), agriculture (AG), and riparian forest (RF) located at the Horticulture and Agroforestry Research Center, New Franklin, Missouri, U.S. Gas samples were collected in a weekly time-period using static chambers. Gas concentrations were measured with a gas chromatography unit (Shimadzu 2014) equipped with an electron capture detector (ECD), and flame ionization detector (FID). Gas fluxes were analyzed with R Studio (version 4.0.2) and HMR package (Flux Estimation with Static Chamber Data, version 1.0.1) with SAS (University Edition) utilized for the statistical analysis. Results revealed that the agroforestry system (AF) has a significantly higher (p<0.0001) nitrous oxide (N2O) emission compared to AG and RF management. There were no significant differences in the case of methane (CH4) emissions between the three different treatments. RF and AF showed significantly higher (p<0.0001) CO2 emissions than AG. The highest GHG emissions happened in June after a flooding event with an average of 224 g N2O-N ha-1 d-1 and 148 g CH4-C ha-1 d-1 from the AF treatment, and 77101 g CO2-C ha-1 d-1 from RF. Conclusions showed that nitrogen-based fertilizer applications, and higher organic matter in the AF site, contribute to the higher N2O emissions compared to RF and AG. AG in contrast had not received any nitrogen fertilizer for two years due to soybean cultivation. Higher organic matter and enzyme activity in RF and AF led to higher CO2 emissions from both sites compared to the AG treatment.

PUBLICATIONS (not previously reported): 2020/03 TO 2021/02
1. Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Ansari, J. and F. Eivazi. 2020.Soil Enzyme Activity as Affected by Selected Land Management in Floodplain Systems.75th SWCS International Annual Conference July 26 - 29, 2020, Des Moines, Iowa;
2. Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Ansari J., S. Anderson, F. Eivazi. 2020. Greenhouse Gas Emissions, Porosity, Microbial Activity, and Enzyme Activity as Affected by Selected Land Management in Floodplains.11th Annual UMCA Agroforestry Symposium, January 30, 2020 at University of Missouri, Columbia, MO.
3. Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Ansari, J. S. Anderson, F. Eivazi. 2020. Soil Enzyme Activities Affected by Selected Land Management. ASA-CSSA-SSSA International Annual Meeting, November 9-13, 2020 in Phoenix, Arizona.