SHELTERBELT STRUCTURE AND FUNCTION IN A CHANGING GREAT PLAINS ENVIRONMENT

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: MCINTIRE-STENNIS
• Reporting Frequency: Annual
• Accession No.: 1017735
• Project Start Date: Oct 17, 2018
• Project End Date: Sep 30, 2021
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF NEBRASKA
(N/A)
LINCOLN,NE 68583

Performing Department
School of Natural Resources

Non Technical Summary
Nebraska has played a key role in the study and management of the Great Plains' shelterbelts (windbreaks) since the 1930's. The University of Nebraska's Agroforestry Research Farm was started in 1965 and has over 8km of experimental shelterbelts. However, in the 21st century shelterbelts, especially those protecting crop fields, are disappearing in the Great Plains. Decades-old windbreaks are being removed despite evidence that these practices can help maintain crop yields under climate change and protect against wind erosion, which is predicted to increase between 15-18% under a warming climate. Other shelterbelts have fallen victim to new pests such as pine wilt and emerald ash borer. The benefits of windbreaks for modern cropping systems, as well as the other ecosystem services they provide, need to be reassessed. In this project, a team of 4 scientists from UNL and collaborators at three agencies, propose two new studies that use the Agroforestry Research Farm's 50-year old shelterbelts to address 21st century issues in the Great Plains. Study 1 uses new methods to analyze the effects of shelterbelts on plant stress, crop productivity and carbon sequestration in a dryland corn/soybean cropping system. Study 2 uses experimental manipulations of our mature green ash windbreaks to examine the potential impacts of emerald ash borer in rural landscapes. Both studies integrate innovative remote sensing research with platforms ranging from ground sensors to aircraft and satellites.

Animal Health Component

75%

Research Effort Categories

Basic

25%

Applied

75%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
125	0199	1070	100%

Knowledge Area
125 - Agroforestry;

Subject Of Investigation
0199 - Soil and land, general;

Field Of Science
1070 - Ecology;

Keywords

windbreaks

shelterbelts

maize

soybean

emerald ash borer

remote sensing

chorophyll fluorescence

plant stress

Goals / Objectives
Goal 1 (Study 1). Document the effects of shelterbelts on a dryland corn/soybean cropping system when compared to a matched, unprotected cropping system.Objective 1.1. Analyse the spatial pattern of crop yield and crop stress using GPS-equipped combines (harvest) and aircraft-borne hyperspectral remote sensing in protected and unprotected fields.Objective 1.2. Document above-canopy fluxes of water vapor and carbon dioxide using eddy covariance techniques in protected and unprotected fields.Objective 1.3. Document soil respiration across a transect from tree windbreaks to crop fields.Goal 2 (Study 2). Experimentally manipulate existing green ash shelterbelts to estimate the impact of emerald ash borer infection on shelterbelt structure and function.Objective 2.1. Document the short-term (1 to 3 year) disruption of ecosystem services (crop protection, wildlife habitat, carbon sequestration) following green ash loss.Objective 2.2. Measure the response of existing redcedars, hardwoods and invasive shrubs to green ash removal.Objective 2.3. Document the abililty of airborne spectrometry to detect green ash stress and death in experimentally manipulated shelterbelts.Goal 3 (Study 3). Use remote sensing, including chlorophyll fluorescence, to characterize plant productivity and the stress of crops, conifers and decidous trees in experimental shelterbelts and associated crop fields.Objective 3.1. Acquire and analyze 4 to 6 aircraft flights for high spatial resolution imagery each year in conjunction with ground-based measurements of leaf biomass and physiological status.

Project Methods
Study 1. This study (J. Gamon, A. Suyker, D. Wedin) combines 50-year old research shelterbelts at UNL's Agroforestry Research Farm (ARF) with UNL's Carbon Sequestration Program (CSP), a global leader in measuring evapotranspiration (ET), CO2 fluxes and carbon sequestration in field-scale corn & soybean production systems since 2001. Tom Sauer (USDA/ARS, Ames, Iowa) is collaborating on this study. In 2016, management was changed in two shelterbelt-protected fields (newly named CSP4) to match the cropping (seed, tillage, chemicals, harvest, etc) of CSP3, a 160-acre dryland field at ARDC with corn/soybean rotation. Remote sensing imagery by UNL's aircraft, combined with yield maps provided by GPS-equipped machinery, will provide high spatial resolution analyses of canopy biophysics and crop stress in sheltered and unsheltered crops. Data Collection: Field measurements for CSP4, led by T. Sauer (USDA/ARS), will have three components: 1) ET, CO2 flux, and canopy microclimate as affected by tree windbreaks, 2) effect of tree litter removal and root pruning on soil CO2 fluxes, and 3) variation in soil CO2 flux across a tree windbreak to crop field transect. Although previous carbon sequestration and crop physiology research at ARF laid the foundation for this study, our new measurements utilize state-of-the-art technology and methodology designed to match, as far as possible, ongoing measurements in CSP3. Although space prohibits listing all methods here, eddy covariance in the smaller, protected fields merits discussion. Above-canopy fluxes of water vapor (ET) and CO2 (NEE) will be measured using eddy covariance (EC) techniques (Hernandez-Ramirez et al., 2011) during the crop growing season in a field sheltered by tree windbreaks. An EC tower with sonic anemometer, open-path infrared gas analyzer, net radiometer, and soil heat flux sensors will be deployed to complete surface energy balance calculations and estimate ET and NEE. The values from the EC station will be compared with similar data from the other CSP fields. Biophysical measurements collected at varying distance from the windbreaks will characterize canopy (height, biomass, yield, light interception, air temperature, relative humidity, leaf temperature) and soil (temperature, water content) properties to enable finer interpretation of the field-scale EC measurements with regard to spatial effects of shelter on crop production.Study 2. Our study uses 50-year old replicated shelterbelts originally planted with green ash and eastern redcedar. The treatments are applied to 16 shelterbelt segments, each 150 yards (137m) in length. Each segment has, on average, 60 mature green ash. This study, which began in February 2018, has 4 treatments, each with 4 replicates: T1 (Control) - No management planned for the next five years unless EAB arrives and dead trees disrupt adjacent crop fields; T2 (Experimentally Stressed Ash) - Half of the green ash will be stressed in Yr1 and half in Yr2. The experimental stress will be done with girdling, which removes the bark and phloem in a band around the lower trunk. Because EAB kills ash trees by excavating networks of tunnels (galleries) in the inner bark and phloem, girdling is a reasonable analog for severe EAB infestation. As girdled trees become starved for carbohydrates, they become increasingly stressed. 50% canopy dieback is predicted in the first year, with most trees (70%) dying within 2 years. Thus, our experimental stand decline will take 2 to 4 years, similar to observed rates once EAB-caused mortality begins. Although girdled ash trees will attract EAB present in the immediate area (<2km), previous research indicates they are unlikely to affect EAB's regional expansion rate; T3 (Ash Removal / Unmanaged Recovery) - Individual mature ash in the unit will be felled and removed in the study's first year. The unit's other trees and shrubs will be left. Each shelterbelt segment contains approximately 30 redcedar, a few (<5) austrian pine, and an unknown number of colonizing mulberry, hackberry, cherry, honeylocust and shrubs. Competition amongst these surviving plants will determine both the composition of the subsequent plant community, as well as the recovery of shelterbelt functioning; T4 (Ash Removal / Managed Recovery) - Individual mature ash in the unit will be felled and removed in the first year of the study. In contrast to T3, the response of remaining trees and shrubs will be managed. Healthy trees, whether originally planted or colonizers, that are reasonably spaced within a zone 12m wide will be left. Other competing shrubs, seedlings, and samplings will be cut, removed and their stumps treated with herbicide to prevent regrowth. This should improve the growth rate and height of the remaining trees. Significant understory openings may decrease the density (porosity) of the shelterbelt, altering its function. This will be assessed in Year 3, and could be addressed by adding additional rows of shrubs or trees, which is a standard windbreak renovation approach. Data Collection: Three 20m long sampling subplots will be established in each of the 16 experimental units. Because the windbreaks are approximately 18m wide, the sampling subplots will be 20m x 20m. In Yr1, diameter, height and species will be measured for all trees and large shrubs in all subplots. One-square-meter quadrats will be used to record seedlings and herbaceous vegetation. This will be repeated annually in mid- to late-summer. Light availability and LAI (Decagon Accupar) will be measured at multiple locations in each subplot at mid-growing season. One datalogger in each replicate (n=16) will record air and soil temperature, and soil moisture. Airborne remote sensing acquisitions will occur between 4 and 6 times per season using UNL's plane. The same images will cover both the green ash experiment and the carbon sequestration research. Because green ash girdling is an effective tool for EAB detection, a subset of girdled "sentinel" trees will be surveyed annually for EAB. Our girdled trees will also be used to study canopy loss and failure of stems and branches for stressed ash. Unexpected branch failure prior to EAB detection in weakened trees is a concern for community forestry.Study 3. As discussed for Studies 1 and 2, four to six remote sensing flights per year will provide imagery covering our green ash shelterbelt experiment, the CSP4 fields at ARF, and CSP Field 3 (unprotected dryland maize/soybean rotation). This allows us to measure the range in spectral signatures at the same time across distinct plant types with high spatial resolution (1 to 4 meters) over the growing season. For example, as drought stress develops in a windbreak-protected field, we expect to find a spatial pattern not seen in fully exposed fields. To understand the fluorescence signature, aircraft imagery at coarse temporal scales will be combined with high temporal resolution fluorescence data at limited locations. In CSP, these data are acquired, starting in 2017, by fluorescence and complementary spectral sensors installed on the flux towers. These sensors and data streams are funded by other sources (Suyker, Gamon, Sauer). For the green ash windbreak study, photosynthesis, transpiration and fluorescence measurements will be made across the growing season for stressed and healthy green ash, and healthy redcedar with a LICOR 6400. These data will be collected by forestry technicians or trained undergrads paid by this grant.

Progress 10/17/18 to 09/30/21

Outputs
Target Audience:The University of Nebraska's Agroforestry Research Farm, supported by McIntire-Stennis funds since 1965, serves diverse scientists, agencies, and stakeholders. Our research is shared by publishing peer-reviewed scientific papers, presentations at national and international scientific meetings, student field trips and teaching materials(e.g. https://app.vidgrid.com/view/RmjTmQXURnAE ),outreach materials produced by our local collaborators (Nebraska Forest Service, USDA National Agroforestry Center), and our USDA/ARS collaborators in Ames, IA (e.g. https://www.youtube.com/watch?v=804f4VTm32g ). The projects in this grant useour 55 year old experimental windbreaks to address three specific research questions, but this facility and its experimental windbreaks and tree plantings are also used by UNL forestry classes, pollinator research on pesticide impacts (e.g. https://www.youtube.com/watch?v=Qzm_gY9WNc4 ), collaborativeresearch on woody plant materials and tree seedling establishment,collaborative industryresearch on tree growth regulators and utility right-of-way management (Rainbow Treecare Scientific Advancements, Minnetonka, MN), and integrated grazing and cropping research. Changes/Problems:COVID-19 made the last two years of this three-year project challenging. It was particularly difficult to get faculty and staff in the field for new data collection. Luckily, the key instruments associated with flux measurements for Goal 1 are automated and became fully operational in 2019. Tom Sauer's technician Jeff Cook from the USDA/ARS team in Ames Iowa did an outstanding jobmaintaining our data stream for the shelterbelt-protected field (CSP4) as part of UNL's Carbon Sequestration Project, which also maintained its data stream fromthe three other CSP fields during the pandemic. The Agroforestry Research Farm managers Bruce Bolander and Doug Watson continued managing agroforestry, forestry and agricultural resources during the pandemic, so the long-term studies at the 500-acre farm are in good shape. However, we were not able to do field work in 2020 and 2021with undergraduates, graduate students and our new post-docs. For Goal 2, we treated hundreds of green ash trees in 50 year old windbreaks in 2018-2019, but were not able to collect field data in 2020 and 2021 on the response of the post-treatment shelterbelts. This is planned for the future with other funding. What opportunities for training and professional development has the project provided?This three-year agroforestry project supportedon-going management and research at UNL's 55 year old Agroforestry Research Farm. During this time,the Agroforestry Farm supported twograduate students, three post-doctoral students, and provided full or partial salary support for 3 research technicians and field managers. The shelterbelts and tree plantings are also used annually by UNL undergraduate classes for field trips and data collection. How have the results been disseminated to communities of interest?This three-year project has produced 5peer-reviewed journal articles, 10 conference presentations (both virtual and in person), 1 book chapter and 2 theses/dissertations. Thisproject and the Agroforestry Research Farm have also been featured in several video and on-line presentations (see Target Audience), which wereuseful during theCOVID pandemic when in-person visits and field trips have been restricted. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Goal 1 (Study 1). Document the effects of shelterbelts on a dryland corn/soybean cropping system when compared to a matched, unprotected cropping system. Goal 2 (Study 2).Experimentally manipulate existing green ash shelterbelts to estimate the impact of emerald ash borer infection on shelterbelt structure and function. Goal 3 (Study 3). Use remote sensing, including chlorophyll fluorescence, to characterize plant productivity and the stress of crops, conifers and decidous trees in experimental shelterbelts and associated crop fields. Our 3-year project utilized the 55-year old shelterbelt plantings at UNL's Agroforestry Research Farm to ask several questions about the role of trees and shrubs in agriculture. Over 30 years ago, the Agroforestry Farm's research demonstrated that shelterbelts can increase crop yields 10-15% compared to unprotected fields. Is thisstill true under the current climate with modern cropping practices and crop varieties? Can modern research techniques including eddy covariance flux measurements and hyperspectralremote sensing help us understandhow and when windbreaks improve productivityin modern cropping systems? To address this we began a new study in 2016to directly compare the productivity, carbon and water balance of non-irrigated fields in a corn-soybean rotation with and without shelterbelt protection. This study integrates three research groups: 1) theAgroforestry Farm's long-term windbreak studies, 2) UNL's twenty year old Carbon Sequestration Program (CSP), which has become the"gold standard" for measuring evapotranspiration, productivity and carbon sequestration in field-scale crop production systems, and 3) researchers from the USDA/ARS National Laboratory for Agriculture and Environment in Ames, IA. New data collectionin the shelterbelt-protected field (CSP4) by the USDA/ARS teamincludes measurements of evapotranspiration, whole-fieldCO2 flux, microclimate and soil CO2 flux thatmatch on-going data collection in CSP3. CSP3 and CSP4 also have matching GPS-referenced crop yield data and aircraft-collected hyperspectral, high spatial resolution remote sensing imagery. Unfortunately, COVID-19 conditions restricted the collection of remote sensing data in years 2 and 3 of this study (2020, 2021). The crop yield data indicates significantly increased yield for the shelter-belt protected fields; comparative analysesof the daily microclimate and flux data continue to explore these differences betweenCSP3 and CSP4. This grant also supported other new and on-going projects at the Agroforestry Research Farm. Goal 2 in this grant was to experimentally manipulate55-year old windbreaks dominated by green ash to study how the death of green ash caused by emerald ash borer will disrupt the function and composition ofexisting windbreaks. Hundreds of green ash were experimentally removed or girdled in 2017-2019, but COVID disrupted our field data and remote sensing data collection in 2020-2021. This is a long-term study and data collection will resume post-pandemic. The Agroforestry Research Farm and its staff have supported pollinator research by Judy Wu-Smart and students (Entomology, UNL) since 2015, resulting in two recent graduate theses. These studies usethe protection provided by shelterbelts in replicated small fields to assess the impacts of pesticides and pollinator resourceson bee populations. Although unplanned, this pollinatorresearch was in the right place to documentmajor pesticide pollution problems caused by theAltEn Mead ethanol plant two miles upstream from the AgroforestryFarm. This recent incidentled to international news coverage, law suits, and new research projects utilizing the AgroforestryFarm and adjacent UNL land, and will shape pollinator research at the Agroforestry Farm for years to come. The AgroforestryFarm continues to maintain provenance trials for six tree species started between 1965 and 1992. These tree plantingsare used for both teaching and research. The small, replicated arable fields at the Agroforestry Farm are also used for cover crop, grazing and wildlife research. Goal 1 - Our study ofprotected (CSP4) and unprotected (CSP3) cropfields continued uninterrupted during 2021. This included management of the existing windbreaks at the Agroforestry Research Farm, and cropping and management of the arable land by UNL staff. Micromet, flux and soil respiration datacollection for Objectives 1.2 and 1.3 was continued byJeff Cook (USDA/ARS, Ames IA) in CSP4 and by Andy Suyker and the UNL CSP team in CSP3. Precision crop yield data was collected by UNL staff. This was the study's sixthcropping season, and the third with complete flux data. 2021 was a corncropping year in both CSP3 and CSP4. Yield data for 2021 indicates a 21%yield increase in windbreak protected fields (231 vs 190 bu/ac). On-going data analyses of theflux databy the USDA/ARS and UNL teams should reveal the seasonal timing of this large productivityadvantagein the protected fields. In 2021, Tom Sauer (USDA/ARS) and colleagues made 2 presentations and published one paper and one chapter using soil respiration and soil organic matter results (Objective 1.3) from the long-term windbreak study. Goal 2 - The shelterbelt green ash treatments wereimposed on hundreds of 50 year old green ash during 2018- 2019.However, field work to measure vegetation and ecosystem response to the green ash manipulations did not occur during 2020-2021 because of COVID-19restrictions. This is planned for 2022. Goal 3 -COVID-19 restrictions continued to disruptcollection ofaircraft-borne imagery with UNL's aircraftin 2021. Analyses by UNL post-doctoral scientist Ran Wang and USDA/ARS technician Jeff Cook to georeference and compare hyperspectral, high-spatial resolution aircraft and ground based spectral and biophysical data from 2019 and 2020 are on-going.

Publications

• Type: Journal Articles Status: Published Year Published: 2021 Citation: Wang, R., J.A. Gamon, R. Moore, A.I. Zygielbaum, T.J. Arkebauer, R. Perk, B. Leavitt, S. Cogliati, B. Wardow and Y.Qi. 2021. Errors associated with atmospheric correction methods for airborne imagine spectroscopy: Implications for vegetation indices and plant traits. Remote Sensing of Environment 265:112663.
• Type: Journal Articles Status: Published Year Published: 2021 Citation: Hernandez-Ramirez, G., T.J. Sauer, Y.G. Chendev, and A.N. Gennadiev. 2021. Nonlinear turnover rates of soil carbon following cultivation of native grasslands and subsequent afforestation of croplands. Soils 7:415-431.
• Type: Book Chapters Status: Published Year Published: 2021 Citation: Sauer, T.J., C. Dold, et al. 2021. Agroforestry practices for soil conservation and resilient agriculture. In: Udawatta R.P., Jose S. editors. Agroforestry and Ecosystem Services. Cham, Switzerland. Springer. P.19-48.
• Type: Journal Articles Status: Published Year Published: 2020 Citation: Donovan, V.M., C.L. Wonkka, D.A. Wedin and D. Twidwell. 2020. Land-use type as a driver of large wildfire occurrence in the U.S. Great Plains. Remote Sensing 12:1869.
• Type: Conference Papers and Presentations Status: Published Year Published: 2021 Citation: Hernandez-Ramirez, G., T. J. Sauer, Yu. Chendev, and A. N. Gennadiev. 2021 Giving credit where credit is due  techniques to determine the source of soil organic matter North American. Agroforestry Conference, June 28-July 2, virtual.
• Type: Conference Papers and Presentations Status: Published Year Published: 2021 Citation: Sauer, T. J., E. C. Brevik, and K. M. Wacha. 2021. Improving soil quality on marginal lands with tree windbreaks. Eurosoil 2021, Aug. 22-27, virtual.
• Type: Theses/Dissertations Status: Published Year Published: 2020 Citation: Vakil, Surabi. 2020. Landscape enhancement options to reduce pesticide contamination in pollinator habitats and increase forage for beneficial insects in agroecosystems [PhD Dissertation, University of Nebraska-Lincoln; Dec 2020]
• Type: Theses/Dissertations Status: Published Year Published: 2020 Citation: Weisbrod, Jennifer. 2020. Effects of pesticide residues on honey bee (Apis mellifera L.) development and implications for hive management [Masters Thesis, University of Nebraska-Lincoln; May 2020].
• Type: Journal Articles Status: Published Year Published: 2021 Citation: Koehler-Cole, K., C.A. Proctor, R.W. Elmore and D. Wedin. 2021. Spring-planted cover crops for weed control in soybean. Renewable Agriculture and Food Systems. 1-8, https://doi.org/10.1017/S1742170521000107.

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

Outputs
Target Audience: Nothing Reported Changes/Problems:Covid-19 made 2020 a challenging year for our project. It was particularly difficult to get faculty and staff in the field for new data collection. Luckily, the key instruments associated with flux measurements for Goal 1 are automated and became fully operational in 2019. Tom Sauer's technician Jeff Cook from the USDA/ARS team in Ames Iowa did an outstanding job of maintaining our data stream for the shelterbelt-protected field (CSP4) as part of UNL's Carbon Sequestration Project, which also maintained its data stream for the three other CSP fields during the pandemic. The Agroforestry Research Farm managers Bruce Bolander and Doug Watson continued managing agroforestry, forestry and agricultural resources during 2020, so the long-term studies at the 500-acre farm are in good shape. However, we were not able to do field work in 2020 with undergraduates, graduate students and our new post-docs. For Goal 2, we treated hundreds of green ash trees in 50 year old windbreaks in 2018-2019, but were not able to collect field data in 2020 on the response of the post-treatment shelterbelts. That is now planned for 2021. Finally, we were not able to acquire aircraft remote sensing imagery for our study in 2020. That will hopefully resume in 2021, which is the final year of this 3-year McIntire-Stennis grant. What opportunities for training and professional development has the project provided?As discussed below (Changes/Problems), we were not able to use undergraduates, graduate students and post-docs in the field for our 2020 research. A new post-doctoral scientist (Ran Wang, Research Assistant Professor) joined co-PI John Gamon and began analysing previously collected remote sensing imagery from our project. A new post-doctoral scientist (Kati Togliatti) replaced post-doc Bing Tong with our USDA/ARS partners in Ames Iowa. She presented an initial synthesis of our flux data from protected and unprotected cropping systems at the Fall 2020 AGU meetings. 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?2021 will be the third and final year for this McIntire-Stennis grant. We have post-docs in place to analyze and summarize both our yield and flux data (Goal 1) and our remote sensing data (Goals 2 and 3). We plan on having undergraduate interns in summer 2020 to assist our technicians in collecting field data for Objectives 2.1 and 2.3 (the response of windbreak structure and species composition to experimental killing of green ash).

Impacts
What was accomplished under these goals? Goal 1 - Document the effects of shelterbelts on a dryland corn/soybean cropping system when compared to a matched, unprotected cropping system. The experiment, which involves 50 year old windbreaks and both protected (CSP4) and unprotected (CSP3) cropfields continued uninterrupted during 2020. This included management of the existing windbreaks at the Agroforestry Research Farm, and cropping and management of the arable land. Data collection for 1.2 and 1.3 was continued by the Ames Iowa USDA/ARS team led by T.J. Sauer. Precision crop yield data was collected by UNL staff. However, because of COVID-19 restrictions, we were unable to collect aircraft-borne imagery in 2020. This was the third cropping season, and the second with complete flux data, for this study. Data analyses of the both the yield data and the flux data continues by T.J. Sauer and his post-doc Kaitlin Togliatti. Because 2020, which was a soybean cropping year, had 45% less annual precipitation than the longterm site average, it will provide a robust test of the effect of windbreak protection on crop moisture stress. Goal 2 - Experimentally manipulate existing green ash shelterbelts to estimate the impact of emerald ash borer infection on shelterbelt structure and function. Because the shelterbelt green ash treatments had been imposed on hundreds of 50 year old green ash during 2018-2019, no further treatments were necessary in 2020 because of COVID-19. However, field work to measure vegetation and ecosystem response to the green ash manipulations did not occur during 2020. This will resume in 2021. Goal 3 - Use remote sensing, including chlorophyll fluorescence, to characterize plant productivity and the stress of crops, conifers and decidous trees in experimental shelterbelts and associated crop fields. Although there was no aircraft-borne remote sensing imagery collected in 2020, a new post-doc joined J. Gamon's research team. Analysis of the 2018-2019 imagery and synthesis with the crop flux and yield data continues.

Publications

• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Sauer, T.J. and E.C. Brevik. 2019. Effect of eastern red cedar plantings on soil hydraulic properties in the U.S. Great Plains. SSSA International Soils Meeting, Nov 2019, San Antonio, TX.
• Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Togliatti, K., B. Tong, T.J. Sauer, C. Dold, D. Wedin and A. Suyker. Growing season water use efficiency and evapotranspiration determined by eddy covariance and surface renewal of a soybean-corn rotation behind a tree windbreak in Nebraska. AGU Fall Meeting, Dec 2020.
• Type: Journal Articles Status: Accepted Year Published: 2021 Citation: Koehler-Cole, K, C.A. Proctor, R.W. Elmore and D.A. Wedin. 2021. Spring-planted cover crops for weed control in soybean. Renewable Agriculture and Food Systems. In press.
• Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Sauer, T., Y. Chendev, E. Brevik. J. Tyndall, K. Wacha and A. Gennadiev. 2020. The Prairie States Forestry Project - looking back to see the way forward. Soil and Water Conservation Society 75th Annual Conf. July 27, Dex Moines, IA.

Progress 10/17/18 to 09/30/19

Outputs
Target Audience:We presented our research results at four international meetings during FY2019. We also used the site for UNL undergraduate field exercises in agroforestry and forest management. Changes/Problems:This project continues 50 years of shelterbelt and plant materials research at UNL's Agroforestry Research Farm funded by McIntire-Stennis. Two projects merit mention here: a 50-year-old bur oak study and a 25-year-old bur oak study, both with seed sources from across the North American range of bur oak. In 2018-2019, forestry technician Dan Betz measured and analyzed the 1991 planting, which was replicated at 16 locations across the Great Plains and Prairie Provinces utilizing seed sources from 229 collection sites in 2 provinces and 11 states. This study contains the largest collection of bur oak genetics done to date. The bur oak study and half a dozen other provenance trials at UNL forestry research facilities were conducted by the GP-13 Tree Improvement Committee, a now defunct state/federal effort in the Great Plains. Unfortunately, most of the 1991 plantings at other sites have been lost. As we continue to lose key Great Plains tree species to disease (e.g. green ash, scotch pine) and face unprecedented climate variability, we face a shortage of appropriate woody plant materials for agroforestry in our region. Although not explicitly listed under this project's objectives, on-going maintenance and data collection in these "legacy" McIntire-Stennis studies is essential in order to maintain the capacity for future agroforestry and Great Plains forestry research. What opportunities for training and professional development has the project provided?Ala Khaleel, an M.S. student at Iowa State University, finished her thesis working with Tom Sauer (USDA ARS) from our project. Our site is also used for UNL undergraduate course exercises in agroforestry and forest management. How have the results been disseminated to communities of interest?No field days were conducted at the research site in 2019, but research presentations on the remote sensing, crop protection and soil carbon sequestration aspects of the project were presented at 4 international scientific meetings. What do you plan to do during the next reporting period to accomplish the goals?After two seasons of data collection (one funded by this project), we have extensive data for all aspects of the study (e.g. remote sensing, crop flux measurements, crop yields, green ash mortality). New post-docs with Tom Sauer (USDA/ARS, Ames Iowa) and John Gamon (SNR, UNL) have begun analyses of these data. Summer 2020 will be the first season for measuring the response of planted and invading woody species to the experimental manipulation of the 50-year-old green ash windbreaks (Obj 2.2).

Impacts
What was accomplished under these goals? Goal 1 (Study 1). Document the effects of shelterbelts on a dryland corn/soybean cropping system when compared to a matched, unprotected cropping system. Objective 1.1. Analyse the spatial pattern of crop yield and crop stress using GPS-equipped combines (harvest) and aircraft-borne hyperspectral remote sensing in protected and unprotected fields.Our carbon and water flux instrumentation within the wind-break protected cropping systems became fully operational in summer 2019 (led by T. Sauer). Carbon and water flux measurements in the matched unprotected field are on-going (led by A. Suyker). Preliminary analyses of the GPS-equipped yield monitors indicate higher yields for protected fields in both 2018 and 2019. The yield and flux data are being analyzed by a new post-doc hired by T. Sauer. Objective 1.2.Document above-canopy fluxes of water vapor and carbon dioxide using eddy covariance techniques in protected and unprotected fields.See Obj 1.1. Objective 1.3. Document soil respiration across a transect from tree windbreaks to crop fields. Our redcedar windbreaks were sampled for soil carbon and other soil properties (pH, texture, bulk density, nutrients) by T. Sauer and graduate student A. Khaleel. Those results were reported in journal article and conference presentations. Soil respiration and microclimate measurements within the windbreaks are ongoing. Goal 2 (Study 2).Experimentally manipulate existing green ash shelterbelts to estimate the impact of emerald ash borer infection on shelterbelt structure and function. Objective 2.1. Document the short-term (1 to 3 year) disruption of ecosystem services (crop protection, wildlife habitat, carbon sequestration) following green ash loss.The remaining green ash trees in Treatment 2 (experimentally stressed ash) were girdled in the winter of 2018-2019. Mortality of trees stressed either 1 or 2 years was measured in summer 2019. Objective 2.2. Measure the response of existing redcedars, hardwoods and invasive shrubs to green ash removal.No data collected or analyzed in FY2019. Objective 2.3. Document the abililty of airborne spectrometry to detect green ash stress and death in experimentally manipulated shelterbelts.Remote sensing imagery of the experimental shelterbelts was collected 3 times in summer 2019. Analyses will happen in 2020. Goal 3 (Study 3). Use remote sensing, including chlorophyll fluorescence, to characterize plant productivity and the stress of crops, conifers and decidous trees in experimental shelterbelts and associated crop fields. Objective 3.1. Acquire and analyze 4 to 6 aircraft flights for high spatial resolution imagery each year in conjunction with ground-based measurements of leaf biomass and physiological status.We conducted three flights with hyperspectral, fluorescence and thermal data over our research sites during summer 2019. We had problems with the fluorescence instrumentation in 2018-2019 but that is now fully operational. Data have had preliminary analysis and georeferencing, but new analyses will be done by a post-doc joining J. Gamon in FY2020.

Publications

• Type: Journal Articles Status: Published Year Published: 2019 Citation: Khaleel, A.A., T.J. Sauer, and J.C. Tyndall. 2019. Changes in deep soil organic carbon and soil properties beneath tree windbreak plantings in the U.S. Great Plains. Agroforestry Systems. https://doi.org/10.1007/s10457-019-00425-0
• Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Gamon, J. et al. 2018. The Nebraska SIF Campaign - a Multi-Scale Field Experiment (B33C-06). AGU. Dec 2018, Washington DC.
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Dold, C., J.H. Prueger, D. Wedin and T.J. Sauer. 2019. Impact of tree windbreaks on annual crops: carbon uptake and water use. 16th North American Agroforestry Conf., June 2019, Corvallis, OR.
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Sauer, T.J. and E.C. Brevik. 2019. Effect of red cedar windbreaks on soil physical properties in the U.S. Great Plains. 16th North American Agroforestry Conf., June 2019, Corvallis, OR
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Khaleel, A., T.J.Sauer, and J. Tyndall. 2019. Changes in soil organic carbon and soil properties beneath tree windbreak plantings in the US Great Plains. SSSA International Soils Meeting, Jan 2019, San Diego, CA.
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Sauer, T., E. Brevik, D. Zamora, J. Tyndall, J.Y. Zhu and G. Wyatt. 2019. Effect of red cedar windbreaks on soil carbon and quality in the U.S. Great PLains. 4th World Congress on Agroforestry, May 2019, Montpellier, France.