ROLE OF PLANT-SOIL FEEDBACK IN THE DECLINE OF OAK SEEDLING REGENERATION IN UPLAND APPALACHIAN FORESTS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: ACTIVE
• Funding Source: OTHER GRANTS
• Reporting Frequency: Annual
• Accession No.: 1030265
• Grant No.: 2023-38821-39802
• Cumulative Award Amt.: $499,633.00
• Proposal No.: 2022-09556
• Project Start Date: Apr 15, 2023
• Project End Date: Apr 14, 2026
• Grant Year: 2023
• Program Code: [EQ]- Research Project

Recipient Organization
TENNESSEE STATE UNIVERSITY
3500 JOHN A. MERRITT BLVD
NASHVILLE,TN 37209

Performing Department
(N/A)

Non Technical Summary
This research focuses on the mechanisms underlying the loss of oak dominant forests in the Eastern US. A sustained decline in oak recruitment will be both ecologically and economically devastating due to the outsized importance of this tree genus. The role of plant-soil feedbacks has been largely ignored as a likely mechanism for exacerbating the decline of oaks as mesophytic species such as red maple increase in abundance in these forests. The feedback between plants and their microbial community has come to the forefront of both plant and forest ecology in the last few decades with research showing large impacts on community dynamics in many ecosystems. In only the last 5 years, have we begun to discover that the type of mycorrhizal symbiont associated with a plant may drastically influence their interactions with the soil microbial community as well as other neighboring plants. We propose that as mesophytic tree species (largely associated with arbuscular mycorrhizal fungi) increase in abundance there is concomitant decline in soils associated with ectomycorrhizal fungi (critical to oak seedling establishment) exacerbating the decline of seedling establishment and recruitment. The complementary greenhouse- and field-based experimental work will complement the continuation of long-term (> 45 years) mapped forest stands that are experiencing a decline in oak and hickory adults as mesophytic trees have increased dramatically in abundance. This project will strengthen fundamental research capacity at 1890 land grant universities as well as instruction by supplementing a course on "Forest Ecology and Management" at Tennessee State University.

Animal Health Component

0%

Research Effort Categories

Basic

100%

Applied

0%

Developmental

0%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
123	0621	1070	100%

Knowledge Area
123 - Management and Sustainability of Forest Resources;

Subject Of Investigation
0621 - Broadleaf forests of the South;

Field Of Science
1070 - Ecology;

Keywords

forest

maple

mesophication

mycorrhiza

oak

pathogen

plant-soil feedback

regeneration

seedling

Goals / Objectives
Goal 1) This project aligns with the USDA strategic plan goals of FY2022-2026 and specifically addresses strategic goal 1, "Combat climate change to support America's working lands, natural resources and communities." This research also supports Tennessee Department of Agriculture's Forest Action Plan 2020-2030. Specifically, the goal of "Enhancing forest health and resilience" and Action 8 "Develop or support initiatives to maintain or restore historic diversity within ecoregions by maintaining or reestablishing native forest tree species: for example, the shortleaf pine and white oak initiative." This research falls under the fundamental, basic science category. We primarily, aim to "advance scientific understanding of process" by investigating plant-soil feedback as a mechanism behind the decline of oak seedling establishment as mesophytic species abundance increase in once oak-hickory dominated forests. Understanding the role of plant-soil feedback in this widespread problem will help us to incorporate soil microbial 'health' (widely ignored process in silviculture) into guidelines for practices that facilitate oak regeneration.Objectives to reach the prior goals, include:Describe the long-term (46-yrs) abundance and spatial distribution of xerophytic / EMF associated tree species (e.g., oaks) relative to mesophytic / AMF associated tree species (e.g., maples) in two upland Cumberland Plateau forests.Investigate whether the increases in mesophytic tree species (AMF associated) are reducing seedling performance of oaks (EMF associated) through biotic-mediated plant-soil feedback.Goal 2) Our project aligns with TSU's strategic goals for 2025 one, two, and five. One, "Attract, prepare, and graduate scholars to change the world". PI-McCarthy-Neumann is a new faculty hire in the Department of Agriculture and Environmental Sciences and expands research and curriculum opportunities of the department into the field of forest ecology. Second, "Cultivate an organizational climate that promotes collaboration, continuous improvement, and high performance." Involvement of two within-college research groups at TSU (McCarthy-Neumann and Dumenyo) together with a liberal-arts college (Evans; University of the South)clearly addresses the university's strategy to strengthen goals and promote high performance. Finally, by providing monetary support to a new PI's research program and inclusion of field-based projects into the curriculum, this project also addresses goal five "Promote, strengthen, and sustain academic excellence in teaching and learning."Objectives to reach the prior goals, include:Establish a strong forest ecology program at Tennessee State University through student training and mentoring in the field, laboratory, and classroom.

Project Methods
Long-term forest demography assessment.Project Design -We will elucidate the abundance and spatial distribution of adult tree recruitment over the past 47 years in two mature, oak-hickory forests on the Cumberland Plateau (e.g., Cross Creek watershed located in Franklin State Forest and Camp Branch watershed located in Fall Creek Falls State Park). In 1976, both Cross Creek and Camp Branch sites were established as part of a Tennessee Valley Authority community study. In summer of 1998, 2005 and 2015, we re-censused 1-ha permanent plots in Cross Creek watershed. At the Camp Branch watershed, 1-ha permanent plots were re-censused only once in summer 2016. Each one-hectare study plot was subdivided into (100) 10x10 m plots within which we identified, measured to the nearest 0.1cm, and mapped every woody stem over 1.5m in height and 3cm in diameter at breast height (DBH). All measured stems were later classified as being either canopy (>30cm DBH) or subcanopy (<30cm DBH). We will re-census and identify and map all new woody stem recruits in the (5) 1-ha permanent plots at both sites in summer 2023.Analyses -Importance value (IV) will be used to describe the ecological importance of each species and functional group (e.g., drought tolerance and mycorrhizal association) in the canopy or sub-canopy life history state at each site and for each census year.We will use linear mixed effects models to investigate how time (i.e., year of tree census) and life history state (i.e., canopy or sub-canopy) influences IV and biomass.We will measure the spatial association between overstory trees for each species/functional group and the recruits of each species/functional group with an inhomogeneous bivariate pair correlation function (PCF). The PCF, g(r), is the density of points in a ring of radius r around a focal point divided by the average density of those points. We will then compare each PCF to the expected PCF under a null dispersal model in which recruits were randomly dispersed from adult individuals of that group.We will test the effect of being within 10 m of a tree larger than 30 cm DBH that died between an earlier census interval on the growth of individuals between the later census. We will model average annual DBH growth from the later census interval as a lognormal function of initial DBH:DBH growth=gi*exp−0.5*log((DBH/μi)^2/σi)(eq 1)Where i = 1 for individuals within 10 m of a canopy tree that died between 1977 and 1998, and i = 2 for individuals farther than 10 m for such a tree. Parameters gi μi, and σi will determine the shape of the lognormal growth function.Greenhouse plant-soil feedback experiment.Experimental Design -We will conduct a greenhouse experiment to investigate whether the increase in mesophytic tree species associated with arbuscular mycorrhizal fungi (AMF) are reducing seedling performance of oaks (i.e.,Quercusspp) which are associated with ectomycorrhizal fungi (EMF) through plant-soil feedback (PSF). Soil will be taken from Cross Creek for greenhouse studies comparing seedling performance, mycorrhizal colonization, and the soil microbial community on seedling roots of xerophyte and mesophyte tree species when growth with AMF vs. EMF cultured soils at both low and high light. The experiment will consist of 6 species (3 xerophytic and 3 mesophytic), 8 soil treatments (non-sterile field soil from all seven study species + sterilized field soil from conspecific adult + potting soil) and two light levels (3% and 30% full sun). We will plant 24 seedlings per treatment combination for a total of 2,304 seedlings.We will randomly select four adult trees per species. We will collect soil (top 15cm) within 1m of each focal tree stem. Approximately 10 g of each inoculum soil will be stored in a 15-mL centrifuge tube at -80 °C to investigate soil microbiome via Illumina sequencing. We will sterilize 1/7 of the field and all the potting soil by gamma irradiation prior to the start of the experiment (~40 KGray).We will monitor seedlings for survival twice weekly, and date of death will be assigned as the first census with total leaf and/or stem tissue necrosis. All surviving seedlings will be harvested at 14 weeks. For five randomly selected seedlings per treatment group, we will measure mycorrhizal colonization, pathogen infection, and we will extract genomic DNA from the seedling's roots. Bacterial, fungal and oomycete community structure will be quantified via Illumina amplicon sequencing. For all seedlings, leaves, stems, and remaining roots will then be oven dried at 70°C, and total biomass weighed.Analyses -We will use an individual based counting process in a Cox survival model to analyze seedling survivorship response to treatments.Field plant-soil feedback with common mycorrhizal network experimentExperimental Design -To investigate PSF with and without connections to common mycorrhizal networks (CMN) of the same versus different mycorrhizal types and to test the influence of light on these feedbacks, we will use a field-transplant experiment. Our experimental design includes 768 seedlings: 2 species (1 AMF vs. 1 EMF associated tree species) x 2 soil source (non-sterile soil cultured from conspecific vs. heterospecific adults) x 3 soil treatments (2-mm, 30-μm, 0.5-μm nylon mesh) x 2 light availability (3% vs. 30% full sun) x 32 seedling replicates.A new 1-ha mapped forest stand will be established at Cross Creek where species identification, location and size for all trees ≥ 3 cm diameter are measured. This new plot will allow us to conduct field transplant experiments, including light manipulation, without detrimental effects to the long-term mapped stands. Our study species will include oneQuercusspp. (associated with EMF) and one non-Quercusspp. (associated with AMF).For each study species, we will randomly select 8 adult trees (with DBH in the 75% quartile for that species) and create four (1-m x 0.75-m) sub-plots within 1-m of the bole. Half of the adult trees will be randomly allocated to the low light treatment and the other to the high light treatment. High light trees will have neighboring trees felled or trimmed to increase light availability in the four sub-plots to 25-30% full sun. We will collect soil for fungal and oomycete DNA extraction at each adult tree.Using a hydraulic soil core sampler attached to a UTV, we will remove (12) intact soil cores inside plastic soil core liners at each of the 4 sub-plots near the 8 adult trees per study species. These plastic soil core liners will be turned into seedling pots that manipulate root and hyphal connections between seedlings and the external environment according to the size class of the soil biota. They will be modified with two 7.5 cm diameter holes drilled into the sides, and either 2-mm, 35-μm or 0.5-μm nylon mesh covering holes and the bottom. We will re-insert the seedling pots into the holes where the intact soil cores were collected 1 month before seedling transplantation, to allow recovery from disturbance as most mycorrhizal hyphae usually have a rapid turnover cycle.A single seed with a newly emerged radicles will be planted into each pot. We will census seedlings for emergence and survival twice per week for 16 weeks. For five randomly selected surviving seedlings per treatment group, we will measure mycorrhizal colonization, pathogen infection and we will extract genomic DNA to analyze fungal and oomycete community structure and abundance on experimental roots. For all seedlings, leaves, stems, and remaining roots will then be oven dried at 70°C, and total biomass weighed.Analyses -Statistical analyses will follow what was outlined for the greenhouse PSF experiment, with the addition of soil treatment (access to fine roots and CMN, access to CMN with no roots and no access to CMN or fine roots) as a factor for survival, mycorrhizal colonization and pathogen infection.

Progress 04/15/24 to 04/14/25

Outputs
Target Audience:During the reporting period, the research supported by this grant reached multiple target audiences, including academic and government scientists, students at various educational levels, professional forestry practitioners, and the general public. These audiences were engaged through conference presentations, public media outreach, student training, and research integration into coursework. Each of these groups was targeted for their potential role in advancing forest ecology research, informing forest management practices, or fostering the next generation of environmental scientists. Academic and Government Scientists, and Professional Forestry Practitioners: Research findings were disseminated to scientific and forestry communities through conference presentations, university seminars, and professional meetings. These audiences are key stakeholders in applying plant-soil feedback research to forest management and conservation. Mycorrhizal type and light availability explain differences in tree seedling performance in response to plant-soil feedback. Oral Presentation. North American Forest Ecology Workshop. June 2024. The role of plant-soil feedback in tree seedling establishment. Oral Presentation. UT-Knoxville and TSU Research Summit. August 2024. Potential role of plant-soil feedback in oak regeneration decline. Oral Presentation. International Oak Symposium. October 2024. The role of mycorrhizal mismatch in tree seedling plant-soil feedbacks: A potential driver of oak regeneration decline. Oral Presentation. Tennessee State University, Environmental Sciences Department Seminar. October 2024. The role of plant-soil feedback on the Cumberland Plateau's forest understory. Oral Presentation and Panel Member. The University of the South, Tennessee Plant Conservation Alliance. April 2025. General Public: To extend the impact of the research beyond the scientific community, findings were featured in public media. In September 2024, Nashville Public Radio aired a story highlighting the research's role in informing the management of Tennessee's state forests. This outreach aimed to increase public awareness of forest ecology challenges and the importance of science-based conservation strategies. Undergraduate and Graduate Students: Educational engagement was a key component of this project, reaching students through research experiences, conference presentations, and course integration. Research-Integrated Coursework: Twenty-four undergraduate students enrolled in BIOL 209 at the University of the South used the species list for the Cross Creek site to identify plant species of conservation concern for Franklin State Forest. Their understanding of habitat context was enhanced through exposure to old-growth forest characterization from this research. Graduate Student Engagement: Maria Schutte, a graduate student, presented the following research posters: Low oak regeneration in Kalmia latifolia thickets is primarily explained by low light availability. Ecological Society of America Annual Meeting, Long Beach, CA. August 2024. The effect of mountain laurel soil on emergence and survival of two hardwood species. 47th Annual University-wide Research Symposium, Tennessee State University. March 2025. Undergraduate Student Engagement: Katrina Seaman presented the poster Plant-soil feedbacks as a mechanism for oak recruitment decline at the MANRRS 39th Annual Training Conference and Career Expo in April 2025 in Memphis, TN. Nine undergraduate students from Tennessee State University (3), The University of the South (4), and Michigan State University (1) engaged in field, lab, and greenhouse research on oak seedling decline and mesophication, gaining hands-on experience in ecological research methods. By targeting these specific audiences, this project ensured that findings were shared with those best positioned to apply them--whether through advancing scientific knowledge, informing land management decisions, or training future environmental scientists. Changes/Problems:Deciding to add spatial mapping of all saplings to our long-term forest plots significantly extended the timeline for this task, requiring two full summers instead of the originally scheduled one. We had planned to collect light and soil moisture data in summer 2024 to complete data collection from the long-term forest plots. However, our newly purchased LAI C2200 malfunctioned (though Li-COR has since replaced the unit, resolving the issue), and by the time our back-ordered soil moisture sensors arrived, both sites were experiencing moderate to severe drought. This made it impossible to differentiate soil moisture conditions across the plots and sites. We will return in June 2025 to take these measurements. The plant-soil feedback greenhouse experiment faced challenges with poor seed germination, particularly severe for Nyssa sylvatica (one of the mesophytic species) and moderately poor for the other two mesophytic species. We plan to analyze the current results, and if necessary, conduct an additional smaller experiment in fall 2026 to address the germination issue. This supplementary experiment will be paired with the current greenhouse experiment to fully answer our original hypotheses. A key setback occurred when the master's student conducting this experiment for his thesis left the graduate program 85% of the way through the greenhouse harvest. He withdrew due to personal reasons--his wife experienced pregnancy complications, and he needed a higher income to support his family. His departure delayed our laboratory measurements, including pathogen lesion quantification, mycorrhizal root colonization assessment, and soil-borne microbial DNA analysis. To address this, we plan to hire a lab technician for the next six months to complete these outstanding tasks. The field-based plant-soil feedback experiment was initially scheduled for summer 2024 in a 1-ha mapped stand at Cross Creek. However, we now plan to request a no-cost, one-year extension on the grant for two primary reasons: The long-term forest demography plot census took two full summers instead of one due to our decision to expand mapping to all individuals >50 cm in height. Cross Creek Watershed, part of Franklin State Forest, has faced multiple closures affecting research access. The forest was closed to all public and research activities from July to September 2024 due to vandalism and theft of Tennessee Division of Forestry (TDF) equipment. In mid-October 2024, TDF again suspended public access to the eastern half of Franklin State Forest, which includes our study site, until August 2025. We are working with TDF to explore options for regaining access. If that is not feasible, we will pivot to constructing a 1-ha mapped stand in a similar upland Plateau oak-hickory forest owned by The University of the South in summer 2025 and conduct the proposed field transplant experiment in summer 2026. What opportunities for training and professional development has the project provided?This grant has supported two graduate students and provided mentorship to a diverse group of students, including one post-baccalaureate and seven undergraduate students. Under the guidance of PI McCarthy-Neumann and Co-PI Evans, students gained hands-on experience in experimental design, tree identification and measurement, seedling planting and harvesting, assessing seedling health and survival, biomass weighing, mycorrhizal colonization analysis, and scientific writing and presentations. As a result of their involvement in this project and mentorship from the PI and Co-PIs, one student earned honors in their degree, another will enroll as a master's student in the Department of Environmental Sciences at Tennessee State University in McCarthy-Neumann's Forest Ecology Lab, and another secured a post-baccalaureate research position in forest ecology. Maria Schutte, one of the MS graduate students, attended and presented a poster at the Ecological Society of America's national meeting in August 2024. Robert Phillips used data generated from him involvement over the course of two summers to write his undergradute thesis 'Long-term change in oak and maple distributions and abundance at Cross Creek Experimental Watershed, Franklin State Forest' as part of his Honors program in the Department of Biology at the University of the South. Katrina Seaman, an undergraduate student from TSU, attended and presented a posterat MANRRS 39th Annual Training Conference and Career Expo in April 2025 in Memphis, TN. PI-Neumann hosted a one day workshop on how to measure mycorrhizal coloniation on tree seedling roots to one graduate student, and two undergraduate students. How have the results been disseminated to communities of interest? McCarthy-Neumann, S.Mycorrhizal type and light availability explain differences in tree seeding performance in response to plant-soil feedback. Oral Presentation. North American Forest Ecology Workshop. June 2024. McCarthy-Neumann, S.The role of plant-soil feedback in tree seedling establishment.Oral Presentation. UT-Knoxville and TSU Research Summit. August 2024. McCarthy-Neumann, S.Potential role of plant-soil feedback in oak regeneration decline.Oral Presentation. International Oak Symposium. October 2024. McCarthy-Neumann, S.The role of mycorrhizal mismatch in tree seedling plant-soil feedbacks: A potential driver of oak regeneration decline.Oral Presentation. Tennessee State University, Environmental Sciences Department Seminar. October 2024. McCarthy-Neumann, S.The role of plant-soil feedback on the Cumberland Plateau's forest understory.Oral Presentation and Panel Member. The University of the South, Tennessee Plant Conservation Alliance. April 2025. Schutte, M.Low oak regeneration in Kalmia latifolia thickets is primarily explained by low light availability. Poster.Ecological Society of America. August 2024. Schutte, M.The effect of mountain laurel soil on emergence and survival of two hardwood species. Poster.47th Annual University-wide Research Symposium at Tennessee State University. March 2025. Seaman, K.Plant-soil feedbacks as a mechanism for oak recruitment decline. Poster. MANRRS 39th Annual Training Conference and Career Expo. April 2025. Phillips, R.Long-term Change in Oak and Maple Distribution and Abundance at Cross Creek Experimental Watershed, FRanklin State Forest, TN. Honors Thesis. April 2025. PI Neumann and Co-PI Evans were interviewed by a reporter from the Tennessee Conservationist Magazine for a feature article scheduled for publication in May/June 2025. The article will discuss the research supported by this grant with a focus on the importance of belowground interactions for forest community dynamics and successful forest management. Lastly, this research is emphasized on both PI-Neumann's Forest Ecology Labwebsite (https://www.mccarthy-neumannlab.com/) and CoPI-Evans Plant Ecology and Conservation Lab website(https://www.evanslab.org/). What do you plan to do during the next reporting period to accomplish the goals?Spring/Summer 2025 We will write and publish two research articles based on our study: Changes in species composition and productivity (1970s-2023/2024): This paper will address Research Question 1 of the long-term forest demography assessment (Objective 1). Effect of Kalmia latifolia on hardwood seedling regeneration through plant-soil feedbacks: This paper will contribute to Objective 2. Additionally, we will collect data for the long-term forest demography assessment (Objective 1, outlined in B.2.1 of the original grant): Canopy openness (%) and soil moisture (%): Measurements will be taken from 250 locations evenly distributed across each of the 1-ha forest plots at the Cross Creek and Camp Branch study sites. For the plant-soil feedback greenhouse experiment (Objective 2, outlined in B.2.2 of the original grant), we will complete: Pathogen lesion quantification Mycorrhizal colonization assessment Microbial DNA extraction from roots and soils Statistical analyses Fall 2025 We will analyze data and write three research papers: Spatial association between canopy adults and recruits: Investigating whether recruits are conspecifics or heterospecifics of the same or different mycorrhizal types (Research Question 2, Objective 1). Environmental context and spatial associations: Examining how factors such as light availability, soil moisture, nutrients, aspect, and slope influence tree recruitment patterns (Research Question 2, Objective 1). Plant-soil feedback differences between ectomycorrhizal and arbuscular mycorrhizal tree species (Objective 2). Spring 2026 We will prepare for the field plant-soil feedback with common mycorrhizal network experiment (Objective 2, outlined in B.2.3). Additionally, we will analyze data and write two research papers: Legacy effects of conspecific or con-mycorrhizal adults on recruitment after large tree mortality: This paper will address Research Question 2, Objective 1. Growth response of adult trees based on basal area of neighboring canopy trees: Investigating whether neighboring trees are conspecifics or heterospecifics of the same or different mycorrhizal type (Research Question 3, Objective 1).

Impacts
What was accomplished under these goals? Goal 1: Advancing Scientific Understanding of Plant-Soil Feedbacks in Oak Regeneration We have made significant progress toward Goal 1--to "advance scientific understanding of process"--by investigating plant-soil feedbacks as a mechanism driving the decline of oak seedling establishment in forests where mesophytic species are increasing. Understanding the role of plant-soil feedbacks in this widespread shift will help integrate soil microbial 'health'--a largely overlooked factor in silviculture--into management guidelines that promote oak regeneration. Objective 1: Long-Term Changes in Forest Composition and Structure The first objective under this goal is to describe the long-term abundance and spatial distribution of xerophytic, ectomycorrhizal (EMF)-associated tree species (e.g., oaks) relative to mesophytic, arbuscular mycorrhizal (AMF)-associated tree species (e.g., maples) in two upland Cumberland Plateau forests. Key accomplishments: Vegetation Mapping Completed: We have completed a full census of saplings and adult woody vegetation across both study sites, recording 58,427 unique individuals at Cross Creek and 37,842 at Camp Branch. Productivity and Compositional Analysis Completed: We have analyzed species compositional changes and productivity shifts from the 1970s to the present. As anticipated: The importance value of pyrophytic species (e.g., oaks and hickories) has decreased. Mesophytic species (e.g., maples, tulip poplar, and sassafras) have increased in dominance. Species with intermediate shade tolerance have also declined. EMF-associated species have declined in importance value, while species associated with AMF or ericoid mycorrhizal fungi have increased. Objective 2: Plant-Soil Feedbacks and Oak Seedling Performance The second objective is to investigate whether the increase in mesophytic, AMF-associated tree species is reducing oak (EMF-associated) seedling performance through biotic-mediated plant-soil feedbacks. Key accomplishments: We completed a large greenhouse plant-soil feedback experiment using six study species (three AMF-associated and three EMF-associated) to test this hypothesis. Data Entry and Quality Control Completed: We have finished processing emergence, survival, and biomass data. Statistical Analysis to Begin Shortly. Goal 2: Establishing a Strong Forest Ecology Program at Tennessee State University The second goal of this project is to strengthen forest ecology training and mentoring at Tennessee State University (TSU) through research opportunities in the field, laboratory, and classroom. Key accomplishments: Undergraduate Mentorship: The PI has mentored nine undergraduate students in forest ecology: Three from Tennessee State University Four from The University of the South One from Michigan State University Student Success: One student has secured a post-baccalaureate research position in forest ecology. Another will begin a master's program in Dr. McCarthy-Neumann's lab at TSU in Fall 2025. Another student is receiving honors for their undergraduate degree based on research conducted through this project. Forest Ecology Journal Club: We have continued a joint Forest Ecology journal club, hosted by PI McCarthy-Neumann, with participation from Co-PI Evans and students from both institutions. This initiative has enhanced collaboration and expanded opportunities for students. Guest Speaker and Seminar: The Forest Ecology Lab hosted Dr. Andrew L. Hipp, Director of the Herbarium and Senior Scientist in Plant Systematics at Morton Arboretum, for: A book discussion on Oak Origins: From Acorns to Species and the Tree of Life. A research seminar as part of the Department of Environmental Sciences Seminar Series.

Publications

Progress 04/15/23 to 04/14/24

Outputs
Target Audience:McCarthy-Neumann (PI from Tennessee State University) and Evans (Co-PI from The University of the South) hosted a field tour of the Cross Creek Experimental Watershed, presented on the USDA-funded project and led a roundtable discussion on connecting science and management for forests on the Cumberland Plateau to the following stakeholders: TN Div of Forestry US FWS TN Office TDEC Division of Natural Heritage TDEC South Cumberland State Park Center for Biological Diversity Sierra Club TN Heartwood Tenngreen Land Conservancy In addition, one of the graduate students, Maria Schutte, supported by this grant presented a poster on preliminary findings from this projectto the Ecological Society of Americain August 2023in Portland, OR at their annual national meeting. Lastly, 12 graduate students enrolled in AGSC 5530 took a field trip to Cross Creek Experimental Watershed, which is one of this project's field sites to learn about oak seedling decline and mesophication. Changes/Problems:Deciding to add spatial mapping of all saplings into our long-term forest plots took a considerable amount of time and resulted in our only being able to complete one of the two sites in the first summer. Investigating recruitment patterns necessitated our need to increase the resolution of the sapling and seedling data than we had ever collected in the past. We anticipate a greater ability to test our original questions posed in the grant as well as additional questions with this new approach. However, our timeline for finishing the long-term forest demography study will be pushed back by one year and we will have to conduct the planned field transplant experiment in summer 2025 instead of summer 2024. These changes should not change expenditures but will likely result in us in the future requesting a no-cost, 1-year extension on the end date of the grant. We collected seeds for our plant-soil greenhouse experiment from the same forest site where the soil was collected for the treatments in that experiment (Cross Creek Experimental Watershed) and the long-term forest demography data for the project has been collected. We collected 3-10 times as much seed as we anticipated needing but three out of the six study species are currently experiencing poor germination. We are reducing replicates as well as trying various approaches to improve/speed up the germination for these species. If we don't end up with enough replicates we may run an additional smaller experiment for the three species with poor germination in winter 2025 and pair that with our current greenhouse experiment so we can fully answer the original hypotheses posed for this project. What opportunities for training and professional development has the project provided?Two graduate students have been supported by this grant and a variety of post-baccularate, undergraduate and high school students have been mentored as well. Through the course of this project students have learned through training by PI-Neumann and CoPI-Evans experimental design, tree identification and measurement, planting and harvesting seedlings, quantifying health and survival of seedlings, weighing biomass, measuring mycorrhizal colonization on tree root and scientific writing and presentations. Maria Schutte, one of the MS graduate students, attended the Ecological Society of America's national meeting in August 2023. PI-Neumann hosted a three day workshop on how to measure mycorrhizal coloniation on tree seedling roots to two graduate students, one post-baccularate student and two high school students. How have the results been disseminated to communities of interest?We are still actively collecting data but we had a few avenues for dissemination of our motivation for this research and our preliminary results. The first being a poster presentation at the Ecological Society of America's national meeting, a field tour and roundtable discussion on connecting science and management for forests on the Cumberland Plateau with a variety of stakeholders and field trips to one of the study sites in a course and with high school students as part of the their Summer Apprenticeship Program. To reach a broader audience, sixshort (2-5 minute) videos were produced by Tennessee Heartwood about research being conducted at the Cross Creek Experimental Watershed all of which highlighted various aspects of this research project and were posted on YouTube. An article was published in the Sewanee Plant Press, which can be found both the The University of the South's website and in print version that is mailed to hundreds of subscribers,describing the research project. Lastly, this research is emphasized on both PI-Neumann's Forest Ecology Lab website (https://www.mccarthy-neumannlab.com/) and CoPI-Evans Plant Ecology and Conservation Lab website (https://www.evanslab.org/). What do you plan to do during the next reporting period to accomplish the goals?We will finish the plant-soil feedback greenhouse experiment in early May 2024 and this upcoming summer we will re-census (5) 1-hectare forest plots at our second field site Camp Branch located in Fall Creek Falls State Park. We plan on presenting our results at a variety of scientific meetings, such as: Ecological Society of America, International Oak Symposium and North American Forest Ecology Workshop and hope to have at least 2 publications by the end of the next reporting period. With respect to mentoring and teaching students, we will continue to support 2 MS graduate students (Maria Schutte and Jack Wilkerson) and one Mariawill defend her thesis 'The influence of mountain laurel on hardwood regeneration through plant-soil feedback' that has been partially supported by this project.In addition we will train andwork with 8-9 undergraduate students over the course of the next year.

Impacts
What was accomplished under these goals? We have made considerable gains in accomplishing goal 1 to"advance scientific understanding of process" by investigating plant-soil feedback as a mechanism behind the decline of oak seedling establishment as mesophytic species abundance increase in once oak-hickory dominated forests. Understanding the role of plant-soil feedback in this widespread problem will help us to incorporate soil microbial 'health' (widely ignored process in silviculture) into guidelines for practices that facilitate oak regeneration. The first objective todescribe the long-term abundance and sptial distribution of xerophytic/EMF associated tree species (e.g., oaks) relative to mesophytic / AMF associated tree species (e.g., maples) in two upland Cumber land Plateau forest was partially accomplished byre-censusing the forest plots at Cross Creek Experimental Watershed. Due to the time-intensive nature of expanding the vegetation data from just adults to a spatially mapped sapling layer(resulting in 50,000 indivdiuals worth of data) we were only able to complete the Cross Creek site and will take data at Camp Branch in summer 2024.The results from this work have not been fully analyzed, especially the spatially explicit data, but our preliminary results on composition change indicates that the importance value of mesophytic species (e.g., maples, tulip poplar and sassafras) have increased from teh 1970s to present day whereas pyrophytic species (e.g., oaks and hickories) have declined. Indicative of how most of the mesophytic species are also assocaited with arbuscular mycorrhizal fungi (AMF) and the oaks and hickories with ectomycorrhizal fungi (EMF) there importance values changed with AMF associated tree species gaining in importance value and EMF associated tree species declining. The second objective under this first goal is to investigate whether the increase in mesophytic tree species (AMF associated) are reducing seeding performance of oaks (EMF associated) through biotic-mediated plant-soil feedback. We are in the process of conducting a large greenhouse plant-soil feedback experiment with six study species (three associated with AMF and three associated with EMF) to help answer this question. This experiment should conclude in May 2024. Our second goal had one objective to establish a strong forest ecology program at Tennessee State University through student training and mentoring in the field, laboratory, and classroom. We have a strong record in our first year of meeting this objective.Through this project the PI was able to mentor a diverse assemblage of potential scientists in the field of forest ecology. Two graduate students and 9undergraduate or recently graduated BS students were part of the field crew that re-censused the Cross Creek forest plots in summer 2023 and/or worked on the plant-soil feedback greenhouse experiment in winter 2024. Six of the 11 students were female with 2 of those 5 females an under-represented minority in STEM and one additional female undergraduate a non-traditional older student. For the three students who were post-baccularate, two of them have started graduate degrees in forest or plant ecology and another student has started a prestigous fellowship at the Atlanta Botanical Gardens. Students working on this project camefrom PI-Neumann's lab and Co-PI-Evans lab and resulted in a Forest Ecology journal club hosted by PI-Neumann with participation from Co-PI Evans and students from both institutions. This joint journal club has enhanced collaboration and opportunities across both institutions.In addition, two female, minority high-school students were mentored and learned about the project as part of the TSU's College of Agriculture's Summer Apprenticeship Program and12 graduate students took part in field tour at the study site as part of their course on Forest Ecology.

Publications