DISTURBANCE IMPACTS TO FOREST HYDROLOGY AND BIOGEOCHEMISTRY IN THE SOUTHEASTERN UNITED STATES

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: MCINTIRE-STENNIS
• Reporting Frequency: Annual
• Accession No.: 1018784
• Project Start Date: Mar 1, 2019
• Project End Date: Feb 28, 2023
• Program Code: [(N/A)]- (N/A)

Recipient Organization
MISSISSIPPI STATE UNIV
(N/A)
MISSISSIPPI STATE,MS 39762

Performing Department
Dept of Forestry

Non Technical Summary
The tree canopy is the first major compartment encountered by precipitation as it moves through forested ecosystems, and can dramatically transform the fate and transport of water and nutrients. The relationship between canopy-derived inputs of water and nutrients and subsequent changes in soil biogeochemistry is complex and more research is needed to understand how these two components of the biosphere are impacted by disturbance events. In order to enhance the predictive capability of ecosystem models that guide management and policy decisions, it is imperative to understand the physically-based processes that control these fluxes. As such, the proposed research seeks to understand how forest canopies alter the quantity and quality of incident precipitation in a variety of forest types and how these are impacted by disturbance. Furthermore, the proposed research will provide empirical evidence of biogeochemical and hydrological processes that may be incorporated into ecosystem models and used to improve management capabilities.

Animal Health Component

30%

Research Effort Categories

Basic

60%

Applied

30%

Developmental

10%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
123	0320	2050	50%
123	0320	1070	25%
123	0110	2000	25%

Knowledge Area
123 - Management and Sustainability of Forest Resources;

Subject Of Investigation
0320 - Watersheds; 0110 - Soil;

Field Of Science
2050 - Hydrology; 1070 - Ecology; 2000 - Chemistry;

Keywords

forest hydrology

forest biogeochemistry

carbon

disturbance

Goals / Objectives
The proposed research will provide insights into how the forest canopy controls inputs of water and nutrients over a range of forest conditions and disturbance types, and how strongly individual species control these inputs. This work will build upon research completed under a previous McIntire-Stennis grant (MISZ - 069390) and extend the research to focus on specific disturbance regimes throughout the southeastern United States. An improved understanding of forest hydrologic and nutrient inputs will provide an enhanced understanding of the biogeochemical functioning of regional forests and how the ecosystem services they provide may be susceptible to climate change. The specific objectives of this research are:Objective 1 - How do tree species manipulate water and nutrient resources, and how are these processes impacted by the use of prescribed fire?Canopy Hydrology: Quantify differences in canopy partitioning of water into throughfall, stemflow, and interception between upland oaks and mesophytes as a function of canopy architecture and bark morphology. Quantify how these differences are manifested in soil moisture between species. Determine how changes to forest structure following prescribed fire impact these fluxes.Soil Hydrology: Quantify the changes in throughfall kinetic energy, overland flow, and soil erosion resulting from the changes in canopy structure following prescribed fire.Soil Biogeochemistry: Quantify the spatio-temporal impact of prescribed fire on soil respiration and biogeochemistry. Quantify the recovery of soil respiration and biogeochemistry post-fire. Quantify changes in the spatial distribution of soil respiration and biogeochemistry as a function of overhead canopy tree species.Objective 2 - How is the carbon budget of ecosystems changed following insect infestations and tree mortality?Woody Decomposition: Quantify the influence of termites and fungi on the decomposition of dead wood and the biogeochemistry of soils below. Quantify how these biotic factors are influenced by abiotic factors including meteorology and canopy-derived water and nutrient inputs.

Project Methods
Objective 1 - How do tree species manipulate water and nutrient resources, and how are these processes impacted by the use of prescribed fire?In an upland oak-hickory forest in northern Mississippi, an experimental study has been established to quantify the impacts of prescribed fire on oak vs. mesophyte survival and subsequent changes in canopy structure, hydrology, and biogeochemistry. Across three treatments of fire regime (dormant season burn, growing season burn, control/no burn), stemflow collars and throughfall gauges are deployed to overstory and midstory oaks and mesophytes. Stemflow collars consist of plastic tubing cut longitudinally and wrapped around tree trunks, which drain into large collection bins (55 to 70 L). Throughfall gauges are constructed from a 3.78 L collector with a 12.5 cm diameter funnel attached to the mouth. To capture spatial heterogeneity of throughfall, overstory trees have two throughfall gauges deployed: one at the bole of the trunk and one at the midpoint of the tree crown. Midstory trees have only one throughfall gauge due the smaller crown size. Soil moisture is measured instantaneously with a time domain reflectometry probe (TDR) at three depths and at three distances from each tree: trunk, mid canopy, and edge of canopy to ensure sampling of effects of canopy and root heterogeneity. At each distance soil moisture is measured at depths of 7.6 cm, 12.0 cm and 20.0 cm. Structural metrics of the study trees including diameter at breast height, canopy area, canopy depth, branching architecture, bark roughness, and bark thickness will also be measured. Analysis of variance (ANOVA) will be used to test if there are differences in stemflow, throughfall, or soil moisture between species, canopy layers, and burn treatment. Principal components analysis will be used to relate the structural metrics to the hydrology fluxes.Throughfall kinetic energy will be measured by the splash cup method whereby the quantity of sand displaced in a reference cup is compared to throughfall volume and intensity (Geißler et al. 2013). Runoff plots will also be installed to measure the volume of overland flow and the sediments transported in a 2-m2 area. Both splash cups and runoff plots will be located across the three burn treatments and at different slope positions (shoulder, backslope, footslope). ANOVA will be used to test if there are differences in throughfall kinetic energy, overland flow, and sediment transport between slope position and burn treatment.Soil biogeochemical properties will be measured underneath the crowns of oaks and mesophyte trees. Soil respiration will be measured 20 cm diameter PVC collars inserted 5 cm deep into the soil profile. Soil cores from 0-5 cm and 10-20 cm will be obtained with a push probe and analyzed for total carbon and nitrogen on an elemental analyzer. Soil samples will also be analyzed for inorganic nitrogen constituents (nitrate and ammonium) using the KCl extraction and colorimetric determination methods on a discrete analyzer. Incubation tubes will be installed next to the respiration collars and left in situ for 3 weeks, at which point they will be collected and analyzed for inorganic nitrogen constituents to determine rates of mineralization and nitrification. These measurements will be made before and after implementation of burn treatments to determine how soil biogeochemistry changes post-fire and during recovery. ANOVA will be used to test if there are differences in soil biogeochemistry between species and burn treatments.Objective 2 - How is the carbon budget of ecosystems changed following insect infestations and tree mortality?An experimental decomposition study has been established in a loblolly pine plantation in central Mississippi. The experiment was designed to test for the effect of inoculation with bluestain fungi on the recruitment of termites to wood killed by bark beetles and the impact on decomposition and nutrient cycling. Two treatments were employed: an inoculation treatment and an aboveground barrier treatment. The former treatment was designed to test the effect of bluestain fungi versus a water control and the latter treatment was designed to test the effect of subterranean termites and belowground decomposers alone versus the suite of aboveground saproxylic invertebrates (e.g, other wood boring beetles) that can impact decomposition processes through the creation of tunnels and inoculation of additional fungi (Grove 2002). To test these effects, ten 30 x 30-m replicate plots were established to monitor woody decomposition in fall 2014.Ten visually healthy loblolly pine trees were harvested from an adjacent stand. Each tree (1 per plot) was cut into 18 log segments of 0.5-m length and sealed with wax on both ends to minimize desiccation and better approximate water loss of a whole fallen tree. Log segment diameters ranged from 16.0 to 25.4 cm depending on location along tree trunk. One log segment was immediately collected for determination of initial mass, density, moisture, and nutrient content. Additionally, one un-modified log segment was deployed in each plot as an untreated control. The untreated control logs in each plot (n = 10) were intended to serve as long-term, non-destructive control for baseline log and soil respiration measurements. The remaining 16 logs were randomly assigned to one of four treatments including (1) inoculation with the bluestain fungus, the primary bluestain fungi vectored by southern pine beetle in the southeastern United States, (2) control inoculation with sterile distilled water, (3) inoculation with bluestain fungus and covered by a brass cloth cage, and (4) control inoculation with distilled water and covered by a brass cloth cage. Logs from each treatment across the 10 study plots were harvested after 1 year and 2 years of decomposition, respectively. The next harvest interval is planned at the end of 5 years of decomposition.To control for climatic variables, a meteorological station was installed in a central location beneath the forest canopy. A tipping bucket rain gauge was also installed at the station, and roving canopy throughfall collectors were deployed in each of the 10 plots to control for throughfall variability as a result of canopy heterogeneity. Another manual collector and an automated tipping bucket rain gauge were placed 100 m from the study site to monitor open precipitation.Wood decomposition will be measured by comparing mass, density, and moisture content of wood samples from logs prior to deployment and during harvest intervals. To quantify changes in wood nutrient availability, blocks cut from logs both before deployment and at harvest intervals will be analyzed for carbon and nitrogen using elemental combustion analysis. To quantify the movement and mineralization of carbon into terrestrial reservoirs, paired soil samples will be taken directly underneath the harvested logs and at a 0.5 m distance from each harvested log in both the A (0-5 cm) and B (5-10 cm) horizons at the time of harvest. Soil samples will also be taken from a control point in each plot away from any treatment logs at both soil depths. Soil carbon and nitrogen nutrient will be determined using elemental combustion analysis. One week prior to each harvesting interval, logs will be fitted with 10 cm diameter PVC collars, which will be used to measure log respiration. Permanent 20 cm diameter PVC collars will also be deployed in each of the 10 plots to measure soil respiration throughout the study. Invertebrates will be reared from wood samples, and fungal DNA will be extracted as well.ANOVA will be used to test for differences in log chemistry, soil chemistry, log respiration, and soil respiration across the four treatments and across harvesting intervals. Logistic regressions will be used to determine whether the presence/absence of termites has an effect on decomposition or any of the biogeochemical metrics.

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

Outputs
Target Audience:Findings from completed major activities under the project objectives were presented at regional and national meetings including the Society of American Foresters and the Mississippi State University Undergraduate Research Symposium. Findins were published in Catena, Forest Ecology and Management, Journal of Hydrology, and Urban Ecosystems. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Two graduate and two undergraduate students have participated in the project during the reporting period. Students gained valuable field experience in learning to design and implement field projects. Students participated in preparation of scholarly manuscripts and presentations at regional and national conferences. Students also learned to use complex instrumentation in the Forest Hydrology and Soils Laboratory under the supervision of the PI including an ion chromatograph, a discrete colorimetric analyzer, an elemental combustion analyzer, and a total organic carbon analyzer. These are valuable skills that will improve each student's career prospects. How have the results been disseminated to communities of interest?Objective 1. Canopy Hydrology: This MS project investigating canopy water partitioning was published in the MS Thesis and is in preparation for submitting to peer-reviewed journals. For the bark projects, the first study is under review in the journal Trees and the second study is scheduled to be presented at two conferences in the next reporting period and will be published in a conference proceeding and in the peer-reviewed journal Frontiers in Forests and Global Change. Objective 1. Soil Hydrology: The MS project investigating throughfall kinetic energy and soil erosion was presented at the Society of American Foresters Annual Convention and an abstract has been accepted at a regional conference in the next reporting period. The outcomes of this research are in preparation for submitting to peer-reviewed journals. Objective 2. Woody Decomposition: The MS project investigating decomposition in the southeastern US was presented at the Society of American Foresters Annual Convention. An abstract has been accepted for the MS project investigating decomposition in Arizona, Honduras, and Mississippi at a regional conference in the next reporting period. The outcomes of this research are in preparation for submitting to peer-reviewed journals. What do you plan to do during the next reporting period to accomplish the goals?During the next reporting period, I will continue to collect data from all aspects of the project. The overarching project objective of understanding how forest disturbances affect water and nutrient cycles in forest ecosystems, especially in the southeastern United States, will provide necessary understanding of the impacts to ecosystem services from disturbance and management activities. Data collected in the upcoming reporting period will be combined with data from the previous reporting period, analyzed, and prepared for conference presentations and publications.

Impacts
What was accomplished under these goals? Impact Statement: The tree canopy is the first major compartment encountered by precipitation as it moves through forested ecosystems, and can dramatically transform the fate and transport of water and nutrients. The relationship between canopy-derived inputs of water and nutrients and subsequent changes in soil biogeochemistry is complex and more research is needed to understand how these two components of the biosphere are impacted by disturbance events. In order to enhance the predictive capability of ecosystem models that guide management and policy decisions, it is imperative to understand the physically-based processes that control these fluxes. The proposed research will provide field-based evidence of changes to water and nutrient cycles that can be leveraged by land managers to understand ecosystem-level impacts of different management objectives. Objective 1. Canopy Hydrology: An MS student concluded and submitted her thesis project exploring how a shift in forest composition could impact rainwater distribution. We measured measured stemflow, throughfall, and surface soil moisture monthly for overstory and midstory trees of oaks and hypothesized mesophytes (hickory, red maple, winged elm) in northern Mississippi. Overstory oaks partitioned 5% of rainwater into stemflow, while mesophytic species partitioned 7%, leading to 4% wetter soils under mesophytes. The hydrology of mesophyte canopies may reduce forest flammability and promote conditions favorable for mesophyte regeneration, ultimately compromising long-term oak regeneration. In Fall 2019, Dr. Anna Ilek, a visiting scientist from Poznan University in Poland conducted research in my laboratory for 3 months. We initiated several studies to understand how bark morphological and structural characteristics affect canopy water partitioning and water storage. In one study, we tested the hypothesis that bark hygroscopicity will represent a large fraction of bark water storage capacity which will vary among species due to differences in internal bark structure. We conducted laboratory experiments to measure interspecific differences in bark physical structure as it relates to water storage mechanisms among common tree species (hickories, oaks, sweetgum, loblolly pine) in the southeastern US. We found a distinct difference between hickory and oak, whereby hickory had 5.6% lower specific density, 31.1% higher bulk density, and 22.4% lower total porosity of outer bark resulting in higher hygroscopicity compared to oaks. Overall, bark hygroscopicity may constitute an average of 30% of total bark water storage capacity. Therefore, in humid climates like those of the southeastern US, the proportion of bark that remains saturated during non-storm conditions cannot be assumed negligible. In a second study, we collected bark samples from mature loblolly pine and chestnut oak from sites across the Bankhead National Forest in Alabama, US under three different burn regimes: 3-year cycle, 9-year cycle, and no fire. Bark physical properties such as thickness, density, and porosity have known associations with fire tolerance among species. These physical properties simultaneously influence rainfall interception and canopy storage and thus are of interest across a range of disciplines. Furthermore, while these characteristics are innate to a species, it is unknown whether repeated exposure to fire facilitates physical change in bark structure and whether these changes are consistent among species. Samples were analyzed in the laboratory for bulk density, porosity, water storage capacity, and hygroscopicity (the amount of atmospheric water vapor absorbed by bark during non-rainfall conditions). Drying rates of saturated samples under simulated wetting conditions were also assessed. Oak bark had higher bulk density, lower porosity, and dried slower than pine bark. Interestingly, bark from both species had lower bulk density, higher porosity, greater water storage capacity, and dried faster in stands that were burned every 3 years compared to other fire regimes (p<0.001). Preliminary findings suggest that bark structure does indeed change with repeated exposure to fire leading to increases in water storage capacity and slower evaporation. In a third study, we have initiated the collection of bark samples along tree trunks of 4 species in the southeastern US and of 3 species in Poland. The goals of this project are to expand the findings of our previous work to understand how bark structure and morphology changes along the tree trunk. This will help refine estimates of water absorption and retention in bark at the whole-tree level. Sample collection has been completed but laboratory analysis is still pending. Soil Hydrology: An MS student has completed all the field work and sample processing on his thesis project examining how forest structure affects the redistribution of rainfall into throughfall, the kinetic energy associated with throughfall (TKE), and the subsequent impacts on overland flow and soil erosion. The student is currently writing up his final thesis manuscript, which found that season, slope position, canopy cover, and total throughfall amount had a significant relationship with TKE. We found that TKE increased during the growing season as raindrops coalesced on leaf surfaces resulting in larger droplets with higher kinetic energy. As total throughfall amount increased, TKE increased, but was not correlated with throughfall intensity. TKE was also higher at lower slope positions, possibly reflecting differences in species composition. Results for overland flow and soil erosion are pending. Soil Biogeochemistry: To understand the species-level controls on soil biogeochemistry, we have been samples soils for total C, total N, inorganic N availability, and soil respiration since 2017. In this reporting period, an undergraduate student has been working on processing soil samples. Our preliminary results suggest that C and N concentrations are higher in soils around oak trees compared to non-oak trees (C: p=0.012, N: p=0.026) with no differences observed in soil respiration. Inorganic nitrogen availability results are still pending. Objective 2. Woody Decomposition: A MS student is finishing up sample processing and data analysis to understand how long-term coarse woody debris decomposition rates and biogeochemical cycles are impacted by bark beetle infestations and the interactions with termite and fungal decomposers. In a five-year field study in the Southeastern US, we found that sapwood density only declined by 4% when invertebrates were excluded compared to a decrease of 26% when invertebrates were present. Soil N decreased 7-11% below logs inoculated with bluestain fungi by year 5 and increased 9-14% in soils below logs where bluestain was excluded. Soil C decreased 16-25% below inoculated logs but increased 18-25% below non-inoculated logs. Soil CN ratios declined by 7-10% below inoculated logs and increased below non-inoculated logs by 6-17%, indicating less-desirable conditions for soil microorganisms when bluestain fungi are excluded. Wood chemistry data are still pending. Results from a separate two-year decomposition study conducted in Arizona, Mississippi, and Honduras revealed that in Arizona, C was 53% higher and N was 62% higher under non-caged logs than aboveground-caged logs. Soil N was 11% higher in the A-horizon and 27% higher in the B-horizon below beetle-infested wood. In Mississippi, wood source treatments led to differences in soil C and N in year 1, where A-horizon carbon was 11% higher and N was 12% higher in year 1, but there were no differences between treatments in year 2.

Publications

• Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Siegert CM, Limper KE, Drotar NA, Siegle-Gaither ML, Burton M, Lowery JA, Alexander HD. 2020. Effects of canopy structure on water: implications for changing forest composition. In Bragg DC, Koerth NE, Holley A G, eds. Proceedings of the 20th Biennial Southern Silvicultural Research Conference. eGen. Tech. Rep. SRS253. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 338 p.
• Type: Journal Articles Status: Published Year Published: 2020 Citation: Dowtin AL, Siegert CM,Levia DF. 2020 Comparisons of flux-based stemflow enrichment ratios for two Quercus spp. within the megalopolis of the eastern USA. Urban Ecosystems.
• Type: Journal Articles Status: Under Review Year Published: 2020 Citation: Siegert CM, Suriano ZJ, Leathers DJ, Gold AJ, Addy K, Schroth AW, Seybold E, Inamdar S, Levia DF. (In Review). Effects of atmospheric circulation on stream chemistry in forested watersheds across the Northern United States: Part 1. Synoptic-Scale Forcing. Journal of Geophysical Research - Atmospheres.
• Type: Journal Articles Status: Under Review Year Published: 2020 Citation: Suriano ZJ, Siegert CM, Leathers DJ, Gold AJ, Addy K, Schroth AW, Seybold E, Inamdar S, Levia DF. (In Review). Effects of atmospheric circulation on stream chemistry in forested watersheds across the Northern United States: Part 2. Interannual Weather Type Variability. Journal of Geophysical Research - Atmospheres.
• Type: Journal Articles Status: Under Review Year Published: 2020 Citation: McDaniel JK, Alexander HD, Siegert CM, Lashley MA. (In Review). Shifting tree species composition of upland oak forests alters leaf litter structure, moisture, and flammability. Forest Ecology and Management.
• Type: Conference Papers and Presentations Status: Other Year Published: 2020 Citation: Nation R, Plauche EB, McDaniel JK, Alexander HD, Siegert CM. 2020. Impacts of single and mixed tree species composition on leaf litter decomposition rates. Society of American Foresters National Convention, virtual platform. Poster.
• Type: Conference Papers and Presentations Status: Other Year Published: 2020 Citation: Nation R, Plauche EB, McDaniel JK, Alexander HD, Siegert CM. 2020. Impacts of single and mixed tree species composition on leaf litter decomposition rates. Mississippi State University Fall Undergraduate Research Symposium, virtual platform. Poster.
• Type: Conference Papers and Presentations Status: Other Year Published: 2020 Citation: Nation R, McDaniel JK, Alexander HD, Siegert CM. 2020. Impacts of single and mixed tree species composition on leaf litter decomposition rates. Mississippi State University Undergraduate Research Symposium. Starkville, MS. Poster (Canceled due to COVID-19).
• Type: Conference Papers and Presentations Status: Other Year Published: 2020 Citation: Kruckeberg W, Siegert CM, Alexander HD, Granger JJ. 2020 Influence of canopy gaps and rainfall on splash erosion in upland hardwood forests. Society of American Foresters National Convention, virtual platform. Poster.
• Type: Conference Papers and Presentations Status: Other Year Published: 2020 Citation: Pace K, Siegert C, Clay N, Riggins J, Tang J. 2020 Response of soil chemistry to the simulated bark beetle infestation of a southeastern pine forest. Society of American Foresters National Convention, virtual platform. Poster.
• Type: Theses/Dissertations Status: Published Year Published: 2020 Citation: Drotar NA. 2020. Effects of tree morphology on rainwater partitioning in an upland oak forest.
• Type: Journal Articles Status: Under Review Year Published: 2020 Citation: Ilek A, Siegert CM, Wade A. (In Review). Hygroscopic contributions to bark water storage and controls exerted by internal bark structure over water vapor absorption. Trees.
• Type: Journal Articles Status: Under Review Year Published: 2020 Citation: Alexander HD, Siegert C, Brewer S, Kreye J, Lashley M, McDaniel J, Paulson A, Renninger H, Varner J. (In Review). Mesophication of oak landscapes: evidence, knowledge gaps, and future research. BioScience.
• Type: Conference Papers and Presentations Status: Other Year Published: 2020 Citation: Siegert CM. A tale of tree bark: how morphology and structure influence hydrology. Auburn University 2020 Fall Seminar Series. (Invited)

Progress 03/01/19 to 09/30/19

Outputs
Target Audience:Findings from completed major activities under objectives have been presented at regional and national meetings of professional societies including: Biennial Southern Sivicultural Research Conference, Ecological Society of America, Fire in Eastern Oak Forests Symposium, the Society of American Foresters Mississippi Loblolly Chapter, and the Southern Hardwood Forest Research Group Meeting. A day-long field trip was also conducted at Bernheim Research Forest and Arboretum during the Ecological Society of America Meeting. Findings have been published in Forest Ecology and Management, Geosciences, and the Proceedings of the 20th Biennial Southern Silvicultural Conference. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Three graduate and three undergraduate students have participated in the project during the reporting period. Students gained valuable field experience in learning to design and implement field projects. Students participated in preparation of scholarly manuscripts and presentations at regional and national conferences. Students also learned to use complex instrumentation in the Forest Hydrology and Soils Laboratory under the supervision of the PI including an ion chromatograph, a discrete colorimetric analyzer, an elemental combustion analyzer, and a total organic carbon analyzer. These are valuable skills that will improve each student's career prospects. How have the results been disseminated to communities of interest?Objective 1. One manuscript and one conference proceeding were published during the reporting period and several others are in prepartation. Results have been presented at state, regional, and national meetings. Objective 2. One manuscript has been submitted for publication. What do you plan to do during the next reporting period to accomplish the goals?During the next reporting period, I will continue to collect data from all aspects of the project. The overarching project objective of understanding how forest disturbances affect water and nutrient cycles in forest ecosystems, especially in the southeastern United States, will provide necessary understanding of the impacts to ecosystem services from disturbance and management activities. Data collected in the upcoming reporting period will be combined with data from the previous reporting period, analyzed, and prepared for conference presentations and publications.

Impacts
What was accomplished under these goals? Impact Statement: The tree canopy is the first major compartment encountered by precipitation as it moves through forested ecosystems, and can dramatically transform the fate and transport of water and nutrients. The relationship between canopy-derived inputs of water and nutrients and subsequent changes in soil biogeochemistry is complex and more research is needed to understand how these two components of the biosphere are impacted by disturbance events. In order to enhance the predictive capability of ecosystem models that guide management and policy decisions, it is imperative to understand the physically-based processes that control these fluxes. The proposed research will provide field-based evidence of changes to water and nutrient cycles that can be leveraged by land managers to understand ecosystem-level impacts of different management objectives. Objective 1. Canopy Hydrology: An MS student concluded her thesis project exploring how the physical traits of shade-tolerant and fire-sensitive species alter canopy partitioning of water and radiative energy to create and promote mesic understory conditions that are less favorable for management with prescribed fire and subsequent oak regeneration. To better understand how a shift in forest composition could impact rainwater distribution, we measured throughfall and stemflow beneath oak and non-oak species (e.g., hickory, maple, winged elm) in a series of experimental studies across the southeastern United States. We also measured canopy and bark structural characteristics to understand the relationship between tree structure and forest floor moisture. We found that overstory oaks partitioned 5.1% of rainwater into stemflow while mesoOnphytes species partitioned 7.2%, leading to 3.5% wetter soils under mesophtyes. In contrast, leaves of mesophyte species retain more intercepted rainwater than leaves of oak species and that water storage capacity was temporally variable among species depending on time of year. Objective 1. Soil Hydrology: An MS student continued to work on his thesis project exploring how prescribed fire impacts short-term erosion potential in upland hardwood ecosystems in northern Mississippi. We established study plots to measure throughfall kinetic energy and changes in overland flow and suspended sediment transport in hillslopes. After one dormant season burn, we found that prescribed fire did not increase soil erosion hazard and that changes in throughfall kinetic energy were due to changes in canopy leaf coverage. Objective 1. Soil Biogeochemistry: A project was established in Spring 2017 to explore how soil carbon and nitrogen are impacted following prescribed fire and how these responses are controlled by individual tree species. In the reporting period, we have continued to measure soil respiration and soil chemistry. We have found that soil CO2 emissions are greater from burned soils but return to un-burned levels by 6 months, that both soil carbon and nitrogen were greatest around Post Oak, and that the largest decreases in soil carbon and nitrogen were observed under Post Oak in response to fire. Objective 2. Woody Decomposition: A new PhD student began working on a long-term coarse woody debris decomposition project that explores how bark beetle infestations and interactions with termites and fungal decomposers lead to changes in decomposition rates and biogeochemical cycles. During the reporting period, we collected wood and soil samples that were deployed in a Mississippi forest 5 years previously. The PhD student is processing the samples and will combine year 5 data with previous years to address the long-term impacts to nutrient cycles.

Publications

• Type: Journal Articles Status: Under Review Year Published: 2019 Citation: Siegert CM, Renninger HJ, Clay NA, Hornslein N, Riggins JJ. (In Review). Changes in forest hydrology and biogeochemistry following a simulated tree mortality event by bark beetles. Soil Biology and Biochemistry.
• Type: Journal Articles Status: Accepted Year Published: 2019 Citation: Babl E, Alexander HD, Siegert CM, Willis JL. (Accepted). Could canopy, bark, and leaf litter traits of encroaching non-oak species influence future flammability of upland oak forests? Forest Ecology and Management.
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Siegert CM, Drotar NA, Alexander HD. 2019. Spatial and temporal variability of throughfall among oak and co-occurring non-oak tree species in an upland hardwood forest. Geosciences 9: 405.
• Type: Journal Articles Status: Accepted Year Published: 2019 Citation: Siegert CM, Limpert KE, Drotar NA, Siegle-Gaither ML, Burton M, Lowery JA, Alexander HD. (Accepted). Effects of canopy structure on water: implications for changing forest composition. Proceedings of the 20th Biennial Southern Silvicultural Conference.
• Type: Conference Papers and Presentations Status: Other Year Published: 2019 Citation: Alexander HD, Nation R, Izbicki B, McDaniel JK, Paulson A, Lashley MA, Siegert CM, McEwan RW. 2019. Fire impacts on oak acorn germination and early establishment and oak seedling growth relative to co-occurring competitors. Ecological Society of America. August 12-16. Louisville, Kentucky.
• Type: Conference Papers and Presentations Status: Other Year Published: 2019 Citation: Siegert CM, Drotar NA, Alexander HD, Burton M, Lowery JA. 2019. Water and nutrient availability in upland oak forests: species-specific response to prescribed fire. Ecological Society of America. August 12-16. Louisville, Kentucky.
• Type: Conference Papers and Presentations Status: Other Year Published: 2019 Citation: Alexander HD, Siegert M, Izbicki B, Paulson A, Nation R, Denny G, Babl E, McDaniel J, Lashley M, Drotar N, Frey B, McEwan R. 2019. Prescribed fire, oak regeneration, and future forest flammability. Fire in Eastern Oak Forests. July 23-25. State College, Pennsylvania.
• Type: Conference Papers and Presentations Status: Other Year Published: 2019 Citation: Siegert CM, Limpert KE, Drotar NA, Siegle-Gaither ML, Alexander HD. 2019. Effects of canopy structure on water and nutrient cycles: Implications for changing forest composition in the Central Hardwoods. 20th Biennial Southern Silvicultural Research Conference. March 13-14. Shreveport, Louisiana.
• Type: Conference Papers and Presentations Status: Other Year Published: 2019 Citation: Kruckeberg W, Siegert C, Alexander H, Granger J. 2019. Impacts of prescribed fire on soil erosion potential in northern Mississippi. Ecological Society of America. August 12-16. Louisville, Kentucky.
• Type: Conference Papers and Presentations Status: Other Year Published: 2019 Citation: McDaniel JK, Alexander HD, Siegert CM, Lashley MA. 2019. Mesophication of upland oak forests: shifting species composition alters fuelbed flammability. Ecological Society of America. August 12-16. Louisville, Kentucky.
• Type: Conference Papers and Presentations Status: Other Year Published: 2019 Citation: McDaniel JK, Alexander HD, Siegert CM, Lashley MA. 2019. Shifting species composition of upland oak forests alters fuelbed flammability. Fire in Eastern Oak Forests. July 23-25. State College, Pennsylvania.
• Type: Conference Papers and Presentations Status: Other Year Published: 2019 Citation: Lowery, JA, Siegert CM, Renninger HJ, Rousseau R. 2019. Hydrological effects of short rotation woody crops. Mississippi State University Undergraduate Research Symposium. April 16. Mississippi State, Mississippi.
• Type: Conference Papers and Presentations Status: Other Year Published: 2019 Citation: Drotar NA, Siegert C, Alexander H, Granger J. 2019. Comparing the effects of fire on water use in oak and mesophytic species. Southern Hardwood Forest Research Group Meeting. April 25, 2019. Stoneville, Mississippi. Poster.
• Type: Conference Papers and Presentations Status: Other Year Published: 2019 Citation: Kruckeberg W, Siegert C, Alexander H, Granger J. 2019. Impacts of prescribed fire on erosion potential in upland hardwood forests. Southern Hardwood Forest Research Group Meeting. April 25, 2019. Stoneville, Mississippi. Poster.
• Type: Conference Papers and Presentations Status: Other Year Published: 2019 Citation: Drotar NA, Siegert C, Alexander H, Granger J. 2019. Effects of prescribed burning on canopy structure and water partitioning in an upland oak forest. Quarterly Meeting of the Society of American Foresters Mississippi Loblolly Chapter. April 4, 2019. Starkville, Mississippi. Poster.
• Type: Conference Papers and Presentations Status: Other Year Published: 2019 Citation: Kruckeberg W, Siegert C, Alexander H, Granger J. 2019. Impacts of prescribed fire on erosion potential in upland hardwood forests. Quarterly Meeting of the Society of American Foresters Mississippi Loblolly Chapter. April 4, 2019. Starkville, Mississippi. Poster.
• Type: Conference Papers and Presentations Status: Other Year Published: 2019 Citation: Drotar NA, Siegert C, Alexander H, Granger J. 2019. Effects of prescribed burning on canopy structure and water partitioning in an upland oak forest. 20th Biennial Southern Silvicultural Research Conference. March 13-14. Shreveport, Louisiana. Poster.
• Type: Conference Papers and Presentations Status: Other Year Published: 2019 Citation: Kruckeberg W, Siegert C, Alexander H, Granger J. 2019. Impacts of prescribed fire on erosion potential in upland hardwood forests. 20th Biennial Southern Silvicultural Research Conference. March 13-14. Shreveport, Louisiana. Poster.