Source: TEXAS A&M UNIVERSITY submitted to NRP
VEGETATION CHANGE AND THE BIOGEOCHEMISTRY OF GRASSLAND AND SAVANNA ECOSYSTEMS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
Reporting Frequency
Annual
Accession No.
1020427
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Jul 29, 2019
Project End Date
Jul 29, 2024
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
TEXAS A&M UNIVERSITY
750 AGRONOMY RD STE 2701
COLLEGE STATION,TX 77843-0001
Performing Department
Ecosystem Science & Management
Non Technical Summary
Woody plant encroachment into grass-dominated ecosystems has been a globally significant land-cover change during the last century, and has been documented in grasslands and savannas of North America, South America, Africa, Europe, and Asia. This dramatic land cover change appears to be driven largely by livestock grazing and the suppresion of natural fire regimes. Both woody encroachment and livestock grazing have strong potential to influence the storage of key soil nutrients, including carbon, nitrogen, and phosphorus. In addition, grazing and woody encroachment may also modify the biodiversity and functional attributes of the bacterial and fungal communities present in the soil environment. Thus, woody encroachment and livestock grazing may interact to modify nutrient cycles, the availability of limiting nutrients, and the structure and function of soil microbial communities at scales ranging from the ecosystem to the globe, and potentially influence the sustainability of livestock production systems. To better understand how woody encroachment and livestock grazing may interact to modify soil nutrient storage and cycling, we will quantify the magnitude of changes in soil carbon, nitrogen, and phosphorus storage in soils following woody encroachment in both grazed and ungrazed ecosystems. In these same study areas, we will also examine the impact of woody encroachment, grazing, and their interaction on the structure and function of soil bacterial and fungal communities. Results of this study will afford a unique opportunity to explore potential interactions between grazing and woody plant encroachment on belowground portions of the ecosystem that are critical for soil nutrient storage and availability. At present, these interactions remain largely unexplored and limit our understanding of the structure and function of grasslands, savannas, and other dryland ecosystem types. Results should also contribute to the development of more science-based methodologies for managing livestock grazing in these ecosystems that will help ensure the long-term sustainability of ecosystem services provided by these ecosystems.
Animal Health Component
10%
Research Effort Categories
Basic
85%
Applied
10%
Developmental
5%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
10207991070100%
Goals / Objectives
Arid and semiarid ecosystems such as deserts, grasslands, savannas, and dry woodlands cover approximately 40% of the Earth's surface, conduct 41% of terrestrial net primary productivity, and store 37% of soil organic carbon. Drylands also play a key role in the provision of ecosystem services, including the maintenance of biodiversity, hydrologic processes, biogeochemical functions, and the climate system. These ecosystems are also sensitive to natural and anthropogenic forcing factors such as fire, herbivory, and drought, causing them to be structurally and functionally dynamic. Woody plant encroachment into these ecosystems is a globally extensive land cover change that has been occurring during the past 150 yrs., and rates of increase in woody cover range from 0.1 to 2.3% yr-1 in grasslands and savannas throughout the world. This important vegetation change is likely driven by several potentially interacting local and global phenomena, including reduced fire frequencies, chronic livestock grazing, rising atmospheric CO2 concentrations, and climate change. The purpose of this research is to evaluate the long-term impacts of woody plant encroachment, herbivory, and their interaction on the biogeochemistry of soil C, N, and P, and on soil microbial community structure and function in juniper-oak savannas of the southern Great Plains. We will test the hypotheses that: (1) Long-term livestock grazing will reduce stores of soil C, N, and P; (2) Portions of the landscape dominated by woody plants will have larger pool sizes of soil organic C, total N, and total P than grass-dominated areas; and (3) Plant community composition and herbivory will interact to influence the structure, function, and size of the soil microbial compartment. This proposed research will be part of the Savanna Long-Term Research and Education Initiative in the Department of Ecosystem Science and Management at Texas A&M University. This program is aimed at understanding ecosystem function, dynamics, and processes within the grasslands and savannas of central Texas. This large interdisciplinary effort should generate new and significant ecological insights regarding the structure and function of savanna landscapes that will help landowners and land managers to develop proactive management practices that will help ensure the sustainability of ecosystem services in this region.
Project Methods
Research will be conducted at the Texas A&M AgriLife Sonora Research Station, a 1400 ha facility located 35 km S of Sonora, TX, USA, near the western edge of the Edwards Plateau. Climate is dry-subhumid with a mean annual temperature of 17.9° C, and mean annual precipitation of 586 mm. Soils within the areas sampled in this study are silty clays or stony clays of the Tarrant series (clayey-skeletal, smectitic, thermic Lithic Calciustolls) which lie atop indurated limestone bedrock from the Lower Cretaceous (USDA/NRCS 2015). Soils are generally shallow (<15 cm), although deeper patches may develop where the limestone is fractured. Current vegetation in the study area consists of savannas and woodlands. Over the past century, J. ashei appears to have increased markedly in grasslands and open parklands throughout the Edwards Plateau region. Analyses of recent aerial photographs (1985, 1996, 2004, and 2014) of the Sonora Research Station indicate that woody plant cover has increased from 25% in 1985 to 33% in 2014. The area that now comprises the Sonora Research Station was grazed heavily by livestock (cattle, sheep, and goats) at a stocking rate of 2 ha/animal unit/yr (1 animal unit = 12 kg per day dry biomass requirement) from the time of European settlement around 1880 until 1948. At that time, several long term grazing treatments and grazing exclosures were established and remained in place at the time of this study (~68 years). To test our hypotheses, we will sample three portions of the Sonora research site with contrasting grazing histories: (1) a control site protected from livestock grazing, (2) a moderately grazed site, and (3) a heavily grazed site. The control site (11 ha) has been protected from grazing by domestic herbivores since 1948, but has remained accessible to wild herbivore species, mainly white-tailed deer (Odocoileus virginianus) and axis deer (Axis axis). The moderately grazed site (24 ha) was part of a 4-pasture, 3-herd rotational grazing system that has been grazed by various combinations of cattle, sheep, and goats since 1948 at stocking rates of 6-8 ha/animal unit/yr. The heavily grazed site (7 ha) has been grazed continuously at stocking rates of 2-5 ha/animal unit/yr. The ratio of cattle:sheep:goats in the grazed areas has been approximately 60:20:20 since 1948, although cattle (but not sheep and goats) have been excluded from the moderately grazed site for the past 10 years. Neither the controls nor the grazing treatments have burned since the treatments were initiated in 1948. Between the 1880's and 1948, fires were unlikely due to high animal stocking rates that kept plant fuel loads at a minimum. Within each grazing treatment, 15 sites will be selected for plant, litter, and soil sampling. These sites consist of portions of the landscape dominated by: (a) open grasslands (n = 5), (b) juniper woodlands (n = 5), and (c) oak mottes (n = 5). At each sampling site, three surface litter samples (each taken within separate 0.1 m2 quadrats) will be collected within an area of approximately 4 m2 and then pooled and mixed to create one litter sample per site. Within each of the same quadrats where litter samples will be collected, soil samples will be collected to a depth of 10 cm, pooled and mixed to create a single sample, frozen within 5 hours of collection, and stored for subsequent analyses. Due to the presence of limestone parent material at or near the surface, it is challenging to collect soil from depths >10 cm. However, we will use a backhoe to excavate some trenches to deeper depths in order to access pockets of deeper soil that might not otherwise be accessible using a soil core or shovel. Litter samples will be cleaned gently with distilled water, dried, weighed to compute litter mass, pulverized, and weighed into tin capsules for elemental analyses. Air-dried soil samples will be passed through a 2-mm sieve to remove coarse organic fragments and rock fragments. An aliquot of sieved soil will be used to determine soil texture by the hydrometer method. Soil pH will be determined on a 1:2 (soil: 0.01M CaCl2) mixture using a using an Accumet Basic pH meter. An aliquot of sieved soil will be dried at 60° C for 48 h and pulverized in a centrifugal mill. For each pulverized soil sample, one aliquot will be weighed into a tin combustion capsule (5 x 7 mm) for analysis of total N. A separate aliquot of each soil sample will be weighed into a silver capsule (5 x 7 mm), treated with HCl vapor in a desiccator to remove carbonates for 8 h, dried, and analyzed for organic C concentration. Litter and soil samples will be analyzed for concentrations of organic C and total N using a Costech ECS 4010 elemental analyzer. Total P concentrations in litter and soils will be determined by lithium metaborate fusion coupled with the molybdenum blue colorimetry method. The concentration of P will be measured on a Spectronic 20D+ spectrophotometer and referenced with a standard curve of potassium phosphate solutions (KH2PO4 at 0, 0.125, 0.25, 0.375, 0.5, and 0.625 μg P/mL) verified against NIST SRM 2709a (San Joaquin soil). Carbon, N, and P stocks in litter will be computed as the product of litter dry mass (g m-2) and concentrations of C, N, and P (g g-1) in that litter, respectively. An aliquot of each soil sample will be extracted to obtain soil DNA for community analysis using MoBio Power Soil DNA extraction kits. The DNA will be subjected to a phylogenetic survey by analyzing the 16S ribosomal subunit to characterize prokaryotes using primers 515F (5'-GTGCCAGCMGCCGCGGTAA-3') and 806R (5'-GGACTACHVGGGTWTCTAAT-3'), and the ITS regions using primers ITS1 (5′-TCCGTAGGTGAACCTGCGG-3') and ITS2 (5'-GCTGCGTTCTTCATCGATGC-3') to characterize the fungi. Following library preparation, synthesis based sequencing will be performed using an Illumina MiSeq platform according to the manufacturer's protocol which will yield paired-end reads of 367 ± 39 bp for 16S and 423 ± 64 for ITS. Raw illumine reads will be deposited in NCBI's sequence read archive. Reads will be analyzed using the QIIME 1.9.1 pipeline. Resulting 16S and ITS OTU tables will be used to make predictions for bacterial metabolism using PICRUSt and to classify fungi into ecological guilds using FUNGuild. Each response variable will be analyzed by two-way ANOVA to assess the effects of grazing treatment (control, moderate, heavy), vegetation type (oak, juniper, grassland), and their interactions. When differences are significant, the Tukey-Kramer method will be utilized to assess posthoc contrasts with significance inferred at p ≤ 0.05. R Non-metric multidimensional scaling (NMDS) based on normalized Bray-Curtis distance matrices will be used to evaluate statistical community structure for bacteria and fungi. Differences in microbial community functions among treatments will be evaluated using response ratios.

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

Outputs
Target Audience:The target audience for this research is primarily the scientific community working in the area of terrestrial biogeochemistry. Efforts to reach this group were achieved through publications in journals and presentations at international professional meetings during this reporting period. In addition, my teaching program, which reached graduate students in my ESSM 600 (Principles of Ecosystem Science and Management) and ESSM 622 (Biogeochemistry of Terrestrial Ecosystems) provided another important mechanism for knowledge transfer. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The following postdoctoral fellow received training during the past year as part of research program: Dr. Che-Jen Hsiao - Postdoctoral Fellow, Texas A&M University How have the results been disseminated to communities of interest?Portions of this work have been presented at the Annual Meeting of the American Geophysical Union, the Annual Soil Survey and Land Resource Workshop, and the Ions @ Work Symposium in 2020. In addition, our lab hosted a group of high school AP Biology students and their teachers from Our Lady of the Hills High School in Kerrville, TX. We provided them with several presentations on our current research activities, and gave them an in depth tour of our stable isotope biogeochemistry laboratory. What do you plan to do during the next reporting period to accomplish the goals?At the same research site described in the Accomplishments section above, we have initiated a study to assess how juniper and oak encroachment into areas that were once grassland might influence soil trace emissions. Study areas have been established in grasslands, juniper patches, and oak patches. Soil collars have been installed on which sampling chambers can be perched to facilitate trace gas collection. Rates of CO2, CH4, and N2O fluxes will be quantified using gas chromatographic measurements on a diurnal and seasonal basis for a period of two years. Soil moisture manipulations will be used to assess how trace gas flux rates might change in response to changes in rainfall predicted for the future.

Impacts
What was accomplished under these goals? Throughout the US southern Great Plains, Juniperus (juniper) and Quercus (oak) species have increased in abundance. To evaluate the biogeochemical consequences of this vegetation change, we quantified soil organic C (SOC), total N (TN), and their isotopic composition in samples taken from 6 soil trenches passing through grassland, juniper, and oak patches on soils developed on either Edwards or Buda limestone on the Edwards Plateau of central Texas. Trench depths varied from 0.3-2.0 m, depending on depth to bedrock. Research was conducted at the Texas A&M AgriLife Research Station located near Sonora, TX on the western edge of the Edwards Plateau. The δ13C values of SOC under grasslands were -19‰ while those under woody patches were -21 to -24‰, indicating woody areas were relatively recent components of the landscape. Soil δ15N values ranged from 3-7‰, and were affected by a complex depth x vegetation x geology interaction. Both SOC and TN were significantly higher under oak and juniper (SOC = 45-105 g kg-1; TN = 3-8 g kg-1) than under grasslands (SOC = 40-45 g kg-1; TN = 3-4 g kg-1) on both Buda and Edwards parent material. In addition, SOC and TN were significantly higher on Edwards than on Buda soils. LOWESS smoothing plots showed soils beneath oak and juniper had higher SOC and TN than grasslands throughout the profile on soils derived from both Edwards and Buda limestone; concentrations were highest in the interiors of woody patches, decreased towards the edges of those patches, and reached lowest values in the surrounding grasslands. The spread of juniper and oak into areas that were once grassland has altered spatial variation in soil C and N across this landscape and to considerable depth, suggesting significant changes in the relative rates of nutrient inputs vs. losses in this system following vegetation change. Woody encroachment has been geographically widespread throughout the world's drylands during the past century, suggesting that changes in SOC and TN storage documented here may have implications for regional and global C and N cycles and potentially the climate system.

Publications

  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Adams RE, Hyodo A, SantaMaria T, Wright CL, Boutton TW, West JB. 2020. Bound and mobile soil water isotope ratios are affected by soil texture and mineralogy, whereas extraction method influences their measurement. Hydrological Processes 34: 991-1003.
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Torres Z, Mora MA, Boutton TW, Morrow M. 2020. Diet sources of the endangered Attwaters prairie-chicken in Texas: Evidence from d13C, d15N, and Bayesian mixing models. Ecosphere 11(10): e03269.10.1002/ecs2.3269.
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Deshpande AG, Boutton TW, Lafon CW, Moore GW. 2020. Bottomland hardwood forest growth and stress response to hydroclimatic variation: Evidence from dendrochronology and tree-ring d13C values. Biogeosciences https://doi.org/10.5194/bg-2020-131 (in press).
  • Type: Journal Articles Status: Awaiting Publication Year Published: 2020 Citation: Hines SL, Fulbright TE, Ortega JA, Webb SL, Hewitt DG, Boutton TW. 2020. Compatibility of dual enterprises for cattle and deer in North America: A quantitative review. Rangeland Ecology and Management (in press).
  • Type: Journal Articles Status: Submitted Year Published: 2020 Citation: Innocenti RA, Feagin RA, Charbonneau BR, Figlus J, Wengrove M, Lomonaco P, Puleo J, Huff TP, Rafiti Y, Hsu T, Tsai B, Boutton TW, Pontiki M, Smith J, Moragues MV. 2020. The effects of plant structure and fluid properties on the physical response of coastal foredune plants to wind and wave run-up. Estuarine, Coastal, and Shelf Science (submitted).
  • Type: Journal Articles Status: Submitted Year Published: 2020 Citation: Kjeldgaard M, Eyer P, McMichael C, Bockoven A, King J, Hyodo A, Boutton TW, Vargo E, Eubanks M. 2020. Do polygyne ants cooperate? Colony boundaries and larval discrimination in multiple-queen colonies of the red imported fire ant (Solenopsis invicta). Molecular Ecology (submitted).
  • Type: Journal Articles Status: Submitted Year Published: 2020 Citation: Zhou Y, Hyodo A, Boutton TW. 2020. Ecosystem sulfur accumulation following woody encroachment drives a more open S-cycle in a subtropical savanna Ecology (submitted).
  • Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Boutton TW, Hsiao CJ, Hyodo A. 2020. Trace gas fluxes from a warm-temperate savanna: Influence of vegetation cover and simulated rainfall events. Abstracts, Annual Meeting of the American Geophysical Union 2020: GC055-0010.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Hsiao CJ, Leite PAM, Hyodo A, Boutton TW. 2020. Soil carbon and nitrogen storage in juniper-oak savanna: Role of vegetation and geology. Abstracts, Annual Meeting of the American Geophysical Union 2020: GC004-0014.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Deshpande AG, Boutton TW, Hyodo A, Moore GW. 2020. N cycling and retention through plant and soil pools in a bottomland hardwood forest with elevated N deposition. Abstracts, Annual Meeting of the American Geophysical Union 2020: B115-0009.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Hsiao CJ, Hyodo A, Boutton TW. 2020. Soil CO2, CH4, and N2O emissions from a juniper-oak savanna in the southern Great Plains. Soil Survey and Land Resource Workshop, Texas A&M University.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Hsiao CJ, Hyodo A, Boutton TW. 2020. Soil carbon and nitrogen storage in calcareous soils of the southern Great Plains. Soil Survey and Land Resource Workshop, Texas A&M University.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Hsiao CJ, Hyodo A, Boutton TW. 2020. Carbon and nitrogen isotopic evidence for changes in land cover and ecosystem processes in a juniper-oak savanna. Ions@Work Symposium 2020, Texas A&M University.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Kjeldgaard MK, Underwood J, Hyodo A, Boutton TW, Eubanks MD. 2020. Spiking the ant punch: Evaluation of stable isotope tracers in the red imported fire ant. Ions@Work Symposium 2020, Texas A&M University.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Adams RE, Hyodo A, SantaMaria T, Wright CL, Boutton TW, West JB. 2020. Bound and mobile soil water isotope ratios are affected by soil texture and mineralogy, whereas extraction method influences their measurement. Abstracts, Ecological Society of America Annual Meeting 2020.


Progress 07/29/19 to 09/30/19

Outputs
Target Audience:The target audience for this research is primarily the scientific community working in the area of terrestrial biogeochemistry. Efforts to reach this group were achieved through my teaching program, which reached graduate students in my ESSM 600 (Principles of Ecosystem Science and Management) and ESSM 622 (Biogeochemistry of Terrestrial Ecosystems) classes at Texas A&M.In addition, my students and I gave several presentations at international professional meetings during this reporting period. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The following graduate students and postdoctoral fellows received training during the past year as part of research program: Dr. Che-Jen Hsiao - Postdoctoral Fellow, Texas A&M University Lifei Sun - Visiting Ph.D. Student, Chinese Academy of Sciences, Beijing How have the results been disseminated to communities of interest?Portions of this work have been published in refereed journal articles, and presented at the International Soils Meeting in San Diego in 2019, and at the Annual Meeting of the American Geophysical Union in 2019. In addition, our lab hosted a group of high school AP Biology students and their teachers from Our Lady of the Hills High School in Kerrville, TX. We provided them with several presentations on our current research activities, and gave them an in depth tour of our stable isotope biogeochemistry laboratory. What do you plan to do during the next reporting period to accomplish the goals?We will be continuing our field and laboratory assessments of grazing, vegetation change, and fire effects on soil biogeochemical properties and processes in juniper-oak savanna in west central Texas. We have initiated and continue to conduct field work to acquire spatially specific soil samples from long-term experimental treatments. We have initiated routine field sampling of soil trace gas emission rates that will be conducted monthly for the next several years. In the lab, we will be analyzing soils for carbon, nitrogen, sulfur, and phosphorus concentrations. Soils will also be analyzed for d13C, d15N, and d34S to better understand the processes influencing changes in the pool sizes and flux rates of those elements.

Impacts
What was accomplished under these goals? Semi-arid grasslands and savannas of the southern Great Plains USA are utilized extensively for livestock grazing. In this region, Juniperus (juniper) and Quercus (oak) species have increased in abundance during the past 100-150 years, likely in response to intensive livestock grazing and the concomitant decrease in fire frequency. Using a long-term (71 years) grazing experiment on the Edwards Plateau in west-central Texas, we explored the interaction of livestock herbivory (none, moderate, and heavy grazing) and vegetation cover (grassland, juniper, and oak) on concentrations of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP), as well as soil microbial community composition and predicted function. Concentrations of both SOC and TN were 50-150% greater under juniper and oak canopies compared to grasslands, and 10-30% lower in grazed treatments vs. controls. There was a significant vegetation x grazing interaction, with soils under oaks showing greater losses of SOC and TN in grazed areas than those under juniper and grassland. Soil TP was significantly higher in ungrazed controls vs. grazed areas, and higher beneath oak and juniper canopies compared to grasslands. Soil microbial DNA sequencing revealed that both bacterial and fungal community structure were significantly different between all three vegetation types. In contrast, grazing affected only bacterial communities. Non-metric multidimensional scaling indicated that SOC, TN, and TP were the vectors describing the majority of differentiation in bacterial and fungal community structure. Changes in the abundances of bacterial phyla in response to vegetation cover were linked to four key metabolic pathways: energy metabolism, carbohydrate metabolism, terpenoid/polyketide metabolism, and xenobiotic metabolism. These results are among the first to indicate that long-term livestock grazing and woody plant encroachment have both direct and interactive effects on soil C, N, and P storage, and alter the structural and functional attributes of soil microbial communities. In addition, these findings will help guide the incorporation of land cover/land use effects in dryland ecosystems into coupled biogeochemistry-climate models aimed at representing future global change scenarios.

Publications

  • Type: Journal Articles Status: Accepted Year Published: 2020 Citation: Adams RE, Hyodo A, SantaMaria T, Wright CL, Boutton TW, West JB. 2019. Bound and mobile soil water isotope ratios are affected by soil texture and mineralogy while extraction method influences their measurement. Hydrological Processes doi: 10.1002/hyp.13633 (in press).
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Zhou Y, Boutton TW, Wu XB. 2019. A three-dimensional assessment of soil ?13C in a subtropical savanna: Implications for vegetation change and soil carbon dynamics. Soil Systems 3: 73; doi:10.3390/soilsystems3040073.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Veldman JW, Aleman JC, Alvarado ST, Anderson TM, Archibald S, Bond WJ, Boutton TW, Buchmann N, Buisson E, Canadell JG, et al. 2019. Comment on the global tree restoration potential. Science 366 (6463): doi: 10.1126/science.aay7976.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Zhou Y, Watts SE, Boutton TW, Archer SR. 2019. Root density distribution and biomass allocation of co-occurring woody plants on contrasting soils in a subtropical savanna parkland. Plant and Soil 438: 263-279.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Mushinski RM, Boutton TW, Gentry T. 2019. Forest organic matter removal leads to long-term reductions in bacterial and fungal abundance. Applied Soil Ecology 137: 106-110.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Hyodo A, Malghani S, Zhou Y, Mushinski RM, Toyoda S, Yoshida N, Boutton TW, West JB. 2019. Biochar amendment suppresses N2O emissions but has no impact on 15N site preference in an anaerobic soil. Rapid Communications in Mass Spectrometry 33: 165175.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Ahmed I, Karim A, Boutton TW, Strom KB. 2019. On the prediction of uncertainty in a sediment provenance model. Research and Advances: Environmental Sciences 1: 45-60.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Deshpande A, Sedaghatdoost A, Hyodo A, Boutton TW, Moore GW. 2019. Nitrogen-carbon-water interactions under elevated N deposition in a seasonally flooded bottomland hardwood forest. Abstracts, Annual Meeting of the American Geophysical Union 2019: B13E-2553.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Schirmacher M, DeLaune P, Gentry T, Mubvumba P, Boutton TW. 2019. Impacts of cover vs. double cropping on soil health in Texas no-till wheat systems. Abstracts, International Soils Meeting (SSSA, CSSS, MSSS) 2019: Session 74: 1116.