Progress 10/01/14 to 09/30/18
Outputs
Target Audience:The target audiences reached by our research include the scientific community, university students, professional soil scientists and natural resource managers, and the general public. Efforts to reach these target audiences included publishing peer-reviewed papers; making research presentations at scientific meetings; formal classroom instruction; laboratory instruction; and presentations for a general audience. Specific examples from the final year of the project include twopeer-reviewed journal articles accepted for publication, two invited research presentations at scientific conferences, incorporation of research results into an introductory soil science course and an upper level soil ecology course, and an outreach presentation at the New Hampsire Farm and Forest Expo in Concord, NH. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project has provided an opportunity for a Master's student (Shana Whitney), a Ph.D. student (Eric Morrison), and a postdoctoral researcher (Dr. Kevin Geyer) to use current methods for assessing microbial carbon use efficiency and to apply these methods to better understand the factors controlling carbon use efficiency and its implications for soil carbon storage. We are also collaborating with several other research groups (laboratories of Dr. Stuart Grandy at the University of New Hampshire, Dr. Kristen DeAngelis at the Univeristy of Massachusetts--Amherst, and Dr. Johannes Rousk at Lund University in Sweden), providing opportunities for our students to participate in interdisciplinary and international science. How have the results been disseminated to communities of interest?Efforts to reach target audiences included publishing peer-reviewed papers; making research presentations at scientific meetings; formal classroom instruction; laboratory instruction; and presentations for a general audience. Refer to "Target Audience" section for more information. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Soil organic matter is the primary source of plant-available nutrients in terrestrial ecosystems and thus the maintenance of organic matter levels is critical for ecosystem sustainability. In addition to being an important nutrient reservoir, soils are an important source of carbon dioxide (CO2) to the atmosphere. Agricultural soils globally have lost a significant fraction of their soil organic matter reserve due to intensive cultivation, with agricultural soils in the U.S. having lost 25-50% of their original soil carbon (C) over the past century. This loss of C from agricultural soils has diminished native soil fertility and has contributed significantly to rising atmospheric CO2 levels. There is considerable interest in restoring at least some portion of this lost nutrient reserve, both to enhance nutrient availability for plant production and as one potential mitigation strategy to offset rising atmospheric CO2 levels. The overarching goal of this research was to understand the factors influencing how soil organic matter is gained and lost so that soils can be more sustainably managed, optimizing their ability to provide nutrients to enhance plant productivity and to mitigate climate change. Soil microorganisms are the engines of organic matter cycling in soils. The growth, turnover and efficiency of soil microbes are important controls of organic matter decay and soil C storage. The amount of soil organic matter lost through decomposition is a consequence of trade-offs between microbial growth rate and efficiency.Previous research has documented that small changes in microbial efficiency can have large effects on soil C levels. Yet how microbial growth, turnover, and efficiency respond to environmental factors (e.g., temperature, nutrient availability, substrate quality, moisture) is still poorly understood. The specific objectives of this project were to: Objective 1: COMPARE METHODS FOR ASSESSING MICROBIAL GROWTH AND EFFICIENCY. Our first task under this objective was to conduct a synthesis of existing information on microbial carbon utilization efficiency. This work has been published (Geyer et al., 2016; full citation given in 2016 report). A second goal under this objective was to experimentally compare the available methods for measuring microbial growth and efficiency. This work was completed in 2017 and a manuscript detailing the results was recently accepted in Soil Biology and Biochemistry for publication in 2019. In this study, we compared five currently used methods: 13C and 18O isotope tracing approaches which directly estimate microbial growth and efficiency; calorespirometry that infers growth and efficiency from heat flux and respiration; metabolic flux analysis which determines microbial efficiency from the balance between biosynthesis and respiration using position-specific carbon dioxide production of added substrates; and stoichiometric modeling which derives microbialefficiency from elemental ratios of biomass and substrate. The microbialefficiency estimates obtained were method-dependent, ranging from ~0.35 (substrate-independent methods of 18O and stoichiometric modeling) to ~0.70 (13C method, metabolic flux analysis). Each method addresses different aspects of microbial metabolism, growth and death, and efficiency. This makes the parallel use of multiple methods attractive for a more holistic perspective on microbial functioning than any single method can provide alone. This research provides researchers with information on the pros and cons of each method, so they canbetter determine which method is most appropriate for their specific research question. Objective 2: INTERACTIVE EFFECTS OF LAND MANAGEMENT, TEMPERATURE, MOISTURE, AND NUTRIENT AVAILABILITY ON CARBON USE EFFICIENCY. We addressed this objective in several ways: (1) analysis of soil samples collected from field sites under different management, climate, and nutrient regimes, (2) lab incubations using artificial soils, and (3) lab incubations of pure cultures of soil microorganisms. This research provides much-needed estimates of microbial growth and efficiency under a range of environmental conditions. These data that are now being used by ecosystem and Earth system modelers to better predict the effects of different land management practices and environmental changes on soil carbon storage. Objective 3: INCORPORATION OF RESULTS INTO MODELS. We are collaborating with several modeling groups who are working to incorporate microbial physiology into soil organic matter, ecosystem, and Earth system models. Our primary goal under this objective is to test our new understanding of the factors controlling microbial metabolismand its implications for soil C dynamics using the trait-based Decomposition Model of Enzymatic Traits (DEMENT) and the ecosystem Microbial-Mineral Carbon Stabilization Model (MIIMICS) and Stoichiometrically Coupled, Acclimating Microbe-Plant Model (SCAMPS). One peer-reviewed paper based on this collaborative work has been accepted for publication in Global Change Biology.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2019
Citation:
Geyer, K.M., P. Dijkstra, R. Sinsabaugh, and S.D. Frey. 2019. Clarifying the interpretation of carbon use efficiency estimates in soil through methods comparison. Soil Biology & Biochemistry 128, 79-88.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2018
Citation:
Geyer KM, Dijkstra P, Sinsabaugh R, and Frey SD. 2018. Clarifying the interpretation of carbon use efficiency estimates in soil through methods comparison. European Geophysical Union Annual Meeting, Vienna, Austria (invited presentation)
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2018
Citation:
Geyer KM, Schnecker J, Grandy AS, Richter A, and Frey SD. 2018. Microbial exudates: Incorporating an overlooked precursor to stable organic matter into the concept of carbon use efficiency. American Geophysical Union Annual Meeting, Washington, DC (invited presentation)
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Progress 10/01/16 to 09/30/17
Outputs
Target Audience:The target audiences reached by our research efforts include the scientific community, university students, professional soil scientists and natural resource managers, and the general public. Efforts to reach these target audiences included publishing peer-reviewed papers; making research presentations at scientific meetngs; formal classroom instruction; laboratory instruction; and presentations for a general audience. Specific examples include incorporating our research into an introductory soil science course (NR 501 Studio Soils) and an upper level course (NR 706/806 Soil Ecology). I also wrote an article in 2017 for the general public on the role of soils in forest management. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project has provided an opportunity for a Master'sstudent (Shana Whitney), a Ph.D. student (Eric Morrison), and a postdoctoral researcher (Kevin Geyer) to use current methods for assessing microbial carbon use efficiency and to apply these methods to better understand the factors controlling carbon use efficiencyand its implications for soil carbon storage. We are also collaborating with several other research groups (laboratories of Dr. Stuart Grandy at the University of New Hampshire, Dr. Kristen DeAngelis at the Univeristy of Massachusetts--Amherst, and Dr. Johannes Rousk at Lund University in Sweden), providing opportunities for our students to participate in interdisciplinary and international science. How have the results been disseminated to communities of interest?Efforts to reach target audiences included publishing peer-reviewed papers; making research presentations at scientific meetngs; formal classroom instruction; laboratory instruction; and presentations for a general audience. Refer to "Target Audience" section for more information. What do you plan to do during the next reporting period to accomplish the goals?We will complete our soil analyses for Objective 2and continue our modeling collaboration (Objective 3). We anticipate at least twomanuscripts will be prepared and submitted for peer-review and publication during the next reporting period. We will also continue our outreach efforts to key stakeholder groups.
Impacts
What was accomplished under these goals?
Agricultural productivity is dependent on nutrient cycling processes which are mediated by soil microorganisms. Microbial activity in turn is controlled to a large degree by temperature, moisture, substrate quality, and nutrient availability. Human-induced environmental change (e.g., climate warming, land-use change) may alter the microbial community and the nutrient cycling processes it mediates. This research will examine the factors influencing microbial activity, with specific focus on soil carbon dynamics. Objective 1: COMPARE METHODS FOR ASSESSING MICROBIAL CARBON UTILIZATION EFFICIENCY. Our first task under this objective was to conduct a synthesis of existing information on microbial carbon utilization efficiency. This work has been published (Geyer et al., 2016; full citation given in 2016 report).A second goal under this objective wasto experimentally compare the available methods for measuring microbial efficiency. This work was completed in 2017 and a manuscript detailing the results is under review in the journal Soil Biology & Biochemistry.In this study, wecompared five currently used methods: 13C and 18O isotope tracing approaches which directly estimate microbial growth and carbon use efficiency; calorespirometry which infers growth and carbon use efficiencyfrom heat flux and respiration; metabolic flux analysis which determines carbon use efficiencyfrom the balance between biosynthesis and respiration using position-specific carbon dioxideproduction of added substrates; and stoichiometric modeling which derives carbon use efficiencyfrom elemental ratios of biomass and substrate. The carbon use efficiencyestimates obtained were method-dependent, ranging from ~0.35 (substrate-independent methods of 18O and stoichiometric modeling) to ~0.70 (13C method, metabolic flux analysis). Each method addresses different aspects of microbial metabolism, growth and death, and carbon use efficiency. This makes the parallel use of multiple methods attractive for a more holistic perspective on microbial functioning than any single method can provide alone. Objective 2: INTERACTIVE EFFECTS OF LAND MANAGEMENT, TEMPERATURE, MOISTURE, AND NUTRIENT AVAILABILITY ON CARBON USE EFFICIENCY. We are addressing this objective in several ways: (1) analysis of soil samples collected from field sites under different management, climate, and nutrient regimes, (2) lab incubations using artificual soils, and (3) lab incubations of pure cultures of soil microorganisms. This work is ongoing. Objective 3: INCORPORATION OF RESULTS INTO MODELS. We are collaborating with several modeling groups who are working to incorporate microbial physiology into soil organic matter, ecosystem, and Earth system models. Our primary goal under this objective is to test our new understanding of the factors controlling carbon use efficiencyand its implications for soil C dynamics using the trait-based Decomposition Model of Enzymatic Traits (DEMENT) and the ecosystemMicrobial-Mineral Carbon Stabilization Model (MIIMICS) and Stoichiometrically Coupled, Acclimating Microbe-Plant Model (SCAMPS). This work is ongoing.
Publications
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2017
Citation:
Geyer, K.M. and S.D. Frey. 2017. Soil carbon in the balance: The causes and consequences of altered microbial carbon use efficiency in a changing world. Ecological Society of America Annual Meeting, Portland, OR.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2017
Citation:
Geyer K.M., S.D. Frey, P. Dijkstra, and R. Sinsabaugh. 2017. What do the numbers say? Clarifying our interpretation of CUE in soil. American Geophysical Union Annual Meeting, New Orleans, LA.
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Progress 10/01/15 to 09/30/16
Outputs
Target Audience:The target audiences reached by our research efforts include the scientific community, university students, and the general public. Efforts to reach these target audiences included publishing peer-reviewed papers; making research presentations at scientific meetngs; formal classroom instruction; laboratory instruction; and presentations for a general audience. Specific examples include incorporating our research into an introductory soil science course (NR 501 Studio Soils) and anupper level course (NR 706/806 Soil Ecology). I also presented aspects of our work to professional soil scientists at the NH Soils Matter Conference organized by the Natural Resources Conservation Service (NRCS)and held in Concord, NH in 2016. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project has provided an opportunity for an undergraduate student (Shana Whitney), a Ph.D. student (Eric Morrison), and a postdoctoral researcher (Kevin Geyer) to use current methods for assessing microbial carbon use efficiency (CUE)and to apply these methods to better understand the factors controlling CUE and its implications for soil carbon storage. We are also collaborating with several other research groups (laboratories of Dr. Stuart Grandy at the University of New Hampshire, Dr. Kristen DeAngelis at the Univeristy of Massachusetts--Amherst, and Dr. Johannes Rousk at Lund University in Sweden), providing opportunities for our students to cross-fertilize and participate in interdisciplinary and internationalscience. How have the results been disseminated to communities of interest?Efforts to reach target audiences included publishing peer-reviewed papers; making research presentations at scientific meetngs; formal classroom instruction; laboratory instruction; and presentations for a general audience. Refer to test in "Target Audience" section for more information. What do you plan to do during the next reporting period to accomplish the goals?We will complete our methods comparison (Objective 1), continue the soil analyses for Objective 2, and continue our modeling collaboration (Objective 3). We anticipate at leastthree manuscripts will be prepared and submitted for peer-review and publication during the next reporting period. We will also continue our outreach efforts to key stakeholder groups.
Impacts
What was accomplished under these goals?
Agricultural productivity is dependent on nutrient cycling processes which are mediated by soil microorganisms. Microbial activity, in turn, is controlled to a large degree by temperature, moisture, substrate quality,and nutrient availability. Human-induced environmental change (e.g., climate warming, land-use change) may alter the microbial community and the nutrient cycling processes it mediates. This research will examine the factors influencing microbial activity, with specific focus on soil carbon dynamics Objective 1: COMPARE METHODS FOR ASSESSING MICROBIAL CARBON UTILIZATION EFFICIENCY (CUE). Our first task under this objective was to conduct a synthesis of existing information on microbial carbon utilization efficiency. This work has been completed and published (Geyer, K.M., E. Kyker-Snowman, A.S. Grandy, and S.D. Frey. 2016. Microbial carbon use efficiency: Accounting for population, community, and ecosystem-scale controls over the fate of metabolized organic matter. Biogeochemistry DOI 10.1007/s10533-016-0191-y). In this paper, we outline the processes underlying microbial efficiency and propose a conceptual framework that structures the definition of CUE according to increasingly broad temporal and spatial drivers where (1) Carbon Use Efficiency for microbial population (CUEP ) reflects population-scale carbon use efficiency of microbes governed by species-specific metabolic and thermodynamic constraints, (2) Carbon Use Efficiency for microbial communties (CUEC ) defines community-scale microbial efficiency as gross biomass production per unit substrate taken up over short time scales, largely excluding recycling of microbial necromass and exudates, and (3) Carbon Use Efficiency at the Ecosystem level (CUEE) reflects the ecosystem-scale efficiency of net microbial biomass production (growth) per unit substrate taken up as iterative breakdown and recycling of microbial products occurs. CUEE integrates all internal and extracellular constraints on CUE and hence embodies an ecosystem perspective that fully captures all drivers of microbial biomass synthesis and decay. These three definitions are distinct yet complementary, capturing the capacity for carbon storage in microbial biomass across different ecological scales. By unifying the existing concepts and terminology underlying microbial efficiency, our framework enhances data interpretation and theoretical advances. A second goal under this objective is toexperimentally compare theavailable methods for measuring microbial efficiency. This work is ongoing, with sample and data analysis in progress. A manuscript summarizing these results is in progress. Objective 2: INTERACTIVE EFFECTS OF LAND MANAGEMENT, TEMPERATURE, MOISTURE, AND NUTRIENT AVAILABILITY ON CUE. We are addressing this objective in several ways: (1) analysisof soil samples collectedfrom field sitesunder different management, climate, and nutrient regimes, (2) lab incubations using artificial soils, and (3) lab incubations of pure cultures of soil microorganisms. This work is ongoing, but results to date indicate that soil carbon accumulation is highly correlated with CUE and that soils with the highest soil carbon accumulation exhibit higher fungal relative abundances and CUE (Kallenbach, C.M., A.S. Grandy, and S.D. Frey. 2016. Direct evidence for microbial-derived soil organic matter formation and its ecophysiological controls. Nature Communications 7:13630 DOI: 10.1038/ncomms13630). Objective 3: INCORPORATION OF RESULTS INTO MODELS. Weare collaborating with several modeling groupswho areworking to incorporatemicrobial physiologyinto soil organic matter, ecosystem, andEarth system models. Our primary goal under this objective is to test our new understanding of the factors controlling CUE and its implications for soil C dynamics using the trait-based Decomposition Model of Enzymatic Traits (DEMENT) and the ecosystemMicrobial-Mineral Carbon Stabilization Model (MIIMICS) and Stoichiometrically Coupled, Acclimating Microbe-Plant Model (SCAMPS). This work is still in the early stages of development.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Geyer, K.M., E. Kyker-Snowman, A.S. Grandy, and S.D. Frey. 2016. Microbial carbon use efficiency: Accounting for population, community, and ecosystem-scale controls over the fate of metabolized organic matter. Biogeochemistry DOI 10.1007/s10533-016-0191-y
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Kallenbach, C.M., A.S. Grandy, and S.D. Frey. 2016. Direct evidence for microbial-derived soil organic matter formation and its ecophysiological controls. Nature Communications 7:13630 DOI: 10.1038/ncomms13630.
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Progress 10/01/14 to 09/30/15
Outputs
Target Audience:I made outreach presentations to the general public that reached approximately 125 adults. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project is training one postdoctoral scientist, one PhD student, and one undergraduate student. How have the results been disseminated to communities of interest?One peer-reviewed manuscript has been accepted for publication in the journal Biogeochemistry. Results have also been presented to the general public at several outreach presentations. What do you plan to do during the next reporting period to accomplish the goals?We will complete the methods comparison (Objective 1) and complete and submita peer-reviewed manuscript. We will complete the analysis of soil samples collected to address Objective 2 and will prepare a second manuscript for publication. We will continue our modeling collaboration to address Objective 3.
Impacts
What was accomplished under these goals?
Agricultural productivity is dependent on soil nutrient cycling processes which are mediated by soil microorganisms. Microbial activity in turn is controlled to a large degree by temperature, moisture, substrate quality, and nutrient availability. Human-induced environmental change (e.g., climate warming, land-use change) may alter the microbial community and the nutrient cycling processes it mediates. This researchis examining the factors influencing microbial activity, with specific focus on soil carbon dynamics. Objective 1 METHODS COMPARISON:A synthesis of existing information on microbial carbon utilization efficiency was completedand a comparison of available methods for measuring microbial efficiency was initiated. One manuscript has been accepted for publication and a second manuscript is in preparation for submission in 2016. Objective 2 FACTORS CONTROLLING MICROBIAL EFFICIENCY: Soil samples were collected and are in the process of being analyzed. Objective 3 INCORPORATING MICROBIAL EFFICIENCY INTO EARTH SYSTEM MODEL: We haveinitatied a collaboration with an Earth System modeler to incorporate our results into the Community Land Model, the terrestrial component of the Community Earth System Model used for climate change assessments.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Geyer, K. and S.D. Frey. 2015. Unifying concepts for defining and quantifying measures of growth efficiency. Presentation in Organized Oral Session at the Ecological Society of America Annual Meeting, Baltimore, MD.
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