ACCELERATION OF INORGANIC NUTRIENT RELEASE AND MINERAL-ORGANIC MATTER ASSOCIATION BY BIOPHYSICAL SOIL MIXING ALONG AN EARTHWORM INVASION CHR

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: NRI COMPETITIVE GRANT
• Reporting Frequency: Annual
• Accession No.: 0226072
• Grant No.: 2008-35107-30632
• Proposal No.: 2011-03586
• Project Start Date: Aug 1, 2010
• Project End Date: Jul 31, 2013
• Grant Year: 2011
• Program Code: [25.0]- Soil Processes

Recipient Organization
UNIV OF MINNESOTA
(N/A)
ST PAUL,MN 55108

Performing Department
Soil, Water, and Climate

Non Technical Summary
Minnesota forested soils have evolved without the presence of earthworms since the last glacial retreat. When exotic earthworms arrive, enhanced soil bioturbation often results in dramatic morphological and chemical changes in soils with negative implications for the forests' sustainability. However, the impacts of earthworm invasion on geochemical processes in soils are not well understood. Here we are investigating how the invasion of earthworms in the previously earthworm-free forests affects the carbon cycle and mineral weathering in the soils that have significant bearing in sustainably managing the forests. Below are the summaries of the findings from this project in the past year. -Carbon cycle We broadly agree that the interactions of organic matter and minerals contribute to soils' capacity to store carbon. Such interactions may be controlled by the processes that determine the availability of organic matter and minerals, and their physical contacts. We are studying carbon mineral interaction along an approximately 200 meter long earthworm invasion transect in a hardwood forest in northern Minnesota. With the advent of earthworm invasion, the litter layer disappears and the carbon-rich mineral soil horizons (A horizons) thicken at the expense of the litter layer. In addition, organic carbon contents in the A horizons significantly increase with the arrival of earthworms. Simultaneously, measured mineral specific surface areas suggest that minerals' capacities to complex the organic matter appear to be greater in soils with active earthworm populations. Based on the data from the two end member soils along the transect, mineral's specific surface area in the A and E horizons are larger in the earthworm invaded soil than in the pre-invasion soil. While the amounts of organic matter and the minerals' capacity to complex carbon increase in the A horizon with the earthworm invasion, they are also more vigorously mixed. -Weathering This study attempts to quantify the role of earthworm invasion in mineral chemical weathering and nutrient dynamics along an earthworm invasion chronosequence in a sugar maple forest in Northern Minnesota. Depth and rates of soil mixing can be tracked with atmospherically derived short lived radioisotopes such as 210Pb and 137Cs. Their radio activities increase in the lower A horizon at the expense of the peak activities near the soil surface, which indicate that soil mixing rate and its depth reach have been enhanced by earthworms. Biologically cycled calcium and phosphorous have peak concentrations near the soil surface prior to earthworm invasion. However, these peak abundances significantly declined in the earthworm invaded soils presumably due to enhanced soil mixing. It is clear that enhanced soil mixing due to earthworms also profoundly altered the vertical distribution of most of mineral species within A horizons. As much as earthworms vertically relocated minerals and elements, they also intensify the contacts between organic matter and cations as shown in the increased amount of Ca and Fe in organically complexed and in exchangeable pools.

Animal Health Component

20%

Research Effort Categories

Basic

80%

Applied

20%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
101	0199	2061	40%
102	0199	2061	30%
104	0199	2061	30%

Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships; 104 - Protect Soil from Harmful Effects of Natural Elements; 101 - Appraisal of Soil Resources;

Subject Of Investigation
0199 - Soil and land, general;

Field Of Science
2061 - Pedology;

Keywords

earthworm invasion

sugar maple

soils

biogeochemistry

mineral weathering

carbon cycle

carbon mineral complexation

bioturbation

soil mixing

leaching

calcium cycle

Goals / Objectives
The project's goal is to test the following three hypotheses using an earthworm invasion chronosequence in a sugar maple forest in Northern Minnesota. Hypothesis 1: Vertical soil mixing rates along an earthworm invasion chronosequence are a multivariate function of earthworm species composition and species-specific biomass. Hypothesis 2: Rates that ions are released from minerals increase as a function of increasing biophysical mixing. Hypothesis 3: The rate that OM complexes with minerals (sorption to mineral surfaces and protection within aggregates) increases as a function of increasing biophysical mixing. To test the three hypotheses, we are making efforts on the following six objectives: 1.Develop time-dependent mathematical models that relate biophysical soil mixing, elemental leaching from mineral dissolution, organo-mineral association, and OM stabilization. 2.Determine earthworm species composition and species specific biomass along an invasion chronosequence. 3.Quantify vertical soil mixing rates and their depth profiles along an invasion chronosequence. 4.Quantify the concentrations and leaching rates of cations and anions in soil solution along an invasion chronosequence. 5.Quantify rates of net OM stabilization due to changes in mineral-associated OM pools along an invasion chronosequence 6.Test our three hypotheses by combining rates (Objective 2 to 5) with models (Objective 1). Below are the expected outcomes given the current stage of the project. -The amount of soil C inventory is determined by the function of earthworm biomass and earthworm species composition. -Earthworms increase the mineral surface area that can be covered by organic matter. -Greater fraction of mineral surface area is complexed by organic matter with earthworms' biophysical soil mixing. -Earthworms negatively affect the storage of Ca in the soils' A horizons. -The rate and degree of soil mixing is tightly controlled by the species composition of invading earthworms.

Project Methods
At a well characterized earthworm invasion chronosequence, the impacts of earthworm driven soil mixing on biogeochemical soil properties is being described and quantified. Measurements from the field will be combined with mathematical models that embody the hypotheses described above. Actual procedures we are currently undertaking can be summarized in the following list of activities: -We are developing a mass balance that relates biophysical soil mixing to mineral dissolution that could be constrained with empirical data from the invasion chronosequence. -We are developing a time dependent model that allows determining the rate that organic matter becomes associated with minerals along the earthworm invasion chronosequence. -We are measuring the profiles of bulk soil 210Pb and 137Cs activities along earthworm invasion chronosequences. -We are combining radionuclide data with a mass balance model to calculate the vertical soil mixing rates as a function of soil depth. -We are measuring solute concentrations in soil water that are collected from soil lysimeters. -We are conducting supplementary measurements that will provide geochemical/mineralogical context of the elemental leaching. -We are quantifying the changes in sizes of mineral-protected vs. mineral-free OM pools along an invasion chronosequence using the micromertics surface area and porosity analyzer. The outputs from these measurements and field works will be assessed toward testing the hypotheses as described below. Hypothesis 1: Vertical soil mixing rates along an earthworm invasion chronosequence are a multivariate function of earthworm species composition and species specific biomass. A 3-way Analysis of Variance (ANOVA) will be applied to differences in mixing rates (Objective 3) for each earthworm species biomass (Objective 2), while also assessing depth effects and assessing interaction terms. Hypothesis 2: Rates that ions are released from minerals increase as a function of increasing biophysical mixing. The concentrations and leaching rates of cations and anions (Objective 4) are compared to the biophysical soil mixing rates (Objective 3), with an expectation of positive correlation. Hypothesis 3: The formation rate of OM-mineral associations (sorption to mineral surface and occlusion within aggregates) increases as a function of increasing biophysical mixing. From our measurements of sizes of the mineral-free and mineral-associated OM pools in a series of pits with different times since worm invasion (Objective 5), we are calculating the change in the total OM storage and OM-mineral pool for given time intervals. We will then combine our mixing rates (Objective 3) with measured profiles of OM-free minerals and mineral-free OM to calculate their mixing-driven vertical fluxes, which we will use to assess what fraction of biophysically-moved OM and minerals result in OM-mineral associations.

Progress 08/01/10 to 07/31/13

Outputs
Target Audience: Academic communities in ecology, biogeochemistry, geochemistry, hydrology, and forestry. Forest managers in the glaciated part of N. America. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Two female graduate students completed their MS. thesis research on this project. The data and publications from this project have been actively used in the PD's graduate course "Soil Genesis and Landscape Evolution." The data and publications from this project have been used as a foundational inforation for "Invasion Biology" module in the PD's undergraduate course "Environmental Problem Solving" which is a required course for all undergraduate students majoring Environmental Science, Policy, and Management at the University of Minnesota. How have the results been disseminated to communities of interest? The results from this project have been disseminated to the communities of interests through (1) peer-reviewed publications, (2) Invited and voluntary presentations at International Conferences, and (3) Invited seminars at other universitieis. Detalied list of these activities is provided in the "Products". What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Our completed study has the following novel aspects that will have significant impacts on the community interested in forest biogeochemistry and invasion biology. 1. This is the first study that applied geochemical mass balance approach to quantify the role of exotic invasive organisms in altering biogeochemical processes in soils. Geochemical mass balance approach has been widely and successfully used to address soil formation over long time scales (>1,000 years). This study shows that this approach – when applied appropriately – works extremely well to document soils’ biogeochemical responses to changes in soil dwelling ecosystem engineers in short time frames less than 100 yrs. 2. This is the first study that applied BET measurements of mineral surface area and carbon sorption to quantify the changing dynamics of C-mineral associations in response to the population dynamics of soil dwelling organisms. 3. This work documented for the first time that earthworm invasion results in three stages of biogeochemical responses in soils: (1) Ca, P, and K in A horizons are enriched in the A horizons due to biological recycling and retention of these nutrient elements. (2) With the arrival of epi-endogeic and epi-endo-anecic earthworms that incorporate litter material into A horizon, there is further enrichment of these elements in the A horizons. (3) Such enrichments almost completely vanish with the arrival of endogeic earthworms. 4. This study provided the first evidence the cycles of organic matter and inorganic nutrients are tightly coupled in their responses to earthworm invasion. 5. This study documented for the first time that C-mineral sorption is limited by mineral surface area in the pre-earthworm invasion soils. However, with the arrival of endogeic earthworms, the limiting condition shifts to available organic matter. 6. This study shows that the impacts of exotic earthworms on the fluxes of inorganic nutrients and interactions between organic matter and minerals vary greatly with (a) the existing depth profiles of soil mineralogy and texture and (b) earthworm species compositions present.

Publications

• Type: Theses/Dissertations Status: Published Year Published: 2013 Citation: Carbon-mineral interactions and bioturbation: an earthworm invasion chronosequence in a sugar maple forest in Northern Minnesota. 2013. Amy Lyttle. MS Thesis. University of Minnesota. St. Paul.
• Type: Theses/Dissertations Status: Published Year Published: 2013 Citation: Impacts of earthworm bioturbation on elemental cycles in soils: An application of a geochemical mass balance to an earthworm invasion chronosequence in a sugar maple forest in Northern Minnesota. 2013. Kathryn Resner. MS Thesis. University of Minnesota. St. Paul.
• Type: Journal Articles Status: Published Year Published: 2011 Citation: Resner Kathryn, Kyungsoo Yoo, Cindy Hale, Anthony Aufdenkampe, Alex Blum, Stephen Sebestyen, 2011, Elemental and mineralogical changes in soils due to bioturbation along an earthworm invasion chronosequence in Northern Minnesota, Applied Geochemistry, Volume 26, Supplement, June 2011, Pages S127-S131.
• Type: Journal Articles Status: Published Year Published: 2011 Citation: Lyttle Amy, Kyungsoo Yoo, Cindy Hale, Anthony Aufdenkampe, Stephen Sebestyen, 2011, Carbon mineral interactions along an earthworm invasion gradient at a Sugar Maple Forest in Northern Minnesota, Applied Geochemistry, Volume 26, Supplement, June 2011, Pages S85-S88
• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Yoo K, Resner K, Lyttle A, Hale C, Aufdenkampe A & Sebestyen S. 2013. Invited: Feedbacks between Biological Retention of Nutrients, Carbon-Mineral Sorption, and Pore Space Generation along an Earthworm Invasion Chronosequence. Goldschmidt Conference, Florence. Italy.
• Type: Other Status: Published Year Published: 2013 Citation: Invited Presentation Ume� University, Sweden. Dept. of Ecology and Environmental Science. Biogeochemistry of Earthworm Invasion. Biogeochemistry of Earhthworm Invasion. March. 2013.
• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Resner et al., 2013. EXOTIC EARTHWORM INVASION: CONSEQUENCES FOR SOIL BIOGEOCHEMICAL CYCLES AND SOIL MORPHOLOGY IN A MINNESOTA SUGAR MAPLE FOREST. Geological Society of America, Annual Meeting, Denver, Colorado.
• Type: Conference Papers and Presentations Status: Published Year Published: 2012 Citation: Resner, K., Yoo, K., Lyttle, A., Audenkampe, A., Sebestyen, S. 2012. Soil and elemental mixing rates across an earthworm invasion chronosequence. American Geophysical Union Annual Meeting. San Francisco.
• Type: Conference Papers and Presentations Status: Published Year Published: 2012 Citation: Amy Lyttle, Kyungsoo Yoo, Anthony Aufdenkampe, Stephen Sebestyen, Cindy Hale. 2012. Interactions between organic matter and mineral surfaces along an earthworm invasion gradient in a sugar maple forest of Minnesota. . American Geophysical Union Annual Meeting. San Francisco.
• Type: Conference Papers and Presentations Status: Published Year Published: 2012 Citation: Timothy Filley, Anthony Aufdenkampe, Cindy Hale, Amy Lyttle, Yini Ma, Melissa McCoemick, Kathryn Resner, Kathy Szlavecz, Kyungsoo Yoo, 2012. Altered soil-plant-microbe interactions from biological invasion of ecosystem engineers: Invasive earthworms in North American forests. Geobiology Annual Meeting, Wuhan, China
• Type: Conference Papers and Presentations Status: Published Year Published: 2011 Citation: Lyttle A.*, K. Yoo, A.K. Aufdenkampe, C. Hale, S.D. Sebestyen, 2011. Earthworm species influence on carbon-mineral association in a sugar maple forest in northern Minnesota. American Geophysical Union, Dec.5-Dec.9 2011, San Francisco.
• Type: Conference Papers and Presentations Status: Published Year Published: 2011 Citation: Resner K.*, K. Yoo, A.K. Aufdenkampe, Lyttle A., B. Weinman, S.D. Sebestyen, A. Blum, C. Hale, 2011. Soil chemical weathering and nutrient budgets along an earthworm invasion chronosequence in a northern Minnesota forest. American Geophysical Union, Dec.5-Dec.9 2011, San Francisco.
• Type: Conference Papers and Presentations Status: Published Year Published: 2011 Citation: Resner, Kathleen. E.*, Yoo, Kyungsoo, Sesbestyen, Stephen D., Aufdenkampe, Anthony, Lyttle, Amy M., and Hale, Cindy M., 2011. Differences in soil chemical weathering and nutrient fluxes along an earthworm invasion chronosequence in a Minnesota sugar maple forest. Geological Society of America Annual Meeting, Oct 9th-12th, 2011, Minneapolis.
• Type: Conference Papers and Presentations Status: Published Year Published: 2011 Citation: Lyttle A.*, K. Yoo, A.K. Aufdenkampe, C. Hale, S.D. Sebestye. 2011. Organic mineral interactions along an earthworm invasion chronosequence. Geological Society of America Annual Meeting, Oct 9th-12th, 2011, Minneapolis
• Type: Conference Papers and Presentations Status: Published Year Published: 2011 Citation: Resner K.*, A., Yoo K., Hale C., Aufdenkampe A.K., Sebestyen S., 2011, Elemental and mineralogical changes in soils due to bioturbation along an earthworm invasion chronosequence in Northern Minnesota. Ninth International Symposium on Geochemistry of the Earths Surface, Organized by the International Association for Geochemistry (IAC), June 3-7, 2011, Boulder Colorado.
• Type: Conference Papers and Presentations Status: Published Year Published: 2011 Citation: Lyttle A.*, Yoo K., Hale C., Aufdenkampe A.K., Sebestyen S., 2011, Carbon mineral interactions along an earthworm invasion gradient at a sugar maple forest in Northern Minnesota. Ninth International Symposium on Geochemistry of the Earths Surface, Organized by the International Association for Geochemistry (IAC), June 3-7, 2011, Boulder Colorado

Progress 08/01/11 to 07/31/12

Outputs
OUTPUTS: (1)We completed laboratory analyses of ~50 soil and litter samples collected in the 2011. The analysis includes carbon and nitrogen contents, their stable isotope ratios, major elemental compositions, cation exchangeable capacity, exchangeable cations, pH, extractable iron and aluminum oxides, and total and C-covered mineral specific surface area. (2)We completed and organized the data set from biweekly water sampling from the 21 lysimeters and 6 piezometers that had been installed along the earthworm invasion chronosequence. We completed laboratory analysis of the >500 water samples for total elemental concentrations (cations and anions), alkalinity, DOC, DON, NO3-, NH4+, and pH. (3)For ~20 samples (subset of A horizon samples) that we separated by densities, we have determined mineral specific surface area and C and N contents and their stable isotope ratios. (4)In the Sept. 2011, we conducted a field work to collect A and E horizon soil materials and litter biomass along the 190 meter long invasion transect at every 10 meter intervals with three replicates in order to obtain statiscally meaningful measures of A horizon thickness, litter layer biomass, and their C inventories . We have completed the chemical analyses of these samples that include their C and N contents, bulk density, and mineral specific surface areas. (5)Two graduate students are currently working on their MS. theses on this topic. They will finish their degrees by the end of this this year. There will be three peer review papers from their theses. Meeting presentations Amy Lyttle, Kyungsoo Yoo, Anthony Aufdenkampe, Stephen Sebestyen, Cindy Hale. 2012. Interactions between organic matter and mineral surfaces along an earthworm invasion gradient in a sugar maple forest of Minnesota. . American Geophysical Union Annual Meeting. San Francisco. Resner, K., Yoo, K., Lyttle, A., Audenkampe, A., Sebestyen, S. 2012. Soil and elemental mixing rates across an earthworm invasion chronosequence. American Geophysical Union Annual Meeting. San Francisco. Timothy Filley, Anthony Aufdenkampe, Cindy Hale, Amy Lyttle, Yini Ma, Melissa McCoemick, Kathryn Resner, Kathy Szlavecz, Kyungsoo Yoo, 2012. Altered soilplant- microbe interactions from biological invasion of ecosystem engineers: Invasive earthworms in North American forests. Geobiology Annual Meeting, Wuhan, China. PARTICIPANTS: 1Amy Lyttle [e-mail] Dept. of Soil, Water, and Climate University of Minnesota 439 Borlaug Hall 1991 Upper Buford Circle St. Paul, MN, 55108-6028 Tel: [phone]Kyungsoo Yoo *Corresponding Author [e-mail] Dept. of Soil, Water, and Climate University of Minnesota 439 Borlaug Hall 1991 Upper Buford Circle St. Paul, MN, 55108-6028 Tel: [phone] Fax: [phone]Cindy Hale, Ph.D. [e-mail] University of Minnesota Duluth The Natural Resources Research Institute 5013 Miller Trunk Hwy. Duluth, MN 55811 [phone] 4Anthony K. Aufdenkampe, Ph.D. Assistant Research Scientist - Isotope & Organic Geochemistry Stroud Water Research Center 970 Spencer Road Avondale, PA 19311 Tel: [phone] ext. 263 Fax [phone]Stephen D Sebestyen, PhD, [e-mail] Research Hydrologist USDA Forest Service, Northern Research Station Grand Rapids, MN, 55744-3399 TEL: [phone]Alex E. Blum [e-mail] U.S. Geological Survey 3215 Marine St., Boulder, CO 80303 Tel: [phone] TARGET AUDIENCES: Academic community in ecology, biogeochemistry, geochemistry, hydrology. Forest managers in the glaciated part of N. America. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Context: This context was included in the last year's annual report as well. Minnesota forested soils have evolved without the presence of earthworms since the last glacial retreat. When exotic earthworms arrive, enhanced soil bioturbation often results in dramatic morphological and chemical changes in soils with negative implications for the forests' sustainability. We are studying carbon mineral interaction along an approximately 200 meter long earthworm invasion transect in a hardwood forest in northern Minnesota. This transect extends from the soils where earthworms are absent to soils that have been invaded by earthworms for nearly 30-40 years. This study attempts to quantify the role of earthworm invasion in (1) mineral chemical weathering and nutrient dynamics and (2) carbon cycle along an earthworm invasion chronosequence in a sugar maple forest in Northern Minnesota. Findings: (1) There are debates whether invasive earthworms increase or decrease soil carbon storage. We found that the answer partly depends on the stage of earthworm invasion and the depth of soil sampling. At the beginning of invasion, it is O horizon that is lost. However, O horizon contributes to less than 5% of total soil C pool. After the loss of O horizon, which occurs with the arrival of endogeic species, further decrease of soil C storage does not occur despite the decrease of A horizon soil C concentration. This is because the thickening of A horizon and the increase of A horizon bulk density compensate for the reduction in C concentration. (2) We found that minerals' surface area to complex C in A horizon is significantly reduced after the arrival of endogeic earthworm species. With detailed analysis of extraction chemistry of iron oxides and fine depth interval measurements of fall out radio isotope (137Cs), we now conclude that such reduction in mineral surface area is largely due to the new incorporation of E horizon materials that are made of silts with low specific surface area. This newly incorporated silt materials, however, are further coated with organic matter, which partly contributes to stabilizing A horizon C inventory across the invasion gradient. (3) Geochemical mass balance analysis of soil materials shows that earthworm invasion results in making the A horizon soils significantly denser. However, the A horizon materials are still 2 to 3 times volumetrically dilated when compared to the underlying loess materials that serve as parent materials for the A horizon. When we combine elemental chemistry and 137Cs data, we find that earthworm burrowing not only physically translocate elements but also significantly affects biogeochemical processes significantly altering vertical distribution elemental concentrations in soils. The relative significance of bioturbation and biogeochemical processes in re-contouring the elemental depth profiles depends on the solubility and biological demands of the elements.

Publications

• No publications reported this period

Progress 08/01/10 to 07/31/11

Outputs
OUTPUTS: We completed the third round of major field sampling in the Sept. 2011. During the field trip, we collected ~50 soil samples and litter biomass that are being currently analyzed for carbon and nitrogen contents, their stable isotopes, major elemental composition, cation exchangeable capacity, exchangeable cations, pH, extractable iron and aluminum oxides, and total and C-covered mineral specific surface area. -We have conducted biweekly water sampling from the 21 lysimeters and 6 piezometers that had been installed along the earthworm invasion chronosequence. This water sampling effort resulted in >500 water samples that have been and are being analyzed for total elemental concentrations (cations and anions), alkalinity, DOC, DON, NO3-, NH4+, and pH. -For ~20 samples (subset of A horizon samples), we have conducted density fractionation. The fractionated samples are being analyzed for mineral specific surface area, C and N contents and their stable isotope rations, and radio carbon isotope. Presentations were made at the following meetings: Lyttle A., K. Yoo, A.K. Aufdenkampe, C. Hale, S.D. Sebestyen, 2011. Earthworm species influence on carbon-mineral association in a sugar maple forest in northern Minnesota. AGU, San Francisco. Resner K., K. Yoo, A.K. Aufdenkampe, Lyttle A., B. Weinman, S.D. Sebestyen, A. Blum, C. Hale, 2011. Soil chemical weathering and nutrient budgets along an earthworm invasion chronosequence in a northern Minnesota forest. AGU, San Francisco. RESNER, Kit E., YOO, Kyungsoo, SEBESTYEN, Stephen D., AUFDENKAMPE, Anthony, LYTTLE, Amy M., and HALE, Cindy M., 2011. DIFFERENCES IN SOIL CHEMICAL WEATHERING AND NUTRIENT FLUXES ALONG AN EARTHWORM INVASION CHRONOSEQUENCE IN A MINNESOTA SUGAR MAPLE FOREST: GSA Annual Meeting, Minneapolis Lyttle A., K. Yoo, A.K. Aufdenkampe, C. Hale, S.D. Sebestye. 2011. ORGANICMINERAL INTERACTIONS ALONG AN EARTHWORM INVASION CHRONOSEQUENCE. GSA Annual Meeting, Minneapolis Resner K., A., Yoo K., Hale C., Aufdenkampe A.K., Sebestyen S., 2011, Elemental and mineralogical changes in soils due to bioturbation along an earthworm invasion chronosequence in Northern Minnesota. Ninth International Symposium on Geochemistry of the Earth's Surface, Boulder Colorado. Lyttle A., Yoo K., Hale C., Aufdenkampe A.K., Sebestyen S., 2011, Carbonmineral interactions along an earthworm invasion gradient at a sugar maple forest in Northern Minnesota. Ninth International Symposium on Geochemistry of the Earth's Surface,Boulder Colorado. K. Resner; K. Yoo; A. K. Aufdenkampe; C. Hale; S. D. Sebestyen, (2010), Geochemistry and Chemical Weathering in Soils along an Earthworm Invasion Gradient. AGU, San Francisco. A. Lyttle; K. Yoo; A. K. Aufdenkampe; C. Hale; S. D. Sebestyen, (2010), Carbon- Mineral Interactions along an Earthworm Invasion Gradient. AGU, San Francisco. Products: The results and the procedures in this study have been incorporated into the curriculum of "Soils and Landscape Relations" class that was taught by the PI, Kyungsoo Yoo in the spring 2011. PARTICIPANTS: PD Kyungsoo Yoo [e-mail] Dept. of Soil, Water, and Climate University of Minnesota 439 Borlaug Hall 1991 Upper Buford Circle St. Paul, MN, 55108-6028 Tel: [phone] Fax: [phone] CoPD Cindy Hale, Ph.D. [e-mail] University of Minnesota Duluth The Natural Resources Research Institute 5013 Miller Trunk Hwy. Duluth, MN 55811 [phone] CoPD Anthony K. Aufdenkampe, Ph.D. Assistant Research Scientist - Isotope & Organic Geochemistry Stroud Water Research Center 970 Spencer Road Avondale, PA 19311 Tel: [phone] ext. 263 Fax [phone] Collaborator Stephen D Sebestyen, PhD, [e-mail] Research Hydrologist USDA Forest Service, Northern Research Station Grand Rapids, MN, 55744-3399 TEL: [phone] Collaborator Alex E. Blum [e-mail] U.S. Geological Survey 3215 Marine St., Boulder, CO 80303 Tel: [phone] Graduate student Amy Lyttle & Kathryn Resner Graduate Student Dept. of Soil, Water, and Climate University of Minnesota 439 Borlaug Hall 1991 Upper Buford Circle St. Paul, MN, 55108-6028 Tel: [phone] TARGET AUDIENCES: Academic community in ecology, biogeochemistry, geochemistry, hydrology. Forest managers in the glaciated part of N. America. PROJECT MODIFICATIONS: We extended the study scope to include optically stimulated luminescence without using additional funding. -We extended the study scope to include magnetic susceptibility without using additional funding.

Impacts
Context: Minnesota forested soils have evolved without the presence of earthworms since the last glacial retreat. When exotic earthworms arrive, enhanced soil bioturbation often results in dramatic morphological and chemical changes in soils with negative implications for the forests' sustainability. We are studying carbon mineral interaction along an approximately 200 meter long earthworm invasion transect in a hardwood forest in northern Minnesota. Pre-invaded soils have approximately five cm thick litter layer, thin (~5cm) A horizon, silt rich E horizon, and clay-rich Bt horizons. Findings:We have made significant progresses on the following research fronts. (1)Depth and rates of soil mixing can be tracked with atmospherically derived short lived radioisotopes such as 210Pb and 137Cs. Their radio activities increase in the lower A horizon at the expense of the peak activities near the soil surface, which indicate that soil mixing rate and its depth reach have been enhanced by earthworms. Enhanced soil mixing by earthworms is consistent with the ways that the vertical profiles of elemental and mineralogical compositions were affected by earthworm invasion. Biologically cycled calcium and phosphorous have peak concentrations near the soil surface prior to earthworm invasion. (2)Though the mechanisms are not clear yet, earthworm invasion appears to have contributed to net losses of clay mineral species and opal from the A horizons. As much as earthworms vertically relocated minerals and elements, they also intensify the contacts between organic matter and cations as shown in the increased amount of Ca and Fe in organically complexed and in exchangeable pools. With future studies on soil mixing rates and elemental leaching, this study will quantitatively and mechanically address the role of earthworms in geochemical evolution of soils and forests' nutrient dynamics. (3)With the advent of earthworm invasion, the litter layer disappears and the A horizons thicken at the expense of the O and E horizons. (a) We have found that, as earthworm invasion proceeds, they affect the total soil carbon storage by altering the followings: (1) O horizon thickness, (2) A horizon thickness, (3) C concentration in A horizons, and (4) bulk density of A horizons. (b) We have also found that these variables systematically vary along the earthworm invasion chronosequence that result in the ups and downs of soil C storage over the sequence of earthworm invasion. (4)Simultaneously, measured mineral specific surface areas suggest that minerals' capacities to complex the organic matter appear to be greater in soils with little earthworm populations. This may be due to the observed decrease in clay contents with increasing intensity of earthworm invasion. However, this trend does not agree with the greater crystalline iron oxide contents observed for densely invaded soils. However, due to the thickening of the A horizon, greater amounts of organic matter and a greater percentage of total organic matter are found in the mineral complexed form in densely invaded soils.

Publications

• Lyttle Amy, Kyungsoo Yoo, Cindy Hale, Anthony Aufdenkampe, Stephen Sebestyen, 2011, Carbon mineral interactions along an earthworm invasion gradient at a Sugar Maple Forest in Northern Minnesota, Applied Geochemistry, Volume 26, Supplement, June 2011, Pages S85-S88
• Resner Kathryn, Kyungsoo Yoo, Cindy Hale, Anthony Aufdenkampe, Alex Blum, Stephen Sebestyen, 2011, Elemental and mineralogical changes in soils due to bioturbation along an earthworm invasion chronosequence in Northern Minnesota, Applied Geochemistry, Volume 26, Supplement, June 2011, Pages S127-S131.