ACCELERATION OF INORGANIC NUT. RELEASE & MINERAL-ORGANIC MATTER ASSOC. BY BIOPHYSICAL SOIL MIXING ALONG AN EARTHWORM INVASION CHRONOSEQUENCE

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: NRI COMPETITIVE GRANT
• Reporting Frequency: Annual
• Accession No.: 0214838
• Grant No.: 2008-35107-04478
• Cumulative Award Amt.: $397,500.00
• Proposal No.: 2008-02761
• Project Start Date: Sep 1, 2008
• Project End Date: Aug 31, 2011
• Grant Year: 2008
• Program Code: [25.0]- Soil Processes

Recipient Organization
UNIVERSITY OF DELAWARE
(N/A)
NEWARK,DE 19717

Performing Department
PLANT & SOIL SCIENCES

Non Technical Summary
Arguably, the two most important terrestrial biogeochemical processes responsible for sustaining the ecosystems are chemical weathering and carbon cycling. While largely ignored, soil animals like earthworms, ants, and rodents are ubiquitous and vertically mix the soils they inhabit. Soil mixing, the PIs propose, has far reaching impacts on the rates of mineral and carbon cycles because soils are defined by steep vertical gradients in the concentrations, compositions and dynamics of minerals and organic matter. Whereas weathering is most intense at or near soil surface, weathering susceptible primary minerals are more abundant nearer to underlying parent materials. Organic matter is most abundant at the soil surface, but minerals stabilizing the carbon are more abundant in the depth. Earthworms, by vertically mixing soils, would substantially reduce the limiting conditions by transporting primary minerals to the soil surface and organic matter to depth and thus may accelerate the release of inorganic nutrients from mineral weathering and the sequestration of organic carbon in soils. The proposed research employs a well-characterized earthworm invasion chronosequence in a National Forest in Minnesota to address the sustainable managements of national forests under the threat of exotic earthworm species. The PIs will test the hypothesis by: (1) measuring depth profiles of elemental, mineralogical and organic matter properties in soils that vary with earthworm species composition and abundance, (2) calculating vertical mixing rates from depth profiles of atmospherically fall-out radionuclides activities, (3) quantifying mineral weathering rates from captured soil solutes and changes to mineral properties, (4) quantifying organo-mineral complexation rates and the turnover times of organic matter and lastly the rates of carbon sequestration.

Animal Health Component

10%

Research Effort Categories

Basic

90%

Applied

10%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
102	0110	2061	50%
123	0120	1070	30%
136	0620	1070	20%

Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships; 136 - Conservation of Biological Diversity; 123 - Management and Sustainability of Forest Resources;

Subject Of Investigation
0120 - Land; 0110 - Soil; 0620 - Broadleaf forests of the North;

Field Of Science
1070 - Ecology; 2061 - Pedology;

Keywords

bioturbation

nutrients

weathering

carbon cycle

carbon sequestration

complexation

earthworms

biological invasion

forest sustainability

Goals / Objectives
Our goal is to understand how and to what degree soil perturbation by earthworms affects rates of inorganic-nutrient (cation) release from mineral weathering and rates of organic matter (OM) stabilization from increased contact and association with soil minerals. Toward the goal, we propose to test three hypotheses: 1. Vertical soil mixing rates along an earthworm invasion chronosequence are a multivariate function of earthworm species composition and species-specific biomass; 2. Rates that ions are released from minerals increase as a function of increasing biophysical mixing; 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 will achieve 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). Highly interdisciplinary nature of the proposed work requires a team of three early career scientists whose expertise cover soil formation and geomorphology (Yoo), organic and isotope geochemistry (Aufdenkampe), and ecosystem ecology (Hale). Yoo will have responsibility for managing and coordinating the project. All participants will participate in field activities. Yoo is responsible for soil description, mineralogical and elemental compositions of soil samples, CEC, radio activities, pH and ionic concentrations of soil water, and model calculations. Aufdenkampe will have responsibility to determine mineral-free vs. mineral complexed carbon pools, their stable carbon isotope ratios, mineral surface area, and alkalinity, major anion and DOC concentrations of soil solutions. Hale will be responsible for site selection, earthworm sampling and identification, and coordinating the data share with her ongoing study on the earthworm invasion in Great Lakes Region. This mixture will ensure cross-disciplinary peer reviewed papers across the fields of earth, ecological, and agricultural sciences, and timely dissemination of our findings to publics concerned about the impact of invasive species on the sustainability of US forest ecosystems.

Project Methods
Measurements from the field and laboratory will be combined with mathematical models that embody the hypotheses. The study site is located at a mature northern hardwood forest in Chippewa National Forest of northern Minnesota. At the site, Hale detailed the dynamics of 4 earthworm invasion chronosequences showing a succession in earthworm species composition and abundance that led to disappearance of forest floor litter at the invasion front increasing A horizon thickness. Objective 1: Develop new time-dependent mathematical models that functionally relate biophysical soil mixing, elemental leaching, and OM-mineral associations. Task 1.1 Develop a mass balance that relates biophysical soil mixing to mineral dissolution; Task 1.2. Develop a time dependent model that allows determining the rate that OM becomes associated with minerals along the invasion chronosequence. Objective 2: Determine species specific earthworm biomass along the invasion chronosequence. The earthworm populations spanning the invasion chronosequence were characterized in detail for a four year period (1998-2001), which we will repeat for this study in the first and third year of the project. This provides a measurement of change over 10 years. Objective 3. Quantify the vertical soil mixing rates and their depth profiles along the invasion chronosequence. First, we will measure the average bulk soil mixing rates using gamma spectrometry. Second, the fine scale soil movements via earthworm castings on the surface and burrows will be tracked with alpha spectrometry. Lastly, we will combine radionuclide data with a mass balance model to calculate the vertical soil mixing rates as a function of soil depth. Objective 4. Quantify concentrations and leaching rates of cations and anions in soil solution along the invasion chronosequence. We focus on soil water chemistry as plant available elemental pool and the elemental leaching rate as a proxy for mineral chemical weathering rate because these respond rapidly to changing conditions and can be readily observed from the chemistry of soil water. Objective 5. Quantify rates of net OM stabilization due to changes in mineral-associated OM pools along an invasion chronosequence. We will adopt the wet-sieving, size-fractionation approach that resolves two soil OM pools (mineral free vs. mineral complexed). Specific tasks are: 1. Quantify changes in sizes of mineral-protected vs. mineral-free OM pools along an invasion chronosequence; 2. Calculate the formation rate and decomposition rate of mineral-associated OM pools; 3. Conduct supplementary measurements that will significantly enhance the data interpretation. The outcomes from this study will be the rates of soil mixing, inorganic nutrient release from mineral weathering, and organo-mineral complexation as a function of earthworm species and population density. Quantification of these rates and the mechanistic coupling of ecological dynamics of soil organisms with soil bigeochemical processes have not been made before.

Progress 09/01/08 to 08/31/11

Outputs
OUTPUTS: (A) Field sampling was conducted in the Sept. 2009. This effort resulted in (1) sampling earthworms along the earthworm invasion chronosequence, (2) identifying the earthworm species, (3) sampling ~300 soil samples for biogeochemioal analyses, (4) sampling 6 samples for optically stimulated luminescence analyses, and (5) installing six soil pits with lysimeters and Piezometers. (B) Since the snowmelt this spring (April), we have sampled soil water from the installed lysimeters and Piezometers biweekly. Rebecca Knowles from the Leech Lake Band of Objiwe and Stephen Sebestyen at the Forest Service have been in charge of the daily operation. This activity has resulted in ~80 soil water samples that are being analyzed for their elemental chemistry, DOC/DON cooentrations, stable isotope ratios of DOC and DON, total nitrogen and nitrate concentrations, and alkalinity. (C) All of the soil samples have been pulverized and analyzed for their total elemental chemistry using lithium-borate fusion and ICP-MS. (D) Subset (~15) of the soil samples have been analyzed for their 210Pb and 137Cs activities. These data will be used to estimate soil mixing rates. (E) Subset (~30) of the soil samples have been leached with ditionite-citrate, ammonium oxalate, and sodium pyrophosphate for estimating various iron oxide pools. (F) The PI attended an annual USDA soils program PI meeting held in Washington DC. (G) The PI and a graduate student, Cristina Fernandez, presented the preliminary results at the 2010 American Geophysical Union Meeting, San Francisco. (H) The PI presented the progress of this study in the invited talks at the Pennsylvania State Univ., University of Calgary, and University of Pittsburgh. (I) A new collaborative network has been created with Stephen Sebestyen who is a research hydrologist at the USDA Forest Service Northern Research Station. (J) Two new graduate students, Kitty Resner and Amy Lyttle, were recruited to this project. They will conduct their MS. research on this project starting the fall 2010. (K) The PI used the field data (reported in the outcomes/impacts in the previous report)in teaching his graduate course, "weathering system." PARTICIPANTS: PD. Kyungsoo Yoo. University of Minnesota, Twin Cities. Yoo relocated from the Univ. of Delaware to the Univ. of Minnesota. His new position as an assistant professor at the department of soil, water, and climate at UMN started in the August 2010. Yoo is supervising the progress of entire projects. The coPDs include Anthony Aufdenkampe at the Stroud Water Research Center and Cindy Hale at the University of Minnesota, Duluth. We also recruited a new collaborator,Stephen Sebestyen, a research hydrologist at USDA Forest Service, Northern Research Station. Graduate Student, Cristina Fernandez. has moved to Geological Sciences Department at the Univ. of Delaware as Yoo relocated to UMN. However, two new graduate students, Kit Resner and Amy Lyttle, will join the PI's program and work on this project as their MS. thesis research starting the fall 2010. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: There is no major change in the direction and the contents of the proposed research. However, it should be noted that the PI has relocated to the Univ. of Minnesota. Cristina Fernandez joined the PI's graduate program in the Sept. 2009 but decided to stay in the University of Delaware, departing Yoo's program, as the PI relocates to the Univ. of Minnesota. However, the PI succeeded in recruiting two graduate students starting fall 2010. Furthermore, closer access to the field site will facilitate the progress of the project.

Impacts
Please note that our project was delayed by a year and started in the Sept. 2009 due to a delay in recruiting graduate students. Our previous report covered the outcomes up to the Dec. 2009. Therefore, the outcomes between the Sept. 2009 and Dec. 2009 should be found in the previous report. During the past seven months, we focused on pulverizing soil samples, determining their elemental and mineralogical compositions. For a subset (~20) of the samples, we have determined short lived radio isotope activities and various iron oxide pools. The 210Pb activity data, though limited, suggests that earthworm invasion has resulted in accelerating soil mixing rates significantly. Our preliminary calculation indicates the mixing rate of up to 1cm/yr. Additionally, biweekly sampling of soil water from all lysimeters and piezometers has been conducted. The data are currently being analyzed, and we will soon begin to grasp the large patterns of chemical weathering and carbon-mineral interactions in their responses to earthworm invasion.

Publications

• Below are the publications from the Sept. 2009 to the present. These also appear in the previous report because the previous report covered the time frame from the Sept.2008 to Dec. 2009.
• Cristina Fernandez, K. Yoo, A. Aufdenkampe, C. Hale, Intensified Weathering Control of Carbon Cycle along an Earthworm Invasion Chronosequence: Preliminary Data. 2009, American Geophysical Union, San Francisco, USA.
• Kyungsoo Yoo, Simon Marius Mudd, Chunmei Chen, Anthony Aufdenkampe, Beth Weinman, Junling Ji, Martin Hurst, and Jonatan Klaminder, Invited, How does biological and anthropogenic soil mixing contribute to morphologic evolution of landscapes and terrestrial carbon cycles 2009, American Geophysical Union, San Francisco, USA.
• A. K. Aufdenkampe; K. Yoo; R. E. Aalto; C. Chen; C. Fernandez Is mineral motion the ultimate control on critical zone carbon sequestration. 2009, American Geophysical Union, Session, San Francisco, USA.

Progress 09/01/08 to 08/31/09

Outputs
OUTPUTS: Though our funding started in the Sept.1 of 2008, our effort was delayed by a year due to graduate student recruitment. Cristina Fernandez joined our research team as a graduate student in the Sept. 2009. In Sept 2009, we had the first major field trip in the Chippewa National Forest. This field trip involved Yoo (PI), Aufdenkampe (CoPI), Hale (CoPI), and Fernandez. We further built collaboration with Sebestyen, who is a research hydrologist at USDA Forest Service, Northern Research Station. We achieved the following four goals during the field trip. (1)Earthworm sampling: Using mustard extraction technique, we sampled earthworms at 30 plots along three transects of earthworm invasion chronosequence. Because of the possibility that mustard liquid may not reach deep burrowing species and thus lead to underestimating their density/biomass, we also counted earthworm middens. The species of the collected earthworms were identified and their biomasses were recorded. (2)Soil sampling: Based on the earthworm sampling, we excavated 6 soil pits with varying degrees of earthworm invasion. Detailed soil morphologic description was made at the field. From each soil pit, we sampled two sets of samples by horizons. One set of samples were for the following analyses: elemental composition, C and N concentrations and their stable isotope ratios, mineralogical compositions, and the activities of short-lived isotopes. Another set of samples were collected specifically for 14C analysis. Additionally, we used sliding hammer to collect bulk density soil samples from each soil horizon. Lastly, we collected litter layers. We also used a hammering corer to sample two replicates per each excavated soil pit. (3)Lysimeter and Piezometer Installation: At each excavated soil pit, we installed three zero tension lysimeters below A and E1 horizons and at the depth of 45 cm. Additionally, five piezometers were installed. The lysimeters and piezometers will be allowed to equilibrate with the surrounding environments until the next snow melt when water sampling will begin. (4)Building collaborative network: During our field trip, we had visits from local agencies including Jim Barott (Forest Soil Scientist at Chippewa National Forest), Rebecca D. Knowles, Ph.D. (Plant Ecologist/ Planner Leech Lake Band of Ojibwe), and Randy Kolka (Research Soil Scientist Center for Research on Ecosystem Change USDA Forest Service - Northern Research Station). We will continue to develop this network to enrich the natural history background our project and to make the future outcomes available to the sustainable management of Chippewa National Forest. -As a part of effort to extend the scope of this NRI project, Fernandez applied to NCALM (National Center for Airborne Laser Mapping) seed grant for graduate student. -Our project was featured in the following media (1) Earthworm Invasion, Nov. 25 2008, Delaware News broadcast, University of Delaware, Student Television Studio. (2) Prof. Yoo studies earthworms' role in forest sustainability, Nov. 24 2008, Science Daily (http://www.sciencedaily.com/releases/2008/11/081122083747.htm) PARTICIPANTS: PD. Kyungsoo Yoo. University of Delaware, Yoo led the field trip organization and led soil sampling. CoPD, Anthony Aufdenkampe, Stroud Water Research Center, Aufdenkampe led the 14C clean soil sampling and the installation of CO2 sampling tubes. CoPD, Cindy Hale, University of Minnesota, Duluth, Hale lead earthworm sampling and species identification. Graduate Student, Cristina Fernandez. This project will be Fernandez's MS thesis. We also recruited new collaborator, Stephen Sebestyen, Ph.D., who is a research hydrologist at USDA Forest Service, Northern Research Station. He led the manufacturing and installing lysimeters and piezometers. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Based on our extensive field observations, we learned the followings that will be used to interpret the future geochemical data. 1. Our earthworm survey showed that the anecic L. terrestris have advanced by about 20-30 meter since the last survey in 2000. Endogenic L. rubellus have also advanced since 2000. 2. There is a very tight and positive relationship between the thickness of A horizons and the degree of earthworm invasion. 3. There is a very tight and negative relationship between the thickness of E horizon and the degree of earthworm invasion. 4. The combined thickness of A and E horizons are relatively uniform across the entire length of the earthworm invasion chronosequence. 5. There is a strong textural contrast within every soil that is consistent through the entire transect. Their texture suggests that the E horizons and the part of Bt horizons are aeolian blankets overlying the lower Bt horizons derived from the underlying carbonate rich glacial till materials. 6. The thickness of the clay rich Bt horizon varies with local topography. The observation 1 shows that our earthworm invasion chronosequence is currently active. The observations 2-4 show that our hypothesis about earthworms' positive impacts on carbon-mineral complexation is likely to be true. Observation 4 and 5 show that we can consistently use the textural and geochemical contrast within soil profiles to understand the role of soil mixing on soil chemical weathering. The observation 5 brings another complicating but interesting factor of topography into this research project. In addition to achieving the original goal to quantify the impact of earthworm invasion on chemical weathering and carbon-mineral complexation rates, we expect that the future laboratory data, when combined with the field observations, will elucidate (1) the geochemical soil evolution in the context of glacial and aeolian activities and (2) the combined effects of topography and earthworm invasion on soil nutrient dynamics in the Chippewa National Forest. We are currently preparing the samples for biogeochemical analyses and radio activity analysis. However, we generated preliminary data on elemental chemistry, specific surface area of minerals, and 210Pb activities of two soil profiles from pre-invasion and heavily invaded locations. The preliminary results show that these measures (and our methods) are consistent with our hypotheses and are highly sensitive to earthworm-driven soil mixing. For example, the greater fraction of Fe and Al were bound to organic matter in the earthworm invaded sites, which strongly suggests that earthworms enhance the complexation between metals and organic matter. Likewise, we also found that the crystalline forms of iron and aluminum oxides significantly increase in their abundances with earthworm invasion. Given the high specific surface area of pedogenic iron and aluminum oxides, the chemical weathering altered by earthworm invasion may have significant implications on the complexation of organic matter on mineral surface. Aufdenkampe (coPD) presented some of these preliminary results in the 2009 NRI PD meeting.

Publications

• Cristina Fernandez, K. Yoo, A. Aufdenkampe, C. Hale, Intensified Weathering Control of Carbon Cycle along an Earthworm Invasion Chronosequence: Preliminary Data. 2009, American Geophysical Union, San Francisco, USA.
• Kyungsoo Yoo, Simon Marius Mudd, Chunmei Chen, Anthony Aufdenkampe, Beth Weinman, Junling Ji, Martin Hurst, and Jonatan Klaminder, Invited, How does biological and anthropogenic soil mixing contribute to morphologic evolution of landscapes and terrestrial carbon cycles 2009, American Geophysical Union, Session: Quantifying Hillslope Processes and Rates of Landscape Evolution (U07), San Francisco, USA.
• A. K. Aufdenkampe; K. Yoo; R. E. Aalto; C. Chen; C. Fernandez Is mineral motion the ultimate control on critical zone carbon sequestration. 2009, American Geophysical Union, Session, San Francisco, USA.