Kenneth Takagi

Current Research:

A δ44Ca based comparison of Ca cycling in tropical and temperate ecosystems

Plot of 44Ca vs. streamflow for a river in New Hampshire. At high flows the Ca isotope ratios become lighter, suggesting increased export of biologically cycled Ca by streamwater.

A motivating question for my research is how the cycling of calcium between vegetation, soil and waters responds to ecosystem disturbance. To address this, our research uses stable isotopes of calcium (44Ca/40Ca) to better understand the internal cycling of calcium within forested watersheds. Plants discriminate slightly against the heavy isotope of calcium during uptake from soil solution, producing fractionations that can be used to trace processes in the calcium cycle. Measurement of natural variations in calcium isotope ratios is analytically challenging primarily because the total range in 44Ca/40Ca is small relative to other stable isotope systems. We are developing procedures in the BU TIMS Facility, based on the established double-spike method, that will allow us to confidently determine these small variations in natural abundance ratios of calcium isotopes. This project is being carried out under the supervision of my advisor Dr. Andrew Kurtz.

Publications and Presentations
2. Kurtz, A., Takagi, K., 2012. Ca isotopic fractionation patterns in forest ecosystems. 2012 AGU Fall Meeting. (Presentation)

2. Takagi, K., A. Kurtz, S. Bailey, 2011. Ca isotopes as a new geochemical tool to investigate response and recovery of a New England watershed to whole-tree harvesting. 2011 AGU Fall Meeting. (Poster)

3. Takagi, K., A. Kurtz, S. Bailey, 2011. Using Ca isotopes to constrain sources of streamwater Ca following clear-cutting of a New England watershed. 2011 Gordon Research Conference: Catchment Science: Interactions of Hydrology, Biology & Geochemistry. (Poster)

Past Research:

Spatial and Temporal Variability in Soil moisture at the Catchment Scale

Time series of soil moisture spatial variability at multiple depths at the Shale Hill Critical Zone observatory, interpolated from point measurements. White area indicate bedrock (ie. no soil present).

Soil moisture plays an important role in the non-linear response of streamflow to precipitation events. Better understanding of soil moisture temporal and spatial variability will improve hydrologic models performance, help resource managers protect sensitive waterways and aid in the design of soil mositure monitoring campaigns.
Utilizing a long-term database of soil moisture measurements made at 100+ locations with the Shale Hills watershed, I investigated the physical factors (topography, soil phyical properties, and hydrologic characteristics of the watershed) that controlled the spatial variability of soil mositure. This project was completed while a MS student in the Crop and Soil Science Dept. at Penn State University, under the supervision of Dr. Henry Lin.

Publications and Presentations
1. Takagi, K., H. Lin, 2008. Influence of storm event characteristics on soil moisture at the Shale Hills catchment. First International Hydropedology Conference. (Poster)

2. Takagi, K., H. Lin, 2009. Factors Controlling the Soil Moisture Spatial-Temporal Variability in the Shale Hills Watershed: A Hydropedologic Perspective. 2009 ASA-CSSA-SSSA International Annual Meeting. (Poster)

3. Takagi, K., H.S. Lin. 2011. Temporal Dynamics of Soil Moisture Spatial Variability in the Shale Hills Critical Zone Observatory. Vadose Zone J. 10:832842. doi:10.2136/vzj2010.0134.

4. Takagi, K., H.S. Lin. 2012. Changing controls of soil moisture spatial organization in the Shale Hills Catchment. Geoderma 173174: 289-302. doi: 10.1016/j.geoderma.2011.11.003.

5. Zhao, Y., J. Tang, C. Graham, Q. Zhu, K. Takagi, H. Lin, 2012. Hydropedology in the Ridge and Valley: Soil Moisture Patterns and Preferential Flow Dynamics in Two Contrasting Landscapes. In: Lin, H. (Ed.), Hydropedology: Synergistic Integration of Soil Science and Hydrology. Academic Press, Elsevier B.V., pp. 381411.