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Ota, Masakazu; Nagai, Haruyasu; Koarashi, Jun
Journal of Geophysical Research; Biogeosciences, 118(4), p.1646 - 1659, 2013/12
Times Cited Count：40 Percentile：75.68(Environmental Sciences)We investigated the role of root litter input and dissolved organic carbon (DOC) transport in controlling subsurface SOC dynamics by a soil C model. The model involves C turnover by decomposition, interaction between SOC and DOC, and DOC transport along water flows, for three C pools (characterized by turnover times of years, decades and millennia). Model simulations with a range of rooting profiles demonstrated a large proportion (36-78%) of SOC is apportioned to the subsurface (below the first 30 cm) soils and a significant part (39-73%) of the subsurface SOC turns over decadally. DOC transport appeared to be dominant for distributing the C to the deeper horizons. Our results suggest soil C studies focusing on the surface alone significantly underestimate the stock of decadally cycling C and underpredict the responses of soil C to global changes.
Koarashi, Jun; Hockaday, W.*; Masiello, C.*; Trumbore, S.*
Journal of Geophysical Research; Biogeosciences, 117, p.G03033_1 - G03033_13, 2012/09
Times Cited Count：47 Percentile：78.15(Environmental Sciences)Subsurface horizons contain more than half of the global soil carbon (C), yet the dynamics of this C remains poorly understood. We estimated the amount of decadally-cycling subsurface C from the incorporation of "bomb' radiocarbon (
C) using samples taken over 50 years from grassland and forest soils in the Sierra Nevada Mountains, California. The C content of all organic matter fractions increased from the pre- to post-bomb samples, indicating about half of the subsoil C consists of C fixed since 1963. The C content of mineral-associated C increased rapidly from 1992-2009, indicating a significant time lag (
20 years) for the arrival of "bomb" C to this fraction. Our results demonstrate that a lagged response of the large subsurface C stores to changes in environmental conditions is possible.
Lee, C.*; Park, K. G.*; Matsuoka, Toshiyuki; Matsuoka, Toshifumi*
Geosciences Journal, 14(4), p.393 - 401, 2010/12
Times Cited Count：1 Percentile：5.56(Geosciences, Multidisciplinary)Image Point (IP) transform integrates along a hyperbolic path and converts data to a point in the IP domain so that the reflection events are accumulated to the image point for given sources in the IP domain. In addition, the image point by definition is uniquely determined and the midpoints between sources and the image points always lie on the reflector surface. Exploiting these two facts, the image point transform technique for VSP to reverse VSP data is expanded to suggest a new method called the midpoint imaging method for imaging reflectors such as fractures. Applying the transform with synthetic data for 2-D models with single reflector and two reflectors, we confirms and demonstrates that the reflection events are clearly identifiable. The midpoint imaging method can successfully image the reflector surfaces and the dip information even with only two shot records in a simple case.
Cs found in the surface soils of Nagasaki, JapanKokubu, Yoko; Yasuda, Kenichiro; Magara, Masaaki; Miyamoto, Yutaka; Sakurai, Satoshi; Usuda, Shigekazu; Yamazaki, Hideo*; Mitamura, Muneki*; Yoshikawa, Shusaku*
Journal of Geosciences, Osaka City University, 50, p.7 - 13, 2007/03
no abstracts in English
