Emeritus Professor, Department of Biology
Hiroshi Koizumi
(hkoizumi@waseda.jp)
Hiroshi Koizumi is a plant ecologist who earned his PhD at the Institute of Biology, Waseda University, in1985, and has since conducted most of his research at National Institute of Agriculture and Environments (Tsukuba), Gifu University (Gifu) and Waseda University (Tokyo). His early work focused on the relationships between the life history of forest floor plants and light environments (sunflecks), and over time his research interests have evolved, as outlined below.
Major research themes
* Sunfleck: Light environment and the life history of understory herbs associated with sunfleks in a deciduous forest* Soil respiration: The development and examination of methods for measuring soil respiration
* Carbon dynamics: Carbon budgets and CO2 evolution of various agricultural and terrestrial ecosystems
* SATECO: Satellite Ecology (SATECO)-linking ecology, remote sensing and micro- meteorology, from plot to regional scale, for the study of ecosystem structure and function
Major findings
All of the following findings are original contributions of Koizumi and colleague.
*Sunflecks: The hourly total sunfleck duration varied seasonally; that is, 30-40 min in spring and autumn and 15-20 min in summer. The emergence frequency of sunflecks was 1.3-4.8 per h with two peaks, one in the morning and one in the afternoon. Using the light photosynthetic curves of forest floor plants (Koizumi 1985), the contribution of sunflecks to the dry matter production of the understory species was evaluated. The sunflecks contributed 7-10 % of the carbon gain in Syneilesis palmate, but only 2-3 % of that in Pyrola japonica (1993).
*Soil respiration: Soil respiration refers to the release of CO2 from the soil into the atmosphere, driven by root metabolism and microbial activity. We famously established foundational methodologies for accurately measuring soil respiration rate and understanding how different global ecosystems respond to temperature and moisture. The seminal our study, "Examination of four methods for measuring soil respiration (1997)," is one of the most cited works in this subfield. Moreover, we introduced a new multiple- microchambers method (2018) for measuring soil respiration without disturbing the soil or vegetation.
*Carbon dynamics: Research on carbon dynamics by Koizumi and colleagues focuses on the carbon budgets and CO2 evolution of various agricultural and terrestrial ecosystems.
1. Upland cropping system carbon budgets (1994, 1996)
- Soil respiration and loss: Research on double-cropping agro-ecosystems (e.g. upland rice, barley, peanut, and wheat) shows that soil carbon is consumed rapidly (400-600 g Cm-2 yr-1) through root and microbial respiration.
- Carbon source: Without heavy residue additions, these upland agro-ecosystems often act as net sources of CO2 to the atmosphere rather than carbon sinks.
2. Land use change and soil emissions (2001)
- Paddy vs. upland conversion: Koizumi's studies emphasize the vulnerability of soil carbon pools during land use transitions. Converting traditional paddy rice fields to upland crop cultivation has been shown to cause significant losses of soil carbon due to changes in soil moisture, temperature, and microbial.
*SATECO: Satellite Ecology (often referred to as SATECO) is a highly specialized, interdisciplinary field that bridges ecology, micrometeorology, and remote sensing (2008). It aims to measure and model ecosystem structures, functions, and plant ecophysiological processes (like gross primary production) across varying scales, from localized plots to entire regions.
Takashi Ohyama
(ohyama@waseda.jp)
Takashi Ohyama is a molecular biologist who earned his PhD at the Institute of Molecular Biology, Nagoya University, in 1986, spent nine years at corporate research institutes, and has since conducted most of his research at Konan University (Kobe) and Waseda University (Tokyo). He has sought to establish new paradigms in basic biology by elucidating previously unknown principles underlying biological systems, and he continues to pursue his research within this framework. His early work focused on the role of DNA conformation in gene regulation. Over time, his research interests have evolved, as outlined below.
Major research themes
*Self-organization/self-assembly of genetic materials*Genetic information encoded in the physical properties of DNA
*Evolutional pathway of carnivorous plants
Major findings
All of the following findings are original contributions of his group
1. Under physiological magnesium concentrations, both DNA and nucleosomes can discriminate self from non-self and identical entities selectively assemble (2007, 2013). Nucleosome self-assembly occurs even within chromatin fibers and the identity of the DNA nucleotide sequence plays a decisive role in this process.
2. Genetic information is also encoded in the physical properties of DNA.
For example:
- Information about the positions of gene promoters and the basis of their functions reside not in the nucleotide sequence, but in the physical properties of DNA (2004, 2005).
- In yeast, the three-dimensional organization of the genome in the nucleus is governed primarily by the physical properties of DNA and nuclear size (2013).
3. Digestive enzyme genes in carnivorous plants are derived from genes originally functioning in environmental response pathways (since 2005).