Ecohydrology Research Institute (ERI)

1. History and Summary

Ecohydrology is an interdisciplinary field studying the interactions between water and ecosystems. Areas of research in ecohydrology include transpiration and plant water use, adaption of organisms to their water environment, influence of vegetation on stream flow and function and feedbacks between ecological processes and the hydrological cycle. The Research Forests of the Ecohydrology Research Institute (ERI) were established in 1922 under the name of University Forest in Aichi on degraded hill areas in Aichi Prefecture. Their purpose was experimental research and training in forest hydrology and erosion control engineering for the University of Tokyo. As a result of a program of continuous erosion control work since ERI's foundation, mainly hillslope planting, almost all of the 1,294ha of hills are now covered with vegetation.

2. Location

The ERI consists of an administration office with a research laboratory located in Goizuka-cho, Seto city, 20 km northeast of Nagoya, and three research forests. The Akazu Research Forest (AKRF, 745ha) is located in the eastern part of Seto city, spreading over the eastern edge of the Owari district. The northern part of AKRF is in the foothills of Mt. Mikuni along the border with Gifu prefecture and the southern part is Mt. Sanage. The Inuyama Research Forest (IRF, 442ha) is located in the eastern part of Inuyama city, 20 km north of Nagoya. The Ananomiya Research Forest (ANRF, 77ha) is located to the north of Seto city.

3. Land Condition

The Akazu Research Forest and most parts of ANRF lie on Mesozoic deeply weathered granite. The average inclination is 25 degrees in AKRF (altitude 244-692m), 19 degrees in ANRF (130-272m). The Inuyama Research Forest is situated mainly on Neogene strata, and Palaeozoic sandstone is partly found in its upper area. According to the data from Shirasaka in AKRF which has been gathered for 30 years (1985-2014), the average monthly temperature in January, the coldest month, is 1.4ºC and in August, the hottest month, it is 24.5ºC. The annual average temperature is 12.8ºC. Annual average precipitation is 1860mm, so the climate is warm and humid.

4. Forest Condition

At the time of its establishment, almost all of the research forests were degraded hill regions. As a result of restoration work over many years, these regions have turned into secondary or artificial forests. Many secondary forests are composed mainly of Quercus serrata and Pinus densiflora or deciduous and evergreen broadleaved trees in mixture. In addition, Cryptomeria japonica, Chamaecyparis obtusa and various kinds of pine are planted as artificial forest.

5. Education

As an institute for both natural- and social- science educations dealing with the interactions between forest, water and humans, ERI promotes educational programs on these topics for both undergraduate and graduate students at the Faculty of Agriculture and Graduate School of Agricultural and Life Sciences, the University of Tokyo. Research guidance for bachelor, master, and PhD theses is also provided. Not only are the students mentioned above catered for, but also others at the University of Tokyo are provided with various educational programs, such as Integrated Courses and Topical Courses for undergraduate students of the Junior Division, College of Arts and Sciences, the University of Tokyo. ERI's educational programs are also readily available for students of other universities.


Research is based mainly on watershed-scale field experiments, the effects of forest ecosystems on water budgets and intra-system cycling of water, nutrients, carbon dioxide, sediment and other materials. On the basis of such investigations, a knowledge base has been built that facilitates scientific understandings of 1) the function of headwater forest ecosystems in regulating water resources for humans downstream, and 2) the trade-off relationship between the functions of the forest as water and sediment controllers and its other multiple functions such as timber production, sequestration of atmospheric carbon dioxide, conservation of biodiversity and recreation space. Techniques for evaluating the function of present-day forest ecosystems as water and sediment controls and for strengthening these functions is also under development. In addition to this research undertaken from a natural science viewpoint, work is also carried out which analyzes how local people have recognized the relationship between the forest and water/sediment in the past, how they have utilized various products from the forest, and how they have overused the forest. Furthermore, ERI is concerned with the future desirable relationship between forest and people from historical, social, cultural, economical and legal perspectives.

6.1. Main topics at ARF

The Akazu Research Forest is the main research forest where much research related to ecohydrology and relevant research fields is conducted. The following topics are of particular importance. 1) For more than 90 years, the rainfall-runoff processes at two different watersheds of Shirasaka and Ananomiya have been investigated. By continuing the long-term hydrological measurement, the effects of ongoing climate change around AKRF and sporadically occurring forest disturbance e.g. forest decline due to disease, on water yield from the three forested watersheds can be analyzed. 2) The paired watershed method is applied to a small watershed in Shirasaka Experimental Watershed in order to evaluate directly the effect of anthropogenic manipulation on runoff and evaporation processes in the treated watershed. 3) To understand the long-term dynamics and succession of a secondary broadleaved forest and accompanying avifauna, long-term ecological research (LTER) in a permanent plot in the AKRF is being conducted.

6.2. Main topics at IRF

Surface geology in IRF differs from that in AKRF (see Section 3) and its forest succession from denuded hills is delayed as compared with AKRF. Considering these differences from AKRF, in IRF, the following research topics are being promoted. 1) With the purpose of understanding the effect of surface geology and forest type on water yield from forested watersheds, simultaneous measurements of stream flow at a number of catchments, each with a different geological condition and forest type is being undertaken. 2) In order to examine the effect of a heavy thinning of a dense Cypress forest on water and sediment yields, a watershed-scale manipulation experiment is underway in IRF. 3) As in AKRF, it is planned to launch a LTER project.

7. Contribution to society

Interest by the general public in nature and the forest environmental service has become greater and greater. As a result the number of people who visit the Research Forests of ERI is increasing. The ERI organizes symposiums and workshops and regularly publishes a series of booklets and leaflets to introduce natural and social scientific research findings to the public.