Updated: 2012-09-05

Kahoku experimental watershed (KHW)

Sonic anemometer-thermometer installed on meteorological observation tower

Overview of this site

Kahoku experimental watershed is covered by an evergreen coniferous forest located in northern part of Kumamoto Prefecture. Its dominant species are over 50 years old of Sugi cedar and Hinoki cypress which are planted after the WW-II. The climate of this area is warm-temperate and summer is very hot and humid that daytime temperature can reach over 35°C while in winter, it sometimes drops below 3°C. This area is also a pluvial region that annual precipitation usually excess 2000mm. We are observing the CO2 and energy budget in a typical planted Sugi-Hinoki forest of southwestern Japan.

Position33 deg 8.222 min N (33.137 deg N),
130 deg 42.572 min E (130.7095 deg E)
Slope16° (average value around the tower)
Climate ClassificationTemperate (Cfa, Temperate - Fully humid - Hot summer)
Annual Mean Temperature15.1°C(year 2000-2003)
Annual Mean Precipitation2106mm(year 2001-2003)
Annual Mean Solar Raadiation13.5MJm-2day-1(year 2000-2003)
Monthly mean temperature (year 2000-2003) and
precipitation (year 2001-2003)
Monthly mean solar radiation (year 2000-2003)
VegetationEvergreen needleleaf forest
Areaapprox. 12.7ha
Dominant SpeciesCryptomeria japonica (Sugi cedar), Chamaecyparis obtusa (Hinoki cypress): plantimal
Castanopsis cuspidata, Fagus japonica (japanese beech): grown in gaps
Canopy Height10-35m
Breast High Diameter50cm (max, Sugi cedar)
Age52-59 years (Sugi cedar), 36-59 years (Hinoki cypress)
Leaf Area Index3.6-5.2 (estimated by LAI-2000)
Community StructureOverstory, partly understory (evergreen and deciduous broadleaf), and forest floor (fern)
Soil TypeModerately moist brown forest soil, BD
Artificial Disturbanceapprox. 500m from golf course
Observation Period
Period1 November 1999 to present
Tower Height50 m
Access to Tower TopPossible
Electric Power SupplyCommercial power supply AC100V 20A(30A max.)
Communication EquipmentNot available
AccommodationNot available


 Name and ModelLevel
Downward Short-wave RadiationKipp&Zonen, CNR 450.5 m
Upward Short-wave RadiationKipp&Zonen, CNR 450.5 m
Downward Long-wave RadiationKipp&Zonen, CNR 450.5 m
Upward Long-wave RadiationKipp&Zonen, CNR 450.5 m
Downward PPFDLI-COR, LI190-SA50.5 m
Upward PPFDLI-COR, LI190-SA50.5 m
Net Radiation above canopyKipp&Zonen, CNR 450.5 m
Air temperaturePlatinum resistance thermometer
Vaisala HMP115A
46.9, 31.6, 16.3, 1.9 m
HumidityCapacitive hygrometer
Vaisala HMP115A
46.9, 31.6, 16.3, 1.9 m
Air temperature (dry-bulb)EKO, MH-020L41.5, 22.0 m
Humidity (dry-bulb)EKO, MH-020L41.5, 22.0 m
Wind SpeedKAIJO DAT-600-3T51.0 m
Wind DirectionKAIJO DAT-600-3T51.0 m
Barometric PressureVaisala PTB-21051.0 m
Soil TemperaturePlatinum resistance thermometer (Pt100)0.02, 0.05, 0.10, 0.20, 0.50 m deep
Soil Heat FluxREBS HFT-3.10.05 m deep
Soil Water Content (moisture content)Campbell, CS616-L0.05, 0.10 m deep
PrecipitationIKEDA RT-5approx. 1.2m, Open space
Data Logger
Sampling Period30sec
Averaging Period10min
RecorderCampbell CR10X and PC
MediaMemory and HDD

Turbulence Fluctuation Method (Eddy Covariance Method)

Systemclosed-path and open-path system
Sonic anemometer-thermometerKAIJO DAT-600-3T Sensor span0.2m
Level51.0 m
Height from Canopy Surface16 m
Gas Analyzer
LI-COR LI-7000 Distance between
gas intake and analyzer
approx. 60m
Height of intake51.0 m
Height from Canopy Surfaceapprox. 16 m
Distance between
gas intake and analyzer
0.1 m
Gas Analyzer
LI-COR LI-7500 Distance between
gas intake and analyzer
0.3 m
Data Logger
Sampling MethodContinuous
Averaging Period0 sec
Sampling Frequency10Hz
Filters for AntialiasingAvailable
CutOff Frequency24 Hz
Recording RangeAll data
RecorderTEAC DR-M3b
Flux Calculation
Calculation Period1800s
MethodDetrendingw, u, Ta, CO2, H2O
Coordinate rotationCorrected
Line AveragingNot-corrected
Sensor SeparationCorrected
Humidity Correction of Virtual TemperatureCorrected

Vertical profiling CO2 Concentration in Canopy

InstrumentsLI-COR LI-6262
Sampling10 seconds
Sampling PeriodEvery 120 seconds at a level x 8 levels
Averaging Period10 sec
PurposeTo obtain the vertical profile of CO2 concentration inside and above canopy

Other Observation

MethodPhotosynthesis of cedar leaf, transpiration rate, diurnal variation of stomatal conductance
InstrumentLI-COR LI-6400
Observation FrequencyOnce a month
Vegetation Coverage
Methodoptical method(LI-COR LAI-2000)
Observation FrequencyOnce a month
MethodDiameter, height (at 8 plots)
Observation FrequencyOnce a few years
Stem Temperature
MethodSeveral spots in each direction
Observation FrequencyContinuous
Outlet Flow
MethodSmall drainage basin (3 spots), Float type water-level gauge (IKEDA HDR-115D)
Observation FrequencyContinuous
Method3 spots, trained into large tipping bucket (UIZ-TB200) after collecting
Observation FrequencyContinuous


SHIMIZU Takanori (2007): Practical applicability of high frequency correction theories to CO2 flux measured by a closed-path system. Boundary-Layer Meteorology, 122(2):417-438

SHIMIZU Takanori(2005): Kahoku Experimental Watershed - The Southernmost Observation Site of FFPRI FLUXNET -. Asiaflux Newsletter, 13:9-10.

SHIMIZU Akira, SHIMIZU Takanori, MIYABUCHI Yasuo, OGAWA Yasuhiro(2003): Evapotranspiration and runoff in a forest watershed, western Japan. Hydrological Processes, 17(15):3125-3139.

KUMAGAI Tomo'omi, TATEISHI Makiko, SHIMIZU Tkanori, OTSUKI Kyoichi (2008): Transpiration and canopy conductance at two slope positions in a Japanese cedar forest watershed. Agricultural and Forest Meteorology, 148(10):1444-1455

KUMAGAI Tomo'omi, AOKI Sayaka, SHIMIZU Takanori and OTSUKI Kyoichi (2007): Sap flow estimates of stand transpiration at two different slope positions in a Japanese cedar forest watershed. Tree Physiology, 27(2):161-168

ISHIZUKA Shigehiro, SAKATA Tadashi, SAWATA Satoshi, IKEDA Shigeto, SAKAI Hisao, TAKENAKA Chisato, TAMAI Nobuaki, ONODERA Shin-ichi, SHIMIZU Takanori, KAN-NA Kensaku, TANAKA Nagaharu, TAKAHASHI Masamichi (2009): Methane uptake rates in Japanese forest soils depend on the oxidation ability of topsoil, with a new estimate for global methane uptake in temperate forest. Biogeochemistry, 92(3):281-295

ISHIZUKA Shigehiro, SAKATA Tadashi, SAWATA Satoshi, IKEDA Shigeto, TAKENAKA Chisato, TAMAI Nobuaki, SAKAI Hisao., SHIMIZU Takanori, KAN-NA, Kensaku, ONODERA Shin-ichi, TANAKA Nagaharu, TAKAHASHI Masamichi(2006): High potential for increase in CO2 flux from forest soil surface due to global warming in cooler areas of Japan. Annals Forest Science, 63(5):537-546

KOBAYASHI Masahiro, SHIMIZU Takanori(2007):Soil water repellency in a Japanese cypress plantation restricts increases in soil water storage during rainfall events. Hydrological Processes, 21(17): 2356-2364

SHIMIZU Takanori SUZUKI Masakazu and SHIMIZU Akira (1999): Examination of a Correction Procedure for the Flow Attenuation in Orthogonal Sonic Anemometers. Boundary-Layer Meteorology, 93(2):227-236

Research Fund

- Major Facility Installation for Carbon Dioxide Monitoring, Forestry Agency, MAFF*

- Research Grant, FFPRI

- Research Fund (Evaluation, Adaptation and Mitigation of Global Warming in Agriculture, Forestry and Fisheries: Research and Development), MAFF*

- Global Environment Research Account for National Institutes, MOE***

* MAFF: Ministry of Agriculture, Forestry and Fisheries of Japan
*** MOE: Ministry of the Environment


Kenzo KITAMURA, Takanori SHIMIZU, Hiroaki HAGINO, Koji TAMAI

Cooperative Researchers

Shigehiro ISHIZUKA, Masahiro KOBAYASHI (FFPRI), Tomo'omi KUMAGAI (Kyushu Univ.)

Contact Information

Environmental Conservation Lab.,
Kyushu Research Center,
Forestry and Forest Products Research Institute (FFPRI)
Address: 4-11-16 Kurokami, Kumamoto, Kumamoto, 860-0862 JAPAN
TEL: +81-96-343-3168 (main)