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[B-4.2 Modeling of the Carbon Cycle in Forest Ecosystems through Field Measurements]

[Contact Person]

Susumu Yamamoto
Chief Senior Researcher
National Institute for Resources and Environment, AIST, METI
Onogawa 16-1, Tsukuha, Ibaraki, 305-8569, Japan
Tel:+81-298-61-8350 Fax:+81-298-61-8358
E-mail: yamamoto.emtech@aist.go.jp

[Total Budget for FY1999-FY2000]

47,590,000 Yen (FY2000;  23,779,000 Yen)

[Abstract]

　Larch forests broadly distributed eastern Eurasian Continent is expected to fix elevated atmospheric CO₂.From this view, the measurements of fluxes of CO₂ have been carried out at Tomakomai Flux Research Site(a larch forest)in Hokkaido of Japan.Simultaneously,daily and seasonal changes in photosynthetic capacity of Japanese larch trees and soil respiration were measured at the same site.Also,measurement results in a cool-temperate forest at Takayma Site in Honshu of Japan were collected.These data were analyzed synthetically and carbon budgets in two sites were investigated.
 (1) Fluxes of CO₂, water vapor, and sensible heat have been measured by the eddy covariance method at Tomakomai Site since July 2000. Two ctosedpafli type flux measurement systems have heights of a meteorological tower with 40 m high.During the period from July 2000 to June 2001,CO₂ flux and evapotranspiration over the forest showed clear seasonal changes sccording to change in the leaf area of larch trees.
 (2) Seasonal change in photosynthetic capacity of short- and long-shoot needles of Japanese larch trees were measured with an open system of infrared gas analyzer from April 1999 in Tomakomai Site in order to evaluate the CO₂ flux. Light compensation point of both short- and long-shoot needles increased with increasing age of needles. Seasonal change in chlorophyll content of needles was coincided with the net photosynthetic rate. The relationships among intercellular CO₂ concentration, the vapor pressure deficit, and net photosynthetic rate were investigated.
 (3) Open-top-chamber techniques to measure the CO₂ efflux from soil were examined in a simulator of temperature, humidity and blowing conditions. And, daily and seasonal changes of soil respiration in two Research Sites were measured using the open-flow infra-red gas analyzer method
 (4) Net primary production(NPP) was studied in a cool-temperate deciduous forest at Takayama Site. The mean litter production of foliage and branches were 3.30 and 1.09 ton ha^-1 yr^-1. NPP was calculated as the sum of aboveground growth, coarse roots growth and litter production. NPP in the stand for the mean value of the past 10 years (1989-1998) were 6.65 ton ha^-1 yr^-1 and 5.99 by the SA-method and the CS-method, respectively. The annual soil CO₂ efflux of 1994,1995 and 1996 were 602.7, 570.9 and 457.7(gC m^-2 y^-1), respectively.

[Key Words]

Carbon Cycle, Forest Ecosystems, CO₂ Flux, Photosynthesis, Soil Respiration, Net Primary Production(NPP),Open-flow method