Eurasian journal of forest research;Vol.15-1


Functional Consequences of Differences in Canopy Phenology for the Carbon Budgets of Two Cool-Temperate Forest Types : Simulations Using the NCAR/LSM Model and Validation Using Tower Flux and Biometric Data

Saitoh, Taku M.;Nagai, Shin;Yoshino, Jun;Muraoka, Hiroyuki;Saigusa, Nobuko;Tamagawa, Ichiro

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KEYWORDS : carbon budget;deciduous broad-leaved forest;evergreen coniferous forest;modeling


We quantified the sensitivity of estimated carbon budgets in Japanese evergreen coniferous and deciduous broad-leaved forests using NCAR/LSM simulations under two climatic conditions: the relatively warm end of the cool-temperate zone (i.e., 800 m a.s.l., annual average temperature of 9.4℃, annual average precipitation of 1700 mm), and the relatively cold end of this zone (i.e., 1420 m a.s.l., 7.2℃, and 2400 mm). To improve the model's performance for both forests, we modified parameters such as biomass and plant area index (PAI) based on measured values and calibrated the model using field-measured tower flux and biometric data at two AsiaFlux sites near Takayama City, Japan. The seasonal patterns and annual cumulative values of gross primary production (GPP), ecosystem respiration (RE), and net ecosystem production (NEP) predicted by the model agreed well with field measurements at the two sites. Our sensitivity analysis of the impact of growing period length on the carbon budget in the deciduous broad-leaved forest showed that GPP and NEP increased by 12.7% and 48.0%, respectively, when we considered the temperature dependency of the growing period length. In simulations under both climatic conditions, NEP peaked between April and June in the evergreen coniferous forest, and between July and September in the deciduous broad-leaved forest. The different seasonal patterns of NEP between the two forest types were determined primarily by differences in GPP that resulted from differences in PAI from April to June. The annual values of GPP, RE, and light-use efficiency were clearly greater in the evergreen coniferous forest than in the deciduous broad-leaved forest. Our simulation results suggest that the evergreen coniferous forest has higher metabolic activity than the deciduous broad-leaved forest in this region due to its larger biomass.