PARENT SESSION
Poster Session 2: Forest Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Evaluation of empirical regression models for predicting interannual variation in soil respiration in a cool-temperate deciduous broad-leaved forest in Japan.

Lee, Mi-Sun^*,1, Koizumi, Hiroshi¹, ¹ Gifu University, Gifu, Japan

ABSTRACT- Soil respiration is an important component of the annual carbon balance of forests, but few studies have evaluated empirical regression models in soil respiration. The objectives of this study were to examine the relationship between soil respiration rates and soil temperature in a cool-temperate deciduous broad-leaved forest soil and to evaluate empirical regression models for predicting interannual variation in soil respiration using soil temperature and soil water content. We have been measuring soil respiration, using open-flow gas-exchange system with an infrared gas analyzer during the snow-free season from 1999 to 2001 at the Takayama Forest in Japan. To determine the annual soil respiration, we compared with a simple exponential regression (flux=ae^bt: Eq. (1)) and two polynomial multiple-regression models (flux=ae^bt×(−c)×(d−)^f: Eq.(2) and flux=ae^bt×(1−(1−(/c))²): Eq. (3)) that included two variables (soil temperature: t and soil water content: ) and that used hourly data for respiration. In generally, daily mean soil respiration rates were positively well correlated with soil temperature, but no significant correlation were often observed between the soil temperature and soil respiration rates on periods of a day based on hourly respiration data. The Eq. (2) has many site-specific parameters than Eq. (3) and derived underestimated significantly. Empirical regression (Eq. (3)) was best explained by interannual variation, because it provided a more unbiased fit to the data compared to Eq. (2). The addition of soil water content function (Eq. (3)) also increased the predictive ability compared to Eq (1), increasing the R² from 0.71 to 0.78.

Key words: annual soil respiration, empirical regression model, soil temperature, soil water content