Abstract:

In the spring, summer, autumn and winter, for the low-quality forest stands of Lesser Khingan Range after selective cutting, the soil CO₂ flux of the low-quality forest stands was observed by the LI-8100 CO₂ flux automatic monitoring system. The influence of cutting intensity on the soil CO₂ flux, soil temperature and moisture was analyzed using methods of statistical analysis. The results showed that the soil CO₂ flux in the selective-cutting zone was higher than that in the check zone, and with the increase of cutting intensity, the soil CO₂ flux had the trend of decrease in the cutting intensity at 22%-47%，then stabilized. In the spring, summer, autumn and winter, the maximum value of soil CO₂ flux appeared in the conditions of the low and moderate cutting intensity forest stands. With the increase in harvesting intensity soil temperature increased, soil moisture reduced.The index model was suitable to the relationships between soil CO₂ flux and soil temperature which was 10 cm from the surface of the earth, and the quadratic model was suitable to the relationships between soil CO₂ flux and soil moisture. According to the standardized regression equation, soil temperature and moisture were the main reasons which effect the soil CO₂ flux, furthermore, the influence of soil moisture was bigger than soil temperature. Cutting intensity and soil CO₂ flux had a negative correlation, the relationship between the two was suit able to the hyperbola.

Key words: low-quality forest stands, cutting intensity, soil CO₂ flux, soil temperature, soil moisture