Seasonal Dynamics of Energy Return Through Litterfall of A Mixed Forest of Chinese Fir and T. odorum

Based on the measurement of monthly litterfall and their gross caloric values, the seasonal dynamics of energy return through litterfall were determined in a pure and a mixed T. odorum (Tsoongiodendron odorum Chun)forests with Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) in Sanming, Fujian Province. Annual energy return through litterfall was estimated as 12.648×10⁶ J·m^-2 for the mixed forest, being 4.2% higher than that of the pure forest, and a large proportion of the energy return comprised leaf litter. The conversion efficiency of solar radiation energy into litterfall was 0.56% for mixed forest and 0.54% for pure forest, respectively. The monthly energy flux in litterfall of Chinese fir showed a three-apex curve, peaked in March, August and December, respectively, which was similar to that in various fractions of leaf, twig, flower and fruit litter. The consistency in monthly patterns among different litter fractions of Chinese fir was attributed to their solid connections all the while. The monthly energy flux in litterfall of T. odorum culminated in January, May and August, the same was true for its leaf and twig litter. However, energy flux in flower litter only occurred during March to May and that in fruit litter appeared in January and March. The monthly dynamics of energy flux through litterfall of the two forests were both determined by their respective litterfall pattern of Chinese fir. Seasonal energy flux in litterfall for both mixed and pure forests followed the sequence of spring > winter > summer > autumn, but fluctuations in the former were less distinct than those in the latter.