Characteristics on Soil Respiration of Eucalyptus Plantation with Four Years Old in Beihai of Guangxi, Southern China

This experiment was conducted on the 4 years old Eucalyptus plantation in Beihai of Guangxi, southern China. From January to December 2013, in the spring, summer, autumn and winter, seasonal variation and diurnal variation of the soil respiration and its environmental factors had been observed, respectively. The results showed that: (1) Soil respirations has obvious seasonal characteristics, the soil respiration rate in each seasons showed that: summer> spring > autumn > winter. The heterotrophic respiration rate was higher than the autotrophic respiration rate. The contribution of autotrophic respiration rate in winter was higher than that in other three seasons. (2) Soil respiration has obvious diurnal characteristic, it could be expressed as a single-peak curve. But the maximum value of soil respiration appeared in different times in different seasons. (3) There existed positive correlation index exponential relationships between the soil temperature and the soil respiration rate and its components. Soil temperature changes could explain soil respiration, autotrophic respiration and heterotrophic respiration by 90.2%, 27.5% and 92.8%. Temperature sensitivity showed following order: the heterotrophic respiration rate> the soil respiration rate> the autotrophic respiration rate, in terms of affected by temperature, the heterotrophic respiration was higher than the autotrophic respiration. (4) There were notable positive correlations between soil moisture content and soil respiration rate. Obviously, soil moisture content could promote soil respiration in a certain range.