Abstract:

This study aims at revealing seasonal changes of soil respiration(R_s) without roots and its relationship with soil temperature and humility at 5 cm depth in a Pinus massoniana plantation in the Tianjiling National Forest Park (113°01′—113°02′ E, 28°06′—28°07′ N) of Changsha, Hunan Province, China. A trenching method, in which the roots existing in a given area were severed at the plot boundary but not removed, was used to determine the contribution of the root respiration to total soil CO₂ efflux. The R_s rates were measured from January 2007 to December 2008 by using infrared gas exchange analyzer of Li-Cor 6400-09. The results showed the rates of soil CO₂ efflux in the trenched and control plots ranged 0.25-2.33 and 0.29-3.19 μmol ·m^-2s^-1 respectively. The mean annual R_s in the trenched and control plots was 1.03 and 1.56 μmol·m^-2s^-1, respectively. The R_s rates in trenched plots were decreased by 12.2%～55.1% when compared with the control plots. Therefore, an annual value of the roots contributed around 28.3% of the total soil respiration. There was a significant exponential relationship between R_s in the trenched plots and the soil temperature. The Q₁₀ value, representing the sensitivity of R_s to soil temperature, was lower in the trenched plots (1.82) than the control plots (2.10), The Q₁₀ value of root respiration was estimated 2.94. There was no significant relationship found between the R_s rates in the trenched plots and the soil humility, however relationship between the root respiration and the soil humidity could be well described by a linear equation: y=0.019w+0.209, R²=0.154，P＝0.023.

Key words: Pinus massoniana plantation, soil respiration, root respiration, contribution