RESPONSES OF SOIL RESPIRATION AND ITS TEMPERATURE SENSITIVITY TO SOIL TEMPERATURE VARIATION AND SIMULATED NITROGEN DEPOSITION IN SUBTROPICAL MIXED FOREST IN SOUTHWEST, CHINA

This paper investigated soil respiration and the variations in its sensitivity to temperature (Q(10)) at different temporal scale. The mechanisms of the response to T variation and different levels of N treatment were also investigated. Results indicated that: (1) diurnal variation of Rs exhibited a unimodal curve trend, with maximum and minimum at around 14:00 and 2:00, respectively, and soil respired much faster during daytime than nighttime; There was a clear monthly variation of Rs, with the three years all showing as similar pattern of a unimodal curve. Yearly variation of Rs was insignificant. (2) There was a significant correlation between Rs and T (p<0.05), and an exponential model was selected for use in this study. (3) Q(10s) had obvious unimodal monthly variation and significant negative correlation with T (p<0.05). T was the main factor driving variation in Q(10s). Differences in Q(10y) during these three years were not significant (p>0.05) and the maximum was in 2012 (1.95). There were significant differences in the comparisons between Q(10y) and the mean value of Q(10s) for each year. (4) Rs at diurnal and monthly scales were repressed after short-term N deposition, and the inhibiting effects were greater as N treatment levels increased. The mean values of Rs for CK and LN treatments showed no significant differences (p>0.05) while that for HN treatment was notably lower than for the CK. Q(10) values for the four N deposition levels were in the following order: CK (1.68)>LN (1.66)>MN (1.61) > HN (1.57).