Effects of Temperature and Element Content on the Seasonal Dynamics of Coarse Woody Debris Respiration of 2 Tree Species in Liuxihe National Forest Park, Guangzhou

Objective To study the effects of temperature and elemental content on annual seasonal dynamic of coarse woody debris (CWD) respiration rate (R_CWD) and provide reference for calculating the carbon flux of CWD respiration and the establishment of carbon pool model.

Method The R_CWD of Pinus massoniana and Lithocarpus glaber were measured using an infrared gas exchange analyzer (Li-Cor8100) and the CWD initial element content. The effect of temperature and element content on R_CWD were discussed.

Result The dynamics of R_CWD were in accordance with the trend of seasonal temperature, which showed a distinct single peak curve pattern. Within the temperature range of 14.5-28.5℃ measured, the R_CWD was significant positively correlated with temperature (p < 0.01). The temperature can predict 64.0%-75.6% of P. massoniana R_CWD, and 69.3%-86.2% of L. glaber R_CWD. The Q₁₀ of P. massoniana (3.05) was significantly lower than that of L. glaber (5.05). The R_CWD of P. massoniana was less than that of L. glaber, meanwhile the initial C content of P. massoniana was significantly higher than that of the L. glaber, and the initial N and P content was significantly lower than that of the L. glaber. R_CWD was negatively correlated with initial C content, C/N and C/P, and the correlation coefficients R² were 0.383, 0.590 and 0.546 respectively. R_CWD was positively correlated with the initial N content, the correlation coefficient R² was 0.416. But there was no significant correlation among R_CWD, P content and N/P. These indicated that initial element content can explain the 38.3%-59.0% of the R_CWD changes.

Conclusion The study showes that temperature and initial C/N can explain more than half R_CWD changes in what place. Temperature and initial element content significantly affect the whole process of CWD respiration or decomposition.