Abstract:The relationship between CO2 efflux respired from coarse woody debris (CWD) decomposition (RCWD) and temperature is basis for estimating annual RCWD in forest ecosystems, and changes with tree species and time. However, the temporal dynamics of this relationship is not clear. In this study, we measured the RCWD of 11 major tree species in natural secondary temperate forests in northeastern China using an infrared gas exchange analyzer (L I-6400 IRGA) to examine temporal dynamics in RCWD, focusing on the diurnal change and response of RCWD to temperature. The tree species examined included Betula platyphylla, Populus davidiana, Tilia amurensis, Juglans mandshurica, Quercus mongolica, Acer mono, Ulmus japonica, Pinus koraiensis, Phellodendron amurense, Larix gmelinii, and Fraxinus mandshurica. The results indicated that the diurnal variation of RCWD showed an overall bell-shaped curve during the growing season examined except for July and August, mainly driven by CWD temperature at 10 cm depth (TCWD). The maximum RCWD occurred between 13:00 and 15:00, substantially delaying to the maximum daily air temperature (TA). In July and August, the diurnal changes in RCWD displayed non-peak or multi-peak patterns, less responding to the temperature change. The mean RCWD during the daytime was greater than that during the nighttime for all tree species. The RCWD was positively correlated with TCWD and TA (P<0.05). However, the RCWD was more significantly related with the TA at 2 hours before the measurement, rather than the instant TA, implying a hysteresis response of RCWD to the TA. The temperature coefficient of RCWD (Q10) averaged 2.61, and changed with tree species and seasons. The Q10 values varied from 1.74 for B. platyphylla to 4.20 for Q. mongolica, tending to decrease with TCWD rising. We suggest that accurate estimation of CO2 emission from CWD should take the temporal and inter-specific changes in temperature sensitivity of RCWD into account.