11种温带树种粗木质残体呼吸的时间动态

粗木质残体(CWD)呼吸释放出的CO2(RCWD)与温度的关系是森林生态系统RCWD年通量估测的基础,是随树种和时间而变化的,但这种关系的时间动态目前尚不清楚。采用红外气体分析法测定自然条件下东北东部山区典型天然次生林中11个主要树种RCWD的时间动态,尤其注重于其日变化格局及其对温度的响应。测定树种包括:白桦、山杨、紫椴、胡桃楸、蒙古栎、色木槭、春榆、红松、黄檗、兴安落叶松和水曲柳。结果表明:在测定的生长季期间,11个树种RCWD的日动态多表现为受10cm深的CWD温度(TCWD)驱动的单峰曲线日变化格局,RCWD最高值出现在13:0015:00时,明显滞后于气温(TA)的日变化。然而,在7月和8月份RCWD对温度的响应不明显,呈现出无峰或多峰的日变化格局。各树种均表现为白昼RCWD平均值高于黑夜。RCWD与TCWD、TA有显著的相关关系(P0.05),但与测定前两个小时的TA相关更紧密,说明RCWD对TA响应的滞后性。RCWD温度系数(Q10)平均为2.61,但随树种和季节而变化。Q10值波动在1.74(白桦)和4.20(蒙古栎)之间,并有随温度升高而减小的趋势。本研究结果表明粗木质残体分解碳释放的估算应该考虑RCWD温度敏感性随树种和时间的变化特性。

Temporal dynamics of coarse woody debris respiration for 11 temperate tree species

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.