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树干CO_2释放通量(E_s)是森林生态系统碳收支的重要组分,但是目前对E_s的季节动态和树种间差异的调控认识不足。该文采用红外气体分析法于2013年7–10月和2014年3–7月原位测定了东北温带森林中4个针叶树种(红松(Pinus koraiensis)、红皮云杉(Picea koraiensis)、樟子松(Pinus sylvestris var.mongolica)和落叶松(又名兴安落叶松)(Larix gmelinii))的E_s、树干温度(Ts)等因子,旨在比较分析E_s的季节动态和树种间差异及其驱动因子。结果发现:整个测定期间4个树种E_s的时间动态总体上与Ts变化一致,高峰值出现在温度较高和生长迅速的夏季(5月末–7月初),最小值则出现在温度较低的春季(3月末–4月末)或秋季(10月)。Ts分别解释了所有树种生长季(5–9月)和非生长季(其他月份)E_s变异性的42%–91%和56%–89%。进一步分析发现,除了Ts之外,生长季期间4个树种的E_s与日胸围生长量、樟子松和落叶松的E_s与空气相对湿度、樟子松的E_s与边材氮浓度也显著相关。这些结果表明Ts是影响E_s的主导环境因子,但影响程度随树种、生长节律变化而变化。同一树种生长季的E_s显著高于非生长季,而同一季节不同树种之间E_s差异显著。生长季不同树种E_s的温度系数(Q10值)的差异不显著(波动在1.64–2.09之间),但在非生长季却存在显著性差异(波动在1.80–3.14之间);并且红皮云杉、樟子松和落叶松生长季的Q10值均显著低于非生长季,说明不同树种E_s对温度变化响应的差异主要表现在非生长季。上述这些温带针叶树E_s的季节和种间变化受温度等多因子联合驱动,因此采用单一的E_s温度响应方程会增大E_s年通量估测的不确定性。
The stem CO2 flux (E_s) is an important component of forest ecosystem carbon budget, but the current lack of understanding of the seasonal dynamics of E_s and the regulation of inter-species differences. In this paper, four coniferous species (Pinus koraiensis, Picea koraiensis, Picea koraiensis) in temperate forests of Northeast China were determined in situ from July to October in 2013 and March to July in 2014 by using infrared gas analysis method. Pinus sylvestris var. Mongolica and Larix gmelinii) and the trunk temperature (Ts) were used to analyze the seasonal dynamics of E_s and the differences among species Drive factor. The results showed that the temporal dynamics of four species E_s during the whole period of the survey were in general consistent with the change of Ts, the peak appeared in the summer with high temperature and rapid growth (late May-early July), and the lowest appeared in the spring with relatively low temperature (Late March - late April) or autumn (October). Ts explained 42% -91% and 56% -89% of the E_s variability for all species in the growing season (May-September) and in the non-growing season (other months), respectively. Further analysis showed that except for Ts, the E_s and BST, the E_s of Pinus sylvestris var. Mongolica and Larix were significantly correlated with the relative humidity of air and E_s of Pinus sylvestris var. Mongolica and the sapwood nitrogen concentration. These results show that Ts is the dominant environmental factor affecting E_s, but the degree of influence varies with tree species and growth rhythm. The E_s of the same tree growing season was significantly higher than that of the non-growing season, while E_s was significantly different among different tree species in the same season. There was no significant difference (Q10 value) in the temperature coefficient (Q10 value) between different species of growing season, but there was a significant difference (fluctuation between 1.80 and 3.14) in the non-growing season; The Q10 values of fir, Pinus sylvestris var. Mongolica and larch growing season were significantly lower than those of non-growing season, indicating that the difference of E_s response to temperature was mainly in non-growing season. The seasons and interspecific variations of E_s in these temperate coniferous trees are driven by multiple factors such as temperature. Therefore, using a single E_s temperature response equation will increase the uncertainty of E_s annual flux estimation.