亚热带4种行道树树干表面CO_2释放速率昼夜动态

Diurnal Dynamics of CO_2 Released from Bole Surface of Four Street Tree Species in Subtropical Region of China

采用LI-8100土壤碳通量自动测量系统,与自制的树干呼吸观测气室相连,原位观测亚热带春、秋2个季节4种行道树树干呼吸速率及相关环境因子的昼夜动态.结果表明:在秋季土壤水分较低水平下(VWC平均为11.6%),羊蹄甲、香樟树干呼吸速率昼夜动态呈单峰曲线,和温度变化呈极显著指数函数关系,峰值分别出现在17:00和13:00;芒果和高山榕树干呼吸速率昼夜动态单峰不明显,白天与树干温度变化呈极显著指数函数关系,但芒果白天与夜间的树干呼吸速率差异不显著,而高山榕树干呼吸速率夜间显著高于白天,二者出现"白昼抑制"现象.在春季土壤水分较高水平下(VWC平均为22.1%),羊蹄甲、芒果和高山榕树干呼吸速率昼夜动态呈单峰型曲线,峰值分别出现在11:00、15:00和14:00;而香樟树干呼吸速率单峰不明显,4种树种的树干呼吸速率昼夜动态均与温度变化呈极显著指数函数关系.2个季节中,树干温度与树干呼吸的指数函数关系最好,秋季羊蹄甲、芒果和香樟树干呼吸速率对树干昼夜温度变化的Q10值分别为2.04、2.37和2.18,春季羊蹄甲、芒果、香樟和高山榕树干呼吸速率对树干昼夜温度变化的Q10值分别为2.27、2.58、1.90和1.83.秋季,羊蹄甲、高山榕、芒果和香樟日均树干呼吸速率分别为10.52、6.86、5.14和4.35μmol.m-2.s-1,春季,高山榕、香樟、羊蹄甲和芒果日均树干呼吸速率分别为14.01、10.59、4.27和4.14μmol.m-2.s-1.

Diurnal variation of stem respiration rate was studied in four classical street trees, Bauhinia purpurea （B）, Mangifera indica （ M）, Cinnamomum camphora （ L. ） Presl. （C） and Ficus altissima （F）, in subtropical region of China using an infra-red gas analyzer （IRGA） method and some environmental factors were observed synchronously. LI-8100 Automated Soil CO2 Flux System was the main equipment which connected a custom-built polyvinyl chloride （PVC） chamber. The stem respiration rates of the four tree species were measured in the discretional sections at 1.3 m height every 1 h in autumn and spring. At the low soil volumetric water content （VWC） level in autumn, the tendencies in diurnal stem respiration of B and C showed clear single-peak patterns, in which the peaks appeared at 13：00 and 17： 00, respectively, and there was a significant positive exponential correlation with the temperatures all the day （P 〈0.01 ）. But in M and F, there were a daytime de- pression and showed unconspicuous single-peak patterns. The stem respiration rates of M and F had a significant exponential positive correlation with the temperature at daytime （P 〈 0. 01 ）, but the rates at night were significantly higher than those in the day. And at the high VWC level in spring, the model of stem respiration rate of B, M and F showed clear single-peak patterns, the peaks appeared at 11： 00, 15：00 and 14： 00, respectively. The C had an unconspicuous single-peak pattern. They all had a significant positive exponential correlation with the temperature all the day in spring （P 〈0. 01）. The stem respiration rate was strongly related to temperature inside the stems at 1 cm depth in two seasons. When the stem respiration rates of the three tree species （B, M, C） were regressed against the stem temperature in autumn, there were similar Q10 values which were 2. 04, 2. 11 and 2. 18, respectively. And in spring, the Q10 values of B, M, C and F were 2.27, 2. 58, 1.90 and 1.83, respectively. In autumn, the average respiration rate all the day of B, F, M, C was 10.52, 6.86, 4.76, 4.35 μm·m^-2·s^-1, respectively. And in spring, the average respiration rate all the day ofF, C, B, M was 14.01, 10.59, 4.27 and 4. 14 μmol· m^-2·s^-1, respectively.