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应用稳定碳同位素技术,对马占相思人工林冠层受光和遮荫叶片的碳同化率(Anet)和叶面积指数(L)进行加权,将叶片水平的13C甄别率(Δi)扩展至冠层光合甄别率(Δcanopy),测定光合固定和呼吸释放的碳同位素通量及其净交换通量.结果表明:Δcanopy的日变化明显,日出前和中午出现较低值(18.47‰和19.87‰),而日落前达到最大(21.21‰);秋季末期(11月)至翌年夏季,Δcanopy逐步升高,年平均为(20.37±0.29)‰.不同季节自养呼吸(日间叶片呼吸除外)和异养呼吸释放CO2的碳同位素比率(δ13C)平均值分别为(-28.70±0.75)‰和(-26.75±1.3)‰,春季林冠夜间呼吸CO2的1δ3C最低(-30.14‰),秋季末期最高(-28.01‰).马占相思林与大气的CO2碳同位素通量在春季和夏季中午时峰值分别为178.5和217μmol.m-2.s-1.‰,日均值分别为638.4和873.2μmol.m-2.s-1.‰.冠层叶片吸收CO2的碳同位素通量较呼吸释出CO2的碳同位素通量高1.6~2.5倍,表明马占相思林日间吸收大量CO2,降低空气CO2浓度,具有改善环境的良好生态服务功能.
The carbon isotope ratio (Anet) and leaf area index (L) of canopy cover were measured by using stable carbon isotope technique, and the 13C screening rate (Δi) at leaf level was extended to that of canopy photosynthesis (Δcanopy) was used to determine the carbon isotope fluxes and net exchange fluxes of photosynthetic fixation and respiratory release.The results showed that the diurnal variation of Δcanopy was obvious, with low values (18.47 ‰ and 19.87 ‰) before and at sunrise, (21.21 ‰) before sunset, and Δcanopy increased gradually with an annual average of (20.37 ± 0.29) ‰ at the end of autumn (November) to the following summer, with autotrophic respiration (excluding day-leaf respiration) and heterotrophic The average carbon isotope ratio (δ13C) of respiratory CO2 was -28.70 ± 0.75 ‰ and -26.75 ± 1.3 ‰, respectively, and the lowest δ13C of night-time CO2 respiration was -30.14 ‰ in spring, the highest was -28.01 ‰.) The carbon and carbon isotope fluxes of Acacia mangium and the atmosphere at spring and summer noon were 178.5 and 217μmol.m-2.s-1. ‰, respectively, and the daily average values were 638.4 and 873.2μmol.m-2 .s-1. ‰. The flux of carbon isotope of CO2 absorbed by canopy leaves is 1.6 ~ 2.5 times, indicating that Acacia mangium absorbs large amounts of CO2 during the day and reduces the concentration of air CO2, which has the good ecological service function of improving the environment.