Zou Lu-Liu, Sun Gu-Chou, Zhao Ping, Cai Xi-An, Zeng Xiao-Ping, Wang Quan
South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China.
Ying Yong Sheng Tai Xue Bao. 2009 Nov;20(11):2594-602.
By using stable carbon isotope technique, the leaf-level 13C discrimination was integrated to canopy-scale photosynthetic discrimination (Deltacanopy) through weighted the net CO2 assimilation (Anet) of sunlit and shaded leaves and the stand leaf area index (L) in an A. mangium plantation, and the carbon isotope fluxes from photosynthesis and respiration as well as their net exchange flux were obtained. There was an obvious diurnal variation in Deltacanopy, being lower at dawn and at noon time (18.47 per thousand and 19.87 per thousand, respectively) and the highest (21.21 per thousand) at dusk. From the end of November to next May, the Deltacanopy had an increasing trend, with an annual average of (20.37 +/- 0.29) per thousand. The carbon isotope ratios of CO2 from autotrophic respiration (excluding daytime foliar respiration) and heterotrophic respiration were respectively (- 28.70 +/- 0.75) per thousand and (- 26.75 +/- 1.3) per thousand in average. The delta13 C of nighttime ecosystem-respired CO2 in May was the lowest (-30.14 per thousand), while that in November was the highest (-28.01 per thousand). The carbon isotope flux of CO2 between A. mangium forest and atmosphere showed a midday peak of 178.5 and 217 micromol x m(-2) x s(-1) x per thousand in May and July, with the daily average of 638.4 and 873.2 micromol x m(-2) x s(-1) x per thousand, respectively. The carbon isotope flux of CO2 absorbed by canopy leaves was 1.6-2.5 times higher than that of CO2 emitted from respiration, suggesting that a large sum of CO2 was absorbed by A. mangium, which decreased the atmospheric CO2 concentration and improved the environment.
通过稳定碳同位素技术，在马占相思人工林中，通过对向阳叶和遮荫叶的净二氧化碳同化量（Anet）以及林分叶面积指数（L）进行加权，将叶片水平的13C判别率整合到冠层尺度的光合判别率（Deltacanopy）中，从而获得了光合作用和呼吸作用的碳同位素通量及其净交换通量。Deltacanopy存在明显的日变化，黎明和中午较低（分别为18.47‰和19.87‰），黄昏时最高（21.21‰）。从11月底到次年5月，Deltacanopy呈上升趋势，年平均值为（20.37±0.29）‰。自养呼吸（不包括白天叶片呼吸）和异养呼吸的二氧化碳碳同位素比值平均分别为（-28.70±0.75）‰和（-26.75±1.3）‰。5月夜间生态系统呼吸的二氧化碳的δ13C最低（-30.14‰），而11月最高（-28.01‰）。马占相思林与大气之间的二氧化碳碳同位素通量在5月和7月出现中午峰值，分别为178.5和217 μmol·m-2·s-1·‰，日平均值分别为638.4和873.2 μmol·m-2·s-1·‰。冠层叶片吸收的二氧化碳碳同位素通量比呼吸排放的二氧化碳碳同位素通量高1.6 - 2.5倍，这表明马占相思吸收了大量二氧化碳，降低了大气中二氧化碳浓度，改善了环境。
