Landcare Research, PO Box 40, Lincoln 7640, New Zealand.
Faculty of Agriculture, Food and Natural Resources, The University of Sydney, Private Bag 4011, Narellan NSW 2567, Australia.
New Phytol. 2011 Jun;190(4):990-1002. doi: 10.1111/j.1469-8137.2010.03635.x. Epub 2011 Feb 7.
The CO₂ respired by darkened, light-adapted, leaves is enriched in ¹³C during the first minutes, and this effect may be related to rapid changes in leaf respiratory biochemistry upon darkening. We hypothesized that this effect would be evident at the ecosystem scale. High temporal resolution measurements of the carbon isotope composition of ecosystem respiration were made over 28 diel periods in an abandoned temperate pasture, and were compared with leaf-level measurements at differing levels of pre-illumination. At the leaf level, CO₂ respired by darkened leaves that had been preadapted to high light was strongly enriched in ¹³C, but such a ¹³C-enrichment rapidly declined over 60-100 min. The ¹³C-enrichment was less pronounced when leaves were preadapted to low light. These leaf-level responses were mirrored at the ecosystem scale; after sunset following clear, sunny days respired CO₂ was first ¹³C enriched, but the ¹³C-enrichment rapidly declined over 60-100 min. Further, this response was less pronounced following cloudy days. We conclude that the dynamics of leaf respiratory isotopic signal caused variations in ecosystem-scale ¹²CO₂/¹³) CO₂ exchange. Such rapid isotope kinetics should be considered when applying ¹³C-based techniques to elucidate ecosystem carbon cycling.
在黑暗、适应光照的叶子中呼吸的 CO₂ 在最初几分钟内会富集 ¹³C，这种效应可能与黑暗条件下叶片呼吸生物化学的快速变化有关。我们假设这种效应在生态系统尺度上是明显的。在一个废弃的温带草原上，我们进行了 28 个昼夜周期的生态系统呼吸碳同位素组成的高时间分辨率测量，并与不同预照光水平下的叶片水平测量进行了比较。在叶片水平上，适应高光的黑暗叶片呼吸的 CO₂ 强烈富集 ¹³C，但这种 ¹³C 富集在 60-100 分钟内迅速下降。当叶片适应低光时，¹³C 富集程度较低。这些叶片水平的响应在生态系统尺度上得到了反映；在晴朗无云的晴天之后，日落时呼吸的 CO₂ 首先 ¹³C 富集，但 ¹³C 富集在 60-100 分钟内迅速下降。此外，阴天时这种反应不那么明显。我们得出结论，叶片呼吸同位素信号的动态变化导致了生态系统尺度上 ¹²CO₂/¹³CO₂ 交换的变化。在应用基于 ¹³C 的技术阐明生态系统碳循环时，应考虑这种快速的同位素动力学。
