Does photosynthesis affect grassland soil-respired CO2 and its carbon isotope composition on a diurnal timescale?
Does photosynthesis affect grassland soil-respired CO2 and its carbon isotope composition on a diurnal timescale?
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DOI：
10.1111/j.1469-8137.2008.02755.x
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
Brüggemann N
中科院分区：
文献类型：
--
作者：
Bahn M;Schmitt M;Siegwolf R;Richter A;Brüggemann N
土壤呼吸是陆地生态系统向大气排放碳的最大通量。本文对光合作用影响草地土壤呼吸CO2及其碳同位素组成（δ 13 CSR）日变化的假说进行了检验。在山地草地上进行了遮光和脉冲标记相结合的试验。用可调谐二极管激光吸收光谱仪以高时间分辨率监测δ 13 CSR。在未标记的样地中，δ 13 CSR的日变化不受土壤温度、水分和通量的影响，并且含有一个与同化物供应无关的分量。在标记的样地中，δ 13 CSR反映了植物新同化碳的快速转移和呼吸利用，以及主要呼吸碳源从最近（即至少1 d）到新鲜（即当天产生的光合同化物）的日变化。我们的结论是，在草原上的植物来源的基质用于土壤呼吸过程在白天变化，光合作用提供了一个重要的和直接的C源。这些研究结果表明，在植物-土壤系统的紧密耦合和植物代谢的重要性，土壤CO2通量。
Soil respiration is the largest flux of carbon (C) from terrestrial ecosystems to the atmosphere. Here, we tested the hypothesis that photosynthesis affects the diurnal pattern of grassland soil-respired CO2 and its C isotope composition (δ13CSR). A combined shading and pulse-labelling experiment was carried out in a mountain grassland. δ13CSR was monitored at a high time resolution with a tunable diode laser absorption spectrometer. In unlabelled plots a diurnal pattern of δ13CSR was observed, which was not explained by soil temperature, moisture or flux rates and contained a component that was also independent of assimilate supply. In labelled plots δ13CSR reflected a rapid transfer and respiratory use of freshly plant-assimilated C and a diurnal shift in the predominant respiratory C source from recent (i.e. at least 1 d old) to fresh (i.e. photoassimilates produced on the same day). We conclude that in grasslands the plant-derived substrates used for soil respiratory processes vary during the day, and that photosynthesis provides an important and immediate C source. These findings indicate a tight coupling in the plant–soil system and the importance of plant metabolism for soil CO2 fluxes.
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