Refixation of respired CO2 by understory vegetation in a cool-temperate deciduous forest in Japan
Refixation of respired CO2 by understory vegetation in a cool-temperate deciduous forest in Japan
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DOI：
10.1016/j.agrformet.2005.10.006
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发表时间：
2005-11-30
影响因子：
6.2
通讯作者：
Koizumi, H
中科院分区：
文献类型：
--
作者：
Kondo, M;Muraoka, H;Koizumi, H
呼吸释放的CO要么通过湍流混合从森林中损失，要么通过冠层内的光合作用（CO2回收）重新固定。森林中的CO2浓度（[CO2]）通常从冠层向土壤表面增加，这是由于植物和土壤呼吸的高[CO2]。因此，林下植被能够通过光合作用固定呼吸的CO2，这一过程将影响森林内的碳动态。本研究通过对不同环境条件下林下植被对CO的再循环以及夏秋季节林下植物光合/呼吸活动的研究，（在森林树冠落叶后），我们测量了[CO，]和碳同位素比值高山试验区冷温性落叶阔叶林从林冠层顶部到林下层的CO2和植物有机质的变化（Δ C-13）。森林的树冠主要是桦树（桦）和橡树（栎），林下主要是万年青矮竹草（Sasa senanensis）。[CO2]CO_2的δ C ~（-13）在盛夏（8月）出现垂直分层，最大值为[CO_2]（约. 478 ppm）和最负的δ C-13值（- 12.5千分之一）附近的土壤表面。[CO2]和δ C-13的日变化在森林中也很明显，白天[CO2]明显低于夜间，这是由于白天光合作用吸收CO2，而夜间呼吸作用CO2的排放和积累发生在茂密的林下植被周围。基于斯滕贝格的模型[斯滕贝格，L.，1989.使用C-13/C-12比率和环境二氧化碳浓度估算森林中二氧化碳再循环的模型。农业森林陨石48，163-173;斯滕贝格，L.，莫雷亚，M.Z.，马丁内利洛杉矶维多利亚，R.L.，Barbsoa，E.M.，Bonates，L.C.M.，Nepstad D.C.，1997.两个亚马逊热带森林的二氧化碳循环。农业森林陨石88，259-268]利用森林中CO和叶片的[CO_2]和δ C ~（-13）值，计算了S. senanensis。S.夏季为15%。秋季（10月）森林冠层落叶后，[CO2]和δ C-13的日变化较小，垂直梯度较小。虽然S. senanensis是增强由于阳光容易到达地面，再固定的CO的百分比，再循环的S。senanensis为1%。我们的研究结果表明，在冷温性落叶林中，茂密的林下植被在呼吸CO的再固定中起着重要的作用。(c)2005 Elsevier B. V.保留所有权利。
CO, released by respiration is either lost from the forest through turbulent mixing or refixed by photosynthesis within the canopy (CO2 recycling). CO2 concentration ([CO2]) in a forest generally increases from canopy layer toward the soil surface due to the high [CO2] by plant and soil respiration. Therefore, the understory vegetation is capable of fixing the respired CO2 through photosynthesis, and this process would influence the carbon dynamics within a forest. In this study, in order to evaluate the magnitude of CO, recycling by understory vegetation under different environmental conditions and co-occurring photosynthetic/ respiratory activity in understory between summer and autumn (after defoliation of forest canopy), we measured [CO,] and carbon isotope ratios (delta C-13) of CO2 and plant organic matter in a cool-temperate deciduous broad-leaved forest at Takayama Experimental Site from the top of the forest canopy to understory layer. The forest canopy is dominated by birch (Betula ermanii) and oak (Quercus crispula), and the understory is dominated by an evergreen dwarf bamboo grass (Sasa senanensis). [CO2] and delta C-13 of CO2 were vertically stratified in the forest in mid-summer (August), with maximum [CO2] (ca. 478 ppm) and most negative delta C-13 value (- 12.5 parts per thousand) near the soil surface. The diurnal variations of [CO2] and delta C-13 were also clearly observed in the forest; daytime [CO,] was considerably lower than that in night due to photosynthetic CO, uptake in the daytime while respiratory CO, efflux and its accumulation occurred around the dense understory vegetation in night. Based on the Sternberg's model [Sternberg, L., 1989. A model to estimate carbon dioxide recycling in forests using C-13/C-12 ratios and concentrations of ambient carbon dioxide. Agric. Forest Meteorol. 48, 163-173; Sternberg, L., Moreia, M.Z., Martinelli, L.A., Victoria, R.L., Barbsoa, E.M., Bonates, L.C.M., Nepstad D.C., 1997. Carbon dioxide recycling in two Amazonian tropical forests. Agric. Forest Meteorol. 88, 259-268] using the data of [CO2] and delta C-13 values of CO and leaves in the forest, we calculated the fraction of respired CO, that was refixed photosynthetically by S. senanensis. The percentage of respired CO, refixed by S. senanensis was 15% in summer. After the forest canopy defoliation in autumn (October), [CO2] and delta C-13 showed small diurnal variation and small vertical gradients. Although the photosynthetic activity of S. senanensis is enhanced due to sunlight readily reaching the ground surface, the percentage of refixed CO, recycled by S. senanensis was 1%. Our result suggests that the dense understory vegetation have an important role in refixing the respired CO, in a cool-temperate deciduous forest. (c) 2005 Elsevier B.V. All rights reserved.