Root xylem CO2 flux: an important but unaccounted-for component of root respiration
Root xylem CO2 flux: an important but unaccounted-for component of root respiration
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DOI：
10.1007/s00468-015-1185-4
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发表时间：
2016-04-01
影响因子：
2.3
通讯作者：
Steppe, K.
中科院分区：
文献类型：
--
作者：
Bloemen, Jasper;Teskey, R. O.;Steppe, K.
根呼吸一直被认为是森林土壤CO2流出的一个重要组成部分，但最近的研究结果表明，它可能比以前的测量结果更重要，因为相当大一部分的根呼吸的CO2仍然在树木的根系和内部移动的蒸腾流。根中的高浓度CO2似乎主要来自根内。植物可以从土壤中吸收溶解无机碳（DIC），但在大多数条件下，由于根-土扩散梯度的存在，植物从土壤中吸收的DIC很小，这表明根木质部中的CO2大部分来自根系呼吸。通过根木质部的CO2内部通量的估计是基于液流和内部[CO2]的联合测量。结果量化根木质部CO2通量，获得有限数量的物种，提出了重要的问题，我们对树木呼吸的理解。总之，这些研究的结果提出了问题的分区生态系统呼吸到地上和地下的组成部分，并重新定义树木根系代谢的能量成本，从而估计地下碳分配。将我们对根木质部CO2通量的观测扩展到更多物种和更长时间尺度，以及改进用于研究这一过程的技术，可能是未来研究的富有成效的途径，有可能大幅修改我们对根呼吸和森林碳循环的理解。
Root respiration has been considered a large component of forest soil CO2 efflux, but recent findings indicate that it may be even more important than previous measurements have shown because a substantial fraction of root-respired CO2 remains within the tree root system and moves internally with the transpiration stream. The high concentration of CO2 in roots appears to originate mainly within the root. It has been suggested that plants can take up dissolved inorganic carbon (DIC) from soil, but under most conditions uptake from soil is minimal due to the root-to-soil diffusion gradient, which suggests that most of the CO2 in root xylem is derived from root respiration. Estimates of the internal flux of CO2 through root xylem are based on combined measurements of sap flow and internal [CO2]. Results quantifying root xylem CO2 flux, obtained for a limited number of species, have raised important concerns regarding our understanding of tree respiration. Taken together, the results of these studies call into question the partitioning of ecosystem respiration into its above- and belowground components, and redefine the energetic costs of tree root metabolism and hence estimates of belowground carbon allocation. Expanding our observations of root xylem CO2 flux to more species and at longer time scales, as well as improving the techniques used to study this process, could be fruitful avenues for future research, with the potential to substantially revise our understanding of root respiration and forest carbon cycles.